Kinetics study on photochemical oxidation of polyacrylamide by ozone combined with hydrogen peroxide and ultraviolet radiation

An investigation on the process of ozone combined with hydrogen peroxide and ultraviolet radiation has been carried out in order to establish the kinetics for photochemical oxidation of polyacrylamide （PAM） in aqueous solution. Effects of operating parameters, including initial PAM concentration, dosages of ozone and hydrogen peroxide, UV radiation and pH value on the photochemical oxidation of PAM, have been studied. There was an increase in photochemical oxidation rate of PAM with increasing of dosages of 03, H2O2 and ultraviolet radiation. Upon increasing of the initial PAM concentration, the photochemical oxidation rate of PAM decreased. Slight effect of pH value on the photochemical oxidation rate of PAM was observed in the experiments. The kinetics equation for the photochemical oxidation of PAM by the system has been established.

Degradation of 2,4-dichlorophenoxyacetic acid in water by ozonehydrogen peroxide process

This study reports an investigation into the degradation of 2,4-dichlorophenoxyacetic acid in bubble contactor column by O2/H2O2 process, which is widely used as a principal advanced oxidation process. The degradation of 2,4-dichlorophenoxyacetic acid was studied under different H202/O3 molar ratio and pH value. Meanwhile, TOC removal was investigated both in distilled water and tap water. The influences of ozone transfer and consumed hydrogen peroxide were also discussed. The degradation products and oxidation intermediates were identified by GC-MS and LC-MS. A possible reaction mechanism was thus proposed.

UV-Catalytic Treatment of Municipal Solid-Waste Landfill Leachate with Hydrogen Peroxide and Ozone Oxidation

The performance of UV/H_2O_2, UV/O_3, and UV/H_2O_2/O_3 oxidationsystems for the treatment of municipal solid-waste landfill leachatewas investigated. Main objective of the experiment was to removetotal organic carbon (TOC), non-biodegradable organic compounds(NBDOC) and color. In UV/H_2O_2 oxidation experiment, with theincrease of H_2O_2 dosage, removal efficiencies of TOC and coloralong with the ratio of biochemical oxygen demand (BOD) to chemicaloxygen demand (COD) of the effluent were increased and a betterperformance was obtained than the system H_2O_2 alone.

Ozonation of refractory chemicals in leachate with hydrogen peroxide

Nearly 97% of organic chemicals in Hong Kong leachate could be effectively removed by the UASB(upflow anaerobic sludge blanket) process followed by the fenton coagulation. The COD of leachate was lowered from an average of 12900 mg/L to 1440 mg/L after the UASB treatment, and was further lowered to 394 mg/L after the fenton coagulation. The remaining refractory residues could be further removed by ozonation with the addition of H 2O 2. The ozonation for the supernatant of the fenton coagulation was most effective at pH 7—8, with the addition of 300 mg/L of H 2O 2, and 30 min of reaction. The final effluent contained only 85 mg/L of COD and l0 mg/L of BOD 5. On the other hand, direct ozonation of UASB effluent lowered the COD to 905 mg/L and BOD 5 to l03 mg/L. Ozonation improved the biodegradability of the organic residues, and also converted part of organic\|N in the leachate into NH 3 N and NO - 3\|N.

Comparisons of the film peeling from the composite oxides of quartz sand filters using ozone, hydrogen peroxide and chlorine dioxide

To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone（O3）, hydrogen peroxide（H2O2） and chlorine dioxide（Cl O2）were examined to peel off the film from the quartz sand surface in four pilot-scale columns.An optimized oxidant dosage and oxidation time were determined by batch tests.Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33（H2O2）and to 53.67 hr（ClO2） after the oxidation treatments, and the increase of backwashing interval after treatment by O3 was much less than for the other two treatments.Interestingly, the treatment efficiency of filters was not affected by O3 or H2O2 oxidation;but after oxidation by ClO2, the treatment efficiency was deteriorated, especially the ammonia removal（from 96.96% to 24.95%）. The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy.Compared with the oxidation by O3 and H2O2, the structures on the surface of filter sands were seriously damaged after oxidation by ClO2. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO2. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H2O2 is a suitable agent for film peeling.

