Sodium sulphate

Urea is a major issue in human wastewater because it may be easily broken down by the urease enzyme produced by bacteria, leading to ammonia production. Due to its ability to increase soil pH and eutrophicate streams, ammonia-containing effluent emissions pose environmental and health risks. This study aimed to evaluate the effectiveness of various treatment approaches in reducing urea concentrations by comparing the removal rates of conducting electrocoagulation (EC), EC followed by chemical coagulation (EC-CC), and CC followed by electrocoagulation (EC-CC). Numerous electrocoagulation parameters have been investigated, including current density, electrode gap distance, electrolyte type, concentration, and electrolysis duration. The electrode morphology was examined using a scanning electron microscope, while the produced sludge was analyzed using Fourier transform infrared spectroscopy. Three kinds of aluminum coagulants—potash alum, aluminum sulfate, and aluminum chloride—were used in the chemical coagulation, while the electrocoagulation was optimized at 30 A/m2. The results of this investigation suggest that the application of EC-CC, regardless of the type of coagulant used in both synthetic and real effluent, could marginally improve the efficacy of urea removal. Conversely, CC-EC exhibits an adverse effect on the efficiency of urea removal in both synthetic and real wastewater. The application of CC-EC demonstrated a significant improvement in the effectiveness of COD removal from actual wastewater, according to experimental results. The study emphasized the effectiveness and economic advantages of electrocoagulation over EC-CC and CC-EC techniques, used to remove urea from both real and synthetic wastewater.

Demand for nickel and cobalt sulfate is expected to increase due to the rapidly growing Li-battery industry needed for the electrification of automobiles. This has led to an increase in the production of sodium sulfate as a waste effluent that needs to be processed to meet discharge guidelines. Using bipolar membrane electrodialysis (BPED), acids and bases can be effectively produced from corresponding salts found in these waste effluents. However, the efficiency and environmental sustainability of the overall BPED process depends upon several factors, including the properties of the ion exchange membranes employed, effluent type, and temperature which affects the viscosity and conductivity of feed effluent, and the overpotentials. This work focuses on the recycling of Na2SO4 rich waste effluent, through a feed and bleed BPED process. A high ion-exchange capacity and ionic conductivity with excellent stability up to 41 °C is observed during the proposed BPED process, with this tempe...

Demand for nickel and cobalt sulfate is expected to increase due to the rapidly growing Li-battery industry needed for the electrification of automobiles. This has led to an increase in the production of sodium sulfate as a waste effluent that needs to be processed to meet discharge guidelines. Using bipolar membrane electrodialysis (BPED), acids and bases can be effectively produced from corresponding salts found in these waste effluents. However, the efficiency and environmental sustainability of the overall BPED process depends upon several factors, including the properties of the ion exchange membranes employed, effluent type, and temperature which affects the viscosity and conductivity of feed effluent, and the overpotentials. This work focuses on the recycling of Na2SO4 rich waste effluent, through a feed and bleed BPED process. A high ion-exchange capacity and ionic conductivity with excellent stability up to 41 °C is observed during the proposed BPED process, with this tempe...

BACKGROUNDThe design of new approaches that help to decrease both the environmental impact of industrial activities and the cost of existing water treatment technologies is becoming a key aspect of research. In the present work, an efficient and easy‐to‐use electrochemical device designed to dose iron coagulants is presented.RESULTSThe proposed device (the Electrochemically‐assisted Coagulant – production & dosing Unit, ECU) exhibits an efficient performance in the dosing of coagulants regardless of the ionic conductivity of the water matrixes tested (within the range 100 to 1000 µS cm−1), covering a wide range of potential real surface waters. The behaviour of the ECU device was compared to that of a conventional chemical dosing of iron, and showed better pH (pH ≈ 8 for ECU but < 4 for equivalent chemical dosing) and conductivity (decrease for ECU but increase up to 60% for equivalent chemical dosing) control. Moreover, the ECU unit produced a noticeable amount of Fe2+ ions, due...

In this paper the process of reagent desalination of mineralized mine waters was studied. The peculiarity of mine waters in many regions of Ukraine is that, along with hardness ions, they also contain sulphates in fairly high concentrations. Therefore, the task of desalination of mineralized waters consists in effective removal of sulphates along with softening of the solution. For effective purification of water from sulphates and hardness ions, 5/6 aluminum hydroxychloride (Al 2 (OH) 5 Cl) and sodium tetrahydroxoaluminate (Na[Al(OH) 4 ]) were used during liming. A significant increase in efficiency of the treatment process was achieved when the solution was acidified with carbon dioxide after treatment with reagents. The directions of processing of the formed sediments as part of building materials have been determined. Complex processing of the generated waste in the process of water treatment allows creating a low-waste technology for the purification of mineralized water.

Electrocoagulation (EC) can be defined as the electrochemical involvement of waste water treatment and an eco-friendly approach. In the traditional approach, direct current was employed to produce coagulants, polymetallic hydroxide species, by electrodissolution of metal electrodes such as aluminium (Al) and iron (Fe). Compared to other waste water treatment processes, the EC is a cost-effective method. However, the traditional electrocoagulation process that was conducted with direct current (DC) associates with certain drawbacks such as deposition of non-conducting material on the anode and passivation limits. The application of alternating current (AC) has been found to be a highly effective method to overcome the drawbacks of DCEC, and minimizes the higher electrode dissolution and minimize nonconducting material deposition by alternating the polarity of electrodes. In this study, current density, applied potential, frequency of current, initial pH, initial conductivity of electrolyte, temperature, operational time, electrolyte composition, electrode material, and configuration were studied for efficient removal of Ca and Mg in water. It was found that, the final pH of treated water depends on the initial composition of the electrolyte in the wastewater. Under optimal conditions of 14.00 volts, 300 Hz AC, and 90 minutes, with Al-Al electrode system, a removal of 80% Ca 2+ and 70% of Mg 2+ were achieved. EC carried out for 1000 µS/cm Na2SO4 and 1000 µS/cm CaCl2 + Mg(NO3)2 solutions, the final pH value reached approximately to 10.04, with the Na2SO4 electrolyte and 8.34 with the CaCl2 + Mg(NO3)2 electrolyte. For other Al-Fe, and Fe-Fe electrode configurations, different efficiencies were investigated.

