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中水是国际公认的第二水源,但目前中水处理后应用的一个主要问题还是氨氮和总磷含量过高,而这部分物质在太阳光的照射下会滋生大量的微生物,使水体发臭,在硝化细菌的作用下会转化成硝酸和亚硝酸,从而影响中水的回用[1-2]。目前脱氮除磷的方法主要有化学沉淀法,物理吸附法和生物法,虽然各有特点,但都不同程度存在设备昂贵、运行费用高、能耗高和易造成二次污染等问题[3]。
硫酸亚铁(FeSO4)絮凝所具有的水质净化效能已在杀菌消毒、氧化除污染、混凝助凝等方面通过大量的工程应用得到了证实。GEORGIOU et al[4]研究了使用FeSO4絮凝处理绵纺织废水的色度和COD,用石灰将废水pH调节至9.0左右,绵纺织废水的色度去除率达到了70%,COD去除率达到50%。ZHU et al [5]使用FeSO4·7H2O处理锑矿的选矿废水,研究了絮凝剂用量,pH值和反应时间对废水中锑的去除效率。得到当七水合硫酸亚铁的用量为0.075∶100,pH为7,絮凝时间为180 min时,锑的去除率达到99.86%。
相比于传统的水处理技术,电化学絮凝在外电场的作用下,金属阳极氧化生成金属阳离子,经过水解和聚合生成具有凝聚和吸附作用的氢氧化物,以此来去除水中的污染物,因为不引入其他化学物质,且处理效率高、操作简便、占地面积小,被用于处理各种废水[6-8]。BAYRAMOGLU et al [9]研究表明,相比于化学混凝,电絮凝处理纺织废水的COD和浊度的效率更高,消耗的材料和产生的污泥更少,同时产生的多核羟基化合物对水中的磷有较好的吸附效果。
文章通过小试考察不同FeSO4投加量、pH值、通电时间和电压分别研究了FeSO4絮凝和电化学絮凝对中水中低浓度的氨氮和总磷的去除效果,以及电化学为主体结合FeSO4絮凝优化对中水脱氮除磷的效果,为中水的深度净化提供基础数据以指导工程实践。
硫酸亚铁结合电化学絮凝处理中水氨氮与总磷的研究
Treatment of Ammonia Nitrogen and Total Phosphorus in Reclaimed Water by combining Ferrous Sulfate with Electrochemical Flocculation
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摘要: 文章分别采用硫酸亚铁絮凝法、电化学法以及硫酸亚铁结合电化学法对中水中低浓度氨氮和总磷的处理效果进行了对比。研究了硫酸亚铁投加量、pH、通电时间和电压对氨氮和总磷去除率的影响。结果表明:采用硫酸亚铁絮凝法,硫酸亚铁投加量为6%,pH为6~7,氨氮去除率为95.45%,总磷去除率92.5%;采用电化学絮凝法,通电时间40 min,通电电压20 V,pH为6~7,中水中氨氮去除率为72.73%,总磷去除率为92.5%;硫酸亚铁结合电化学处理中水,通电电压为20 V,通电时间30 min,硫酸亚铁投加量7%时,中水中氨氮去除率99.09%,总磷去除率92.5%。因为氨直接在阳极失去3个电子被氧化成N2,阳极电解时生成的金属阳离子或其水合物与水中的磷酸盐形成沉淀。而硫酸亚铁通过空轨道吸附铵根中氮的孤对电子后被水解生成的含有Fe3+的羟基络合物絮凝沉淀,Fe2+和Fe3+也都可以与PO43−生成难溶性磷酸盐。Abstract: The treatment effects of low-concentration ammonia nitrogen and total phosphorus were compared with ferrous sulfate flocculation method, electrochemical method, and ferrous sulfate combined with electrochemical method. The effects of the dosage of ferrous sulfate, pH value, the reaction time and applied voltage on the removal rate of ammonia nitrogen and total phosphorus were studied. The experimental results showed: Using ferrous sulfate flocculation method, when the dosage of ferrous sulfate was 6% and pH was 6 ~ 7, the removal rates of ammonia nitrogen and total phosphorus were 95.45% and 92.5% respectively. Using electrochemical flocculation method in pH of 6~7, when the reaction time was 40 minutes and the applied voltage was 20 V the removal rates of ammonia nitrogen and total phosphorus were 72.73% and 92.5% respectively. When the 7% ferrous sulfate combined with electrochemical treatment was used with the voltage of 20 V and the reaction time of 30 minutes, the removal rates of ammonia nitrogen and totoal phosphorus could reach 99.09% and 92.5% respectively. Because ammonia loses 3 electrons directly at the anode, then oxidaizing to N2, metal cations or their hydrates formed during anode electrolysis could precipitae with phosphates in water. And the ferrous sulfate adsorbs the lone pair electrons of nitrogen in the ammonium, and form a Fe3+-containing hydroxyl complex to flocculate and precipitate with pollutants. Fe2+ and Fe3+ can also form poorly soluble phosphate with PO43−.