Formation control of bromate and trihalomethanes during ozonation of bromide-containing water with chemical addition: Hydrogen peroxide or ammonia?

To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br-).Considering the risk of bromate (Br O3-) formation in ozonation of the sand-filtered water,the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia(NH3) on Br O3-formation during ozonation process were compared.The addition of H2O2effectively inhibited Br O3-formation at an initial Br-concentration amended to 350μg/L.The inhibition efficiencies reached 59.6 and 100%when the mass ratio of H2O2/O3was 0.25and>0.5,respectively.The UV254and total organic carbon (TOC) also decreased after adding H2O2,while the formation potential of trihalomethanes (THMs FP) increased especially in subsequent chlorination process at a low dose of H2O2.To control the formation of both Br O3-and THMs,a relatively large dose of O3and a high ratio of H2O2/O3were generally needed.NH3addition inhibited Br O3-formation when the background ammonia nitrogen(NH3–N) concentration was low.There was no significant correlation between Br O3-inhibition efficiency and NH3dose,and a small amount of NH3–N (0.2 mg/L) could obviously inhibit Br O3-formation.The oxidation of NOM seemed unaffected by NH3addition,and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3.Considering the formation of Br O3-and THMs,the optimal dose of NH3was suggested to be 0.5 mg/L.

Tunable catalytic activity of gadolinium-doped ceria nanoparticles for pro-oxidation of hydrogen peroxide

We report a study of the roles of gadolinium(lll)(Gd3+)dopants in influencing the catalytic activity of gadolinium-doped ceria nanoparticles towards the pro-oxidation of hydrogen peroxide to hydroxyl radicals.These doped ceria nanoparticles with dopant concentrations of 0.6 wt.%,3 wt.%,and 6 wt.%Gd^3+were synthesized using an ozone-mediated method for tuning their catalytic activities.The Gd dopants were found to foster an increase in the percentage of Ce^3+ions in the doped ceria nanoparticles.Our reaction kinetic study revealed that the relationship between the overall reaction rates and the Gd dopant concentrations in our doped materials followed a volcano-like trend.In contrast,the apparent activation energy values of these Gd-doped ceria nanoparticles were found to be positively associated with the concentrations of Gd dopants.The overall catalytic activity trend was attributed to the interplay between the promotion and degradation effects of the Gd dopants on the properties of doped ceria nanoparticles.

The mechanism and pathway of the ozonation of 4-chlorophenol in aqueous solution

The removal efficiency of 4-chlorophenol by ozonation was studied, and the reaction mechanism and characteristic of ozonation of 4-chlorophenol were investigated. Ozone and hydroxyl radicals are two strong oxidants during the process of ozonation. The experimental results showed that when there was no scavenger to inhibit OH· radicals, an intermediate product, hydrogen peroxide was formed during the ozonation of 4-chlorophenol. Hydrogen peroxide reacted with ozone at neutral pH and produced hydroxyl radicals. Ozone at the dosage of 113 mg/L could remove 20 mg/L 4-chlorophenol and 39% TOC. With the complete inhibition of hydroxyl radicals, molecular ozone could effectively destroy 4-chlorophenol to form 4-quinone, which was subsequently oxidized to formic acid and oxalic acid. Two reaction pathways of the degradation of 4-chlorophenol by ozone and O3/OH· were proposed in this study. Ozonation is an effective method for reducing 4-chlorophenol, and has potential to practical application.

