Abstract:
Present study highlights scope and process for production of environmentally safe (reduced F, Cr, Cd content) and multi-nutrient (K, P, S) enriched biochar utilizing highly acidic gypsum pond wastewater (GPW; P and S rich) and banana peduncle (K rich) waste. Untreated and treated [potentially toxic elements (PTE) adsorbed on Crassostrea shells] GPW soaked biomass pyrolyzed at 400, 600, 800 degrees C and produced K-P-S enriched biochar (KPS-B-400/600/800 and T-KPS-B-400/600/800). Physicochemical characteristics of biochar were investigated by XRD, FTIR and surface area analyser. The K, P and S contents were 14-15.53, 1.88-2.27 and 3.75-4.77% in the untreated biochar produced at 400, 600 and 800 degrees C respectively, with corresponding values of 15.21-18.43, 2.05-2.91 and 0.62-1.09% in the treated biochar. At various temperatures, K, P and S formed mineral phases such as K(H2PO4), KH5(PO4)2, K2CaP2O7 and K2SO4 in untreated biochar, and K3P, K2SiP2 and K2S in treated biochar. Sulfite (SO32-) was identified as pre-dominant functional group in untreated and treated biochar. Water soluble and Toxicity Characteristic Leaching Procedure (TCLP) F contents in T-KPS-B-800 were lowered to 0.005% and 0.013% respectively and values were well below permissible limits. Toxic Cd TCLP content reduced by 5.75% in T-KPS-800 over KPS-800, whereas Cr reduction of 44% was eastimated in T-KPS-400 with respect to KPS-400 due to treatment of GPW with molluscan shells. Above findings establish an alternative way of nutrients recovery and PTE reduction from phosphate fertilizer industry GPW.