Removal of Organic Pollutants from Reverse Osmosis Concentrate by Electro-Fenton Process

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1 Advanced Materials Research Online: ISSN: , Vols , pp doi:10.28/ Trans Tech Publications, Switzerland Removal of Organic Pollutants from Reverse Osmosis Concentrate by Electro-Fenton Process Huiling Du 1, a *, Baoyuan Pan 1,b, Jing Li 1,c 1 Heilongjiang Institute of Environment Science, Harbin , China a huiling_du@sina.com, b @qq.com, c @qq.com Keywords: pulse electromagnetic field, Fenton reagent, reverse osmosis concentrated, COD Abstract. The RO concentrate containing non-degradation organic pollutants was treated by electro-fenton process. The high voltage pulse generator was used as discharge power. The effects of pulsed electric field parameters, aeration rate and ph on COD removal rate was investigated. The results indicate that the COD removal rate is up to 80.71% when pulsed voltage, pulsed frequency, treatment time, aeration rate and ph are V, 5 Hz, 2 s, 1.0 m 3 /h and 10, respectively. Introduction Membrane technology has been more widely applied to advanced wastewater treatment in industrial and municipal sewage plant recently. However, there is a large amount of concentrate containing non-degradation organic compounds in the process of wastewater treatment by reverse osmosis(ro) membrane. How to removal the non-degradation organic pollutants from RO concentrate is a new challenge and it is paid more attentions accordingly [1]. Most Chinese factories add freshwater or recycled water into reverse osmosis concentrate in order to meet the discharge standards, which will waste water resources and pollute water ecosystem. At present physical-chemical process [2,3] and advanced oxidation process(aop) [2,4-7] are utilized to remove organic pollutants from RO concentrate. Electro-Fenton process has several advantages as on kind of AOPs: the mechanism of automatic generation, high efficiency of OH, more ways for organic compounds degradation, more environmentally friendly and etc [8-11]. In this study, Electro-Fenton is used to treat RO concentrate discharged from the process of refinery sewage advanced treatment. The non-degradation organic compounds are effectively removed from RO concentrate by this simple method. In addition, the research results have important implications for refinery plants to meet the discharge standards and water conservation. Experimental Wastewater samples. The RO concentrate samples were taken from advanced wastewater treatment process of a refinery in Northeast China. Main chemicals. K 2 Cr 2 O 7 (Tianjin Shengmiao Fine Chemical Co., Ltd.), K 2 TiO(C 2 O 4 ) 2 (Tianjin Fine Chemical Institute) and (NH 4 ) 2 FeSO 4 6 O (Tianjin Fengchuan Chemical Reagent Co.) were all analytical grade and used as raw materials without further Purification. Treatment of RO concentrate by Electro-Fenton process ml wastewater sample was added into reaction tank (see Fig.1). A pulsed electric field (PEF) was used to treat the wastewater samples. The samples were filtered after a certain reaction time, then the COD and of the filtered samples were analyzed. Analysis method. The organic compounds of RO concentrate samples were analyzed by GCMS-QP2010 Plus. COD was determined with Dichromate method (GB ) and was measured with Titanium oxalate colorimetry [12]. All rights reserved. No part of s of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-18/09/16,22:24:33)

2 Advanced Materials Research Vols Fig.1. The experimental scheme (1.graphite cathode;2.iron anode;3.reaction tank;4.aerator;5.pef generator) Results and Discussions RO concentrate quality analysis. The temperature, ph, turbidity and COD of RO concentrate samples are K, 7.1, 1.8NTU and mg/l respectively. The organic compounds of RO concentrate samples are shown in table 1. Table 1 Organic component of reverse osmosis membrane concentrate number component [mg/l] number component [mg/l] 1 Dodecane Heptacosane Tridecane Bis(2-chloro ethyl) ether Tetradecand Bis(2-chloro-1-methyl ethyl) ether - 4 Pentadecane Dimethyl phthalate Hexadecane Diethyl phthalate Heptdecane Chloro-4-phenoxybenzene Octadecane N-Nitrosodiphenylamine - 8 Nonadecane Bromophenyl phenyl ether Eicosane Di-n-butylphthalate Heneicosane Butyl Benzyl Phthalate Docosane Bis(2-ethylhexyl) phthalate Tricosane Di-n-octylo-phthalate Tetracosane Ethyl hexanol Pentacosane (1-methyl dodecyl)-benzene Hexacosane (1-hexyl heptyl)-benzene Seen from table 1, the primary non-degradation organic compounds in the wastewater samples are benzene, ether, long-chain alkane, etc. Based on the principle of Fenton reaction, a lot of OH oxidant with high activity are produced in the process of Fenton reaction, the non-degradation organic compounds can be oxidized by OH accordingly.

