Synthesis of chrome-tanning agents from chromate wastewater

Chromium wastewater is one type of wastewater with high toxicity. Currently, the treatment of this wastewater along with resource recovery gains wide attention. In this study, the synthesis of chrome-tanning agent from chromate wastewater was investigated in both laboratory and pilot-scale studies. Hexavalent chromium was reduced to basic trivalent chromium sulfate using glucose as a reducing agent. The factors affecting the reduction of hexavalent chromium, such as sulfuric acid dosage, glucose dosage, pH, reaction time, and reaction temperature, were investigated. The results showed that 0.3 g of glucose and 2.0 mL of sulfuric acid (volume ratio = 1:1) were efficient in treating 100 mL of raw materials when the mass proportion of impurities was below 13%. In addition, the optimal molar ratio of raw materials and reactants was identified as n (H 2 SO 4 )/ n (Na 2 Cr 2 O 7 )/ n (C 6 H 12 O 6 ) of 3:1:0.35. Under the optimum condition, the percentage of Cr 2 O 3 and alkalinity in the generated chrome-tanning agent met the standard I grade for industrial usage. A pilot-scale experiment was conducted subsequently, which exhibited outstanding performance as the lab-scale results.