Efficient removal of cadmium and lead in water by using nano-manganese oxide-loaded hydrochloric acid pretreated biochar

Cadmium (Cd) and lead (Pb) contaminated water pose a serious threat to the safety of aquatic organisms and human food, which is a hot topic in the world. To improve the removal efficiency of straw biochar (BC) on Cd and Pb pollution water, the modified biochar (BCHMn) was manufactured by loading nano-manganese oxide (nano-MnO x ) on hydrochloric acid pretreated BC. The adsorptive properties of Cd 2 + and Pb 2 + for BCHMn were examined by isothermal, kinetic adsorption models, and cycle tests. The results indicated that the adsorption of Cd 2 + and Pb 2 + by BCHMn is suitable for Langmuir, Sips, Avrami, and pseudo-second-order kinetic model, suggesting monolayer and heterogeneous chemical adsorption. The maximum theoretical adsorptive amount of Cd 2 + and Pb 2 + on BCHMn are 108.21 mg/g and 312.16 mg/g, respectively. The adsorption mechanism of BCHMn is primarily mineral precipitation, pi electron interaction, and ion exchange. Moreover, BCHMn contained the special birnessite ( delta-MnO 2 ) structures and MnO x , which can form stable complexes with Cd/Pb (such as Mn-O-Cd/Pb and Mn-R-O-Cd/Pb). These results indicate that BCHMn can efficiently remove Cd 2 + and Pb 2 + from water, and provide a reference for the comprehensive utilization of straw waste and water pollution control.