摘要
中国多数焚烧厂采用“MBR+反渗透”工艺处理渗滤液,该工艺的反渗透膜进水富里酸含量偏高,是导致反渗透膜结垢污染的原因之一。为降低反渗透膜进水中富里酸含量,研究以过硫酸盐协同电化学体系处理自配富里酸废水,讨论体系中去除富里酸的主要活性物质,并考察了初始pH值、过硫酸盐投加量、电流密度、极板间距、NaCl质量浓度对富里酸去除率的影响。在此基础上,考察协同体系处理实际焚烧厂渗滤液MBR出水的效果。结果表明:过硫酸盐协同电化学体系对富里酸的去除能力主要由、·OH和Cl生成的HClO提供,其中HClO有着较大的贡献,其次是·OH,贡献最小。初始pH及极板间距对富里酸去除率的影响不大;富里酸去除率随初始过硫酸盐浓度的增大先升高后降低;随电流密度增加先增加后不变;随Cl质量浓度增大而略微降低。其中,过硫酸盐投加量、电流密度是主要的影响因素。采用过硫酸盐协同电化学体系处理实际焚烧厂渗滤液MBR出水,在电流密度30 mA/c
“膜生物反应器(membrane bioreactor,MBR)+反渗透技术”在中国垃圾焚烧厂渗滤液的处理中应用较多。相关文献表明,焚烧厂MBR出水中富里酸质量浓度较
过硫酸盐高级氧化技术因其对难降解有机物有较强的去除能力,近年来被广泛研
考虑到垃圾焚烧厂与填埋场产生的渗滤液水质不同,焚烧厂MBR工艺处理出水与填埋场渗滤液、纳滤膜浓缩液中所含污染物以及Cl等影响EC+PS体系作用效果的物质浓度也差异显著,本研究以减缓反渗透膜结垢为目标,采用UV254、三维荧光光谱类富里酸区体积积分值为考察富里酸降解的指标参数,研究采用EC+PS体系处理垃圾焚烧厂渗滤液MBR出水富里酸的作用机理和去除效果,即首先通过在自配富里酸废水中投加不同的自由基捕获剂探明体系中的活性物质及其贡献,其次考察初始pH、过硫酸盐投加量、电流密度、极板间距、NaCl质量浓度对富里酸去除率的影响,最后在上述单因素实验的基础上,选取较优的操作参数,对实际焚烧厂渗滤液MBR出水中富里酸的去除效果进行了验证,为减缓焚烧厂渗滤液处理反渗透膜污染提供技术支持。
本研究实验用水为自配400 mg/L的富里酸废水以及重庆丰盛垃圾焚烧厂MBR出水。
实验试剂:富里酸(FA,≥质量分数90%),购自上海阿拉丁生化科技股份有限公司;过硫酸钾(K2S2O8,AR)、甲醇(CH3OH,AR)、氯化钠(NaCl,AR)、浓硫酸(H2SO4,AR)、硫酸铵((NH4)2SO4,AR)均购自重庆川东化工(集团)有限公司;硝酸钠(NaNO3,AR)、氢氧化钠(NaOH,AR)、叔丁醇(C4H10O,AR)均购自成都市科隆化学品有限公司。
实验仪器:直流电源(MP3010DS),深圳迈盛电子仪器设备厂;磁力搅拌器(SH-2),常州市亿能实验仪器厂;pH计(PHS-3C),上海雷磁仪电科学仪器股份有限公司;紫外可见分光光度计(Model721),上海箐华仪器有限公司;荧光分光光度计(日立F-7000型),日立高新技术公司;电化学工作站(CHI660E),上海辰华仪器有限公司。
本研究采用的有机玻璃矩形槽反应器(100 mm×40 mm×100 mm)如

图1 试验装置示意图
Fig. 1 Schematic diagram of experimental device
a—直流电源;b—磁力搅拌器;c—转子;d—目标废水;e—阳极;f—阴极
固定初始PS质量浓度为6 g/L,NaCl质量浓度为3 g/L,极板间距为3 cm,电流密度30 mA/c

图2 自由基捕获剂对EC+PS体系去除富里酸的影响
Fig. 2 Effects of free radical scavenger on the oxidation removal rate of fulvic acid in EC+PS system
从
+Cl→+Cl·,k=6.6×1 | (1) |
Cl·+H2O→ClOH+ | (2) |
Cl·+OH→ClOH,k=1.8×1 | (3) |
ClOH→Cl+·OH,k=6.1×1 | (4) |
为进一步验证EC+PS体系对富里酸的去除机理,在NaCl质量浓度为3 g/L,NaNO3质量浓度为4.37 g/L,初始PS质量浓度为6 g/L,扫描速度0.005 V/s的试验条件下,绘制了不同电解质溶液时的线性扫描伏安特性曲线。如