Electrocoagulation (EC) is an electrochemical method in water treatment. Nowadays, electrochemical disinfections have created great interest in water treatment as an alternative for conventional disinfection. In this study, the effects of electrochemical inactivation with monopolar electrodes on Escherichia coli and Clostridium perfringens bacteria removal from potable water by the EC process were investigated. In addition, the effects of initial pH, reaction time, current density, as well as inter-electrode distance and conductivity on abatement of selected bacteria along with operating costs have been studied. The structure and surface morphology of the alum nanocrystallites were investigated by X-ray fluorescence, N 2 adsorption-desorption, transmission electron microscopy, powder X-ray diffraction, and field emission-scanning electron microscopy. The experiments were performed in a batch reactor. According to the results, the optimum condition for removal efficiency of 100% E. coli and C. perfringens with an 0.6 USD/m 3 operation cost for the treated aqueous solution were as follows: reaction time = 25 min, initial pH = 7, inter-electrode distance = 2 cm, current density = 33.3 A/m 2 , electrical conductivity = 0.75 mS/cm, and initial bacteria count = 10 4 CFU/mL. Findings indicated that increasing pH from 7 to 9 can significantly decrease the removal efficiency for E. coli and C. perfringens from 100% to 74% and 71%, respectively. Increasing reaction time and current density decreased both strains significantly. Inter electrode distance had an intangible effect on strains abatement. Field Emission-Scanning Electron Microscopy analysis revealed morphological variations and the mechanism through which the killing and trapping of the bacteria by alum nanocrystallites occur. The present method is able to reduce the E. coli and C. perfringens count in potable water, which meets the drinking water standards according to WHO guidelines.

Fluoride removal from aqueous solution was investigated using the chemical coagulation-flocculation by alum in reason of the efficiency and the simplicity of the process. Preliminary experiments were carried out to study the effect of some operating parameters such as: pH, initial fluoride concentration, coagulant dose, adjuvant coagulation dose, flocculent dose and settling time. Obtained experimental results showed that the treatment of fluoride by alum coagulation causes acidification of the solution. The effect of the initial pH solution on fluoride removal is negligible. Experimental results proved that coagulation process is effective in waters with low or medium levels of fluoride. Defluoridation rate was seen to increase with increasing coagulant and adjuvant coagulation doses. Optimal flocculent dose and optimal settling time were found 4.2 mg L-1 of FABI and 60 min respectively. Subsequently, experimental design methodology using two-level full factorial design was applied...

The cellulose and paper industry produces large volumes of wastewater which are difficult to treat due to large concentrations of Humic acid (HA). In subsurface water, HA can react with active chlorine to produce carcinogenic compounds causing different ecological problem and danger to human health. The main objective of the present study is to investigate the influence of electrocoagulation (EC) process parameters using aluminum (Al) electrodes to remove HA from synthetic solution, and then studies the efficiency of the coupling of electrocoagulation and the adsorption on active carbon (GAC). It has been observed from the experimental results that the best removal of HA by EC was obtained with the following optimum conditions: initial pH of 4, current density of 1.388 mA cm −2 , Na 2 SO 4 concentration of 150 mg L-1 and EC time of 10 min. These operating conditions allow a removal percentage up to 93% with 0.033 KWh m-3 of power consumption by EC and the same removal ratio was achieved for a treatment time of only 2 min by combining adsorption onto GAC with EC with a decrease of power consumption (0.007 kW h m-3). Accordingly, our results displayed prominently that combination of electrocoagulation with adsorption on GAC notably reduces the treatment duration without inducing a strong increase of cost. The current study extends our investigation of these promising processes to wastewater applications, employing samples of cellulose and paper industrial wastewater. The results suggest that combining adsorption onto GAC with EC could greatly improve the economics of treatment of wastewaters generated in cellulose and paper industry by extending efficiency through reduced treatment time and cost. HA was completely removed from Tunisian industrial wastewater with a very low energy consumption (0.0183 KW h m-3) and treatment cost of 0.233 TND.

High boron levels in drinking water can be toxic to humans. According to the WHO regulations (2011), the boron concentration should be reduced to less than 2.4 mg L-1 for drinking water. The aim of this study is to investigate the feasibility of coagulation-flocculation and electrocoagulation as a pre-treatment process to remove boron from natural water. Standard jar tests using coagulation and flocculation simulator were carried out to determine the effectiveness of chemical pretreatment for removal of boron. (MgCl2, 6H2O) was used as coagulation adjuvant in combination with optimum coagulant dose to observe their differential effects. To optimize the experimental conditions of boron removal, commercial flocculant was used. Afterward the performance of electrocoagulation process to remove boron was investigated by optimizing the experimental conditions, such as pHi, electrolysis time, initial conductivity of the solution ( i), and current density. Experiments were carried out with ...

