Pre-oxidation and coagulation of textile wastewater by the Fenton process

This paper evaluates the Fenton process, involving oxidation and coagulation, for the removal of color and chemical oxygen demand (COD) from synthetic textile wastewater containing polyvinyl alcohol and a reactive dyestuff, R94H. The experimental variables studied include dosages of iron salts and hydrogen peroxide, oxidation time, mixing speed and organic content. The results show that color was removed mainly by Fenton oxidation. The color removal reached a maximum of 90% at a reaction time of 5 min under low dosages of H2O2 and Fe2+. In contrast, the COD was removed primarily by Fenton coagulation, rather than by Fenton oxidation. The ratio of removal efficiency between Fenton process and ferric coagulation was 5.6 for color removal and 1.2 for COD removal. It is concluded that Fenton process for the treatment of textile wastewater favors the removal of color rather than COD.     

The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol

The efficiency of different Fenton-related oxidative processes such as Fenton, solar-Fenton and UV-Fenton were examined using phenol as a model compound in simulated and industrial wastewater. A batch study was conducted to optimize parameters like pH, hydrogen peroxide concentration and ferrous ion concentration governing the Fenton process. At optimum conditions, different Fenton-related processes were compared for the degradation of phenol. Increased degradation and mineralisation efficiency were observed in photo-Fenton processes as compared to conventional Fenton process. The maximum mineralising efficiency for phenol with Fenton, solar and UV-Fenton processes were 41%, 96% and 97% respectively. In Fenton process, carboxylic acids like acetic acid and oxalic acid were formed as end products during the degradation of phenol while in photo-Fenton processes, both these ions were identified during the early stages of phenol degradation and were oxidized almost completely at 120 min of the reaction time. In photo-Fenton processes (solar and UV light) complete degradation were observed with 0.4 mM of Fe2+ catalyst as compared to 0.8 mM of Fe2+ in conventional Fenton process. In Fenton and solar-Fenton processes, an iron reusability study was performed to minimize the amount of iron used in treatment process. The efficacy of Fenton and solar-Fenton processes was applied to effluent from phenol resin-manufacturing unit for the removal and mineralisation of phenol.     

Inhibition of BPA degradation by serum as a hydroxyl radical scavenger and an Fe trapping agent in Fenton process

Identification of reactive oxygen species (ROS) that contribute to bisphenol-A (BPA) degradation and monitoring of BPA at various concentrations in human serum under Fenton reaction conditions were carried out using electron spin resonance (ESR) spectrophotometry and high performance liquid chromatography with electrochemical detection (HPLC-ECD). BPA recovery decreased with increasing Fe concentration and time, both with a Fenton reaction using Fe(II), and with a Fenton-like reaction using Fe(III). In these reactions, BPA dose-dependently decreased the intensity of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-*OH, up to 1 microg/ml BPA, and no change in DMPO-O(2)(?-) intensity was observed. The decrease in BPA recovery was inhibited strongly by addition of serum under Fenton-like reaction conditions, and there was a negative correlation between turbidity and BPA recovery. To clarify the mechanism by which serum inhibits BPA degradation, the relationship between BPA recovery and sample turbidity, and characteristics of the precipitates were investigated using spectrophotometry and X-ray analysis. The precipitate formed in the serum-containing sample consisted of C, S, O, P and Fe. BPA degradation was also inhibited under Fenton-like reaction conditions in phosphate buffered saline (PBS), and a precipitate consisting of O, P, and Fe appeared. Precipitates also appeared in authentic albumin and gamma-globulin when sulfate was added with Fenton reagents. After precipitate removal, both Fe and protein concentrations in the supernatant of the protein solutions with sulfate decreased with increasing Fe addition. We demonstrate here that hydroxyl radical generation from Fenton or Fenton-like reactions can degrade BPA, and that serum strongly inhibits BPA degradation, not only by competing with BPA for hydroxyl radicals, but also by trapping Fe with oxidative components present in the serum.     