图3 Ti/IrO2阳极在不同溶液中的线性扫描伏安曲线
Fig. 3 Linear sweep voltammetry curves of Ti/IrO2 anode in different solutions
固定初始PS为6 g/L,NaCl质量浓度为3 g/L,极板间距为3 cm,电流密度30 mA/c

图4 不同初始pH下富里酸的去除率随时间的变化
Fig. 4 Fulvic acid removal rates with time change under different initial pH values
由
+H2O→+·OH+ | (5) |
2Cl→Cl2+2e, | (6) |
Cl2+H2O→HCl+HClO, | (7) |
Cl2+2OH↔ClO+Cl+H2O, | (8) |
Cl+·OH→ClO+ | (9) |
ClO+·OH→ClO+ | (10) |
ClO+·OH→ClO+ | (11) |
ClO+·OH→ClO+ | (12) |
设定初始pH为7,电流密度为30 mA/c

图5 不同初始PS下富里酸的去除率随时间的变化
Fig. 5 Fulvic acid removal rates with time change under different initial PS values
从
+→+ | (13) |
(14) |
+→+ | (15) |
固定初始pH为7,PS质量浓度9 g/L,极板间距3 cm,NaCl质量浓度为3 g/L。当电流密度分别为20、25、30、35 mA/c

图6 不同电流密度下富里酸的去除率随时间的变化
Fig. 6 Fulvic acid removal rates with time change under different current densities
由
固定初始pH为7,PS质量浓度9 g/L,电流密度为30 mA/c

图7 不同极板间距下富里酸的去除率随时间的变化
Fig. 7 Fulvic acid removal rates with time change under different plate spacings
由
固定初始pH为7,PS质量浓度9 g/L,电流密度为30 mA/c

图8 不同电解质质量浓度下富里酸去除率随时间的变化
Fig. 8 Fulvic acid removal rates with time change under different electrolyte mass concentrations
由
基于上述单因素实验,考察协同体系对实际渗滤液MBR出生中富里酸的处理效果,实验条件如下:PS质量浓度9 g/L,电流密度为30 mA/c

图9 EC+PS体系处理渗滤液MBR出水三维荧光光谱图
Fig. 9 Three-dimensional fluorescence spectra of MBR effluent leachate treated by EC+PS system
由
采用荧光区域积分法计算出上述

