低强度超声波对残留H2O2的去除

A H2O2 composition method to avoid oxidant interference on COD measurement by low intensity ultrasonic irradiation

化学需氧量（COD）会受到来自众多高级氧化技术中添加的过氧化氢（H2O2）的干扰。为了评估低强度超声波辐射结合清除剂（Na2CO3或Na HCO3）分解水样中残留H2O2的可行性,对去离子水、葡萄糖模拟废水和印染废水二级处理出水进行超声（超声波频率为39 k Hz,功率分别为75 W、112.5 W和150 W）处理,H2O2质量浓度为20 mg/L,时间为60 min或80 min,清除剂用量为50 g/L。以20 min的间隔测定H2O2质量浓度和COD。结果表明,COD与H2O2质量浓度的比值取决于废水的性质,去离子水、葡萄糖模拟废水和印染废水二级处理出水的比值分别为0.262 6 mg COD/mg H2O2、0.209 9 mg COD/mg H2O2、0.401 3 mg COD/mg H2O2。超声辐照对去除H2O2有一定的影响,但在去离子水中超声功率为150 W、60 min时的去除率最高,仅为18.1%。超声辐照联合清除剂Na2CO3或Na HCO3的效果更显著。对于印染废水二次处理出水,加入Na HCO3作为羟自由基清除剂,80 min时H2O2去除率达到97.3%。然而,由于Na HCO3和H2O2形成的高度氧化的超氧离子能降解废水中的有机物质,水样的实际COD降低。用超声辐射结合Na2CO3处理80 min,将COD的测定值与通过COD、H2O2质量浓度比值得到的计算值进行比较,以确认经超声波联合Na2CO3处理的印染废水二级处理出水中的有机物未降解。研究表明,超声波照射与Na2CO3结合去除水样中的低浓度H2O2是可行的。

The residual of strong oxidant such as hydrogen peroxide（H2O2）in treated wastewater is an inevitable interference to chemical oxygen demand（COD）measurement.However,although several methods have been reported,there is no simple and effective method available to address this problem.Thus,in this study,ultrasonic irradiation with low intensity was used to compose the residual H2O2in a simple and efficient way.Deionized water,simulated wastewater containing glucose as carbon source,and secondary effluent from treated dyeing wastewater were chosen as the model wastewater.The decomposition of residual H2O2through ultrasonic irradiation at 39 k Hz with power input of 75 W,112.5 W and 150 W was investigated.In addition,Na2CO3and Na HCO3were used as scavenging agent.The results show that the interference value of H2O2on COD measurement depended on the kinds of wastewater,which equal to 0.262 6 mg COD/mg H2O2,0.209 9 mg COD/mg H2O2,0.401 3 mg COD/mg H2O2in deionized water,simulated wastewater containing glucose as carbon source,and secondary effluent from treated dyeing wastewater,respectively.Further,it was found that Na HCO3was an activator for H2O2to generate active oxygen species superoxide ion（·O2^-）,which would degrade the organic pollutants in wastewater and then have negative effect on COD measurement.Thus,Na2CO3was chosen as the suitable scavenging agent,although its scavenge efficiency was lower than that of Na HCO3.Under optimal conditions,which the ultrasonic irradiation was at 39 k Hz with power input of 112.5 W,more than 87%of H2O2in secondary effluent from treated dyeing wastewater was composed after 80 min of irradiation in the presence of 50 g/L Na2CO3.Meanwhile,the organic pollutant in secondary effluent from treated dyeing wastewater was stable after the low intensity ultrasonic irradiation.We hope that this simple and effective method can be available to avoid the oxidant interference on COD measurement in practical applications.