Optimizing the leaching process parameters to yield valuable materials from partially lateralized khondalite rock for industrial application

A bauxite mining waste—partially lateralized khondalite (PLK) rock, was utilized as the feedback for the production of filling material in paper industries for brightening the papers. This product was isolated as the solid residue after leaching of iron ferrooxides (Fe 2 O 3 ) from the bauxite mining waste matrix by using oxalic acid and hydrochloric acid through a synergistic effect. The leaching or extraction process of Fe 2 O 3 was optimized using the concentration of Hydrochloric acid, temperature and extraction time as process variables in the range of 1–3.5 M, 50–90 °C, and 30–240 min, respectively. The extraction was performed with 0.5 Molar concentration of oxalic acid. From the optimization of iron oxide leaching, it was found that 2 M Hydrochloric acid along with 0.5 M oxalic acid reacted at 70 °C with a reaction period of 240 min resulted 64–65% Fe 2 O 3 extraction efficiency. The solid residue obtained from the optimized conditions was characterized using several physicochemical characterization tools such as XRD, FTIR and SEM-EDAX, and also evaluated using the Bureau of Indian Standards for pulp and paper as well as ceramic industries. A statistical design named Box–Behnken is implemented by using Minitab to improve and optimize the process. The findings suggest that PLK rock can be used as a valuable economic resource for several industrial processes.