Removal of carbendazim by sorption onto a continuous fixed bed hybrid filter of calcined clay and waste derived biochar

This study focused on enhanced Carbendazim (CBZ) removal by using dual filter media of calcined clay (CC) and biochar (WB-BC) in a continuous fixed-bed column. The experiments were carried out using synthetic and real water. In the continuous system with an initial CBZ concentration of 0.2 mmol L⁻¹, a flow rate of 4 mL min⁻¹, a bed depth of biochar 1 cm and a pH of 6.8, the optimal values for the mass transfer zone (0.64 cm) and adsorption capacity (0.38mmolg⁻¹) were observed. Furthermore it was observed that the dual filter media of WB-BC and CC effectively adsorbs CBZ from real water matrix, with an average adsorption capacity of 0.33mmolg⁻¹. Significant reduction in the concentrations of chlorides, sulfates, nitrates, Ca²⁺, and Mg²⁺ were also observed in real water samples along with CBZ removal. Analysis using mass-transfer models showed that BDST model effectively described the breakthrough curve data. Density Functional Theory (DFT) calculations revealed that WB-BC exhibits a stronger interaction and higher adsorption capacity for CBZ compared to CC as evidenced by a shorter vertical distance (2.711 Å) and higher adsorption energy value (−42.95kJmol⁻¹) in case of WB-BC-CBZ complex. Additionally, the larger band gap (ΔE) value (2.881 eV) for WB-BC-CBZ complex indicates superior structural stability and chemical hardness.