Life cycle assessment of high concentration organic wastewater treatment by catalytic wet air oxidation

There have been many studies on life cycle assessment in sewage treatment,but there are scarce few studies on the treatment of industrial wastewater in combination with advanced oxidation technology,especially in catalytic wet air oxidation(CWAO).There are no cases of using actual industrialized data onto life cycle assessment.This paper uses Simapro 9.0 software to establish a life cycle assessment model for the treatment of high-concentration organic wastewater by CWAO,and comprehensively explains the impact on the environment from three aspects:the construction phase,the operation phase and the demolition phase.In addition,sensitivity analysis and uncertainty analysis were performed.The results showed that the key factors affecting the environment were marine ecotoxicity,mineral resource consumption and global warming,the operation stage had the greatest impact on the environment,which was related to high power consumption during operation and emissions from the treatment process.Sensitivity analysis showed that electricity consumption has the greatest impact on abiotic depletion and freshwater aquatic ecotoxicity,and it also proved that global warming is mainly caused by pollutant emissions during operation phase.Monte Carlo simulations found slightly higher uncertainty for abiotic depletion and toxicity-related impact categories.

Pretreatment of apramycin wastewater by catalytic wet air oxidation

The pretreatment technology of wet air oxidation(WAO) and coagulation and acidic hydrolysis for apramycin wastewater was investigated in this paper. The COD, apramycin, NH^+_4 concentration, and the ratio of BOD_5/COD were analyzed, and the color and odor of the effluent were observed. WAO of apramycin wastewater, without catalyst and with RuO_2/Al_2O_3 and RuO_2-CeO_2/Al_2O_3 catalysts, was carried out at degradation temperature of 200℃ and the total pressure of 4 MPa in a 1 L batch reactor. The result showed that the apramycin removals were respectively 50 2% and 55 0%, COD removals were 40 0% and 46 0%, and the ratio of BOD_5/COD was increased to 0 49 and 0 54 with RuO_2/Al_2O_3 and RuO_2-CeO_2/Al_2O_3 catalysts in catylytic wet air oxidation(CWAO) after the reaction of 150 min. With the pretreatment of coagulation and acidic hydrolysis, COD and apramycin removals were slight decreased, and the ratio of BOD_5/COD was increased to 0 45, and the effluents was not suitable to biological treatment. The color and odor of the wastewater were effectively controlled and the reaction time was obviously shortened with WAO. HO_2· may promote organic compounds oxidized in WAO of the apramycin wastewater. The addition of CeO_2 could promote the activity and stability of RuO_2/Al_2O_3 in WAO of apramycin wastewater.

A highly hydrothermal stable copper-based catalyst for catalytic wet air oxidation of m-cresol in coal chemical wastewater

Catalytic wet air oxidation(CWAO) can degrade some refractory pollutants at a low cost to improve the biodegradability of wastewater. However, in the presence of high temperature and high pressure and strong oxidizing free radicals, the stability of catalysts is often insufficient, which has become a bottleneck in the application of CWAO. In this paper, a copper-based catalyst with excellent hydrothermal stability was designed and prepared. TiO_(2) with excellent stability was used as the carrier to ensure the longterm anchoring of copper and reduce the leaching of the catalyst. The one pot sol–gel method was used to ensure the super dispersion and uniform distribution of copper nanoparticles on the carrier, so as to ensure that more active centers could be retained in a longer period. Experiments show that the catalyst prepared by this method has good stability and catalytic activity, and the catalytic effect is not significantly reduced after 10 cycles of use. The oxidation degradation experiment of m-cresol with the strongest biological toxicity and the most difficult to degrade in coal chemical wastewater was carried out with this catalyst. The results showed that under the conditions of 140℃, 2 MPa and 2 h, m-cresol with a concentration of up to 1000 mg·L^(-1) could be completely degraded, and the COD removal rate could reach 79.15%. The biological toxicity of wastewater was significantly reduced. The development of the catalyst system has greatly improved the feasibility of CWAO in the treatment of refractory wastewater such as coal chemical wastewater.

