Advanced oxidation processes for the degradation of p‐hydroxybenzoic acid 2: Photo‐assisted Fenton oxidation

Oxidation of p‐hydroxybenzoic acid in aqueous solution by the photo‐assisted Fenton reaction (Fe²⁺ + H₂O₂ + UV) has been studied. The effects of ferrous ion concentration (0.05, 0.14 and 0.29 mmol dm^?3), temperature (10, 20, 30 and 40 °C), and initial hydrogen peroxide concentration (0.7, 1.4, 2.2 and 2.9 mmol dm^?3) on the p‐hydroxybenzoic acid conversion were established. Experimental results indicate that the kinetics of this oxidation process fits pseudo‐first‐order kinetics well. The overall kinetic rate constant was split into two components: direct oxidation by UV radiation (photolysis) and oxidation by free radicals (mainly OH·) generated in the system. The importance of these two reaction paths for each specific value of ferrous ion concentration, temperature and initial hydrogen peroxide concentration was evaluated. A semi‐empirical expression is proposed for the overall reaction rate which takes into account both oxidation pathways and is a function of operating variables. © 2001 Society of Chemical Industry     

Chemical treatment of cork‐processing wastewaters for potential reuse

The chemical treatment of cork‐processing wastewater by ozonation, alone and in combination with hydrogen peroxide and UV radiation was investigated. A reduction of the chemical oxygen demand (COD) ranging from 42% to 76% was obtained during ozonation after 3 h of reaction, depending on the experimental conditions. The additional presence of hydrogen peroxide and UV radiation enhanced the efficiency of the ozonation treatment due to the contribution of the OH radicals formed in the decomposition of ozone. Thus, final reductions of the COD higher than 90% and a complete elimination of phenolic compounds and absorbance at 254 nm were achieved in both Advanced Oxidation Processes (AOPs), O₃/H₂O₂ and O₃/UV. Therefore the effluent resulting from the ozonation treatments can be reused in the cork‐processing industry. In a second step, the chemical treatment was conducted by means of UV radiation alone and by the action of hydroxyl radicals, which were generated by the following AOPs: UV/H₂O₂, Fenton's reagent, and photo‐Fenton system. The single photochemical process resulted in 9% of the organic matter present being removed, while the AOPs significantly enhanced this reduction with values in the range 20–75%. Kinetic studies for both groups of treatments were performed, and apparent kinetic rate constants were evaluated. In the ozone‐based experiments, the rate constants ranged from 1846 to 10922 dm³ mol^?1 O₃ h^?1, depending on the operating conditions. In the oxidation experiments using oxidants other than ozone, the rate constants varied between 0.06 and 1.19 h^?1. Copyright © 2004 Society of Chemical Industry     

Decolourisation of aqueous dyes by sequential oxidation treatment with ozone and Fenton's reagent

Combined oxidation with ozone and Fenton's reagent (‘Fentozone’ process) for decolourisation of aqueous dyes was studied and compared with traditional Fenton's reagent. Although the ‘Fentozone’ process was found to be effective at a wide range of pH values, the maximum colour removal was achieved at pH 4. The effect of pre‐ozonation on colour removal efficiency of aqueous dyestuffs in the subsequent treatment with Fenton's reagent was investigated. The reaction kinetics using water‐soluble acid and reactive dyes were also studied. Our experimental results show that pre‐ozonation can considerably accelerate decomposition of dyestuffs in the subsequent treatment with Fenton's reagent. Different concentrations of ferrous sulfate were used to investigate their influences on the removal of colour. The rate of reaction increased with increasing doses of ferrous sulfate. © 2002 Society of Chemical Industry     

Fenton试剂深度处理胃必治制药废水

胃必治制药废水COD值高且负荷变化大,pH值低,是一种难处理的有机废水。经常规工艺处理后,出水有时仍难达标。采用Fenton试剂对出水进行了氧化降解研究,通过测定废水的COD、UV254值变化以评价氧化的效果,考察了常压下Fenton试剂配比、投加量、氧化时间、温度等因素对制药废水处理效果的影响,初步发现了其氧化规律。在单因素试验的基础上采用正交试验方案,确定最佳工艺条件为:浓度为1mol/L的FeSO4与质量分数为3%的H2O2的体积比为1:2、投加量为150mL/L、反应时间为90min、反应温度为60℃、pH值为3。COD的去除率达到89.50%,出水COD的质量浓度降到了66mg/L以下,达到国家排放标准要求。     

An oxidative desulfurization method using ultrasound/Fenton's reagent for obtaining low and/or ultra-low sulfur diesel fuel

