Chlorine-containing organic waste (COWs) is a big threat for the waste incineration because of the dioxin generation and equipment corrosion. Recently, dechlorination and detoxification of COWs is emergent in order to lower the environmental risk and treatment costs. In this study, base-catalyzed decomposition processes with different hydroxides, hydrogen donors, and catalysts were conducted for pre-treatment of COWs to reduce organic chlorine content, with the TCB as a model compound and industrial rectification residues for verification. Results showed that maximum chlorine retention efficiency (CRE) of four alkalis followed the order of KOH > NaOH–KOH > NaOH > Mg(OH)2, which were 98.3%, 93.4%, 97.2%, and 1.5%, respectively, and could be expressed as an apparent first-order reaction. The differences were resulted from the varying ionic potentials of the metal cations. Hydrogen donors (glycol, glycerol, paraffin oil, and PEG 200) acted as effective dechlorination regents follow the order of PEG > glycol > paraffin oil > glycerol. In addition, Fe, Ni, Cu, and activated carbon catalysts increased the CRE by 68.9% to 92.4%, 91.9%, 89.2%, and 73.3%, respectively. Residue analysis through X-ray diffraction and Fourier transform infrared spectroscopy revealed that KCl, sodium oxalate, and phenol were the main products and a plausible stepwise dechlorination pathway was proposed. The effectiveness of three optimized combinations including NaOH/PEG, KOH/PEG, and NaOH–KOH/PEG (with the Fe catalyst) was confirmed by using them for dechlorinating rectification residues, and they restrained 98.2%, 91.2%, and 94.6% of the chlorine, respectively. The organochlorine content decreased from 19.2 to 1.8% within 180 min, while inorganic chorine content increased from 1.5 to 18.9%, indicating the potential for COWs dechlorination.
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The authors are grateful to the State Key Laboratory of Pollution Control and Resource Reuse, China, who provides us with facilities and equipment for sample testing and analysis.
This work was supported by the National Natural Science Foundation of China (Grant no. 21677112), Chong Qing Municipal Solid Waste Resource Utilization & Treatment Collaborative Innovation Center (Shljzyh2017-006), Science and Technology Program of Ministry of Housing and Urban-Rural Development (2015-K7-021).
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