Goethite modified biochar as a multifunctional amendment for cationic Cd(II), anionic As(III), roxarsone, and phosphorus in soil and water

Environment-friendly, function tunable, and low-cost adsorbents/amendments from agricultural residue-derived biochar show enormous potential for mitigating the environment problems. A series of nano-sized goethite modified biochar (GMB) material were synthesized by co-precipitating with crop residue-derived biochar and could be used for amelioration of cation, anion, antibiotics, and non-point source pollutant in both soil and water. The GMB materials were characterized by SEM-EDS, BET, FTIR, XRD, VSM, and XPS analysis. Their adsorption performance for cationic Cd(II), anionic As(III), antibiotics roxarsone (ROX), and non-point source pollutant phosphorus in water was evaluated by adsorption kinetics and equilibrium experiments. Based on Langmuir model, the maximum adsorption capacities of Cd(II), As(III), ROX, and phosphorus were 31.9, 65.3, 66.5, and 42.7 mg/g, respectively, which were enhanced by 135%, 6279%, 961%, and 2437% compared to pristine biochar. The adsorption behavior of GMB can be explained by non-specific adsorption (electrostatic interaction and physical adsorption), specific adsorption (hydroxyl complex, π-π interaction, surface complexation, ion exchange, etc.), and chemisorption induced by goethite nanoparticles on the GMB. Moreover, GMB (1 wt%) also performed well for immobilization of these four contaminants in soil. After GMB treatment, the concentrations of available Cd, As, ROX, and phosphorus in soil decreased by 74.1%, 58.7%, 70.8%, and 29.1%, respectively. This study proposed that the scalable GMB can be considered as a sustainable multifunctional material for soil and water decontamination.