图10 水样可见光区及紫外光区类富里酸区域积分
Fig. 10 Area integral value of fulvic acid-like in visible and ultraviolet regions of water samples
1)在EC+PS协同体系降解富里酸废水的过程中,提供氧化能力为物质与基团主要为HClO、·OH和,其中HClO有着较大的贡献,其次是·OH,贡献最小。
2)在EC+PS协同体系中,富里酸去除率随初始pH值的升高而略微降低,随过硫酸盐质量浓度的增大先上升后略有降低,随电流密度增加而增大,随极板间距升高而略有降低。在初始pH=7,PS为9 g/L,电流密度为30 mA/c
3)EC+PS协同体系对实际垃圾渗滤液MBR出水中的富里酸有较好的去除效果,在初始PS为9 g/L,电流密度为30 mA/c
参考文献
邓阳, 冯传平, 胡伟武, 等. 电化学氧化垃圾渗滤液生化出水过程中溶解性有机物形态及可生化性[J]. 环境化学, 2018, 37(7): 1647-1659. [百度学术]
Deng Y, Feng C P, Hu W W, et al. DOM composition and biodegradability of biologically treated landfill leachate during electrochemical oxidation degradation[J]. Environmental Chemistry, 2018, 37(7): 1647-1659.(in Chinese) [百度学术]
李堃宇. 反渗透膜处理垃圾焚烧厂与填埋场渗滤液结垢机理研究[D]. 重庆: 重庆大学, 2016. [百度学术]
Li K Y. Study on fouling mechanism of RO membrane treament for incinerators and landfill leachate[D]. Chongqing: Chongqing University, 2016. (in Chinese) [百度学术]
韩文亮, 董林洋. 基于硫酸根自由基的先进氧化活化方法及其在有机污染物降解上的应用[J]. 化学进展, 2021(8): 1426-1439. [百度学术]
Han W L, Dong L Y. Activation methods of advanced oxidation processes based on sulfate radical and their applications in the degradation of organic pollutants[J]. Progress in Chemistry, 2021(8): 1426-1439.(in Chinese) [百度学术]
Fernandes A, Nunes M J, Rodrigues A S, et al. Electro-persulfate processes for the treatment of complex wastewater matrices: present and future[J]. Molecules, 2021, 26(16): 4821. [百度学术]
Song H R, Yan L X, Ma J, et al. Nonradical oxidation from electrochemical activation of peroxydisulfate at Ti/Pt anode: efficiency, mechanism and influencing factors[J]. Water Research, 2017, 116: 182-193. [百度学术]
吴娜娜, 钱虹, 王宇思, 等. 电化学协同过硫酸盐处理有机废水的研究进展[J]. 建筑与预算, 2017(9): 29-33. [百度学术]
Wu N N, Qian H, Wang Y S, et al. Recent advances in electro-persulfate processes in organic wastewater treatment[J]. Construction and Budget, 2017(9): 29-33.(in Chinese) [百度学术]
陈希, 纪志永, 黄智辉, 等. 电化学协同过硫酸盐氧化法处理含盐有机废水[J]. 化工进展, 2019, 38(12): 5572-5577. [百度学术]
Chen X, Ji Z Y, Huang Z H, et al. Electrochemical synergistic persulfate oxidation process for treatment of salty organic wastewater[J]. Chemical Industry and Engineering Progress, 2019, 38(12): 5572-5577.(in Chinese) [百度学术]
冯俊生, 张郓, 王晓红, 等. 石墨烯电极电活化过硫酸盐降解含酚废水研究[J]. 安全与环境学报, 2021, 21(1): 404-410. [百度学术]
Feng J S, Zhang Y, Wang X H, et al. Degrading phenolic sewage via the graphene electrodes through the electrically activated persulfate[J]. Journal of Safety and Environment, 2021, 21(1): 404-410.(in Chinese) [百度学术]
Cui Y H, Xue W J, Yang S Q, et al. Electrochemical/peroxydisulfate/Fe treatment of landfill leachate nanofiltration concentrate after ultrafiltration[J]. Chemical Engineering Journal, 2018, 353: 208-217. [百度学术]
郭晓磊. 过硫酸盐高级氧化技术处理垃圾渗滤液纳滤浓缩液的研究[D]. 武汉: 华中科技大学, 2017. [百度学术]
Guo X L. Treatment of landfill leachate nanofiltration concentrate by persulfate advanced oxidation technology[D]. Wuhan: Huazhong University of Science and Technology, 2017. (in Chinese) [百度学术]
Zhang H, Wang Z, Liu C, et al. Removal of COD from landfill leachate by an electro/Fe/peroxydisulfate process[J]. Chemical Engineering Journal, 2014, 250: 76-82. [百度学术]
谷永, 闫志明, 王兴, 等. 氯离子对过硫酸盐氧化苯胺的影响[J]. 环境工程学报, 2021, 15(8): 2627-2638. [百度学术]
Gu Y, Yan Z M, Wang X, et al. Effect of chloride ions on the oxidation of aniline using persulfate[J]. Chinese Journal of Environmental Engineering, 2021, 15(8): 2627-2638.(in Chinese) [百度学术]
Yu X Y, Bao Z C, Barker J R. Free radical reactions involving Cl, and , and in the 248 nm photolysis of aqueous solutions containing and Cl[J]. The Journal of Physical Chemistry A, 2004, 35(14): 108(2): 295-308. [百度学术]
Li W, Orozco R, Camargos N, et al. Mechanisms on the impacts of alkalinity, pH, and chloride on persulfate-based groundwater remediation[J]. Environmental Science & Technology, 2017, 51(7): 3948-3959. [百度学术]
le Luu T, Kim J, Yoon J. Physicochemical properties of RuO and IrO electrodes affecting chlorine evolutions[J]. Journal of Industrial and Engineering Chemistry, 2015, 21: 400-404. [百度学术]
Gholami M, Fard M B, Zabihzadeh M, et al. Sulphate radical-based advanced oxidation technologies for removal of COD and ammonia from hazardous landfill leachate: a review[J]. International Journal of Environmental Analytical Chemistry, 2021: 1-19. [百度学术]
Sirés I, Brillas E, Oturan M A, et al. Electrochemical advanced oxidation processes: today and tomorrow. A review[J]. Environmental Science and Pollution Research International, 2014, 21(14): 8336-8367. [百度学术]
Xue W J, Cui Y H, Liu Z Q, et al. Treatment of landfill leachate nanofiltration concentrate after ultrafiltration by electrochemically assisted heat activation of peroxydisulfate[J]. Separation and Purification Technology, 2020, 231: 115928. [百度学术]
王维大, 王丽丽, 孙岩柏, 等. 电化学氧化耦合铁感应电极激发过硫酸盐氧化处理焦化废水生化出水[J]. 环境化学, 2019, 38(11): 2563-2572. [百度学术]
Wang W D, Wang L L, Sun Y B, et al. Electrochemical oxidation coupling iron plate induction electrode excited persulfate oxidation treatment of coking wastewater biochemical water[J]. Environmental Chemistry, 2019, 38(11): 2563-2572. (in Chinese) [百度学术]