Selective redox degradation of chlorinated aliphatic compounds by Fenton reaction in pyrite suspension

Selective redox degradation of chlorinated aliphatics by Fenton reaction in pyrite suspension was investigated in a closed system. Carbon tetrachloride (CT) was used as a representative target of perchlorinated alkanes and trichloroethylene (TCE) was used as one of highly chlorinated alkenes. Degradation of CT in Fenton reaction was significantly enhanced by pyrite used as an iron source instead of soluble Fe. Pyrite Fenton showed 93% of CT removal in 140 min, while Fenton reaction with soluble Fe(II) showed 52% and that with Fe(III) 15%. Addition of 2-propanol to the pyrite Fenton system significantly inhibited degradation of TCE (99% to 44% of TCE removal), while degradation of CT was slightly improved by the 2-propanol addition (80-91% of CT removal). The result suggests that, unlike oxidative degradation of TCE by hydroxyl radical in pyrite Fenton system, an oxidation by the hydroxyl radical is not a main degradation mechanism for the degradation of CT in pyrite Fenton system but a reductive dechlorination by superoxide can rather be the one for the CT degradation. The degradation kinetics of CT in the pyrite Fenton system was decelerated (0.13-0.03 min⁻¹), as initial suspension pH decreased from 3 to 2. The formation of superoxide during the CT degradation in the pyrite Fenton system was observed by electron spin resonance spectroscopy. The formation at initial pH 3 was greater than that at initial pH 2, which supported that superoxide was a main reductant for degradation of CT in the pyrite Fenton system.     

超声-Fenton法处理偶氮染料橙黄II的研究

以偶氮染料橙黄II为研究对象 ,考察了Fenton反应在超声辐射条件下 ,pH值、H2 O2 浓度、Fe2 + 离子浓度对COD去除率的影响。实验结果表明 ,超声对Fenton试剂处理偶氮染料橙黄II具有强化作用。超声条件下 ,当染料浓度为10 0mg/L、pH为 3.0、Fe2 + 离子浓度为 10mg/L、H2 O2 浓度为 4 0 0mg/L时 ,反应 90min ,COD去除率最高可达 93%。     

UV-Fenton体系预处理四氢呋喃废水实验研究

采用UV-Fenton体系预处理四氢呋喃废水,实验结果表明,pH值、反应时间、Fe2+和H2O2投加量等因素对处理效果有较大的影响。实验确定的最佳反应条件为:原水pH=5,Fe2+投加量2.5 mmol/L,H2O2投加量12 mmol/L,反应时间90 min,连续曝气,在此条件下,COD去除率可达85%左右。经UV-Fenton体系处理后,废水的B/C值由0.16增至0.47,可生化性提高,可满足后续生化处理的要求。     

Comparison of fenton and photo-fenton processes for livestock wastewater treatment

In this study, the photochemical degradation of livestock wastewater was carried out by the Fenton and Photo-Fenton processes. The effects of pH, reaction time, the molar ratio of Fe(2 +)/H(2)O(2), and the Fe(2 +) dose were studied. The optimal conditions for the Fenton and Photo-Fenton processes were found to be at a pH of 4 and 5, an Fe(2 +) dose of 0.066 M and 0.01 M, a concentration of hydrogen peroxide of 0.2 M and 0.1 M, and a molar ratio (Fe(2 +)/H(2)O(2)) of 0.33 and 0.1, respectively. The optimal reaction times in the Fenton and Photo-Fenton processes were 60 min and 80 min, respectively. Under the optimal conditions of the Fenton and Photo-Fenton processes, the chemical oxygen demand (COD), color, and fecal coliform removal efficiencies were approximately 70--79, 70--85 and 96.0--99.4%, respectively.     