In this study, performance of alum and polyaluminum chloride(PACl) for fluoride removal has been compared in batch and continuous modes. Experiments were performed to determine the optimum doses of coagulant for bringing the fluoride (<1.5 ppm) and aluminum(0.2 ppm) within acceptable limits. The residual fluoride was found to be higher in case of alum as compared to PACl representing less efficient settling of suspensions, primarily comprise of alumino-fluoro complexes. In addition to this, water treated with PACl contains relatively low soluble salts compared to alum & also requires lesser lime for pH compensation due to its lower acidity. It was also observed that the PACl treated water contains less residual aluminium(0.34ppm) compared to alum (0.46 ppm) when initial fluoride concentration of water was 4 ppm. In batch mode, residual Al was found to be 0.182 ppm (alum) & 0.143 ppm (PACl), after subsequent microfiltration which conform to the Al standards in defluoridated

The purpose of this paper is to suggest an efficient defluorination process which does not require a big investment. For this, the electrocoagulation process with aluminium bipolar electrodes was used. In the first step, the influence of parameters such as inter-electrode distance, fluoride concentration, temperature and the pH of the solution, were investigated and optimized with synthetic water in batch mode. In the second step, the optimization process was continued with Oued Souf water (south Algeria) where the influence of the current density and the area/volume ratio on the defluorination process was evaluated. The electrocoagulation process with aluminium bipolar electrodes permitted the defluorination of Sahara water without adding soluble salts to the treated water. The aluminium-fluoride weight ratio attained 17/1. The purpose of this paper is to suggest an efficient defluorination process which does not require a big investment. For this, the electrocoagulation process with aluminium bipolar electrodes was used. In the first step, the influence of parameters such as inter-electrode distance, fluoride concentration, temperature and the pH of the solution, were investigated and optimized with synthetic water in batch mode. In the second step, the optimization process was continued with Oued Souf water (south Algeria) where the influence of the current density and the area/volume ratio on the defluorination process was evaluated. The electrocoagulation process with aluminium bipolar electrodes permitted the defluorination of Sahara water without adding soluble salts to the treated water. The aluminium-fluoride weight ratio attained.

The electrocoagulation was applied to removal of fluoride and coexisting anions from simulated groundwater. The concentration of fluoride, chloride and sulfate was of 5 ppm, 347 ppm and 199 ppm, respectively. The influence of pH, current density, electrolysis time and sulfate presence were studied. Fluoride and sulfate removal efficiency, chloride concentration and specific energy consumption were calculated.

The presence of ultrafine clay particles that are difficult to remove by conventional filtration creates many operational problems in mining processing systems. In this work, the removal of clay suspensions has been investigated using an electroflotation (EF) process with titanium electrodes. The results show that EF is a viable and novel alternative for removing ultrafine particles of kaolinite-type clay present in sedimentation tank overflows with low salt concentrations (<0.1 mol/L) in copper mining facilities based on the saline water splitting concept. Maximum suspended solid removal values of 91.4 and 83.2% in NaCl and KCl solutions, respectively, were obtained under the experimental conditions of the constant applied potential of 20 V/SHE, salinity concentration of 0.1 mol/L, and electroflotation time of 10 and 20 min in NaCl and KCl solutions, respectively. Furthermore, the visual evidence of particle aggregation by flocculation during the experiments indicates a synergy ...

Fluoride ions present in drinking water are beneficial to human health when at proper concentration levels (0.5–1.5 mg L−1), but an excess intake of fluoride (>1.5 mg L−1) may pose several health problems. In this context, reducing high fluoride concentrations in water is a major worldwide challenge. The World Health Organization has recommended setting a permissible limit of 1.5 mg L−1. The application of electrocoagulation (EC) processes has received widespread and increasing attention as a promising treatment technology and a competitive treatment for fluoride control. EC technology has been favourably applied due to its economic effectiveness, environmental versatility, amenability of automation, and low sludge production. This review provides more detailed information on fluoride removal from water by the EC process, including operating parameters, removal mechanisms, energy consumption, and operating costs. Additionally, it also focuses attention on future trends related to...

This review discusses the Brownian motion and coagulation/flocculation (C/F) in water/wastewater treatment. In water/wastewater treatment processes, pertinent questions relating to Brownian motion and C/F are often asked. Some of these questions are: Brownian motion and molecular agitation are favourable or not to separation processes? As high salinity (seawater) decreases disorder, increasing surface water salinity would be a convenient water treatment process or not? The processes of C/F are used to remove dissolved substances and colloids from water in order to assure efficient settling.

This paper explores the use of electrocoagulation to remove boron from waste effluent in comparison with alum coagulation. In treating model test wastes, greater boron removals were achieved with electrocoagulation at low doses than conventional alum coagulation when reaction was undertaken for the same conditions (pH 8.5, and initial boron concentration was 500 mg/L). Al electrocoagulation can achieve good boron removal performance (68.3%) at a dose of 2.1 (as molar ratio of Al:B, and for current density of 62.1 A/m2), while alum coagulation can only achieve the maximum boron removal of 56% at a dose of 2.4. Also, Al electrocoagulation can remove 15–20% more boron than alum coagulation for the same dose compared in the treatment of both model test wastes and industry effluent. The estimation of running costs shows that to achieve 75% boron removal from industry waste effluent, i.e. removing 150 g of boron from 1 m3 of effluent, electrocoagulation was 6.2 times cheaper than alum coa...

of mixing, preparation of samples and curing for various tests are presented. Amount of lime, other additives, their combinations, and curing period are projected in the experimental program in various chapters. The long term effects of varying percentages of sulphate on the physical properties, grain size distribution and free swell index of marine clays

Combined effect of polycarboxylate type superplasticizer and sodium sulphate on the hydration of fly ash blended Portland ® cement has been studied by using different techniques. Water consistency, setting times, non-evaporable water contents, water percolation, air contents, compressive strengths and expansion in corrosive atmosphere were determined. Hydration products were examined with the help of DTA and X-ray diffraction techniques. It is found that the superplasticizer reduces the pore size and its adsorption on cement surfaces is decreased in the presence of sodium sulphate. Mechanism of hydration is discussed.

