Abstract: The hydrolysis of chromium shavings with subcritical water was studied by single factor experiments and optimized by orthogonal test. The optimized parameters were temperature of 150 ℃, liquid ratio of 25, reaction time of 75 min, and calcium oxide dosage of 6%. Under these conditions, the hydrolysis ratio of chromium shavings was (83.98 ± 0.16)%, and the chromium content of the hydrolysate was (34.81 ± 2.29)mg/kg, which was lower than that of the organic fertilizer standard of the agriculture department. The main components of the hydrolysate were peptides and short peptide as well as a small amount of amino acids. The results indicated that the hexavalent chromium content of the hydrolysate and the solid residue were 1.317 mg/kg and 30.882 mg/kg, respectively, which means most of the chromium (trivalent and hexavalent) mainly exists in the solid residue. The leaching chromium content and the hexavalent chromium content in the solid residue were 14.285 mg/L and 1.544 mg/L, respectively, which were lower than the standard limits of “identification standard for hazardous wastes-identification for extraction toxicity”. These results indicate that subcritical water hydrolysis for chrome shavings is a really harmless treatment and resource utilization.

Key words: subcritical water, chromium shavings, hydrolysis, solid residue, leaching to xicity