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表 1 试剂与仪器
试剂与仪器 试剂级别 生产厂家 硫酸亚铁(FeSO4) AR级 天津市科密欧化学试剂有限公司 硫酸(H2SO4) AR级 天津市科密欧化学试剂有限公司 氢氧化钠(NaOH) AR级 天津市科密欧化学试剂有限公司 SX2-4-13直流电源 沈阳节能电炉厂 Oakton pHTestr20笔试pH计 上海涸宇机电科技有限公司 六联电动搅拌机 深圳中润水工业技术有限公司 -
[1] FENG Q, CHENG G D, MASAO M K. Trends of water resource development and utilization in arid north-west China[J]. Environmental Geology, 2000, 39: 831 − 838. doi: 10.1007/s002549900062 [2] 虞启义, 黄种买, 张青. 城市污水回用于冷却水问题的研究[J]. 工业水处理, 2002, 22(8): 19 − 22. doi: 10.3969/j.issn.1005-829X.2002.08.007 [3] 徐丽丽, 施汉昌, 陈金銮. Ti/RuO2-TiO2-IrO2-SnO2电极电解氧化含氨氮废水[J]. 环境科学, 2007, 28(9): 2009 − 2013. doi: 10.3321/j.issn:0250-3301.2007.09.020 [4] GEORGIOU D, AIVAZIDIS A, HATIRAS J, et al. Treatment of cotton textile wastewater using lime and ferrous sulfate[J]. Water Research, 2003, 37(9): 2248 − 2250. doi: 10.1016/S0043-1354(02)00481-5 [5] ZHU J, LI T X. Application of flocculation process in dressing wastewater from antimony mine[J]. Advanced Materials Research, 2012, 518−523: 2370 − 2375. doi: 10.4028/www.scientific.net/AMR.518-523.2370 [6] AKBAL F, CAMC S. Copper, chromium and nickel removal from metal plating wastewater by electrocoagulation[J]. Desalination, 2011, 269(1-3): 214 − 222. doi: 10.1016/j.desal.2010.11.001 [7] BOROSKI M, RODRIGUES A C, Garcia J C, et al. Combined electrocoagulation and TiO2 photoassisted treatment applied to wastewater effluents from pharmaceutical and cosmetic industries[J]. Journal of Hazardous Materials, 2009, 162(1): 448 − 454. doi: 10.1016/j.jhazmat.2008.05.062 [8] TCHAMANGO S, NANSEU-NJIKI C P, NGAMENI E, et al. Treatment of dairy effluents by electrocoagulation using aluminium electrodes[J]. Science of the Total Environment, 2010, 408(4): 947 − 952. doi: 10.1016/j.scitotenv.2009.10.026 [9] BAYRAMOGLU M, EYVAZ M, KOBYA M. Treatment of the textile wastewater by electrocoagulation: Economical evaluation[J]. Chemical Engineering Journal, 2007, 128(2-3): 155 − 161. doi: 10.1016/j.cej.2006.10.008 [10] 徐丰果, 罗建中, 凌定勋. 废水化学除磷的现状与进展[J]. 工业水处理, 2003, 23(5): 18 − 20. doi: 10.3969/j.issn.1005-829X.2003.05.006 [11] 张小霓, 廖冬梅, 陈明静. 城市中水回用于循环冷却水的氨氮去除试验研究[J]. 电力环境保护, 2006(6): 50 − 53. [12] 冯秀娟, 葛天源. 无机混凝剂在印染废水处理中的研究进展[J]. 中国资源综合利用, 2005(10): 6 − 9. doi: 10.3969/j.issn.1008-9500.2005.10.004 [13] 褚衍洋, 杨波, 李玲玲, 等. 氨氮在两种电解质体系下的电化学氧化[J]. 高校化学工程学报, 2010, 24(1): 71 − 75. doi: 10.3969/j.issn.1003-9015.2010.01.013 [14] KIM K W, KIM Y J, KIM I T, et al. The electrolytic decomposition mechanism of ammonia to nitrogen at an IrO2 anode[J]. Electrochimica Acta, 2005, 50(22): 4356 − 4364. doi: 10.1016/j.electacta.2005.01.046 [15] İRDEMEZ S, DEMIRCIOGLU N, YĨLDĨZ Y, et al. The effects of current density and phosphate concentration on phosphate removal from wastewater by electrocoagulation using aluminum and iron plate electrodes[J]. Separation and Purification Technology, 2006, 52: 218 − 223. doi: 10.1016/j.seppur.2006.04.008 [16] 李再兴, 剧盼盼, 左剑恶, 等. 微电解/Fenton法深度处理土霉素废水的研究[J]. 中国给水排水, 2012, 28(5): 74 − 77. doi: 10.3969/j.issn.1000-4602.2012.05.021 [17] ZHANG M, ZHENG K, JIN J J, et al. Effects of Fe(II)/P ratio and pH on phosphorus removal by ferrous salt and approach to mechanisms[J]. Separation and Purification Technology, 2013, 118: 801 − 805. doi: 10.1016/j.seppur.2013.08.034