An experiment was carried out to investigate the effect of substituting synthetic methionine with sodium sulphate and sodium sulphite in maize-soyabean diets fed to broiler chicks on weight and haematological profile. Two hundred and forty (240) unsexed Hubbard day old broiler chicks were fed isocaloric and iso-nitrogenous maize-soyabean diets (3,000 cal/kg and 22% crude protein) for four weeks. There were eight treatment groups, T1-T8, each replicated three times. T1 had no methionine, T2 had 3% methionine, T3 had 3% sodium sulphate, T4 had 3% sodium sulphite, T5 had 1.5% methionine and 1.5% sodium sulphate, T6 had 1.5% methionine and 1.5% sodium sulphate T7 had 1.5% methionine and 1.5% sodium sulphite while T8 had 1.5% methionine and 1% sodium sulphite. Chicks in T6 had the highest average weekly weight gain of 106.58 g while birds in T8 had the lowest average weekly weight gain (79.94 g). The average weekly weight gain of birds in T1, T2 and T5 did not differ significantly (p>0.05) from one another. Likewise the average weekly weight gain of birds in T1, T2, T3 T4 and T5 did not differ significantly (p>0.05) from one another. The average weekly weight gain of chicks in T7 and T8 which had the lowest weight gains, also did not differ significantly (p>0.05). All haematological parameters evaluated fell within safe precincts as stipulated in literature. Treatment 6 is therefore recommended for broiler starter rations alongside T2 and T5 because they did not differ significantly (p>0.05) from one another.

Data analysis and evaluation form the basis of all engineering design. In order to come up with a cost effective design of a water treatment plant in small communities around Maiduguri, Borno State, the population as well as the surface water within the selected localities were evaluated and analyzed leading to a process selection which is expected to provide potable drinking water that satisfies the requirement of WHO (world Health Organization) standard.

Photovoltaic technology has experienced a huge global economic boom in recent decades and a growing trend is expected in the future. This technology consists of the application of a number of processes including growth, oxidation, doping, metallization, etc. In order to reduce the fluoride content in the water below a threshold value that complies with the standards of industrial discharges or water intended for human consumption, various treatment techniques have been implemented. In this respect, electrocoagulation (EC) has been chosen in this study because of its performance compared to other methods. Wastewaters from surface treatment of silicon wafers are rich in fluoride and the lime precipitation is insufficient to comply with environmental standards. In this work, the EC technique, with Fe anodes, was used as an alternative for water purification. By coupling electroflotation to the electrocoagulation in the same cell, the separation of solid/liquid was significantly improved. To study the process performance, tests on the effect of the operational parameters such as current intensity, initial pH, nature of supporting electrolyte and its concentration were carried out on synthetic solutions. The optimal values are: pH o = 4; current = 1.4 A and [NaCl] = 2 g/L. The removal efficiency of 62% was reached starting from an initial concentration of 35 mg/L. A total clarification of the synthetic solution was also obtained.

This study has two main objectives. First, an evaluation of the effects of five operating parameters namely current density (CD), electrolysis time (t e), pH, conductivity (σ i) and stirring speed (SS) on the fluoride removal by electrocoagulation (EC) was conducted through one-way analysis of variance (ANOVA) strategy. Two more performance indicators namely energy consumption and loss of electro-dissolved aluminum electrode were considered. Second, development of three regression models to model and to determine the optimal conditions for electrochemical fluoride reduction process. To this end, EC experiments were carried in batch mode using stirred reactor with Al-Al monopolar configuration. One-way ANOVA results confirm that CD, t e , pH, σ i and SS have significant effects on reactor performance to reduce fluoride. Multiple regression analysis method demonstrates the reliability of the three developed model to predict the outcomes with respective R 2 values of 0.9879, 0.9949 and 0.9813 for fluoride removal efficiency, energy consumption and loss of electrode, respectively. Thus, EC can effectively bring down the fluoride concentration below permissible limits (1.4 mg•L-1) under the optimal conditions. The later are reached when the reactor is stirred at a speed of 102 rpm and the electrochemical cell is operating under a current density of 40.76 A•m-2 for an electrolysis time of 23.38 min and the solution pH is adjusted to 7.17 and a conductivity of 2,374 µS•cm-1. These conditions generate a low energy consumption (54.58 Wh•m-3) and electrode loss equal to 25.51 × 10-3 %.

This work examined boron removal by applying a lab-scale continuous electrocoagulation process. The impact of influent pH (4, 5, 6, 7.45, and 9) and retention time (10, 25, 50, and 100 min) on the treatment process was examined. Plate-type aluminum electrodes were used. The experiments were conducted in continuous mode, and the electric current was kept constant at 5 A. The initial boron concentration was 1,000 mg L-1. The first set of experiments concerning the influence of the influent pH showed that the highest boron removal (67%) was obtained at pH = 6. This pH value was the optimal one for boron precipitation through aluminum borate formation. The increase in the duration of the process from 10 to 100 min resulted in increasing boron removal from 45% to 79%. The longer duration of the electrocoagulation process enabled higher aluminum dissolution, thus allowing the existence of a higher amount of coagulants within the reactor. Moreover, it enhanced boron precipitation because of the longer contact time between the boron ions and the coagulants. By optimizing the key parameters of the process, the continuous electrocoagulation process showed to be an effective alternative for the removal of highly concentrated boron.

