Catalytic dechlorination of 1,2-DCA in nano Cu 0 -borohydride system: effects of Cu 0 /Cu n+ ratio, surface poisoning, and regeneration of Cu 0 sites

Aqueous-phase catalyzed reduction of organic contaminants via zerovalent copper nanoparticles (nCu 0 ), coupled with borohydride (hydrogen donor), has shown promising results. So far, the research on nCu 0 as a remedial treatment has focused mainly on contaminant removal efficiencies and degradation mechanisms. Our study has examined the effects of Cu 0 /Cu n+ ratio, surface poisoning (presence of chloride, sulfides, humic acid (HA)), and regeneration of Cu 0 sites on catalytic dechlorination of aqueous-phase 1,2-dichloroethane (1,2-DCA) via nCu 0 -borohydride. Scanning electron microscopy confirmed the nano size and quasi-spherical shape of nCu 0 particles. X-ray diffraction confirmed the presence of Cu 0 and Cu 2 O and x-ray photoelectron spectroscopy also provided the Cu 0 /Cu n+ ratios. Reactivity experiments showed that nCu 0 was incapable of utilizing H 2 from borohydride left over during nCu 0 synthesis and, hence, additional borohydride was essential for 1,2-DCA dechlorination. Washing the nCu 0 particles improved their Cu 0 /Cu n+ ratio (1.27) and 92% 1,2-DCA was removed in 7 h with k obs = 0.345 h −1 as compared to only 44% by unwashed nCu 0 (0.158 h −1 ) with Cu 0 /Cu n+ ratio of 0.59, in the presence of borohydride. The presence of chloride (1000–2000 mg L −1 ), sulfides (0.4–4 mg L −1 ), and HA (10–30 mg L −1 ) suppressed 1,2-DCA dechlorination; which was improved by additional borohydride probably via regeneration of Cu 0 sites. Coating the particles decreased their catalytic dechlorination efficiency. 85–90% of the removed 1,2-DCA was recovered as chloride. Chloroethane and ethane were main dechlorination products indicating hydrogenolysis as the major pathway. Our results imply that synthesis parameters and groundwater solutes control nCu 0 catalytic activity by altering its physico-chemical properties. Thus, these factors should be considered to develop an efficient remedial design for practical applications of nCu 0 -borohydride.