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随着垃圾渗滤液处理新标准的颁布[1],传统的生化处理工艺无法达标排放,所以必须对生化出水进行深度处理. 截至目前,膜处理已经广泛应用于垃圾渗滤液深度处理,但是垃圾渗滤液经纳滤(NF)、反渗透(RO)等膜过滤处理后截留下的浓缩液,约为垃圾渗滤液总量的20%—30%[2]. 垃圾渗滤液浓缩液呈棕褐色,具有可生化性很差、盐分和难降解有机物含量高等特点[3].目前,垃圾渗滤液浓缩液处理主要通过回灌、蒸发、高级氧化和回喷焚烧等方法[4]. 然而,回灌法会造成有机物和盐分的积累,影响填埋场的稳定性;蒸发法工艺复杂,能耗高;回喷焚烧法存在对于炉膛及相关设备的腐蚀以及结焦结渣问题. 因此,如何有效的对垃圾渗滤液浓缩液进行处理,是垃圾渗滤液处理中的一个新难题.
高级氧化技术(AOPs)是利用光、电、催化剂等方式产生具有强氧化性的自由基(如·OH、SO4−·、·O2−等),将难降解有机污染物氧化降解成为小分子中间产物,甚至直接降解为CO2和H2O[5]. 因其具有高效和易于操作等显著优势,近年来越来越多的被用于垃圾渗滤液浓缩液的处理研究[6-8]. 基于SO4−·高级氧化技术氧化能力更强和半衰期更长,对难降解有机物的去除潜力更大[9]. SO4−·的产生可以通过对过硫酸盐(PS)进行热活化、紫外活化和过渡金属活化等活化方式[10]. 为进一步改良单一活化方式,将电化学引入热活化过硫酸盐不仅能加快反应速率,而且对降低能耗也有很好的效果[11-12]. 此外,垃圾渗滤液浓缩液中盐分含量高,特别是Cl−,经电化学氧化转化为ClO−等强氧化性物质,能够间接氧化、促进难降解有机物的去除[13].
因此,本实验采用电/过硫酸盐催化氧化垃圾渗滤液浓缩液,研究了初始过硫酸盐(PS0)浓度、温度、反应时间和极板间距对氧化效果的影响,并对最佳实验条件下反应前后的垃圾渗滤液浓缩液进行紫外-可见光谱、三维荧光光谱和傅里叶红外光谱分析,以探究其溶解性有机物的降解机理.
电/过硫酸盐催化氧化垃圾渗滤液浓缩液
Coupled heat-activated persulfate/electrochemistry for catalytic oxidation landfill leachate concentrate
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摘要: 垃圾渗滤液浓缩液是垃圾渗滤液生化出水经NF/RO膜截留的废液,盐分和溶解性有机物(DOM)含量高,特别是难降解有机物.实验采用电/过硫酸盐催化氧化垃圾渗滤液浓缩液,研究了初始过硫酸盐(PS0)浓度、温度、反应时间和极板间距对氧化效果的影响,结果表明,在初始pH值为7.8,电流密度为8 A·dm-2,极板间距为1 cm,PS0浓度为10 g·L-1,整个体系保持在70℃反应4 h的最佳实验条件下,色度、COD、氨氮和Cl-去除率分别为100.0%、100.0%、100.0%和64.9%.紫外-可见光谱分析表明,处理后垃圾渗滤液浓缩液中DOM的芳构化程度降低,腐殖化程度降低,腐殖质的分子量及聚合度减小.三维荧光光谱分析表明,处理后的垃圾渗滤液浓缩液中类胡敏酸物质基本被完全氧化去除.傅里叶红外光谱分析表明,处理后的垃圾渗滤液浓缩液中有机物的官能团吸收强度下降,大部分有机物被氧化降解.Abstract: The landfill leachate concentrate is the waste liquid intercepted by the NF/RO membrane from the biochemical effluent of the landfill leachate. It has a high content of salt and dissolved organic matter (DOM), especially the refractory organic matter. The experiment used heat-activated persulfate/electrochemistry to catalyze the oxidation of landfill leachate concentrate, and studied the effects of initial persulfate (PS0) concentration, reaction temperature, reaction time and plate spacing on the oxidation effect. The results showed that the initial pH value of 7.8, the current density was 8 A·dm-2, the plate spacing was 1 cm, the PS0 concentration was 10 g·L-1, and the entire system was kept at 70°C for 4 h. Under the best experimental conditions, the removal rates of chroma, COD, ammonia nitrogen and Cl- were 100.0%, 100.0%, 100.0%, and 64.9%, respectively. UV-vis spectra showed that the degree of aromatization, humus, relative molecular mass and polymerization degree decreased of DOM in the landfill leachate concentrate after treatment. 3D-excitation emission matrix fluorescence spectra(3D-EEMFS) showed that the humic acid-like substances were basically completely oxidized and removed from the landfill leachate concentrate after treatment. FTIR showed that the absorption intensity of functional groups of organic matter in the treated landfill leachate concentrate decreased, and most of the organic matter was oxidized and degraded after treatment.
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Key words:
- landfill leachate concentrate /
- electrochemistry /
- heat activation /
- persulfate
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