The performance of a batch electrocoagulation cell (rotating cylinder electrochemical reactor) in the demulsification of crude oil emulsions was investigated. The cell used a rotating Al cylinder as anode and a stationary cylindrical screen of aluminum as cathode. Parameters studied are the current density, the NaCl concentration, initial pH, the anode rotation speed, initial oil concentration and the nature of the supporting electrolyte. Increasing the current density led to increasing the rate of de-emulsification; a current density of 11.4 mA/cm 2 allowed complete separation in 10 minutes while a current density of 17.1 mA/cm 2 allowed complete separation in 6 minutes. The optimum pH range for the electrocoagulation is 7-11, acidic media (pH 3-5) retarded the electrocoagulation. The increase in the concentration of the NaCl led to an increase in the rate of oil removal. Higher electrolyte conductivity of the emulsion increased the rate of oil removal. Anode rotation was found to have a strong effect in improving oil removal efficiency. The higher the initial concentration of the emulsion, the higher the rate of oil removal. NaOH was found to be the best electrolyte, followed by NaCl, then KCl and finally NH 4 Cl.

In the present work, coagulation, electrocoagulation and sono-electrocoagulation were compared for the treatment of synthetic wastewater, which consists of a solution of Rhodamine 6G (used as a model of dye). The results are discussed in the light of the well-known coagulation mechanism of dyes. These results show that the primary coagulation mechanisms of coagulation and electrocoagulation are different because of the very different pH changes obtained during the treatment, being more relevant the enmeshment into the growing floc of the metal hydroxide precipitate in the electrocoagulation process and the charge neutralisation in the coagulation. Removals of 60% can be obtained for large doses of coagulants (or electric charge applied in the case of electrocoagulation) in both single technologies. Ultrasound irradiation allows the electrocoagulation process to enhance the efficiency up to 95% even if applying a lower electric charge. This enhancement is especially important during the treatment of wastewater with an alkaline initial pH because of the promotion of the floc enmeshment mechanisms. Electrochemically-based processes show an additional advantage: the pH is buffered during the treatment to a range 6-8, which allows the direct disposal of the treated waste without a further neutralisation process.

In the present work, coagulation, electrocoagulation and sono-electrocoagulation were compared for the treatment of synthetic wastewater, which consists of a solution of Rhodamine 6G (used as a model of dye). The results are discussed in the light of the well-known coagulation mechanism of dyes. These results show that the primary coagulation mechanisms of coagulation and electrocoagulation are different because of the very different pH changes obtained during the treatment, being more relevant the enmeshment into the growing floc of the metal hydroxide precipitate in the electrocoagulation process and the charge neutralisation in the coagulation. Removals of 60% can be obtained for large doses of coagulants (or electric charge applied in the case of electrocoagulation) in both single technologies. Ultrasound irradiation allows the electrocoagulation process to enhance the efficiency up to 95% even if applying a lower electric charge. This enhancement is especially important during the treatment of wastewater with an alkaline initial pH because of the promotion of the floc enmeshment mechanisms. Electrochemically-based processes show an additional advantage: the pH is buffered during the treatment to a range 6-8, which allows the direct disposal of the treated waste without a further neutralisation process.

In this study, electrochemical treatment of urban wastewater with electrical conductivity of 1000 μS/ cm, chemical oxygen demand of 250 mg/L was investigated using variables of circulation rate, initial pH value, constant pH value, current intensity and supporting electrolyte type and concentration. Electrocoagulation was used in which aluminum and stainless steel were selected as the electrochemical treatment process. The data obtained in experimental studies show that the COD removal efficiency increases in experiments where the circulation rate is 100 mL/min and the initial pH value is 7. Although the increase in current intensity from 5 A-20 A increases the recovery efficiency from 46%-80%, the COD removal efficiency at a current intensity of 25 A is significantly decreased. While the use of support electrolyte did not contribute to the efficiency of COD removal, it significantly reduced the value of energy consumption. The best removal efficiency according to optimum results was obtained as about 90%, which is 10 A current intensity, 100 mL/min circulation rate, constant pH 7 and no support electrolyte experiments.

Abstract: This study seeks to find a new method to enhance the percentage of boron removed from aqueous solution by using the electrocoagulation process in the presence of curcumin. The optimum current density (CD), pH and dose of curcumin were determined as the operational parameters. The results showed that boron removal increased when CD was increased to 6.0 mA/cm from 1.0 mA/cm. In our laboratory-scale reactor, the 2 2 optimum pH and curcumin dose for the aqueous boron solution before electrocoagulation were 4.0 ...

