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氯酸钠对废水COD测定的干扰研究
Interference of Sodium Chlorate in COD Determination and Its Elimination
投稿时间:2022-09-21  修订日期:2023-02-28
DOI:10.19316/j.issn.1002-6002.2023.04.20
中文关键词:  氯酸钠  COD测定  干扰
英文关键词:sodium chlorate  COD determination  interference
基金项目:湖南省生态环境万科项目(2019120525)
作者单位
朱丹丹 湖南省岳阳生态环境监测中心, 湖南 岳阳 414000 
黄卫* 湖南省岳阳生态环境监测中心, 湖南 岳阳 414000 
张子豪 湖南省岳阳生态环境监测中心, 湖南 岳阳 414000 
吴可方 湖南省岳阳生态环境监测中心, 湖南 岳阳 414000 
彭娴 湖南省岳阳生态环境监测中心, 湖南 岳阳 414000 
符哲 湖南省洞庭湖生态环境监测中心, 湖南 岳阳 414000 
陈兆祺 湖南省岳阳生态环境监测中心, 湖南 岳阳 414000 
通讯作者:黄卫*  湖南省岳阳生态环境监测中心, 湖南 岳阳 414000  
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中文摘要:
      氯酸钠是污水处理厂处理污水时常用的一种氧化剂,会对COD的测定产生负干扰。有的污水处理厂对含过量氯酸钠的污水未进行处理而直接外排;也有的污水处理厂为逃避环保部门的监管,在外排口投入过量氯酸钠,干扰COD测定,人为降低污水COD测定值。因而,研究氯酸钠对废水COD测定的干扰具有重要的现实意义。通过对标准样品和实际样品进行检测,发现氯酸钠对COD测定的干扰程度(真实值与测定值的差值)随着氯酸钠浓度的增加而增大。当氯酸钠浓度在100~1 000 mg/L范围内时,干扰值的大小与氯酸钠浓度呈显著正相关(P<0.05,r=0.997 4),且相同浓度氯酸钠对不同浓度COD测定产生的干扰无显著性差异。从追踪反应过程中不同形式氯元素含量的角度,进一步探究了氯酸钠对COD测定的干扰机理,发现氯酸钠对COD测定的干扰来自两个反应过程,分别是氯酸钠在消解过程中与还原性物质的反应、未完全反应的氯酸钠在滴定过程中与硫酸亚铁铵的反应,并且两个反应过程都会对COD的测定产生负干扰。根据干扰机理,研究建立了干扰校正方法,即校准曲线法。此方法具有较好的精密度和正确度,可以满足实际废水样品的测定要求。
英文摘要:
      Sodium chlorate is an oxidant often used by sewage treatment plants to treat sewage,which can interfere with the determination of COD.At present,some sewage treatment plants directly discharge the sewage containing excessive sodium chlorate without treatment,and some sewage treatment plants put excessive sodium chlorate into the outlet to interfere with the COD determination,thus artificially reducing the COD determination value of the sewage to avoid the supervision of the environmental protection department.Therefore,it is of great practical significance to study the interference of sodium chlorate on the determination of COD in wastewater.By testing the standard samples and the actual samples,it was found that the interference of sodium chlorate on COD determination (the difference between the real value and the measured value) increased with the concentration of sodium chlorate.The interference was significantly positively correlated with the concentration of added sodium chlorate in the range of 100-1 000 mg/L (P<0.05,r=0.997 4),while there was no significant difference in the interference caused by certain concentration sodium chlorate to the determination of COD at different concentrations.The interference mechanism of sodium chlorate on the determination of COD was further explored by tracking the amount of different forms of chlorine elements.It was shown that the interference of sodium chlorate on the determination of COD came from two reaction processes,namely the reaction of sodium chlorate with reducing substances in the digestion process,and the reaction of the unreacted sodium chlorate with ammonium ferrous sulfate in the titration process.Both reaction would have negative interference on the determination of COD.Based on study of interference mechanism,a method of interference elimination,namely the calibration curve method,was established.This method has good precision and accuracy,and can meet the requirements of actual wastewater sample determination.
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