Suitability evaluation of selected sand geological formations for synthesis high purity crystalline silica, Iraq

Abstract

This study aims determination if the sand collected from Injana and Dibdibba Formations are suitable for use as low-cost raw materials in the manufacture of high-purity crystalline silica. Sand is distributed in vast quantities within the two Formations, which occupy large portions of Iraq’s southern desert. Quartz is the predominant mineral phase, followed by calcite, feldspar, and dolomite respectively, based on mineral analysis data. SiO2 is the main oxide in sand with an average of (82.76%), (90.24%) and the rest of oxides are CaO (6.28%), (1.64%), Al2O3 (4.02%),(3.19%), Fe2O3(2.73%), (0.86%), K2O+ Na2O (2.05%), (2.51%), SO3(0.05%), (0.47%), MnO (0.01%), (0.03%) P2O2 (0.23%),(0.03%), and MgO (1.75%), (1.01%) in Injana and Dibdibba Formations respectively, which are considered as impurities impact the manufacturing properties of sand. The coprecipitation method, which produces high purity crystalline silica at a low cost, involves three steps: the first involves soaking raw sand powder in 2M HCl for 24 hours; The second involves mix purified sand with NaOH while stirring and heating it to 95C° to produce Na2SiO3; and the third involves adding 3M HCl to sodium silicate solution to produce Si(OH)4 and drying it to produce high purity of silica. The prepared silica got mineral analysis and chemical analysis. The synthesized silica was in the crystalline phase, according to the results of the mineral characterization. In synthetic silica of Injana and Dibdibba sand, The amount of SiO2 increased according to chemical analysis, reaching 96.62%, and 97.69% respectively, while all other oxides (impurities) were lowered to their lowest levels. FE-SEM revealed the existence of spherical, well-agglomerated synthetic silica particles within the size 28.6 nm and 24.76 nm in synthetic silica particles of Injana sand and Dibdibba sand respectively.