The total development trend in the world is towards continuously lower of sulfur content as a quality standard of diesel fuels. Integrating of an oxidative desulfurization unit with a conventional hydrotreating unit can bring benefits to producing low and/or ultra-low sulfur diesel fuels. Using the hydrotreated Middle East diesel fuel as a feedstock, four processes of the oxidative desulfurization have been studied: a hydrogen peroxide–acetic acid system and a Fenton's reagent system both without/with ultrasound. Results showed that the oxidative desulfurization reaction mechanics fitted apparent first-order kinetics. The addition of Fenton's reagent could enhance the oxidative desulfurization efficiency for diesel fuels and sono-oxidation treatment in combination with Fenton's reagent shows a good synergistic effect. Under our best operating condition for the oxidative desulfurization: temperature 313 K, ultrasonic power 200 W, ultrasonic frequency 28 kHz, Fe²⁺/H₂O₂ 0.05 mol/mol, pH 2.10 in aqueous phase and reaction time 15 min, the sulfur content in the diesel fuels was decreased from 568.75 μg/g to 9.50 μg/g.     

Simultaneous degradation of 2,4,6-trinitrophenyl-N-methylnitramine (Tetryl) and hexahydro-1,3,5-trinitro-1,3,5 triazine (RDX) in polluted wastewater using some advanced oxidation processes

Here we report the study on the utilization of several advanced oxidation processes such as electro-oxidation and Fenton process in simultaneous treatment of two nitramine explosives: 2,4,6-trinitrophenyl-N-metylnitramine (Tetryl) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The preliminary tests indicated that the electrolytic method using a TiO₂/IrO₂/RuO₂-coated electrode could rapidly degrade Tetryl but not RDX. While the addition of certain amount of H₂O₂ induced an increase of Tetryl degradation yield but had insignificant effect on RDX decomposition, the use of Fenton's reagent showed an enhanced efficiency in degradation of both nitramines. It can be concluded that among tested processes, Fenton process is the most effective for treatment of nitramine-containing wastewaters.     

Role of 1,10‐phenanthroline and ortho phosphoric acid on graft polymerization of vinyl monomers from poly (vinyl alcohol) in the presence of Fenton's reagent

The effect and role of 1,10‐phenanthroline (o‐phen) and ortho phosphoric acid on graft polymerization of vinyl monomers from poly (vinyl alcohol) (PVA) in the presence of Fenton's reagent have been studied. Reaction conditions were optimized. Fourier transform infrared (FT‐IR) spectra were used for confirmation of grafting. A probable mechanism of grafting to elucidate the role of phenanthroline and phosphoric has been suggested. Thermal properties of the grafted polymer were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2335–2339, 2005     

Degradation of C.I. Acid Red 88 aqueous solution by combination of Fenton's reagent and ultrasound irradiation

BACKGROUND: Pollution caused by industrial wastewater has become a common problem for many countries. In particular, dye pollutions from industrial effluents disturb human health and ecological equilibrium. The discharge of highly colored synthetic dye effluents is aesthetically displeasing and can damage the receiving water body by impeding penetration of light. Azo dyes can be reduced to more hazardous intermediates on anaerobic conditions. Therefore, an effective and economic treatment of effluents containing a diversity of textile dyes has become a necessity for clean production technology for textile industries. Herein we wish to report the degradation of Acid Red 88 by the combination of Fenton's reagent and ultrasound irradiation. RESULTS: The results show that the combination of ultrasonic irradiation and Fenton's reagent is effective for the degradation of Acid Red 88 aqueous solution. Furthermore, it can achieve better results than either Fenton's reagent or ultrasound alone. The optimum conditions for the degradation of Acid Red 88 aqueous solution were 1.96 mmol L^?1 H₂O₂, 0.108 mmol L^?1 Fe²⁺, pH 3.0, and ultrasonic irradiation frequency of 40 kHz. A degradation efficiency of 98.6% was achieved within 135 min. CONCLUSION: We have provided an efficient and convenient procedure for the degradation of Acid Red 88 aqueous solution. In the present procedure, the azo linkage of Acid Red 88 is broken and some carbonyl compounds are formed, but the complete mineralization of dye cannot be achieved. Copyright © 2008 Society of Chemical Industry     