旋转填充床中Fenton＋O3氧化降解模拟阿莫西林废水

以旋转填充床（RPB）作为反应装置,研究了Fenton工艺与Fenton＋O3工艺处理模拟阿莫西林废水的效果,考察了FeSO4·7H2O的投加量、温度、旋转床转速、液体流量及pH对C0D去除率的影响。实验表明,Fenton＋O3工艺的COD脱除率及BOD5／COD相对于Fenton工艺分别提升26．7％和140％。该工艺在pH为3、温度为25℃、液体流量30L／h、气体流量2．5L／h、转速800r／min、H2O2的投加量为1mmol／L及Fe2＋投加量为0．4mm01／L的条件下,100mg／L的模拟阿莫西林废水中COD的去除率达到57．9％,BOD5/COD从0增加到0．36,满足后续生化处理要求。     

Degradation of rhodamine B by Fe(0)-based Fenton process with H2O2

Degradation of rhodamine B by Fe(0)-based Fenton process with H₂O₂ was investigated. The effects of H₂O₂ dose, Fe(0) dose, initial concentration of rhodamine B and initial pH value on the degradation of rhodamine B were examined. The results showed that the degradation and mineralization of rhodamine B occurred with low dose of H₂O₂ and Fe(0). The intermediates of rhodamine B were analyzed with UV-Vis spectrophotometry and ion chromatography and the mechanism of oxidative degradation of rhodamine B was also discussed. The reactive oxygen species (·OH) produced in Fe(0)-based Fenton process with H₂O₂ is the key to the degradation of rhodamine B by ways of N-de-ethylation, chromophore cleavage, ring-opening and mineralization.     

不同高级氧化法对水中低浓度药物甲硝唑降解过程的比较

采用UV、H₂O₂、UV/H₂O₂、Fenton、UV/Fenton和UV/TiO₂方法,对水中低浓度的药物甲硝唑进行降解。通过HPLC和UV-Vis光谱得到的甲硝唑去除率。详细讨论了Fe²⁺、TiO₂和H₂O₂的初始浓度以及溶液的初始pH值对降解效率的影响。结果表明,UV/Fenton和UV/TiO₂ 2种系统对水中低浓度甲硝唑均有很好的去除效果,但前者的光催化效率更高。在甲硝唑浓度=6 μmol/L,H₂O₂和Fe²⁺的初始浓度分别为0.5 mg/L和2.94 μmol/L,pH=4的条件下,UV/Fenton方法对甲硝唑水溶液光催化的最佳效率为95.8%。     

Sonochemical degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxins in aqueous solution with Fe(III)/UV system

2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) was rapidly decreased by sonication in aqueous solution. The degradation efficiency was strongly influenced by ultrasonic power and reaction temperature. An initial 2,3,7,8-TeCDD concentration of 20 ng l(-1) was completely degraded within 60 min under sonochemical conditions using a 20 kHz frequency with a 150 W ultrasound power. The activation energy is 21.9 kJ/mol in the temperature range of 10-40 degrees C, suggesting a diffusion-controlled reaction. To increase the efficiency of 2,3,7,8-TeCDD treatment, degradation system combined ultrasound with Fe(III) (2 x 10(-4)mol l(-1)) and UV irradiation. Both UV and Fe(III) induced Fenton, Fenton-like and photo-Fenton reactions, leading to additional OH radicals and rapid 2,3,7,8-TeCDD removal.     

Experimental design of Fenton and photo-Fenton reactions for the treatment of cellulose bleaching effluents

Multivariate experimental design was applied to the treatment of a cellulose conventional bleaching effluent in order to evaluate the use of the Fenton reagent under solar light irradiation. The effluent was characterised by the general parameters total organic carbon (TOC), chemical oxygen demand and color, and it was analysed for chlorinated low molecular weight compounds using GC–MS. The main parameters that govern the complex reactive system: Fe(II) and H₂O₂ initial concentration, and temperature were simultaneously studied. Factorial experimental design allowed to assign the weight of each variable in the TOC removal after 15 min of reaction. Temperature had an important effect in the organic matter degradation, especially when the ratio of Fenton reagents was not properly chosen. Fenton reagent under solar irradiation proved to be highly effective for these types of wastewaters. A 90% TOC reduction was achieved in only 15 min of treatment. In addition, the GC–MS analysis showed the elimination of the chlorinated organic compounds initially detected in the studied bleaching effluents.     

