Optimal Condition for Decomposition of Ethylenediaminetetraacetic Acid (EDTA) in Supercritical Water Oxidation

摘要

Supercritical water oxidation (SCWO,P>221 bar,T>374degC) is a promising method for the decomposition of refractory organic compounds.In this study,the SCWO of Ethylenediaminetetraacetic acid (EDTA) was carried out in a tubular-type continusous reactor system with an H_2O_2 oxidant at 387-500degC,250 bar and residence time (RT) of 15.9-88.9 s.The decomposition efficiencies increased with increasing temperature and oxidant amount,while it was inversely proportional to feed flow rate.The decomposition efficiency of 99.6% was obtained at 500degC,250 bar,oxidant amount of 400% and residence time of 40.1 s.The effect of temperature on the decomposition efficiency was more significant than that of oxidant amount.In the case of the decomposition efficiency of 5,000 mg/L of EDTA (3,063 mg/L as COD_(Cr)),the decompostion of 99% or higher was obtained at the condition of over 40.1 s (RT) and 200 stoichiometric % of H_2O_2 in the supercritical water of 500degC and 250 bar.