International Journal of Environmental Science and Technology, Aug 18, 2015
Radioactive cesium (137 Cs) has seriously become a human concern owing to exposure from a nuclear... more Radioactive cesium (137 Cs) has seriously become a human concern owing to exposure from a nuclear accident release at a nuclear plant. Many efforts have focused at the removal of radioactive cesium and remediation of a contaminated environment. To meet these demands, an effective sorbent based on magnetic composites functionalized with synthetic clay minerals was demonstrated. This sorbent shows a high removal efficiency of contaminated water containing suspended sorbents at a level of 0.5 mg ml-1 [ 137 Cs of 84.68 Becquerel (Bq) gram (g)-1 ], decontaminated to 0.47 Bq g-1 (99.44 % removal efficiency) with just one treatment. The radioactive cesium is dramatically adsorbed into synthetic clay minerals. Subsequently, a rapid and easy sorbent separation from the radioactive cesium solution occurs after treatment using a magnetic field. Thus, a magnetic sodium-phlogopite sorbent can offer high potential for in situ remediation.
In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as... more In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as an adsorbent to remove radioactive cesium from environmentally contaminated water. To do this, Fe 3 O 4 nanoparticles prepared using a coprecipitation method were thickly covered with a layer of cationic polymer to attach hollow Prussian blue through a self-assembly process. The as-synthesized adsorbent was confirmed through various analytical techniques. The adsorbent showed a high surface area (166.16 m 2 /g) with an excellent cesium adsorbent capacity and removal efficiency of 32.8 mg/g and 99.69%, respectively. Moreover, the superparamagnetism allows effective recovery of the adsorbent using an external magnetic field after the adsorption process. Therefore, the magnetic adsorbent with a high adsorption efficiency and convenient recovery is expected to be effectively used for rapid remediation of radioactive contamination.
A polymer hydrogel composed of alginate/humic acid/Fe-aminoclay was fabricated and utilized as a ... more A polymer hydrogel composed of alginate/humic acid/Fe-aminoclay was fabricated and utilized as a potential adsorbent for the removal of strontium ions (Sr 2+) from aqueous solution. The effects of adsorbate concentration, reaction pH, and time on the removal efficiency of Sr 2+ were investigated. The results revealed that the adsorption capacity increases as the Sr 2+ concentration increased from 1 to 10 ppm, which might be due to the more available adsorption sites. An additional increase in the Sr 2+ concentration had no effect. The optimal pH and reaction time for the removal of Sr 2+ were identified as pH 7 and 24 h, respectively, with an adsorbent dosage of 20 mg. The adsorption isotherm was fitted to the Freundlich model with a maximum Sr 2+ adsorption capacity of 45.65 mg g-1. The kinetic study showed that the adsorption behavior followed a pseudo-second-order kinetics. The hydrogel showed good selectivity towards Sr 2+ even in the presence of competitive cations having a higher concentration than Sr 2+. From the above results, it is expected that this biocompatible hydrogel material can be used as an adsorbent for the removal of radioactive strontium.
Development of a novel and stable electrochemical sensor electrode for the sensitive and reliable... more Development of a novel and stable electrochemical sensor electrode for the sensitive and reliable determination of p-nitrophenol (p-NP) is of great importance to environment. In the present work, electrocatalysts of Au/ZnS hybrid nanorods were prepared via a facile photo-assisted reduction process for an efficient detection of p-NP. The microscopic analysis revealed the uniform adherence of Au onto ZnS nanorods. As-fabricated AZS nanorods were evaluated for the efficient sensing of p-NP by modifying a glassy carbon electrode (GCE). The cyclic voltammetry analysis revealed the unique oxidative sensing ability of AZS for p-NP at 0.14 V with a low ΔE p (118 mV) when compared to that of bare GCE. Based on the notable sensing ability of AZS, a reliable and sensitive electrochemical method was anticipated for the determination of p-NP. Moreover, the effects of scan rate and pH level were examined to find out the optimized conditions at which higher sensitivity and low detection limit. At optimal conditions, the p-NP oxidation current was found to be follow linear relationships in the concentration range of 150-2000 nM, and the lowest detection limit for p-NP was obtained for 8AZS with a value of 320 nM and a signal-to-noise ratio of 3. The proposed electrochemical method was further evaluated in the presence of other inorganic cations and anions, and it was found that the interference was almost negligible. The real sample analyses confirmed the acceptable recovery levels.
