The Effect of Modified Peanut Shell Biochar by Potassium Permanganate on Cd (II) Removal from Aqueous Media

Cadmium (Cd) is one of the most toxic and non-biodegradable heavy metals which can be emitted into the aquatic ecosystem, accumulated in the food chain and posing a serious threat to the aquatic organism and human health. In this study, the effect of peanut shell (PN), pristine biochar (PBc), and modified biochar by potassium permanganate (PPBc) on cadmium removal from aqueous media was examined. Some characteristics of absorbents such as pH, cation exchange capacity (CEC), surface functional groups, and values of C, N, H and surface area were investigated. Adsorption isotherms (Langmuir, Freundlich, and Temkin) and Kinetic models (pseudo-first-order, pseudo-second-order, and Elovich) were used to explain the adsorption process. Results showed pH, cation exchange capacity and the oxygen containing functional groups such as COOH and Mn-O increased after the chemical treatment of biochar. Maximum sorption capacity obtained at the equilibrium time 120 min, adsorbent dosage of 0.25 g, and pH=6. Langmuir isotherm and the pseudo-second-order kinetic model have the best fitness on cadmium biosorption data. The RL values for adsorbents were calculated to be 0.02 to 0.37 with initial concentration ranging from 10 to 60 mg/L, which indicated the Langmuir isotherm of Cd (II) was a favorable isotherm in the adsorption process. Results showed that the Langmuir maximum Cd adsorption capacities of the modified biochar (28.24 mg/g) is higher than the one in pristine biochar (13.40 mg/g). PN did not show a significant effect on the Cd sorption. This work shows that the modified biochar by potassium permanganate may be an effective, low-cost, and environmentally-friendly adsorbent to remediate Cd contamination in the environment.