污水中不同形态氮稳定同位素预处理方法探究

A stable nitrogen isotope pretreatment method for different forms of nitrogen in sewage

本文提出了有机物中胺基氮消解转化为铵盐后的富集与分离方法,探讨了凯氏氮(KTN)、有机氮(DON)消解转化为铵盐的实验条件,完善了污水中铵盐稳定氮同位素预处理的最佳实验条件.经实验分析,KTN、DON在3 mL5%(W/V)的Cu SO_4、10 mL浓H_2SO_4、6 g K2SO_4条件下消解30 min,可稳定高效地转化为(NH4)HSO_4.研究结果表明,铵盐最佳蒸馏时间为50 min,最适碱投加量为5 mL 40%(W/V)的Na OH溶液,当铵盐浓度在0—80 mg·L^(-1)时,蒸馏过程氮回收率均高于95%;通过对比沸石吸附和酸吸收两种方式,发现酸吸收高效稳定,并优选稀硫酸(0.04 mol·L^(-1))作为吸收液,在pH=3.0±0.3、50℃干燥引起的氮同位素分馏效应最小(<0.04‰).将该方法应用于实际生活污水管网中的氮迁移转化分析,验证了方法的可行性和应用价值.

In this study,a enrichment and separation method of amino nitrogen after conversion to ammonium salt was proposed. The experimental conditions for the conversion of KTN and DON into ammonium salt were investigated,and the optimum pretreatment conditions of stable nitrogen isotope in wastewater were improved. The results showed that KTN and DON were transformed to（NH4） HSO4 in 3 mL 5%（W/V） Cu SO4,10 mL H2SO4 and 6 g K2SO4 for 30 min digestion. The best distillation time was 50 min,and the optimum alkali dosage was 5 mL 40%（W/V） Na OH solution. When the concentration of ammonium salt was in the range of 0 mg·L^-1and 80 mg·L^-1,the recovery of nitrogen was higher than 95% in distillation process. After comparing zeolite adsorption and acid absorption,the result showed that acid absorption was stable and efficient,and dilute sulphuric acid（〈0. 04 mg·L^-1） was optimized as the absorbing liquid. Fractionation efficiency of nitrogen isotope was minimum（ 0.04‰） when drying at 50 ℃ and pH 3.0 ± 0.3. The method was applied to analyze the migration and transformation of nitrogen in sewage pipe network,and the feasibility and application potential of the method were verified.