Application of Catalytic Wet Air Oxidation to Treatment of Landfill Leachate on Co/Bi Catalyst

Catalytic wet air oxidation(CWAO) was employed to reduce the organic compounds in landfill leachate and the effects of temperature, oxygen pressure, catalyst dosage, and concentration of the organic compounds on the TOC and COD Cr removal rates were studied. The degradation kinetics of landfill leachate was also investigated and an exponential experiential model consisting of four influential factors was established to describe the reduction of the organic compounds in the landfill leachate. Meanwhile, the GC-MS technique was used to detect the components of the organic intermediates for the inference of the decomposition mechanisms of the organic compounds in landfill leachate. The results reveal that the reaction temperature and the catalyst dosage are the most important factors affecting the degradation reaction of the organic compounds and that the principal intermediates confirmed by GC-MS are organic acids at a percentage of more than 88% with no aldehydes or alcohols detected. The decomposition mechanisms of the organic compounds in landfill leachate were inferred based on the GC-MS information as follows: the activated gas phase O 2 captured the hydrogen of the organic pollutants to produce free radicals, which then initiated the catalytic reaction. So most of the organic compounds were oxidized into CO 2 and H 2O ultimately. In general, catalytic wet air oxidation over catalyst Co 3O 4/Bi 2O 3 was a very promising technique for the treatment of landfill leachate.

Kinetics study on catalytic wet air oxidation of phenol by several metal oxide catalysts

Four metal oxide catalysts composed of copper(Cu), stannum(Sn), copper-stannum(Cu-Sn) and copper-cerium(Cu-Ce) respectively were prepared by the co-impregnation method, and γ-alumina(γ-Al 2O 3) is selected as support. A first-order kinetics model was established to study the catalytic wet air oxidation of phenol at different temperature when these catalysts were used. The model simulations are good agreement with present experimental data. Results showed that the reaction rate constants can be significantly increased when catalysts were used, and the catalyst of 6% Cu—10%Ce/γ-Al 2O 3 showed the best catalytic activity. This is consistent with the result of catalytic wet air oxidation of phenol and the COD removal can be arrived at 98.2% at temperature 210℃, oxygen partial pressure 3 MPa and reaction time 30 min. The activation energies of each reaction with different catalysts are nearly equal, which is found to be about 42 kJ/mol and the reaction in this study is proved to be kinetics control.

Catalytic wet air oxidation for the treatment of emulsifying wastewater

The wet air oxidation(WAO) and catalytic WAO(CWAO) of the high strength emulsifying wastewater containing nonionic surfactants have been investigated in terms of COD and TOC removal. The WAO and homogeneous CWAO processes were carried out at the temperature from 433 K to 513 K, with initial oxygen pressure 1 2 MPa. It was found that homogeneous catalyst copper(Cu(NO_3)_2) had an fairly good catalytic activity for the WAO process, and the oxidation was catalyzed when the temperature was higher than 473 K. Moreover, several heterogeneous catalysts were proved to be effective for the WAO process. At the temperature 473 K, after 2 h reaction, WAO process could achieve about 75% COD removal and 66% TOC removal, while catalysts Cu/Al_2O_3 and Mn-Ce/Al_2O_3 elevated the COD removal up to 86%—89% and that of TOC up to 82%. However, complete elimination of COD and TOC was proved to be difficult even the best non-noble catalyst was used. Therefore, the effluent from WAO or CWAO process need to be further disposed. The bioassay proved that the effluent from WAO process was amenable to the biochemical method.

Treatment of desizing wastewater from the textile industry by wet air oxidation

This paper describes the application of wet air oxidation to the treatment of desizing wastewater from two textile companies. A two\|liter high temperature, high pressure autoclave reactor was used in the study. The range of operating temperatures examined was between 150 and 290℃, and the partial pressure of oxygen ranged from 0.375 to 2.25 MPa. Variations in pH, COD Cr and TOD content were monitored during each experiment and used to assess the extent of conversion of the process. The effects of temperature, pressure and reaction time were explored extensively. More than 90% COD Cr reduction and 80% TOC removal have been obtained. The results have also been demonstrated that WAO is a suitable pre\|treatment methods due to improvement of the BOD\-5/COD\-\{Cr\} ratio of desizing wastewater. The reaction kinetics of wet air oxidation of desizing wastewater has been proved to be two steps, a fast reaction followed by a slow reaction stage.