Removal of fluoride from drinking water by polyaluminum chloride-chitosan (PACl-Ch) composite coagulant was studied in a batch system. Two types of PACl-Ch coagulant were synthetized as PACl-Ch I and PACl-Ch II with chitosan to aluminum (Ch:Al) weight ratios of 0.5 and 1.0, respectively, and were used for defluoridation under different operating conditions. The composite coagulants were found to be more efficient than both PACl and chitosan. By an increase in the Ch:Al ratio from 0.5 to 1.0, the composite coagulant provided a little more efficiency of fluoride removal and lower residual level of Al. The optimum conditions of pH for fluoride removal by PACl-Ch I and PACl-Ch II were 8.0 and 7.5, respectively. Fluoride removal by the coagulants was not significantly affected by natural organic matter and turbidity, but was declined by high concentrations of common ions. To achieve desirable fluoride levels (lower than 1.0 mg/L) for natural water samples with fluoride levels of 2.0–2.9 ...

Au Maroc, la demande en eau connait une croissance continue en liaison avec l’evolution demographique et les activites consommatrices de cette ressource essentielle. Dans le domaine du textile, plus particulierement, il existe un besoin de recycler les eaux chargees en colorants. Cette etude visait l’elimination des matieres polluantes dans le cas d’un rejet colore de pH neutre et l’optimisation des differents parametres experimentaux influencant celles-ci. La premiere etape de cette etude a ete consacree a la synthese de structures adsorbantes et coagulantes par un procede d’electrocoagulation indirecte en utilisant des electrodes de fer ou d'aluminium, dans une solution electrolytique de chlorure de sodium (10⁻² mol L⁻¹ ), a pH neutre. Dans une deuxieme etape, differents melanges de composes (100% Al, 75% Al et 25% Fe, 50% Al et 50% Fe, 25% Al et 75% Fe et 100% Fe) ont ensuite ete utilises pour le traitement de solutions polluees par un colorant (trypan bleu), du phenol, de l’...

This work investigates the possibility of removing nitrate ions (NO 3-) from wastewater by using monopolar vertical aluminum electrodes in a batch electrochemical unit. Variables studied were current density, initial NO 3 concentration, initial solution pH, electrolysis time and anode diameter. The results show that up to 90% of NO 3 can be removed in approximately 80 minutes. To throw some light on the economy of the process power consumption was measured against current density and percentage removal. The results show that the ratio (% removal/power consumption) dramatically decreased from 34.9 to 0.45 by increasing the current density from 3 to 13 mA/m 2 which suggests that the economy of the process is favored by low current densities.

This study has two main objectives. First, an evaluation of the effects of five operating parameters namely current density (CD), electrolysis time (t e), pH, conductivity (σ i) and stirring speed (SS) on the fluoride removal by electrocoagulation (EC) was conducted through one-way analysis of variance (ANOVA) strategy. Two more performance indicators namely energy consumption and loss of electro-dissolved aluminum electrode were considered. Second, development of three regression models to model and to determine the optimal conditions for electrochemical fluoride reduction process. To this end, EC experiments were carried in batch mode using stirred reactor with Al-Al monopolar configuration. One-way ANOVA results confirm that CD, t e , pH, σ i and SS have significant effects on reactor performance to reduce fluoride. Multiple regression analysis method demonstrates the reliability of the three developed model to predict the outcomes with respective R 2 values of 0.9879, 0.9949 and 0.9813 for fluoride removal efficiency, energy consumption and loss of electrode, respectively. Thus, EC can effectively bring down the fluoride concentration below permissible limits (1.4 mg•L-1) under the optimal conditions. The later are reached when the reactor is stirred at a speed of 102 rpm and the electrochemical cell is operating under a current density of 40.76 A•m-2 for an electrolysis time of 23.38 min and the solution pH is adjusted to 7.17 and a conductivity of 2,374 µS•cm-1. These conditions generate a low energy consumption (54.58 Wh•m-3) and electrode loss equal to 25.51 × 10-3 %.

This study compares the results of the dewatering of coal preparation plants tailings by conventional coagulation processes using different types of coagulants and by electrocoagulation methods carried out by two different electrodes. When the results of electrocoagulation and conventional coagulation experiments were compared (aluminium electrode vs. ferric chloride), it was found that the coagulation efficiencies for both methods were similar, in the case that the aluminium electrode was used, there was a 22.2% decrease in the process cost compared to the use of ferric chloride.

In this work, the removal results of the application of sequential chemical precipitation (CP) and coagulation (CC) over boron-containing industrial wastewater were presented. Effect of amount of Ca(OH) 2 /B 2 O 3 concentration ratio, initial pH and Al 2 (SO 4) 3 •18H 2 O concentration on B 2 O 3 removal was investigated using Box-Behnken based custom experimental design. Response surface methodology (RSM) was used to evaluate the effect of process variables and their interactions on boron removal. Results show that selected operational parameters and obtained regression model were statistically significant. The coefficient of determination was found as 0.9846, indicating that the model has a good fit with experimental data. Water has been obtained in a dischargeable quality according to Water Pollution Control Regulation of Turkish Authorities with 95% B 2 O 3 removal from an initial concentration of 13.23 g/L under optimum operating conditions of 2.01 g Ca(OH) 2 /1 g/L B 2 O 3 ratio, pH 8.12 and 13.5 g/L Al 2 (SO 4) 3 •18H 2 O.

A mathematical model of the organic matter (chemical oxygen demand - COD) removal from synthetic oil-water emulsions by the electrocoagulation process was developed to evaluate the COD abatement. The model comprises the three fundaments of electrocoagulation: electrochemistry, coagulation and flotation. By comparing the experimental and calculated values of COD, it was found that the model was able to adequately predict the concentrations of organic matter (COD) present in the emulsions and satisfactorily describe the electrocoagulation process.