3 2296 Advances in Environmental Technologies III Effects of pulsed voltage. The effects of pulsed voltage on COD removal rate and were investigated under the conditions that the initial ph of wastewater, aeration rate, pulsed frequnency and treatment time were 2, 0.8 m 3 /h, 5 Hz and 60 s respectively. The experimental results are shown in Fig H2 / mg/l pulsed voltage / V 0.02 Fig.2. Effects of pulsed voltage on COD removal rate and As can be seen from Fig.2, with rise in pulsed voltage, an increase in COD removal rate and occurs. This can be attributed to an increase in energy in reaction system with increase in pulsed voltage and thereby increases, Fe 2+ and OH. The higher the pulsed voltage is, the better the treatment effects get. Under the condition of V pulsed voltage, COD removal rate and is up to 42.70% and mg/l respectively. As a result, the optimum pulsed voltage is V. Effects of pulsed frequency. The effects of pulsed frequency on COD removal rate and were investigated under the conditions that the initial ph of wastewater, aeration rate, pulsed voltage and treatment time were 2, 0.8 m 3 /h, 3000 V and 60 s respectively. The experimental results are presented in Fig H2 / mg/l pulsed frequency / Hz Fig.3. Effects of pulsed frequency on COD removal rate and It is evident from Fig.3 that with rise in pulsed frequency, an increase in COD removal rate and occurs. An increase of pulsed frequency is advantageous for Fe 2+ to become Fe 3+, which makes the oxidant in the reaction system decrease. The organic pollutants can not be oxidized by enough oxidants accordingly. In this study, the optimum pulsed frequency is 5 Hz.

4 Advanced Materials Research Vols Effects of treatment time. The effects of treatment time on COD removal rate and were investigated under the conditions that the initial ph of wastewater, aeration rate, pulsed frequency and pulsed voltage were 2, 0.8 m 3 /h, 5 Hz and 3000 V respectively. Fig.4 summarises the experimental results H2 / mg/l pulsed treatment time / s Fig.4. Effects of treatment time on COD removal rate and The COD removal rate and increases (Fig.4) from 42.7 % and mg/l (60 s) to 47.56% and mg/l (2 s), and we get a more satisfied result with the increase of treatment time. An increase of treatment time results in an increase of and Fe 2+, at a constant pulsed voltage and frequency. In this study, the optimum treatment time is 2 s. Effects of aeration rate. The effects of aeration rate on COD removal rate and were investigated under the conditions that the initial ph of wastewater, pulsed voltage, pulsed frequnency and treatment time were 2, V, 5 Hz and 2 s respectively. Fig.5 shows the COD removal rate and at different aeration rate H2 / mg/l aeration rate / m 3 /h Fig.5. Effects of aeration rate on COD removal rate and As can be seen from Fig.5, with rise in aeration rate, an increase in COD removal rate and occurs. This can be attributed to an increase in H2O2 in reaction system with increase in aeration rate. The V H2O2 /V Fe2+ is high result from relatively few Fe 2+. However, the chemical reaction between excessive and OH is happened, and O and are formed [13]. The non-degradation organic pollutants can also be oxidized by and therefor the COD removal rate is still increasing. In this study, the optimum aeration rate is 1.0 m 3 /h.

5 2298 Advances in Environmental Technologies III Effects of initial ph of wastewater. The effects of initial ph of wastewater on COD removal rate and were investigated under the conditions that the pulsed voltage, pulsed frequnency, treatment time and aeration rate were V, 5 Hz, 2 s and 1.0 m 3 /h respectively. The experimental results are depicted in Fig H2 / mg/l ph Fig.6. Effects of ph on COD removal rate and It can be observed from Fig.6 that high can be obtained at low ph (ph<4) and an increase in ph gives rise to a increase in COD removal rate. Low ph favours the generation of and advantages the oxidation reactions between OH and organic compounds. The COD removal rate increases from % (ph=4) to % (ph=10) mainly due to the flocculation at high ph. Conclusions In summary, non-degradation organic compounds can be effectively removed from RO concentrate by electro-fenton process. We have got the proper conditions of RO concentrate containing non-degradation organic pollutants treatment in the process of electro-fenton reaction. The results show that the COD removal rate is up to % at optimum parameters. The removal of non-degradation organic pollutants from RO concentrate is the result of a combination of oxidation, flocculation and pulsed electric field. However, the effects of flocculation and pulsed electric field need to be further researched. Acknowledgements This work was financially supported by the Major Science and Technology Program for Water Pollution Control and Treatment (2012ZX ). References [1] Guo Ruili, Shi Yu, Wang Zengzhang, Research development on organics removal in reverse osmosis concentrates, Technology of Water Treatment. 39 (2013) 1-4. [2] Emmanuel Dialynas, Dionissios Mantzavinos, Evan Diamadopoulos, Advanced treatment of the reverse osmosis concentrate produced during reclamation of municipal wastewater, Water Research. 42 (2008) [3] Zhang Yelai, Zhang Yuxian, He Hui, Wang Lianguo, Study on treatment technology of RO concentrated water reuse, China Water and Wastewater. 26 (2010)

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