Catalytic wet air oxidation of phenol over RuO_2/γ-Al_2O_3 catalyst

A kind of CWAO catalyst, RuO_2/γ-Al_2O_3, was prepared by dipping Al_2O_3into the aqueous solution of RuCl_3·3H_2O. XRD, SEM and TEM were used to determine the catalyticstructure. Influences of the calcination temperature, the initial pH of the feed solution anddegradation temperature on the activity of the RuO_2/γ-Al_2O_3 catalyst were investigated and thereaction mechanism was preliminarily studied. Results showed that uniform dispersion of RuO_2crystallites was observed on the surface of the catalyst. The activity of the catalyst was higher atcalcination temperature of 300℃ for 3 h and the particle reunion occurred and some large RuO_2crystallites were abundant at high calcination temperature of 500℃ The activity of the catalyst wasbetter in the acid solution than in the alkaline solution. Increasing degradation temperature andusing the catalyst could shorten the induction periods so that the phenol and COD removal wereincreased. For RuO_2/γ-Al_2O_3 catalyst, the phenol and COD removal were respectively 98% and 80%in a temperature of 150℃, pH of 5.6 and pressure of 3 MPa after a 2 h reaction. This indicated thatRu/γ-Al_2O_3 catalyst had good activity.

Wet Air Oxidation of Organic Wastewater Catalyzed by Doped Ceria

The catalytic wet air oxidation (CWAO) of H acid and phenol was investigated in the presence of Cu or Fe doped CeOsolid solutions, which were obtained by sol-gel method. The experiment results showed that the incorporation of Cu or Fe into the fluorite lattice of CeOstrongly enhanced the oxidation activity of the catalyst. At 90 ℃ and 0.1 MPa, H acid conversion was 70% for the Ce0.9Fe0.1O2-δ and 60% for the Ce0.9Cu0.1O2-δ catalyst. For phenol removal, the conversion was 70% for the Ce0.9Cu0.1O2-δ catalyst, while for the Ce0.9Fe0.1O2-δ the conversion was 30%. The results indicated that Ce0.9Cu0.1O2-δ was suitable for the treatment of organic wastewaters while Ce0.9Fe0.1O2-δ was suitable for the removal of H acid. The 70% phenol removal rate with Ce0.9Cu0.1O2-δ catalyst was markedly increased to 90% with Ce0.8Cu0.2O2-δ catalyst. However, the phenol removal reduced from 30% to 15% with Fe content increasing from 10% to 20%. For the H acid, the increase of the content of Cu or Fe tended to obviously increase the original reaction rate while the COD removal changed little.

Structure, characterization, and dynamic performance of a wet air oxidation catalyst Cu–Fe–La/γ-Al_2O_3

A Cu–Fe–La/γ-Al_2O_3(CFLA) catalyst was prepared by the excessive impregnation method and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that the catalyst contained mostly Cu^(2+), Fe^(3+), and La^(3+)and a small amount of Cu^+, Fe^(2+), and La. The active components were uniformly distributed in the catalyst, and the particle size of the components was approximately 7.5 nm. The CFLA catalyst was used for the treatment of methyl orange(MO) solution by catalytic wet air oxidation(CWAO), and it exhibited a high catalytic activity. The catalytic reaction involved variable valence states of metals and free-radical reaction mechanism. The CWAO reaction of MO solution was fitted by a segmented first-order dynamic model, and the rapid reaction apparent activation energy was 13.9 k J·mol^(-1).

Role of Bismuth Oxide in Bi-MCo_2O_4(M=Co,Ni,Cu,Zn) Catalysts for Wet Air Oxidation of Acetic Acid

Two series of cobalt(Ⅲ)\|containing spinel catalysts were prepared by the decomposition of the corresponding nitrates. The catalysts doped with bismuth oxide exhibit a higher activity in the wet air oxidation of acetic acid than those without dopant bismuth oxide. The catalysts were investigated by XRD,TEM,ESR,UV\|DRS and XPS,and the interaction between Co and Bi was studied as well. It has been found that nano\|sized bismuth oxide is paved on the surface of cobalt spinel crystal and the structures of cobalt(Ⅲ)\|containing spinel are still maintained. The shift of the binding energy of Bi\-\{\%4f\%\-\{7/2\}\} is related to the catalytic activity of these catalysts doped with bismuth oxide.