Fluoride, an anionic pollutant, when exists in concentrations exceeding the allowed limit of 1.5 mg/L in drinking water, has been reported to cause detrimental impact on human health. The traditionally employed methods for water defluoridation mostly involve Al-based coagulants, which however face some limitations, such as requirement of relatively high dosage and production of excessive amounts of chemical sludge posing problem of its safe disposal. In this study, two Inorganic Polymeric Coagulants of medium (IPC-M) and ultra-high basicity (IPC-UH) were synthesized using polymerization of aluminium tri-hydrate (Al 2 O 3 .3H 2 O) with an aqueous solution of 32% hydrochloric acid. The basicity of coagulants was increased by manipulating the redox reaction of the product with aluminium metal. The synthetic coagulants were analysed using various characterization techniques, viz., FTIR, ESI-MS, FE-SEM with EDS and the main physicochemical properties like %Al 2 O 3 , relative basicity and % chloride. The aluminium species distribution was assessed by ferron assay, and their electrochemical properties like dissolved charge, conductivity, acidity, and pH were also measured. The application of inorganic polymeric coagulants was explored for their fluoride removal efficacy using Jar tests. The outcome showed that IPC-M was the most efficient when applied in a pH range relevant to fluoride-containing water as it was the only coagulant that showed increasing efficiency at pH values > 7. The uptake capacity of coagulants for using synthetic samples prepared in Milli-Q water containing 9 mg/L of raw fluoride concentrations to achieve residual concentration of less than 1.5 mg F/L at the pH value 6.5 ± 0.1 were assessed as 87.68, 68.48 mg F/g Al 2 O 3 for IPC-M and IPC-UH respectively, which were higher than the reported values of 37.42, 37.75 mg F/g Al 2 O 3 for Alum and PAC in earlier published paper 1. The residual aluminium concentration in these experiments ranged at 30 ± 5, 20 ± 5 μg Al/L respectively for IPL-M and IPL-UH, which were well within WHO norm for drinking water (<200 μg /L), indicating their immense application in the field.

The large amount of municipal wastewater discharged into urban rivers sometimes exceeds the rivers' self-purification capacity leading to black-odorous polluted water. Electro-flocculation has emerged as a powerful remediation technology. Electro-flocculation in a bubble column tower with a bipolar electrode (BPE) was tested in an attempt to overcome the high resistance and weak gas-floatation observed with a monopolar electrode (MPE) in treating such water. The BPE reactor tested had a Ti/ Ta 2 O 5-IrO 2 anode and a graphite cathode with an iron or aluminum bipolar electrode suspended between them. It was tested for its ability to reduce turbidity, phosphate and sulphion and to increase the concentration of dissolved oxygen. The inclusion of the bipolar electrode was found to distinctly improved the system's conductivity. The system's electro-flocculation and electrical floatation removed turbidity, phosphate and sulphion completely, and the dissolved oxygen level improved from 0.29 to 6.28 mg/L. An aluminum bipolar electrode performed better than an iron one. Changes in the structure of the microbial community confirmed a significant improvement in water quality.

The durability of concrete has a profound impact on the service life of structural elements. Indonesia has extensive peat soils, which provide a highly aggressive environment for concrete structures. Geopolymer concrete has demonstrated good durability when exposed to acid /sulphate conditions similar to those encountered in peat soils. This paper investigates the performance of geopolymer concretes produced using Indonesian type F fly ash under sulphate and acid chemical attack. Geopolymer concrete specimens have been exposed for 12-months in a range of solutions: 5% sodium sulphate, 5% magnesium sulphate, 1% and 3% sulphuric acid, and simulated peat solution. The mechanical and durability properties of specimens together with a control concrete have been monitored for compressive strength, change in mass, water absorption and volume of permeable voids, ultra pulse velocity, air and water permeability, pH profile, and microstructural analysis (XRD, SEM/EDS). The control immersed in...

In this work, the effect of temperature on behaviour of AASC (Alkali Activated Slag Concrete) with that of Conventional concrete (CC) is made. For this a design mix of M20 grade has been made in accordance with IS 10262:2009. Preliminary investigations has been done for 18 mixes and the mix S-0.5-1-12 M is considered as the best, based on strength characteristics, in which AAS (Alkali Activated Slag) to GGBS (Ground Granulated Blast Furnace Slag) ratio is 0.5 with Na 2 SiO 3 solution (SSS: Sodium Silicate Solution) to NaOH solution (SHS: Sodium hydroxide Solution) ratio1.0 containing concentrated 12 M of NaOH solution. The alkaline solution has been prepared 24 h in advance to the casting process. The conventional method of mixing, compacting and moulding has been followed for the production of AASC. Total of 144 cubes of dimension 150x150x150 mm, 180 cylinders of dimension 150x300mm and 144 prisms of dimension 500x100x100mm were casted. The specimens are subjected to ambient curing for 7, 28, 56 and 91 days and then subjected to temperatures of 27 0 , 100 0 , 200 0 , 300 0 , 400 0 and 500°C for a period of 1 h. From the above study it was found that various Mechanical Properties of AASC mix performing better than CC (Conventional Concrete) mix.

The main objective of our study is to test the performance of aluminum sulfate (AS) and the coagulation-flocculation process in removing a dye widely used in the textile industry called Congo Red (CR). In order to achieve our objective, the jar-test tests were carried out in the laboratory on synthetic solutions. Various reaction parameters were tested such as the effect of variation in coagulant dose, variation in initial CR content, and variation in pH. A combination between the AS and coagulants aid such as powder activated carbon (PAC), polymers, and lime (Ca(OH) 2) has been carried out to improve this process. The results obtained indicated for 30 mg/L concentration of CR, the AS optimal dose is found 40 mg/L. This dose has an elimination yield around to 97.24%. For the pH effect, the best performance was achieved in the range of pH between 4 and 6. Similar efficiency trends were obtained for 50 mg/L of the initial content of the CR. The combination of AS with coagulants aid has also shown that there is a very strong elimination marked by the small amounts of polymer, where the yield exceed 99%, in comparison with PAC and lime.

