Scanning Electron Microscopy

Aim: This study investigates the dissolution of tantalite mineral from granitic pegmatite in Okpella,
Northern Edo State, Nigeria.
Study Design: Elemental and mineral composition analysis of tantalite ore sample from Okpella
was carried out using X-ray fluorescence and X-ray diffraction. Response Surface Methodology(RSM) and the shrinking core model were used in designing the study while the effects of
temperature, stirring speed, particle diameter, and mixed acids concentrations were investigated in
the dissolution rates of the mineral.
Duration of Study: 50 experimental runs were designed using RSM Central Composite Design
(CCD) to optimize variables including HF concentration (1-8 M), H2SO4 concentration (0.5-3 M),
temperature (32-82°C), stirring speed (0-500 rpm), and particle size (0.1-0.3 mm), with a constant
contact time of 240 minutes.
Methodology: Pulverized tantalite samples (0.1-0.3 mm) were reacted with varying concentrations
of hydrofluoric and sulphuric acids (1-8 M and 0.5-3.0 M, respectively) for 240 minutes, with stirring
speeds between 0-500 rpm and temperatures from 32 to 82°C. The mixture was stirred in a water
bath with 50 ml of mixed acids solution and 2 g of ore. After the reaction, the solution was
decanted, and the residual ore was washed, dried at 60 °C, and weighed. The difference between
the initial and final weights indicated the amount of undissolved tantalite ore.
Results: Ore characterization results revealed high concentration of tantalum (34.17%), iron
(12.55%), niobium (8.38%), and titanium (6.01%), with other elements present in smaller amounts.
Optimal conditions were found to be 8 M HF, 0.5 M H2SO4, 82°C, 500 rpm stirring speed, and 0.1
mm particle size, resulting in 97.28% dissolution of tantalite ore. Regression analysis demonstrated
model robustness with an F-value of 16.70 and a P-value of 0.0001, indicating HF concentration
and stirring speed as the most impactful factors. The model’s R² value of 0.9201 and adjusted R² of
0.8650 confirm its predictive accuracy. Analysis using the shrinking sphere model showed that film
diffusion control is the primary limiting step with t/τ=0.999, while reaction control resulted in slightly
lower conversion with t/τ=0.973, highlighting film diffusion as the main constraint but with high
conversion efficiency.
Conclusion: The findings from this investigation not only reveal the dissolution of tantalite ore
through a detailed experimental approach, identifying optimal conditions -8 M HF, 0.5 M H2SO4, 82
oC, 500 rpm stirring speed and 0.1 mm particle size- that achieve a 97.28% dissolution, but they
also enhance our understanding of mineral processing. These understanding are crucial for mineral
dissolution up scaling technologies in industrial applications, which will potentially leads to a more
efficient extraction method that could significantly reduce costs and environmental impacts in the
mining sector. This research could drive advancements in sustainable resource recovery and
contribute to sourcing of critical minerals.

The application of modern methods of materials science to cultural heritage allows us to obtain fundamentally new information about historical materials, necessary for solving both fundamental problems of history and archeology, and applied issues of preservation of cultural and historical monuments. The proposed integrated approach to multilevel research of ceramic historical materials, based on a combination of integrated and localizing physico-chemical structural methods of materials science and developed for the study of antique ceramics. The resulting data set of macro- and micro indicators (the size and quantitative
content of inclusions and pores, mineralogical and elemental composition of natural and artificial impurities etc.) allows us to identify the characteristic parameters of products from various production centers, since it contains information about the specifics of the materials used and the features of the manufacturing technology of the objects under study. This approach has shown its effectiveness for the study of not only ceramics, but also other multiphase multicomponent mineral composite materials of cultural heritage sites of various eras – in particular,
medieval building ceramics (tiles), ancient Roman terra sigillata and medieval mortars and plasters.