Agro-waste based biomass residues valorization for effective adsorption of heavy metal

In this experiment four agro-waste based biomass residues (soybean stover-SSb, buckwheat stover-BWb, Artemisia vulgaris- AVb and Chromolaena odorata-COb) was valorized into low cost amendment called biochar followed by compositional characterization for their application in heavy metal removal. Investigation was carried out on the removal of the most common heavy metal ions including arsenic, cadmium, lead, nickel, zinc, and copper through adsorption on four types of biomass valorised biochar. According to preliminary testing, all the biochar was effective to eliminate a mixture of six heavy metals from the aqueous phase, with the removal of arsenic being the most removed and nickel being the least. In comparison to no biochar treatment, the average removal rate of heavy metal from aqueous solution using four distinct types of biochar was 45.75-62.42% (Cd), 43.64-56.33% (Pb), 41.85-59.73% (Ni), 42.87-60.28% (Zn), 45.64-59.51% (Cu), and 49.02-60.53% (As). The percent decrease of cadmium heavy metal adsorption with increase in maximum contaminant level (MCL) from 1- to fivefold was 20.0 (SSb), 20.7 (COb), 21.6 (BWb), and 22.9 (AVb). The results of the dosage study indicated that As adsorption was the most beneficial on all four types of biochar, whereas Ni adsorption was the least effective. With increase in application rate of biochar the heavy metals adsorption (%) was also increased. Four different agro-waste valorized biochar were used to treat the wastewater, and the physical and chemical changes that occurred both before and after the biochar treatment were noted. There was a drop in the wastewater COD_T, COD_D, TSS, ammonia, TKN, TP and pH values of 79.7-103.5%, 57.7-81.5, 52.3-68.4%, 1.23-2.23%, 14.1-20.6%, and 1.23-3.03%, respectively. Furthermore, after being passed through a biochar, the wastewater's Zn, Pb, Cd, As, Cr and Cu levels decreased by 3.26-6.15%, 0.06-0.34%, 0.01-0.08%, 2.37-3.65%, 3.95-5.53%, and 2.24-3.34%, respectively at 2.5 and 5.0 g/litre of wastewater. Thus, in order to comply with regulations for the disposal of wastewater effluent, the process of valorizing biomass into biochar offered enormous potential for the removal of heavy metals in addition to wastewater treatment.