Measurement Of Total Organic Carbon In Wastewater Based On Supercritical Water(Fenton) Oxidation

The organic pollutants are oxidized quickly and thoroughly based on supercritical water oxidation. According to a series of studies from the research group before shows that the method of employing supercritical water oxidation to measure total organic carbon is feasible. But in the experiment, the temperature of Total organic carbon detection is higher, more oxidants are added, and the utilization efficiency of oxidant is not high. Therefore, it is necessary to realize further improvement and optimization through more experiments.Total organic carbon of simulated wastewater containing potassium hydrogen phthalate was measured by supercritical water oxidation with potassium permanganate, potassium dichromate and hydrogen peroxide as oxidant respectively. The effects of the temperature and oxidant multiple were explored. Results showed that the TOC detection rate X reached 98% when hydrogen peroxide was used as oxidant under the temperature of 440 oC and oxidant multiple of 10. Under the same condition the TOC detection rate X were only 11% and 8% while the potassium permanganate and potassium dichromate were used as oxidant respectively. Therefore under the condition of supercritical water, the oxidation capability of hydrogen peroxide was more outstanding than potassium permanganate or potassium dichromate.At the same time, the detection of total organic carbon in simulated wastewater by Fenton oxidation was studied under the condition of supercritical water. The effects of the p H(2.2~5.2), Fe2+ concentration(0.2~0.8 mg/L), temperature(380~480oC), pressure(23.0~25.0 MPa), and oxidant multiple(1~20) on the measurement results were studied. Results showed that the proper operational conditions are temperature of 420 oC, pressure of 24.0 MPa, oxidant multiple n>= 5, p H of 4.4, Fe2+ concentration of 0.8 mg/L, while the TOC detection rate X was higher than 98%, but the TOC detection rate X was only 87% by supercritical water oxidation under the same conditions. Therefore Fenton oxidation based on supercritical water declined TOC detection temperature, reduced oxidation multiple by improving the utilization efficiency of oxidant.Finally, the performance of TOC determinator that established was tested comprehensively. Repeated experiments of the same potassium hydrogen phthalate sample were performed that the precision of the measurement device RSD was 0.66%. The TOC detection rate was 99.7~101.2%, and the difference was no more than 1.2% that compared with Shimadzu Analyzer. Continuous determination of total organic carbon in the same potassium hydrogen phthalate sample were performed, when TOC concentration was changed(from low to high or high to low), around every 30 min could take a stable NDIR signal. Those showed that the TOC detection device based on supercritical water oxidation had high precision, good accuracy, realize continuous detection, the response time for about 30 min.