电催化臭氧耦合BAC工艺对污水中卡马西平去除和微生物群落影响

以我国南方某市政污水处理厂二沉池出水为研究对象,通过搭建电催化臭氧+生物活性炭(E-H2O2/O3-BAC)为核心工艺的一体化中试系统,评估了系统中高级氧化段和BAC段对癫痫药物卡马西平的降解效果,进一步对不同工艺段出水的细菌群落组成进行了分析。结果表明,单独O3工艺和E-H2O2/O3工艺对卡马西平的去除率分别为95%和90%,经BAC处理后,卡马西平去除率均可达到99%以上。砂滤出水中检测到的条件致病菌属主要包括弓形杆菌属(Arcobacter)、Pseudarcobacter、拟杆菌属(Bacteroides)、嗜肺军团菌(Legionella)和黄杆菌属(Flavobacterium),多种菌属在不同工艺处理后相对丰度发生显著变化(p<0.05)。E-H2O2/O3-BAC处理技术虽然在致病菌杀菌效果上弱于O3-BAC技术,但并未引起致病菌黄杆菌属的显著增加,相较于O3-BAC技术更具有安全性。因此,E-H2O2/O3-BAC深度处理工艺可作为一种有效的技术手段为污水处理厂新污染物的去除和出水微生物安全保障提供支撑,在废水深度处理领域具有良好的应用前景。

基于E-H_(2)O_(2)-O_(3)氧化—BAC滤池工艺的印染废水深度处理应用研究

采用电化学原位合成法制备H_(2)O_(2)(E-H_(2)O_(2))并耦合O_(3)形成了E-H_(2)O_(2)-O_(3)高级氧化技术,并以该技术为核心,采用E-H_(2)O_(2)-O_(3)氧化—BAC(生物活性炭)滤池工艺在中试条件下对印染废水生化出水进行深度处理。E-H_(2)O_(2)-O_(3)氧化的最优工艺参数为O_(3)通入量120 g/h、H_(2)O_(2)浓度0.63 mmol/L、HRT 2.0 h。中试装置在该条件下连续运行31 d(BAC接触时间40 min),COD、UV_(254)、色度的平均去除率分别达56.4%,89.5%,89.3%,运行成本约为3.35元/t(以废水计)。当进水COD小于90 mg/L时,出水COD低于40 mg/L,达到地表水Ⅴ类排放标准。经E-H_(2)O_(2)-O_(3)氧化—BAC滤池工艺处理后,氧化出水和BAC出水的总荧光强度较进水分别下降了92.0%和96.3%。

Decolorization of Blue CL-BR dye by AOPs using bleach wastewater as source of H_2O_2

This research was focused on the investigation of the efficacy of advanced oxidation processes （Fenton, ozonation and UV/H2O2） for decolorization of reactive azo dye （Blue CL-BR） using bleach wastewater as possible source of H2O2. All the experiments were performed on the laboratory scale set-up. The results showed that colour removal efficiencies by UV or bleach （H2O2） alone were not so efficient. Fenton process with bleach wastewater was found to be the most effective at process conditions such as pH of 3 and HEO2/Fe^2＋ ratio of 24：1, resulting in 64% colour removal. Almost complete colour removal, i.e., 99% and 95% were achieved by UV//H2O2 and UV/bleach wastewater in 30 and 60 min, respectively. Ozonation proved an efficient method for decolorization of Blue CL-BR dye at alkaline pH. It was possible to achieve 98% colour removal with 30 min of ozonation at pH 9. The colour removal of dye was found to follow first order kinetics.

Water Content Effect on Oxides Yield in Gas and Liquid Phase Using DBD Arrays in Mist Spray

Electric discharge in and in contact with water can accompany ultraviolet（UV）radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals（OH）, oxygen radical（O）, ozone（O_3） and hydrogen peroxide（H_2O_2）. In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge（DBD）arrays in water mist spray. The relationship between droplet size and water content was examined,and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O_3 and nitrogen dioxide（NO_2） in DBD room decreased with increasing water content. Moreover, the concentrations of H_2O_2, O_3 and nitrogen oxides（NOx） in treated water decreased with increasing water content,and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last,the water containing phenol was tested in this system for the concentration from 100 mg/L to9.8 mg/L in a period of 35 min.

The Impacts of Different Bromide Concentrations and Advanced Oxidation Ways on the Bromate Generation

Taking reservoir water diverting from Yellow River as raw water, and using 5 m^3/h of pilot device, the impacts of different bromide concentrations and advanced oxidation ways on bmmate generation in effluent of ozone -upward flow BAC -sand filtration technology. Results showed that when bromine ion of raw water was about 100 μg/L, and ozone dosage was 2 mg/L, bromate exceeding risk existed in the effluent of ozone - upward flow BAC technology, and bromate content in the effluent reached 10 μg/L. Moreover, generation amount of bromate had certain linear rela- tionship with bromine ion of influent. Both dosing hydrogen peroxide and potassium permanganate could effectively inhibit bromate production, and there was no bromate generation in final effluent of the technology. Moreover, it also could improve the removal of major pollutants in the water by the combined process. Compared with advanced oxidation of hydrogen peroxide, potassium permanganate pre-oxidation could better control production costs.