Kinetics of Wet Air Oxidation of Wastewater from Natural Fiber Web Desizing

This work described the application of wet air oxidation (WAO) to the treatment of desizing wastewater from natural fiber processing. A two-liter autoclave batch reactor was used for the experiments. The range of operating temperature examined was between 150 and 290℃, and partial pressure of oxygen ranged from 0.375 to 2.25 MPa standardized at 25℃. Variations in Chemical Oxygen Demand(COD) and Total Organic Carbon(TOC) were monitored during each experiment and used to assess the performance of the process. Experimental results showed that WAO can be an efficient method for the treatment of desizing wastewater. Furthermore, Catalytic Wet Air Oxidation (CWAO) was applied to reduce the reaction temperature and pressure in WAO process. A higher COD removal ratio was achieved under more mild reaction condition with the aid of CWAO. A mathematical model was also proposed to simulate the WAO process of desizing wastewater, in which three distinct kinetics steps were considered to describe the degradation of starch. The model simulations were in well agreement with the experimental data.

Assessment of NH3 Reduction and N2O Production during Treatment of Exhausted Air from Fattening Pigs Building by a Commercial Scrubber

The use of air scrubbers to reduce ammonia (NH3) emissions from buildings on pig farms is one of the most promising techniques in the GÖteborg protocol and other European regulations including the Industrial Emission Directive. In France, some air scrubbers are currently used on pig farms, mainly to reduce odours from livestock buildings. However, recent research revealed the production of N2O resulting from the treatment of air from pig buildings. In this context, a two-month study was conducted on a pig farm with 750 places for fattening pigs to check the abatement of NH3 emissions and to assess the possible production of N2O during treatment of exhausted air from buildings housing fattening pigs by a air scrubber. Concentrations of NH3 and N2O in the inlet and outlet air of the scrubber were continuously monitored using an Innova 1412 infrared analyzer. With the scrubber operating parameters (airflow, design, size), our results confirmed the production of N2O in the order of 5% of NH3-N reduced. N2O was produced by biological nitrification and/or denitrification inside the air scrubber. Statistical analysis (Pearson’s test) showed that the production of N2O was strongly influenced by the rate of airflow and the outside temperature. The abatement of NH3 emissions from the building was only 33%, i.e. much lower than the 70% - 90% usually cited in the literature.

Fe salts as catalyst for the wet oxidation of o-chlorophenol

Catalytic wet air oxidation (CWAO) of o-chlorophenol in wastewater was studied in a stainless steel autoclave using four different Fe catalysts in the temperature range of 100?200 °C. Experimental results showed that high rate of o-chlorophenol and CODCr (Chemical Oxygen Demand, mg/L) removal by CWAO was obtained at relatively low temperature and pressure. The catalysts Fe2(SO4)3, FeSO4, Fe2O3 and FeCl3 all exhibited high catalytic activity. More than 93.7% of the initial CODCr and nearly 100% of o-chlorophenol were removed at 150 °C after 150 min with FeSO4 as catalyst. The CWAO of o-chlorophenol was found to be pseudo-first order reaction with respect to o-chlorophenol, with activation energy of 75.56 kJ/mol in the temperature range of 100-175 °C.

Use of catalytic wet air oxidation (CWAO) for pretreatment of high-salinity high-organic wastewater

Catalytic wet air oxidation(CWAO)coupled desalination technology provides a possibility for the effective and economic degradation of high salinity and high organic wastewater.Chloride widely occurs in natural and wastewaters,and its high content jeopardizes the efficacy of Advanced oxidation process(AOPs).Thus,a novel chlorine ion resistant catalyst Bsite Ru doped LaFe_(1-x)Ru_(x)O_(3-)δin CWAO treatment of chlorine ion wastewater was examined.Especially,LaFe_(0.85)Ru_(0.15)O_(3-δ)was 45.5% better than that of the 6%RuO_(2)@TiO_(2)(commercial carrier)on total organic carbon(TOC)removal.Also,doped catalysts LaFe_(1-x)Ru_(x)O_(3-)δshowed better activity than supported catalysts RuO_(2)@LaFeO_(3) and RuO_(2)@TiO_(2) with the same Ru content.Moreover,LaFe_(0.85)Ru_(0.15)O_(3-)δhas novel chlorine ion resistance no matter the concentration of Cl^(−) and no Ru dissolves after the reaction.X-ray diffraction(XRD)refinement,X-ray photoelectron spectroscopy(XPS),transmission electron microscope(TEM),and X-ray absorption fine structure(XAFS)measurements verified the structure of LaFe_(0.85)Ru_(0.15)O_(3-)δ.Kinetic data and density functional theory(DFT)proved that Fe is the site of acetic acid oxidation and adsorption of chloride ions.The existence of Fe in LaFe_(0.85)Ru_(0.15)O_(3-)δcould adsorb chlorine ion(catalytic activity inhibitor),which can protect the Ru site and other active oxygen species to exert catalytic activity.This work is essential for the development of chloride-resistant catalyst in CWAO.

