原位生成铁基吸附剂的滤柱除砷工艺性能

为研究不添加氧化剂时，滤柱原位生成的铁基吸附剂净化低浓度As(Ⅲ)污染地下水的可行性及长期运行效果，分别从滤柱除砷最佳铁砷比(质量比)、滤速对滤柱除砷效果影响、砷沿程去除规律及机理等方面，系统分析滤柱除砷工艺性能.结果表明：滤柱R1、R2分别在进水As(Ⅲ)质量浓度为50、100 μg/L，滤速为5 m/h条件下运行，筛选出的最佳铁盐质量浓度为1.2、2 mg/L，对应最佳铁砷比约为20:1.以进水As(Ⅲ)质量浓度为50~70 μg/L、总Fe质量浓度约为2 mg/L的滤柱R3为研究对象，发现滤速提升过程中As去除条带不断下移，主要集中在上部60 cm滤层，而Fe去除条带并没有发生明显变化，Fe在20 cm和20~80 cm滤层内去除质量浓度均约为1 mg/L; 滤速由3 m/h提升至10 m/h过程中，滤柱反冲洗周期出现小幅度缩短但基本维持在72 h以内，滤柱稳定运行的极限滤速为10 m/h.铁盐自催化氧化过程可能生成了利于As(Ⅲ)氧化的中间产物，滤料表面及滤料间形成的r-FeOOH、Fe(OH)3为砷的吸附去除提供充分吸附位点.
The present study was directed towards the feasibility and long-term operation efficiency of the purification of groundwater with low concentration of As(Ⅲ), using iron-based adsorbent which was in-situ formed in the filtration process by dosing ferrous sulfate, without pre-oxidation technique. Several experiments were conducted to analyze the optimal dosage ratio of the Fe and As, and the effect of filtration rate and the arsenic removal mechanism in the filtration process. The results showed that with the influent As (Ⅲ) concentrations of 50 and 100 μg/L respectively for the filter column R1 and R2, and the filtration rate of 5 m/h, the optimal ferrous sulfate dosage was 1.2 and 2 mg/L respectively, and the optimal dosage ratio of Fe and As was about 20:1. The filter column R3 was adopted for advanced research, with the influent As (Ⅲ) concentration of 50-70 μg/L and the total Fe concentration of about 2 mg/L. The As(Ⅲ) removal space in the filter column descended continuously with the increasing of filtration rate, and the removal process mainly occured in the upper 60 cm filter layer. Meanwhile, the Fe removal space basically remained unchanged: the removal concentration was both about 1 mg/L for the filter layer of 0-20 cm and 20-80 cm respectively. In the increase of the the filtration rate from 3 m/h to 10 m/h, the maximum filtration rate of the filter column was confirmed to be 10 m/h, and the backwashing period decreased slightly(remaining within 72 h). Intermediate products might be generated in the autocatalytic oxidation process of ferrous ion, which were of great benefit to the oxidation of As (Ⅲ). The r-FeOOH coated on the filter media surface and the Fe(OH)3 formed in the filter media pore could provide sufficient sites for arsenic adsorption.