Optimization of Quartz Sand Leaching Process Using Design Experiments Method (DOE)

The present study aims at investigating the Algerian quartz sand from Djelfa deposit as a potential source to produce silicon. The sand from the Djelfa deposit has a high concentration but not enough to be used as raw material for pyrometallurgy (97%) of SiO2. Therefore, the quartz was treated using acid leaching process to increase the silica concentration up to 98.5%. Otherwise, we employ Design of Experiments Method Software (DOE) as numerical model to optimize the parameters of leaching and also to predict the etching behavior of sand grains during the primary step of the process. The results show that the effect of acid concentration has more influence than the grains particle sizes and leaching time to obtain the required silica purity. Using DOE numerical method in the first step of leaching, optimal response of purity (ΔP)(ΔP)\\left (\\mathrm \\\\Delta \ P\ \\right ) about 98.48% is obtained. In this context, the optimal grain sizes of sand and the optimal acid concentration are respectively, 276.9 \textmum and 21.15%, for 6 hours leaching time. The obtained response is very close to the experimental values and can be used for the next stage of the silicon production chain

Optical and spectroscopic characterizations of Algerian silica raw material to predict high quality solar-grade silicon

We assess the potential use as raw material for photovoltaics of Algerian silica samples from the quartz veins of the Tirek deposit and quartz sandstones of the Ain Barda deposit. With 97-98% purity, they all require enrichment before their industrial utilization. Acid leaching and gravimetric separation are used to remove the impurities at the grain boundaries and within the crystal lattice. We obtain course, middle, and fine products. The acid leaching process and the gravimetric separation increase the content of SiO2 up to 99.68%; the residue concentration of iron, alumina and zirconium is decreased to 70, 72 and 58 ppm respectively. These values are in agreement with requirements for silica as raw material destined for solar-grade silicon production. (C) 2016 Elsevier B.V. All rights reserved