Efficiency and mechanism of degradation of alachlor in water by O_3/H_2O_2 catalyst system

Alachlor is used widely as a herbicide,but is an environmental endocrine disruptor. O 3/H 2O 2 system is used as catalyst to delve on the degradation efficiency of alachlor. The amount of the catalyst H 2O 2,the pH value of the soluble, the temperature and quality of water sample are changed to investigate the effect of these factors on the degradation of alachlor. The degradation of alachlor is qualitatively analyzed through their GS MS spectra and the possible mechanism of the degradation of alachlor is discussed as well.

Degradation of p-nitrotoluene by O_3/H_2O_2 process and oxidation mechanism

The degradation of p-nitrotoluene by O3/H2O2 process in a bubble contact column was investigated. Effects of the molar ratio of hydrogen peroxide to ozone,pH value and t-butanol on the oxidation process were discussed. It was found that the proper H2O2/O3 molar ratio for the degradation of p-nitrotoluene was around 0.6, different pH values and the presence of t-butanol highly influenced the removal efficiency of p-nitrotoluene. 5-methyl-2-nitrophenol, 2-methyl-5-nitrophenol, (4-nitrophenyl) methanol, 5-(hydroxymethyl)-2-nitro phenol, acetic acid, 2-methylpropane diacid and 2-(hydroxylmethyl)propane diacid were identified as degradation intermediates and products through GC-MS. Radical reaction mechanism and degradation pathway were proposed based on the results of experiments. It is deduced that the benzene ring of p-nitrotoluene can be only destroyed by hydroxyl radicals through a polyhydroxy intermediate pathway. Then unstable polyhydroxy intermediates can be oxidized to different acids with low molecular weight rapidly.

Effects of Coexisting Substances on Nitrobenzene Degradation with O_3/H_2O_2 Process in High-Gravity Fields

This study used nitrobenzene as the simulated pollutant to study the effects of common inorganic sodium salts and organics on nitrobenzene degradation by O_3/H_2O_2 in high-gravity fields. The experiment results showed that the highgravity technology could increase the nitrobenzene removal rate by improving the ozone transfer efficiency and ozone dissolution. Coexisting substances had different effects on the degradation kinetics of nitrobenzene in high-gravity fields. Among such substances, Na_2CO_3, NaOH, Na_3PO_4, and NaNO_3 accelerated the removal of nitrobenzene. The main action principle of nitrobenzene degradation by O_3/H_2O_2 is that the additives can increase the pH value of the solution, stimulate ozonolysis, generate hydroxyl radicals(·OH), and improve oxidation efficiency. By contrast, NaCl, NaHCO_3, NaHSO_4, ethanol(C_2H_5OH), acetic acid(CH_3COOH), formic acid(HCOOH), and tert-butyl alcohol(TBA) inhibited nitrobenzene removal. When NaHCO_3, CH_3COOH, or HCOOH were added, the pH value of the solution decreased and free radical chain reactions were hindered. However, NaCl, NaHCO_3, C_2H_5OH, and TBA consumed ·OH radicals and inhibited nitrobenzene removal.