Materials science & engineering. C, Materials for biological applications, 2018
Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesiz... more Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesized and evaluated for photodynamic therapy (PDT) and cell imaging applications. NP-g-CN particles were prepared through an intercalation process using a rod-like melamine-cyanuric acid adduct (MCA) as the molecular precursor and a eutectic mixture of LiCl-KCl (45:55 wt%) as the reaction medium for polycondensation. The nano-dimensional NP-g-CN penetrated the malignant tumor cells with minimal hindrance and effectively generated reactive oxygen species (ROS) under visible light irradiation, which could ablate cancer cells. When excited by visible light irradiation (λ > 420 nm), NP-g-CN introduced to HeLa and cos-7 cells generated a significant amount of ROS and killed the cancerous cells selectively. The cytotoxicity of NP-g-CN was manipulated by altering the light irradiation and the BP-g-CN caused more damage to the cancer cells than normal cells at low concentrations. As a potential ...
Abstract A 3D cubic structure of mesoporous graphitic carbon nitride (3D-g-CN) was fabricated by ... more Abstract A 3D cubic structure of mesoporous graphitic carbon nitride (3D-g-CN) was fabricated by nano casting using the mesoporous silica hard template KIT-6. The abundant intrinsic amine functionalities of 3D-g-CN were applied as a selective adsorbent for silver ions using the unique affinity of silver and amine functionalities. The large surface area of 3D-g-CN resulted in increased amine functionalities at the surface and enabled it to form complexes with silver ions. As a result, almost 400 mg/g of silver ion could be removed from 100 mM of initial solution at 293.15 K. The isotherm of silver ion adsorption onto 3D-g-CN was described by the Freundlich and Sips models and indicated heterogeneity of the adsorbent surface. Thermodynamic parameters determined from temperature dependent isotherms were verified by the endothermic silver ion adsorption process of 3D-g-CN. The adsorption capacity of silver ion on 3D-g-CN was maintained during several reuses without a significant decrease in capacity. Overall, the results indicate that 3D-g-CN has intrinsic amine functional groups with a large surface area and could therefore be utilized as an efficient selective adsorbent of silver ions for water purification.
Blue-green microalgal blooms have been caused concerns about environmental problems and human-hea... more Blue-green microalgal blooms have been caused concerns about environmental problems and human-health dangers. For removal of such cyanobacteria, many mechanical and chemical treatments have been trialled. Among various technologies, the flocculation-based harvesting (precipitation) method can be an alternative if the problem of the low yield of recovered biomass at low concentrations of cyanobacteria is solved. In the present study, it was utilized mixtures of magnesium aminoclay [MgAC] and cerium aminoclay [CeAC] with different particle sizes to harvest cyanobacteria feedstocks with ∼100% efficiency within 1h by ten-fold lower loading of ACs compared with single treatments of [MgAC] or [CeAC]. This success was owed to the compact networks of the different-sized-ACs mixture for efficient bridging between microalgal cells. In order to determine the usage potential of biomass harvested with AC, the mass was heat treated under the reduction condition. This system is expected to be prof...
Abstract Prussian blue-functionalized magnetic nanoclusters were fabricated for the highly effici... more Abstract Prussian blue-functionalized magnetic nanoclusters were fabricated for the highly efficient removal of radioactive cesium (such as 137 Cs) and rapid magnetic separation of absorbent from 137 Cs-contaminated water. The magnetic nanoclusters, synthesized via the hydrothermal method, were coated with Prussian blue (PB) via a simple reaction with potassium hexacyanoferrate under acidic conditions. The resulting Prussian blue-functionalized magnetic nanoclusters had a large distribution coefficient, even in the presence of 3000 ppm competing ions such as K + , Na + , Ca 2+ and Mg 2+ , and excellent removal efficiency (>99.7%) of radioactive cesium from contaminated water. Furthermore, they possess good saturation magnetization values (27.5 emu/g), allowing for rapid separation from an aqueous solution using an external magnetic field. Therefore, these magnetic adsorbents have promising applications for the treatment of radioactive cesium-contaminated water.
