Removal of 1,2-dichloroethane from groundwater using modified biochar-zerovalent copper nanocomposites in combination with potassium borohydride

Abstract

This study investigated the removal of persistent 1,2-dichloroethane (1,2-DCA) from water using modified biochar-loaded zerovalent copper nanocomposites (nZVC/BBC) combined with potassium borohydride (KBH₄) (nZVC/BBC/KBH₄). Batch experiments demonstrated that 1.5 g/L nZVC/BBC with 25 mmol/L KBH₄ removed 86.94 % of 100 mg/L DCA from 100 mL aqueous solution within 12 h. The removal process followed Pseudo-second-order (PSO) kinetics model, suggesting chemisorption as the dominant mechanism. The pH of the solution of 5–13 resulted in improved removal efficiency; therefore, the composite material was adaptable to a wide pH range. The co-existing ion SO₄²⁻ had inhibitory effects on the removal of 1,2-DCA, whereas the effects of other co-existing ions (K⁺, Ca²⁺, and HCO₃⁻) were minimal. The nZVC/BBC could be regenerated using NaOH, achieving over 70 % efficiency after five cycles when combined with KBH₄ for 1,2-DCA removal. Characterization of the nZVC/BBC composite after the reaction was performed using XRD and XPS analyses. Adsorption kinetic models and gas chromatography-mass spectrometry (GC-MS) analysis indicated that the removal mechanism for 1,2-DCA involved both surface adsorption, pore filling and reduction reactions. In experiments using actual groundwater, the removal rate of 1,2-DCA reached 95 % when nZVC/BBC/KBH₄ were 3.5 g/L and 35 mmol/L. This work has implications for the construction of materials for collaborative removal of 1,2-DCA from water by adsorption-reduction, and provides a new idea for water pollution control.