不同臭氧组合工艺处理含硝基苯类化合物废水的实验研究

为研究臭氧高级氧化技术对含硝基苯类化合物炸药废水的处理效果,采用四种不同组合工艺(旋转填料床(RPB)-O3/H2O2、RPB-O3、曝气反应装置(BR)-O3/H2O2和BR-O3),进行了模拟废水中硝基苯类化合物降解的对比性试验。结果表明,O3/H2O2工艺对硝基苯类化合物表现出较强的降解性能,去除率可达99%,出水指标达到《污水综合排放标准》(GB8978-1996)中硝基苯类化合物排放标准。在相同反应时间下,BR-O3/H2O2和BR-O3工艺对硝基苯类化合物去除率明显偏低。在RPB-O3/H2O2和RPB-O3工艺中,硝基苯类化合物去除率随超重力因子和初始p H值的增加而增大,而随双氧水浓度和液体流量的增加呈先增大后降低的变化趋势。在臭氧浓度为50 mg·L-1,超重力因子为80,初始p H为10.5,双氧水浓度4.9 mmol·L-1和液体流量120 L·h-1的试验条件下,硝基苯类化合物去除效果较好。此条件下硝基苯类化合物的降解过程符合假一级反应动力学。

O_3/H_2O_2去除水中硝基苯效果与机理

以硝基苯为目标反应物,对O3/H2O2体系氧化去除水中硝基苯的效果和机理进行了研究,考察了pH值、H2O2剂量、自由基抑制剂或促进剂对硝基苯的去除效果的影响.研究发现,在pH≤7时,H2O2促进臭氧化去除硝基苯的效果较为明显,当H2O2投加量从1.0 mg/L增加到4.0 mg/L时,在氧化5 min内,硝基苯的去除率明显的升高,但当H2O2投加量由4.0 mg/L提高到20 mg/L时,硝基苯的去除率呈下降趋势;同时发现单独臭氧化硝基苯的过程中能明显产生H2O2;几种有机物的加入,不同程度都降低了硝基苯的去除率.无论单独臭氧化还是催化臭氧化都很难将体系TOC大幅度降低,硝基脱出后几乎完全以NO-3形式存在,反应体系pH随氧化时间的增加而明显的降低.LC-MS和GC-MS的分析表明,硝基苯主要的臭氧化产物为酚类和羧酸类物质.对O3/H2O2与硝基苯反应历程进行推导,认为硝基苯的臭氧化降解分为2个阶段,首先是羟基自由基进攻使苯环羟基化,然后是羟基化的芳环发生开裂,生成各种脂肪族化合物或进一步矿化.

过氧化氢增强紫外-臭氧降解偏二甲肼

建立了氧化偏二甲肼(UDMH)废水的H_2O_2-UV-O_3氧化体系。以偏二甲肼和化学需氧量(COD)的去除率为检测指标,用正交实验确定了反应的主要影响因素和最佳工艺组合。比较了O_3、UV-O_3、UV-H_2O_2、H_2O_2-UV-O_3四种反应体系的降解情况。初步探讨了中间产物的变化规律。结果表明:在pH=9.0,鼓气处理24 h,臭氧投加速率19.6 mg·(L·min)-1,过氧化氢与偏二甲肼的物质的量之比为5∶1,紫外线类型VUV+UV-C,反应时间1.5h的条件下,偏二甲肼废水(质量分数1%)中偏二甲肼去除率和COD去除率可分别达到99.99%和99.30%。

O3/H2O2降解阿特拉津影响因素研究

摘要采用O3/H2O2，氧化去除水中内分泌干扰物阿特拉津，考察了反应条件及水质对去除的影响，并对反应机制进行了初步探讨。阿特拉津初始浓度2mg/L，投量为7．5mg/L的O3，单独氧化去除率为27．2％；相同O3投量下，控制H2O2/O，摩尔比为0．75，5min阿特拉津的去除率最高可达96．5％；pH值为7．5～8．5，温度在25～40℃的范围内，都维持了较高的去除率，表明H2O2/O3，体系对阿特拉津的去除效果良好，降解速度快，反应条件温和。0．5mg/L的腐殖酸，对阿特拉津的去除影响不大，腐殖酸浓度为1、2和5mg/L时，平均去除率分别为63．4％、50．7％和30．2％；碳酸氢钠的浓度为50和200mg/L时，去除率分别为88．1％和73．8％，说明水质对阿特拉津的去除影响较大。叔丁醇的浓度为5和20mg/L时，阿特拉津的去除率分别降低到44．7％和27．5％，去除率随自由基抑制剂叔丁醇增加而降低，说明H2O2/O3降解阿特拉津主要为该体系产生的羟基自由基的贡献。