Multi‐phase electro‐chemical catalytic oxidation of wastewater

The removal of organic pollutants from synthetic wash wastewater by a combined multi‐phase electro‐catalytic oxidation method was evaluated using porous graphite as anode and cathode, and CuO–Co₂O₃–PO₄^3? modified kaolin as catalyst. The synergic effect on COD removal was studied when integrating the electro‐chemical reactor with the effective modified kaolin in a single undivided cell; the results showed that higher COD removal efficiency was obtained than those obtained using the individual processes. Under optimal conditions of pH 3, 30 mA cm^?2 current density, very effective reduction of organic pollutants was achieved with this combined electro‐chemical method. High removal efficiency (90%) of the chemical oxygen demand (COD) was obtained in 60 min in the treatment of simulated wash wastewater (anionic surfactant, sodium dodecyl benzene sulfonate [DBS]). This method was also applied to treat wastewater form paper‐making and resulted in a COD reduction of 84%. Based on the investigation, a possible mechanism of this combined electro‐chemical process was proposed. The pollutants in wastewater could be decreased by the high reactive OH? that were produced via the decomposition of electro‐generated H₂O₂ activated by the synergic effect of electro‐field and catalyst. The results indicate that the multi‐phase catalytic electro‐chemical oxidation process is a promising technique for wastewater treatment. Copyright © 2006 Society of Chemical Industry     

Fenton试剂-混凝沉降法处理丁苯橡胶生产废水中试

采用Fenton试剂-混凝沉降法,对某石化公司的丁苯橡胶废水进行了为期3个月的中试处理研究。结果表明,在进水的化学需氧量(COD)为600~1 100 mg/L、生化需氧量(BOD5)为140~250 mg/L、悬浮物(SS)为0~400 mg/L、pH值为4~11的情况下,经过Fenton试剂-混凝沉降法处理,系统出水COD小于350 mg/L,BOD5小于150 mg/L,SS小于50 mg/L、pH值为6~9,出水水质满足GB 8978—1996三级标准的排放要求,出水的BOD5/COD值由0.15~0.28提高至0.33~0.45,可生化性大幅提高。     

NaClO氧化去除高盐废水中氨氮的影响因素及其动力学研究

采用NaClO氧化降解高盐废水中的氨氮,对其影响因素及动力学进行研究。结果表明:NaClO对氨氮的氧化降解过程符合伪一级反应动力学模型,影响其降解效果的因素有NaClO的投加量、氨氮的初始浓度、盐分、温度等。当NaClO投加量为0.6%时,反应速率常数高达0.015 75 min~(-1)。氨氮初始浓度越大,氧化反应效果越差,且初始质量浓度不超过45 mg/L时,随着初始浓度的增加,其对氧化反应速率常数的影响增大。低浓度盐分对氨氮氧化基本无影响,但超过2.0%时,随着盐分的增加,其对氨氮氧化效果的抑制作用增强,反应速率常数明显降低。提高反应温度,有利于氨氮的氧化降解,当温度从10℃增加至35℃的过程中,反应速率常数从0.001 88 min~(-1)增加至0.010 43 min~(-1)。     

浆态光催化反应器有机模拟废水光催化氧化特性与动力学

采用循环式浆态光催化反应器对苯甲酰胺模拟废水光催化氧化特性和动力学进行了研究,系统地考察了操作条件对模拟污染物光催化降解的影响,并与搅拌式和鼓泡床式浆态光催化反应器中苯甲酰胺的降解效果进行对比.结果表明,循环式浆态光催化反应器中光催化剂的用量、污染物的初始浓度和初始pH值对模拟污染物光催化降解性能的影响存在适宜值;体系中H₂PO^-₄、Cl^-、Cu²⁺、Al³⁺对其光催化降解过程有明显的抑制作用.与传统的搅拌式和鼓泡床式浆态光催化反应器相比,循环式浆态光催化反应器中催化剂和废水的混合效果较好,光利用率高,较大程度上减少催化剂的用量和提高废水处理能力.同时,对不同催化剂的用量和污染物初始浓度下的光催化氧化反应动力学研究表明,此过程符合拟一级动力学,催化剂表面反应速率常数k₀和催化剂吸附平衡常数K_TiO2分别为0.0279 min^-1和17.99 L•g^-1.     

Oxidation of phenol in a bioremediation medium using chlorine dioxide

BACKGROUND: High concentrations of phenol in wastewater are difficult to remove by purely biological methods. Chemical oxidation is one way to treat high concentrations of phenol but complete oxidation will make the treatment process uneconomical. For the purpose of integrating chemical and biological treatment, the oxidation of phenol using chlorine dioxide was investigated in a medium suitable for bioremediation. The effects of chlorine dioxide concentration (500 to 2000 mg L^?1), temperature (10 to 40 °C) and pH (3 to 7) on the oxidation of 2000 mg L^?1 of phenol were determined. RESULTS: Chlorine dioxide concentration was found to be the dominant parameter for the removal of phenol in the nutrient rich medium. The optimal concentration of chlorine dioxide to completely oxidize 2000 mg L^?1 of phenol was 2000 mg L^?1. Compared with Fenton's reagent, half as much chlorine dioxide was needed to oxidize 2000 mg L^?1 phenol. The reaction of chlorine dioxide with phenol was very fast and reached equilibrium within 10 min. The main oxidation products were identified as 1,4‐benzoquinone and 2‐chloro‐1,4‐benzoquinone. CONCLUSION: Compared with Fenton's reagent, chlorine dioxide is a superior oxidant for removal of phenol from both pure water and bioremediation medium. Copyright © 2010 Society of Chemical Industry     