Biodiesel is a fatty acid alkyl ester produced by chemical reaction of a vegetable oil or animal ... more Biodiesel is a fatty acid alkyl ester produced by chemical reaction of a vegetable oil or animal fat and an alcohol. It is getting attention as a clean alternative energy that can replace gas oils. In this study, strong acidic ion exchange resin was introduced in the pretreatment process of the used cooking oil and rapeseed oil to enhance the conversion of the oil to the biodiesel by removing FFA(free fatty acid). More than 90% FFA was removed. Dry resins showed higher FFA removal efficiency than wet resins. Using transesterification the conversion of triglyceride into fatty acid methyl ester was raised up to 98%. These results can be applicable to the pretreatment of biodiesel feedstocks having high acidic value.
Synthesis of aminoclay-templated nanoscale zero-valent iron (nZVI) for efficient harvesting of ol... more Synthesis of aminoclay-templated nanoscale zero-valent iron (nZVI) for efficient harvesting of oleaginous microalgae was demonstrated. According to various aminoclay loadings (0, 0.25, 0.5, 1.0, 2.5, 5.0, and 7.5 aminoclay-nZVI ratios), the stability of nZVI was investigated as a function of sedimentation rate. Aminoclay-coated nZVI (aminoclay-nZVI composites) showed optimal dispersibility at the 1.0 ratio, resulting in the smallest aggregated size and uniform coating of aminoclay nanoparticles onto nZVI due to electrostatic attraction between nZVI and aminoclay nanoparticles. This silica-coated nZVI composite (ratio 1.0) exhibited a highly positively charged surface ($+40 mV) and a ferromagnetic property ($30 emu g À1). On the basis of these characteristics, oleaginous Chlorella sp. KR-1 was harvested within 3 min at a > 20 g L À1 loading under a magnetic field. In a scaledup (24 L) microalga harvesting process using magnetic rods, microalgae were successfully collected by attachment to the magnetic rods or by precipitation. It is believed that this approach, thanks to the recyclability of aminoclay-nZVI composites, can be applied in a continuous harvesting mode.
Extraction of succinic acid and acetic acid by tri-n-octylamine (TOA) was studied under various p... more Extraction of succinic acid and acetic acid by tri-n-octylamine (TOA) was studied under various pHs of their aqueous solutions. For the extraction of both acids, the loading values decreased with increasing values of pH. In the extraction of acetic acid, the sharp decrease in loading values with increasing pH began at higher values than that of succinic acid extraction due
Hierarchical structures of hybrid materials with the controlled compositions have been shown to o... more Hierarchical structures of hybrid materials with the controlled compositions have been shown to offer a breakthrough for energy storage and conversion. Here, we report the integrative assembly of chemically modified graphene (CMG) building blocks into hierarchical complex structures with the hybrid composition for high performance flexible pseudocapacitors. The formation mechanism of hierarchical CMG/Nafion/RuO 2 (CMGNR) microspheres, which is triggered by the cooperative interplay during the in situ synthesis of RuO 2 nanoparticles (NPs), was extensively investigated. In particular, the hierarchical CMGNR microspheres consisting of the aggregates of CMG/Nafion (CMGN) nanosheets and RuO 2 NPs provided large surface area and facile ion accessibility to storage sites, while the interconnected nanosheets offered continuous electron pathways and mechanical integrity. The synergistic effect of CMGNR hybrids on the supercapacitor (SC) performance was derived from the hybrid composition of pseudocapacitive RuO 2 NPs with the conductive CMGNs as well as from structural features. Consequently, the CMGNR-SCs showed a specific capacitance as high as 160 F g À1 , threefold higher than that of conventional graphene SCs, and a capacitance retention of >95% of the maximum value even after severe bending and 1000 charge-discharge tests due to the structural and compositional features.