Combined effect of polycarboxylate type superplasticizer and sodium sulphate on the hydration of fly ash blended Portland ® cement has been studied by using different techniques. Water consistency, setting times, non-evaporable water contents, water percolation, air contents, compressive strengths and expansion in corrosive atmosphere were determined. Hydration products were examined with the help of DTA and X-ray diffraction techniques. It is found that the superplasticizer reduces the pore size and its adsorption on cement surfaces is decreased in the presence of sodium sulphate. Mechanism of hydration is discussed.

Fast electroflotation extraction of heavy metals from wastewater is described. The results of experimental investigations of the extraction of iron, aluminium and chromium hydroxides from aqueous solutions in the presence of surfactants of various natures and ions of calcium by electroflotation are presented. It was found that the presence of Ca 2+ in the solution at a concentration of 0.5 g/L reduced the degree of electroflotation extraction of Al(OH) 3 , Fe(OH) 3 , Cr(OH) 3 regardless of the nature of the electrolyte. The addition of surfactants in the system in the presence of Ca 2+ increased the amount of extraction of the dispersed phase. The greatest effect is achieved with the help of anionic surfactant sodium dodecyl sulphate, while the degree of extraction reached 98%. The high efficiency of the process of electroflotation extraction of the dispersed phase was due to the hydrophobization of the particle surface owing to the adsorption of surfactants on the surface of hydroxides. The recent method is useful to treat wastewater contaminated with aluminium, iron and chromium metal ions. The reason is that this method is very fast working within 20 min; Moreover, pH 7.0 working made this method ideal for utilisation in natural water treatment economically.

An experiment was carried out to investigate the effect of substituting synthetic methionine with sodium sulphate and sodium sulphite in maize-soyabean diets fed to broiler chicks on weight and haematological profile. Two hundred and forty (240) unsexed Hubbard day old broiler chicks were fed isocaloric and iso-nitrogenous maize-soyabean diets (3,000 cal/kg and 22% crude protein) for four weeks. There were eight treatment groups, T1-T8, each replicated three times. T1 had no methionine, T2 had 3% methionine, T3 had 3% sodium sulphate, T4 had 3% sodium sulphite, T5 had 1.5% methionine and 1.5% sodium sulphate, T6 had 1.5% methionine and 1.5% sodium sulphate T7 had 1.5% methionine and 1.5% sodium sulphite while T8 had 1.5% methionine and 1% sodium sulphite. Chicks in T6 had the highest average weekly weight gain of 106.58 g while birds in T8 had the lowest average weekly weight gain (79.94 g). The average weekly weight gain of birds in T1, T2 and T5 did not differ significantly (p>0.05) from one another. Likewise the average weekly weight gain of birds in T1, T2, T3 T4 and T5 did not differ significantly (p>0.05) from one another. The average weekly weight gain of chicks in T7 and T8 which had the lowest weight gains, also did not differ significantly (p>0.05). All haematological parameters evaluated fell within safe precincts as stipulated in literature. Treatment 6 is therefore recommended for broiler starter rations alongside T2 and T5 because they did not differ significantly (p>0.05) from one another.

The experimental design herein was used to evaluate the influence of electrocoagulation parameters, such as initial pH and electrolyte support (Na 2 SO 4) concentration, on Escherichia coli (E.coli) removal. The initial pH and Na 2 SO 4 concentration influenced the response variable. E.coli removal is more efficient with a decrease in pH and an increase in Na 2 SO 4 concentration. The predicted values from the empirical model were consistent with the experimental values. In a final experiment under optimal conditions (2.5 mg L-1 of Na 2 SO 4 and initial pH 4.0), the electrocoagulation with aluminum electrodes was able to remove 1-log after 40 min and 1.9-log in a contact time of 90 min of E.coli. The study shows electrocoagulation as a promising alternative to remove microorganisms in water.

The adsorption characteristics of phosphate adsorption on the dewatered alum sludge were identified as a function of pH and ion strengths in solution. In addition, adsorption mechanisms were investigated by conducting batch tests on both the hydrolysis and P-adsorption process of the alum sludge, and making a comparative analysis to gain newer insights into understanding the adsorption process. Results show that the adsorption capacity decreased from 3.5 to 0.7 mg-P/g-sludge when the solution pH was increased from 4.3 to 9.0, indicating that adsorption capacity is largely dependent upon the pH of the system. The results of the competitive adsorption between phosphate and typical anions found in wastewater, such as SO 4 2and Cl-, onto alum sludge reveal that alum sludge can selectively adsorb phosphate ions. The insignificant effect of SO 4 2and Clon P-adsorption capacity indicates that phosphate adsorption is through a kind of inner-sphere complex reaction. During the adsorption process, the decrease of phosphate concentration in solution accompanied with an increase in pH values and concentrations of SO 4 2-, Cland TOC (total organic carbon) suggests that phosphate replaced the functional groups from the surface of alum sludge which infers that ligand exchange is the dominating mechanism for phosphate removal. At the same time, the simultaneous decreases in PO 4 3and total aluminium concentration in solution indicate that chemical reaction and precipitation are other mechanisms of phosphate removal.