Effect of acid concentration and reaction time on structural and surface properties of waste mica

Abstract India is rich in mica deposits, and, after extraction, ~75% of the mica material is discarded as waste during the cleaning and processing stages. Effective modification methods may enhance the properties of the waste mica, making it suitable for a number of environmental applications, but this has received limited attention despite its availability. The present study focused on mining-derived waste mica and was aimed specifically at assessing the effects of controlled acid modification on its structural and physico-chemical properties. To achieve this, waste mica was ground and activated using various concentrations of sulfuric acid (1 M, 2 M, and 3 M) under continuous shaking at room temperature for periods varying from 24 to 72 h. The physico-chemical characteristics of the waste mica and acid-treated waste mica were studied by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), zeta potential, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The molecular arrangement of the raw and acid-activated waste mica was elucidated using VESTA software. The waste mica was identified as biotite based on structural and compositional characteristics. The XRF and XRD studies indicated that acid activation leads to progressive expansion of the interlayer space of waste mica by way of cation leaching and the subsequent weakening of interlayer forces. After conversion to nanoform and treating the waste mica with 2 M sulfuric acid for 48 h, the characteristic mica peak shifted from 8.99 to 8.76°2θ, indicating the enlargement of interlayer space with a concomitant increase in the specific surface area from 4.32 to 228.02 m 2 g –1 . The structural and surface modifications achieved through acid treatment enhanced the functional characteristics of the waste mica, indicating its suitability as a cost-effective and sustainable alternative to conventional adsorbents for use in environmental remediation.