International Journal of Environmental Science and Technology, Aug 18, 2015
Radioactive cesium (137 Cs) has seriously become a human concern owing to exposure from a nuclear... more Radioactive cesium (137 Cs) has seriously become a human concern owing to exposure from a nuclear accident release at a nuclear plant. Many efforts have focused at the removal of radioactive cesium and remediation of a contaminated environment. To meet these demands, an effective sorbent based on magnetic composites functionalized with synthetic clay minerals was demonstrated. This sorbent shows a high removal efficiency of contaminated water containing suspended sorbents at a level of 0.5 mg ml-1 [ 137 Cs of 84.68 Becquerel (Bq) gram (g)-1 ], decontaminated to 0.47 Bq g-1 (99.44 % removal efficiency) with just one treatment. The radioactive cesium is dramatically adsorbed into synthetic clay minerals. Subsequently, a rapid and easy sorbent separation from the radioactive cesium solution occurs after treatment using a magnetic field. Thus, a magnetic sodium-phlogopite sorbent can offer high potential for in situ remediation.
In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as... more In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as an adsorbent to remove radioactive cesium from environmentally contaminated water. To do this, Fe 3 O 4 nanoparticles prepared using a coprecipitation method were thickly covered with a layer of cationic polymer to attach hollow Prussian blue through a self-assembly process. The as-synthesized adsorbent was confirmed through various analytical techniques. The adsorbent showed a high surface area (166.16 m 2 /g) with an excellent cesium adsorbent capacity and removal efficiency of 32.8 mg/g and 99.69%, respectively. Moreover, the superparamagnetism allows effective recovery of the adsorbent using an external magnetic field after the adsorption process. Therefore, the magnetic adsorbent with a high adsorption efficiency and convenient recovery is expected to be effectively used for rapid remediation of radioactive contamination.
A polymer hydrogel composed of alginate/humic acid/Fe-aminoclay was fabricated and utilized as a ... more A polymer hydrogel composed of alginate/humic acid/Fe-aminoclay was fabricated and utilized as a potential adsorbent for the removal of strontium ions (Sr 2+) from aqueous solution. The effects of adsorbate concentration, reaction pH, and time on the removal efficiency of Sr 2+ were investigated. The results revealed that the adsorption capacity increases as the Sr 2+ concentration increased from 1 to 10 ppm, which might be due to the more available adsorption sites. An additional increase in the Sr 2+ concentration had no effect. The optimal pH and reaction time for the removal of Sr 2+ were identified as pH 7 and 24 h, respectively, with an adsorbent dosage of 20 mg. The adsorption isotherm was fitted to the Freundlich model with a maximum Sr 2+ adsorption capacity of 45.65 mg g-1. The kinetic study showed that the adsorption behavior followed a pseudo-second-order kinetics. The hydrogel showed good selectivity towards Sr 2+ even in the presence of competitive cations having a higher concentration than Sr 2+. From the above results, it is expected that this biocompatible hydrogel material can be used as an adsorbent for the removal of radioactive strontium.
Development of a novel and stable electrochemical sensor electrode for the sensitive and reliable... more Development of a novel and stable electrochemical sensor electrode for the sensitive and reliable determination of p-nitrophenol (p-NP) is of great importance to environment. In the present work, electrocatalysts of Au/ZnS hybrid nanorods were prepared via a facile photo-assisted reduction process for an efficient detection of p-NP. The microscopic analysis revealed the uniform adherence of Au onto ZnS nanorods. As-fabricated AZS nanorods were evaluated for the efficient sensing of p-NP by modifying a glassy carbon electrode (GCE). The cyclic voltammetry analysis revealed the unique oxidative sensing ability of AZS for p-NP at 0.14 V with a low ΔE p (118 mV) when compared to that of bare GCE. Based on the notable sensing ability of AZS, a reliable and sensitive electrochemical method was anticipated for the determination of p-NP. Moreover, the effects of scan rate and pH level were examined to find out the optimized conditions at which higher sensitivity and low detection limit. At optimal conditions, the p-NP oxidation current was found to be follow linear relationships in the concentration range of 150-2000 nM, and the lowest detection limit for p-NP was obtained for 8AZS with a value of 320 nM and a signal-to-noise ratio of 3. The proposed electrochemical method was further evaluated in the presence of other inorganic cations and anions, and it was found that the interference was almost negligible. The real sample analyses confirmed the acceptable recovery levels.
