Assessment of goethite-combined/modified biochar for cadmium and arsenic remediation in alkaline paddy soil.

The opposed transformation of arsenic (As) and cadmium (Cd) in paddy soil postures numerous challenges for their simultaneous remediation. An incubation study was conducted on the immobilization of Cd and As by biochar (BC), goethite (G), goethite-combined biochar (BC + G), and goethite-modified biochar (GBC). The results showed that biochar effectively immobilized Cd while significantly increasing As mobility, whereas goethite effectively immobilized As more than Cd. BC + G treatment significantly decreased toxicity characteristics leaching procedure (TCLP) and CaCl2-extractable Cd by 22.70% and 40.15%; meanwhile, TCLP and NaHCO3-As were significantly reduced by 38.25% and 31.87%, respectively, compared with the control. This study found that GBC was the optimum amendment within the immobilization efficiency for CaCl2-Cd (57.03%) and TCLP-As (61.11%). BC + G and GBC applications showed some interactions between biochar and goethite, which played an essential role in immobilizing Cd and As simultaneously. Therefore, GBC showed a great benefit in being a low-cost and efficient environmental amendment for Cd and As remediation in alkaline co-contaminated paddy soil.