| Leather sludge is a very serious source of pollution, rich in hazardous organics and heavy metals such as chromium. The current treatment methods can’t effectively deal with organics and stability of metals simultaneously without secondary pollution. Therefore, it is very essential to find an effective treatment process to decompose leather sludge to meet the demand of environment protection. Results show that su-percritical water oxidation (SCWO) process can oxidize the organic pollutants and stabilize the heavy metals efficiently in the leather sludge without secondary pollution. It is a promising technology for the leather sludge.The effectiveness of SCWO process for the destructions of hazardous organics and leaching toxicity of heavy metals from leather sludge was investigated. Batch tests were performed at distinct conditions of reaction temperature, oxygen coefficient, residence time and oxidizing agent.99%COD conversion rate is obtained at400℃,29MPa,300%oxygen excess,1min, with30%H2O2as oxidant. The liquid product appears clear, while the metal composition and sediment deposit at the bottom of the reaction vessel by separation. Increasing reaction temperature, oxygen coefficient or residence time help to improve the removal rate of COD.The impact of various fac-tors on the COD removal efficiency of primary and secondary order is:reaction tem-perature>coefficient peroxide> oxidants> residence time.Converting from soluble to insoluble species with ash, the leaching toxicity of heavy metals is dropped simultaneously. Metal leaching toxicity stability ratio of Cr, Zn, Fe and Cu reach up to90%at400℃,29MPa,150%oxygen excess,1min, with O2as oxidant. The recovery rate of CrO42-reaches96%while the residence time is3min. All leachabilities meet with the level of national emission standards. |
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