Materials science & engineering. C, Materials for biological applications, 2018
Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesiz... more Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesized and evaluated for photodynamic therapy (PDT) and cell imaging applications. NP-g-CN particles were prepared through an intercalation process using a rod-like melamine-cyanuric acid adduct (MCA) as the molecular precursor and a eutectic mixture of LiCl-KCl (45:55 wt%) as the reaction medium for polycondensation. The nano-dimensional NP-g-CN penetrated the malignant tumor cells with minimal hindrance and effectively generated reactive oxygen species (ROS) under visible light irradiation, which could ablate cancer cells. When excited by visible light irradiation (λ > 420 nm), NP-g-CN introduced to HeLa and cos-7 cells generated a significant amount of ROS and killed the cancerous cells selectively. The cytotoxicity of NP-g-CN was manipulated by altering the light irradiation and the BP-g-CN caused more damage to the cancer cells than normal cells at low concentrations. As a potential ...
Abstract A 3D cubic structure of mesoporous graphitic carbon nitride (3D-g-CN) was fabricated by ... more Abstract A 3D cubic structure of mesoporous graphitic carbon nitride (3D-g-CN) was fabricated by nano casting using the mesoporous silica hard template KIT-6. The abundant intrinsic amine functionalities of 3D-g-CN were applied as a selective adsorbent for silver ions using the unique affinity of silver and amine functionalities. The large surface area of 3D-g-CN resulted in increased amine functionalities at the surface and enabled it to form complexes with silver ions. As a result, almost 400 mg/g of silver ion could be removed from 100 mM of initial solution at 293.15 K. The isotherm of silver ion adsorption onto 3D-g-CN was described by the Freundlich and Sips models and indicated heterogeneity of the adsorbent surface. Thermodynamic parameters determined from temperature dependent isotherms were verified by the endothermic silver ion adsorption process of 3D-g-CN. The adsorption capacity of silver ion on 3D-g-CN was maintained during several reuses without a significant decrease in capacity. Overall, the results indicate that 3D-g-CN has intrinsic amine functional groups with a large surface area and could therefore be utilized as an efficient selective adsorbent of silver ions for water purification.
Blue-green microalgal blooms have been caused concerns about environmental problems and human-hea... more Blue-green microalgal blooms have been caused concerns about environmental problems and human-health dangers. For removal of such cyanobacteria, many mechanical and chemical treatments have been trialled. Among various technologies, the flocculation-based harvesting (precipitation) method can be an alternative if the problem of the low yield of recovered biomass at low concentrations of cyanobacteria is solved. In the present study, it was utilized mixtures of magnesium aminoclay [MgAC] and cerium aminoclay [CeAC] with different particle sizes to harvest cyanobacteria feedstocks with ∼100% efficiency within 1h by ten-fold lower loading of ACs compared with single treatments of [MgAC] or [CeAC]. This success was owed to the compact networks of the different-sized-ACs mixture for efficient bridging between microalgal cells. In order to determine the usage potential of biomass harvested with AC, the mass was heat treated under the reduction condition. This system is expected to be prof...
Abstract Prussian blue-functionalized magnetic nanoclusters were fabricated for the highly effici... more Abstract Prussian blue-functionalized magnetic nanoclusters were fabricated for the highly efficient removal of radioactive cesium (such as 137 Cs) and rapid magnetic separation of absorbent from 137 Cs-contaminated water. The magnetic nanoclusters, synthesized via the hydrothermal method, were coated with Prussian blue (PB) via a simple reaction with potassium hexacyanoferrate under acidic conditions. The resulting Prussian blue-functionalized magnetic nanoclusters had a large distribution coefficient, even in the presence of 3000 ppm competing ions such as K + , Na + , Ca 2+ and Mg 2+ , and excellent removal efficiency (>99.7%) of radioactive cesium from contaminated water. Furthermore, they possess good saturation magnetization values (27.5 emu/g), allowing for rapid separation from an aqueous solution using an external magnetic field. Therefore, these magnetic adsorbents have promising applications for the treatment of radioactive cesium-contaminated water.
