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Fu Q.,South China University of Technology | Hu Y.,South China University of Technology | Hu Y.,The Key Laboratory Of Pollution Control And Ecosystem Restoration In Industry Clusters Of Min Of Educ
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2013

Congo red wastewater was treated by aluminum-carbon microelectrolysis, and key factors affecting the decolorization and COD removal were investigated by batch and orthogonal experiments. Decolorization products were determined by UV spectrum, ion chromatography and LC-MS. The results showed that the decolorization and COD removal of Congo red increased with the dosage of aluminum powder in the range of 8~24 g·L-1, and the appropriate dosages were determined in the range of 16~24 g·L-1. The decolorization and COD removal of Congo red first increased and then decreased with increase of the Al/C mass ratio and the appropriate ratio was determined as 1:3~1:1. Initial pH was the key factor affecting the treatment process. The decolorization of Congo red was significantly enhanced with increasing pH in the range of 10~12.5. An increase in DO in the range of 1.25~7.59 mg·L-1 led to decreased decolorization and COD removal of Congo red. Under the optimum conditions (aluminum powder 24 g·L-1, Al/C mass ratio 1:2, pH=12 and reaction time 90 min), the decoloration and COD removal of Congo red rose up to 90.4% and 78.6%, respectively. The decolorization pathways of Congo red are proposed as follows: the azo linkage within Congo red molecule is firstly broken down by [H] and two intermediates, 3, 4-diaminonaphthalene-1-sulfonate and 4-amino-3-((4'-amino-[1, 1'-biphenyl]--4-yl) diazenyl) naphthalene-1-sulfonate, are formed; the latter is further transformed to 3, 4-diaminonaphthalene-1-sulfonate and benzidine, 4-amino-3-((4'-amino-[1, 1'-biphenyl]-4-yl) diazenyl)-1-sulfonate and 2-((4'-amino-[1, 1'-biphenyl]-4-yl) diazenyl) naphthalen-1-amine are formed due to ring opening of naphthalene and breakdown of C-S linkage. Congo red cannot be mineralized by aluminum-carbon microelectrolysis. Source


Wu Y.,South China University of Technology | Wu Y.,The Key Laboratory Of Pollution Control And Ecosystem Restoration In Industry Clusters Of Min Of Educ | Luo H.,South China University of Technology | Luo H.,The Key Laboratory Of Pollution Control And Ecosystem Restoration In Industry Clusters Of Min Of Educ | Wang H.,Hunan University
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2014

In this study, cetyltrimethylammonium bromide (CTAB)-modified sawdust was applied to remove conge red (CR) from aqueous solutions. The characteristics of sawdust and modified sawdust were characterized by Fourier transform infrared spectrum (FTIR) and scanning electron microscopy (SEM). The effect of factors, including pH, contact time, temperature, dosage, and salt concentration, on the adsorption properties of CR by modified sawdust were investigated. The results revealed that the addition of CTAB in preparation can significantly increase the adsorption capacity of CR. The maximum adsorption capacity of CR on sawdust and modified sawdust inferred from the Langmuir model was 30.30 and 111.36 mg·g-1 at 328 K, respectively. The adsorption processes were rapid within the first 20 min and reached equilibrium in about 120 min. The adsorption kinetics fitted well with pseudo-second-order model. The optimal reaction temperature was 328 K, the optimum adsorbent dosage was 0.09 g, the initial pH value of the solution had significant impact on the amount of adsorption, and the adsorption capacity of the modified sawdust increased with increasing salt concentration. Adsorption isotherm fitted better with the Langmuir model and the adsorption was an endothermic process. Source


Li W.,South China University of Technology | Hong T.,South China University of Technology | Hu Y.,South China University of Technology | Hu Y.,The Key Laboratory Of Pollution Control And Ecosystem Restoration In Industry Clusters Of Min Of Educ | And 3 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2014

The vacuum ultraviolet (VUV) and high-frequency ultrasound (US) were combined to treat tail water from printing and dyeing wastewater. In order to determine the best power of the VUV-US combined system, the effects of the power of VUV, US and VUV-US on the degradation of the printing and dyeing wastewater were compared in terms of TOC and UV254. The influences of reaction time, reaction temperature and initial pH value on the degradation performance of the VUV-US combined system were investigated through batch experiments, and the degradation kinetics of TOC and UV254 were explained. The removal mechanism of residual refractory organics by the VUV-US combined system was revealed by analyzing the degradation products. The results showed that the optimum power was 16 W for VUV and 100 W for US, respectively, and there is synergistic effect between VUV and US. 27.68% of TOC and 93.03% of UV254 can be removed within 120 minutes by the VUV-US combined system. The reaction temperature and initial pH value had insignificant effects on the performance of the VUV-US combined system. The degradation kinetics of TOC and UV254 by the VUV-US combined system showed a good compliance with the apparent second-order kinetic model and the apparent first-order kinetic model, respectively. VUV-US combined treatment is a synergistic process including VUV direct photolysis, thermal cracking in the ultrasonic cavitation bubbles and hydroxyl radicals oxidation. Hydroxyl radicals oxidation was mainly responsible for the degradation of refractory benzene compounds in the printing and dyeing wastewater. Source

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