Advances in the Electro‐Fenton Process for Remediation of Recalcitrant Organic Compounds

The electro‐Fenton (EF) process is a promising method combining electrochemical reactions and Fenton's reagent. In this hybrid process, the electrical current induces the in situ generation of H₂O₂ via reduction of oxygen, and the catalytic reaction is propagated by Fe²⁺ regeneration, which can take place by reduction of Fe³⁺ with H₂O₂, hydroperoxyl radical, organic radical intermediates, or directly at the cathode. Recent advances in the EF process are discussed and several key variables analyzed, including electrode material, initial pH, and Fenton's reagents, in order to extend the applicability of this technology.     

US/Fenton氧化-混凝法对焦化废水的预处理研究

采用US/Fenton氧化-混凝法对高浓度焦化废水进行预处理.考察了对处理效果的影响因素,确定了最适工艺条件.结果表明,在超声波功率500W,H2O2投加质量浓度为6.0 g/L,Fe2 为400 mg/L,pH 3,Al2(SO4)3、PAM投加量分别为480、4.0 mg/L的条件下,COD、NH3-N、CN-和色度的去除率分别达75.1%、53.4%、62.8%和83.1%,废水的COD由处理前的4 799mg/L降至1 195 mg/L,BOD/COD由0.196提高到0.373,出水可生化性良好.US/Fenton氧化-混凝法可作为高浓度焦化废水的一种有效的预处理方法.     

Fenton氧化降解焦化废水的影响特性及动力学模型

为研究Fenton试剂氧化降解焦化废水的影响特性及动力学机理,采用小试烧杯实验考察初始COD、H2O2投加量、Fe2+投加量和反应温度等因素对处理效果的影响。结果表明,原水COD为260 mg/L、H2O2投加量为666mg/L、Fe2+投加量为200 mg/L、温度为298 K时,COD去除率达到89.53%;反应初始阶段COD氧化降解的表观反应动力学模型与实验数据得到较好的拟合,因此该动力学模型能较好地预测Fenton试剂对焦化废水的氧化降解情况;反应总级数为2.001 7,其中H2O2的反应分级数(0.568 5)高于Fe2+的反应分级数(0.494 0),说明Fenton氧化降解COD过程中H2O2浓度的影响比Fe2+的大;较低的反应活化能说明反应较易进行。     

Anaerobic co‐digestion of potato processing wastewater with pig slurry and abattoir wastewater

BACKGROUND: Small‐scale experimental investigations were carried out on the anaerobic digestion of potato processing wastewater and its co‐digestion with pig slurry and/or abattoir wastewater. A simple and rapid procedure was used to determine the suitability of these wastes for digestion. RESULTS: During the initial 5‐day acclimation phase, the seed (digested brewery waste) was replaced by the test waste before allowing the tests to incubate without further addition, where methanogenesis was measured. Although potato processing wastewater has low pH, with high fat content treatment via anaerobic digestion was still feasible in spite of low methane production. Co‐digestion with pig slurry and abattoir wastewater was therefore investigated to enhance the process. Pig slurry improved the process, which, when co‐digested with potato processing wastewater in equal ratio achieved 72% volatile solids removal, 35 mL average daily biogas production and 32% maximum methane content in 22 days (following the acclimation period). Co‐digestion with abattoir wastewater did not improve the digestion process due to poor buffering and low pH value. CONCLUSION: Anaerobic co‐digestion may be a feasible treatment option for industrial bio‐wastes and livestock wastes produced in Cyprus and indeed in similar other countries of comparable market size and activities. Copyright © 2008 Society of Chemical Industry     

Electric‐oxidation kinetics of molybdenite concentrate in acidic NaCl solution

The electric‐oxidation kinetics of molybdenite concentrate in NaCl electrolyte was investigated in this study. The effects of liquid‐to‐solid ratio, stirring speed, and concentration of NaCl on the dissolution rate were determined. It was found that the dissolution rate increases with increase in liquid‐to‐solid ratio, stirring speed, and concentration of NaCl. A shrinking particle model is presented to describe the dissolution and to analyse the data. The apparent activation energy of this dissolution process was found to be 8.2 kJ/mol; it was established that the leaching process is mainly controlled by diffusion, and the kinetics formula of this research system can be expressed as: .