Iron-loaded mangosteen as a heterogeneous Fenton catalyst for the treatment of landfill leachate

Iron-loaded mangosteen shell powder (Fe-MSP) was found as an effective heterogeneous Fenton catalyst for the treatment of stabilized landfill leachate. Sonolytically produced catalyst has higher efficiency than other catalysts. At the optimal conditions (pH 3, catalyst concentration of 1,750 mg/L and hydrogen peroxide concentration of 0.26 M), 81 % of the chemical oxygen demand (COD) was removed effectively from the landfill leachate. But, the efficiency of Fe-MSP was reduced in the first recycling due to the poisoning of active sites. A metal leaching study indicated that the degradation of the pollutant is mainly due to solid Fe ions present in Fe-MSP rather than the leached ferrous and ferric ions. Hydroxyl radical production in the system was confirmed by the Fenton oxidation of benzoic acid. Compared to the homogeneous Fenton process, the heterogeneous Fenton process using Fe-MSP had higher COD removal efficiency, indicating the practical applicability of the prepared catalyst.     

MnO2催化Fenton试剂降解苯酚废水

实验对MnO2催化Fenton试剂氧化高浓度苯酚废水的动力学特性和去除效果进行了研究。结果表明,MnO2可以提高Fenton试剂体系对苯酚的降解率以及COD的去除率;Fenton试剂以及MnO2催化Fenton试剂氧化苯酚废水体系中苯酚的降解都符合拟一级动力学模型。在MnO2催化Fenton试剂氧化体系中,苯酚的降解速率常数有明显提高,反应活化能也有所降低,说明MnO2的加入可以使反应容易进行。废水降解前后紫外可见吸收光谱和红外谱图表明,Fenton试剂法将苯酚可能降解为羧酸、烯烃等有机物中间体。     

Parathion degradation and its intermediate formation by Fenton process in neutral environment

The purpose of this study is to investigate parathion degradation by Fenton process in neutral environment. The initial parathion concentration for all the degradation experiments was 20 ppm. For hydrogen ion effect on Fenton degradation, the pH varied from 2 to 8 at the [H₂O₂] to [Fe²⁺] ratio of 2-2 mM, and the result showed pH 3 as the most effective environment for parathion degradation by Fenton process. Apparent degradation was also observed at pH 7. The subsequent analysis for parathion degradation was conducted at pH 7 because most environmental parathion exists in the neutral environment. Comparing the parathion degradation results at various Fenton dosages revealed that at Fe²⁺ concentrations of 0.5, 1.0 and 1.5 mM, the Fenton reagent ratio ([H₂O₂]/[Fe²⁺]) for best-removing performance were found as 4, 3, and 2, resulting in the removal efficiencies of 19%, 48% and 36%, respectively. Further increase in Fe²⁺ concentration did not cause any increase of the optimum Fenton reagent ratio for the best parathion removal. The result from LC-MS also indicated that hydroxyl radicals might attack the PS double bond, the single bonds connecting nitro-group, nitrophenol, or the single bond within ethyl groups of parathion molecules forming paraoxons, nitrophenols, nitrate/nitrite, thiophosphates, and other smaller molecules. Lastly, the parathion degradation by Fenton process at the presence of humic acids was investigated, and the results showed that the presence of 10 mg L⁻¹ of humic acids in the aqueous solution enhanced the parathion removal by Fenton process twice as much as that without the presence of humic acids.     

Fenton试剂法降解餐厨垃圾异味

自行设计Fenton试剂法降解还原性气体异味的反应器,研究了Fenton试剂法处理餐厨垃圾异味主要成分(苯、乙酸乙酯、苯乙烯)的降解效果。以苯为典型代表物,优化得出该实验的最佳反应条件为:pH=3,FeSO4.7H2O投加量为1 g/L液相,30%H2O2投加量为10 mL/L液相,紫外光源辅助。结果证明,Fenton试剂法处理单一异味气体的效果较理想,在前180 min内能达到90%以上,该法在处理气态异味污染物方面具有广阔的应用前景。     

