Experimental and kinetic study of removal of lead (Pb+2) from battery effluent using sweet lemon (Citrus limetta) peel biochar adsorbent

The main polluting agents of the environment are different anthropogenic activities; among them, industries are the primary one. Lead (Pb2+) is an extremely toxic metal ion and is the main raw material of lead–acid batteries. The present study focuses on adsorptive removal of lead from battery manufacturing industrial effluent by sweet lemon (Citrus limetta) peel biochar (SLPB). The removal efficiency was about 97.11% at optimum contact time of 160 min with optimum dosage of 3.5 g L−1 at constant temperature. The optimum pH and temperature were recorded to be 5 and 55 ºC with their maximum adsorption capacities of 55.67 and 53.89 mg g−1, respectively. The process obeyed second-order kinetics favoring chemisorption over physisorption. The adsorbent was also characterized by SEM–EDX, XRD, BET and FTIR to validate the results obtained. The results were justified by the functional groups present and changes in morphology of the biochar after treating wastewater. Further, adsorption process preferred Freundlich (r2 = 0.98) adsorption isotherm in comparison with Langmuir (r2 = 0.95) adsorption isotherm. The adsorption process demonstrated that the removal process was multilayered and heterogeneous with maximum adsorption capacity (qmax) of 2840.91 mg g−1 which was higher than most of the values obtained from other materials. Thus, the study concluded that SLPB might be used to overcome the pollution level of metals in our water bodies to maintain the quality of water bodies.