Modified mine waste as an adsorbent for fluoride removal from contaminated water

Shale is a coal mine waste belongs to sedimentary type of rocks. These wastes are generated in tons per year from various mine sectors. In this study shale samples collected from Samleshwari open cast mine were used as an adsorbent for defluoridation of mine waste water. The two types of shale samples, that is, old shale sample (OSS) and new shale sample (NSS) were collected from Samleshwari open cast mine located in IB valley coalfields of MCL mine, Odisha. The fluoride removal efficiency of the samples were increased by using heat activation (100 degrees C, 500 degrees C, and 800 degrees C) and chemical activation using different chemicals (KOH, NaOH, K2CO3, H2SO4, and ZnCl2). The effect of different parameters were also taken in to consideration during the batch adsorption process. The pH of the resulting water decreased slightly but maintained in between 4.5 and 7.5 confirms it's applicability for drinking purpose. Maximum fluoride Removal obtained using OSS 800 and OSS KOH (heat) were 85.01% and 92.23%, respectively, at initial concentration of 3 ppm, contact time 60 min, dose 10 mg and pH 4.9. The process followed Freundlich isotherm and data were well fitted to pseudo second order kinetics upon analysis with adsorption capacity 42.66 mg/gm and 45.16 mg/gm for OSS 800 and OSS KOH (heat), respectively.