Fe/C微电解和Fenton氧化联合处理印刷电路板废水

研究了Fe/C微电解和Fenton氧化处理印刷电路板废水的最佳条件和联合工艺的处理效果。结果表明,Fe/C微电解最佳工艺条件为：pH=2,Fe/C质量比为2∶1,投加药剂量为30 g/L,停留时间为30 min;Fenton氧化最佳工艺条件为：pH=3,H2O2投加量为6 mL/L,停留时间为2 h。将2种方法联用并进行中试实验,结果表明,对原水的COD去除率可达80%,而且Fenton反应可利用微电解产生的Fe2＋,节约成本,运行稳定,效果良好。     

Modified Fenton reaction for trichlorophenol dechlorination by enzymatically generated H2O2 and gluconic acid chelate

Glucose oxidase is a well-known enzyme that catalyzes the oxidation of β-d-glucose to produce gluconic acid and hydrogen peroxide. Fenton reaction is a powerful oxidation technology used for the oxidation of groundwater pollutants. For the application of Fenton reaction in groundwater remediation, successful operation of Fenton reaction near neutral pH, and on-site generation of both H₂O₂ and chelate will be beneficial. The focus of this experimental study was to couple the glucose oxidation reaction with chelate-based Fenton reaction. The idea was to use the hydrogen peroxide and chelate gluconic acid generated during glucose oxidation for the dechlorination of 2,4,6-trichlorophenol (TCP) by Fenton reaction. The oxidation of glucose was achieved using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for each system, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. In the case of free enzyme reaction, separation of the enzyme was achieved using an ultrafiltration membrane before initiating the Fenton reaction. The oxidation of TCP by Fenton reaction was performed at varying ratios of gluconic acid/Fe, and its effect on the decomposition of TCP and H₂O₂ was studied. TCP degradation was studied both in terms of parent compound degradation and free chloride generation.     

建立数学模型分析UV-Fenton对金属切削液废水的降解

采用UV/Fenton技术处理金属切削液废水,并通过正交实验和单因素实验得到了最佳工作条件为:pH=2.5,H2O2(浓度30%)投加量=127.5 mL/L,Fe2+投加量=24.8 mmol/L,总反应时间=3 h,投加次数6次,此条件下金属切削液废水COD去除率达到95%。最后,通过正交实验数据和单因素模型方程利用1st Opt进行多元非线性拟合建立UV/Fen-ton对金属切削液废水COD降解率的数学模型方程,然后进行分析讨论。     

Iron-mediated reactions of polychlorinated biphenyls in electrochemical peroxidation process (ECP)

A study was conducted to explore some of the basic processes of polychlorinated biphenyl (PCB) destruction by a new technology termed electrochemical peroxidation process (ECP). ECP represents an enhancement of the classic Fenton reaction (H2O2 + Fe2+) in which iron is electrochemically generated by steel electrodes. Focus was on the extent of adsorption of a mixture of Aroclor 1248 on steel electrodes in comparison to iron filings. Commercially available zero-valent iron filings rapidly adsorbed PCBs from an aqueous solution of Aroclor 1248. Within 4 h, all the PCBs were adsorbed at 1%, 5%, and 10% Fe0 (w/v) concentrations. Little difference in adsorption was found between acidic (2.3) and unamended solutions (pH 5.5), even though significant differences in iron oxidation state and Fe2+ concentrations were measured in solution. PCB adsorption also occurs on steel electrodes regardless of the pH or electric current applied (AC or DC), suggesting the combination of oxidizing (free radical-mediated reactions) and reducing (dechlorination reactions) iron-mediated degradation pathways may be possible. Extraction of the iron powder after 48 h of contact time yielded the progressive recovery of biphenyl with increasing Fe mass(from 0.4% to 3.5%) and changes of the PCB congener-specific pattern as a consequence of dechlorination. A variety of daughter congeners similar to those accumulated during anaerobic microbial dechlorination of Aroclor 1248 in contaminated sediments indicate preferential removal of meta- and para-chlorines.