Abstract
Hazardous waste of chemical oxygen demand (COD) test (HWCOD) is one of the most common laboratory wastewaters, containing large amounts of H2SO4 and highly toxic Cr3+ and Hg2+. Current treatment methods suffered from incomplete removal of Cr3+ and high-cost. Herein, a humic acid-coated zirconium oxide-resin nanocomposite (HA-HZO-201) was fabricated for efficient recovery of Cr3+ and Hg2+ in HWCOD. The synthesized HA-HZO-201 shows excellent tolerance to wide pH range (1–5) and high salinity (3.5 mol/L NaCl), as well as adsorption capacity for Cr3+ (37.5 mg/g) and Hg2+ (121.3 mg/g). After treating with HA-HZO-201 by using a fixed-bed adsorption procedure, the final Cr3+ and Hg2+ concentrations in HWCOD decreased to 0.28 and 0.02 mg/L, respectively. In addition, the HA-HZO-201 can be regenerated by desorption and recovery of Cr3+ and Hg2+ using HNO3 and thiourea as eluents, respectively. After 5 cycles of adsorption/desorption, the removal efficiencies still reach up to 86.0% for Cr3+ and 89.7% for Hg2+, indicating an excellent regeneration of HA-HZO-201. We hope this work open new opportunities for treatment of HWCOD with high-efficiency and low-cost.
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