Biodiesel is a fatty acid alkyl ester produced by chemical reaction of a vegetable oil or animal ... more Biodiesel is a fatty acid alkyl ester produced by chemical reaction of a vegetable oil or animal fat and an alcohol. It is getting attention as a clean alternative energy that can replace gas oils. In this study, strong acidic ion exchange resin was introduced in the pretreatment process of the used cooking oil and rapeseed oil to enhance the conversion of the oil to the biodiesel by removing FFA(free fatty acid). More than 90% FFA was removed. Dry resins showed higher FFA removal efficiency than wet resins. Using transesterification the conversion of triglyceride into fatty acid methyl ester was raised up to 98%. These results can be applicable to the pretreatment of biodiesel feedstocks having high acidic value.
Synthesis of aminoclay-templated nanoscale zero-valent iron (nZVI) for efficient harvesting of ol... more Synthesis of aminoclay-templated nanoscale zero-valent iron (nZVI) for efficient harvesting of oleaginous microalgae was demonstrated. According to various aminoclay loadings (0, 0.25, 0.5, 1.0, 2.5, 5.0, and 7.5 aminoclay-nZVI ratios), the stability of nZVI was investigated as a function of sedimentation rate. Aminoclay-coated nZVI (aminoclay-nZVI composites) showed optimal dispersibility at the 1.0 ratio, resulting in the smallest aggregated size and uniform coating of aminoclay nanoparticles onto nZVI due to electrostatic attraction between nZVI and aminoclay nanoparticles. This silica-coated nZVI composite (ratio 1.0) exhibited a highly positively charged surface ($+40 mV) and a ferromagnetic property ($30 emu g À1). On the basis of these characteristics, oleaginous Chlorella sp. KR-1 was harvested within 3 min at a > 20 g L À1 loading under a magnetic field. In a scaledup (24 L) microalga harvesting process using magnetic rods, microalgae were successfully collected by attachment to the magnetic rods or by precipitation. It is believed that this approach, thanks to the recyclability of aminoclay-nZVI composites, can be applied in a continuous harvesting mode.
Extraction of succinic acid and acetic acid by tri-n-octylamine (TOA) was studied under various p... more Extraction of succinic acid and acetic acid by tri-n-octylamine (TOA) was studied under various pHs of their aqueous solutions. For the extraction of both acids, the loading values decreased with increasing values of pH. In the extraction of acetic acid, the sharp decrease in loading values with increasing pH began at higher values than that of succinic acid extraction due
Hierarchical structures of hybrid materials with the controlled compositions have been shown to o... more Hierarchical structures of hybrid materials with the controlled compositions have been shown to offer a breakthrough for energy storage and conversion. Here, we report the integrative assembly of chemically modified graphene (CMG) building blocks into hierarchical complex structures with the hybrid composition for high performance flexible pseudocapacitors. The formation mechanism of hierarchical CMG/Nafion/RuO 2 (CMGNR) microspheres, which is triggered by the cooperative interplay during the in situ synthesis of RuO 2 nanoparticles (NPs), was extensively investigated. In particular, the hierarchical CMGNR microspheres consisting of the aggregates of CMG/Nafion (CMGN) nanosheets and RuO 2 NPs provided large surface area and facile ion accessibility to storage sites, while the interconnected nanosheets offered continuous electron pathways and mechanical integrity. The synergistic effect of CMGNR hybrids on the supercapacitor (SC) performance was derived from the hybrid composition of pseudocapacitive RuO 2 NPs with the conductive CMGNs as well as from structural features. Consequently, the CMGNR-SCs showed a specific capacitance as high as 160 F g À1 , threefold higher than that of conventional graphene SCs, and a capacitance retention of >95% of the maximum value even after severe bending and 1000 charge-discharge tests due to the structural and compositional features.
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