LaFeO_(3)钙钛矿催化剂的制备及其对苯酚的降解处理

采用球磨、溶胶凝胶和共沉淀3种方法制备了LaFeO_(3)钙钛矿催化剂前驱体,通过改变焙烧温度获得了一系列LaFeO_(3)钙钛矿催化剂。利用XRD、FT-IR、N2物理吸脱附、H2-TPR和XPS等手段对催化剂的结构和性质进行了表征,并考察了其催化湿式空气氧化苯酚性能。结果表明,制备方法对催化性能有较大影响。同时低温还原能力强、氧空位多的催化剂催化活性较高。采用溶胶凝胶法,800℃焙烧制备的催化剂的催化活性较好,在反应温度为200℃,空气压力为5 MPa,苯酚初始浓度为4000 mg·L^(-1)的条件下,最终(240 min)的COD去除率为95.4%。

MnCeO_(x)催化湿式氧化处理丙烯腈废水

采用柠檬酸络合法制备了系列MnCeO_(x)催化剂,运用SEM、TEM、XRD和H_(2)-TPR等技术对其进行了表征,并将MnCeO_(x)应用于催化湿式氧化处理丙烯腈废水,考察了Mn与Ce的摩尔比、焙烧温度、反应温度等因素对处理效果的影响。结果表明:当Mn与Ce的摩尔比为7∶3、焙烧温度为500℃时,所制备的Mn_(0.7)Ce_(0.3)O_(x)催化剂活性最好,当pH 7.00、反应温度250℃、反应时间1 h时,丙烯腈废水经催化湿式氧化处理后,COD去除率为95.5%,BOD_(5)/COD从0.04提高至0.65,总氰质量浓度从9.10 mg/L降低至0.06 mg/L,去除率为99.3%;当反应温度250℃、压力7 MPa、丙烯腈废水pH 7.00、进水流量1 mL/min、停留时间1 h时,Mn_(0.7)Ce_(0.3)O_(x)在连续运行500 h后,活性组分Mnn+的质量分数从41.17%降至40.90%,COD去除率稳定在90%以上,表现出良好的活性和稳定性。

催化湿式氧化处理含模板剂有机胺废水

采用催化湿式氧化法处理含有机胺高化学需氧量(COD)废水。考察了催化剂类型和反应温度对废水处理效果的影响。结果表明:以贵金属为催化剂时,COD降幅最高,达到96%;当反应温度为270℃时,能耗较低,尾气中氧气体积分数约为13.1%,COD降幅约为96%,处理效果较佳。采用贵金属催化剂,在温度为270℃、压力为7.6 MPa的最优条件下,催化湿式氧化设备连续运行140 h,产水COD的平均降幅在96%以上。同时进行设备材料腐蚀试验和加速氧化小型试验,通过调整反应原水的pH,解决了设备腐蚀问题。从处理效果和运行成本综合考虑,催化湿式氧化法处理含有机胺高COD废水具有一定竞争力。

CuO/活性炭催化湿式氧化甲基橙废水的研究

基于以硝酸铜为活性组分的前驱物,采取浸渍焙烧法制备了CuO/活性炭催化剂,并以H_(2)O_(2)为氧化剂,对比了在常压条件下催化湿式氧化工艺中处理质量浓度500 mg·L^(-1)甲基橙模拟废水的效果,分别考察了不同CuO/活性炭催化剂加入量、质量分数30%的H_(2)O_(2)氧化剂用量、脱色反应时间、脱色反应温度对甲基橙废水脱色率的影响。结果表明:随着CuO/活性炭催化剂加入量、30%H_(2)O_(2)氧化剂用量、反应温度的不断增加,甲基橙废水的脱色率明显增大;而增加反应时间对甲基橙废水脱色率增加幅度较小。当CuO/活性炭催化剂加入量为0.1 g、质量分数30%H_(2)O_(2)氧化剂加入量为6 mL、催化反应时间为2 h、催化反应温度为35℃时,其对甲基橙废水的脱色率可达到82.44%。

Catalytic wet air oxidation of phenol with functionalized carbon materials as catalysts:Reaction mechanism and pathway

The development of highly active carbon material catalysts in catalytic wet air oxidation（CWAO）has attracted a great deal of attention. In this study different carbon material catalysts（multi-walled carbon nanotubes,carbon fibers and graphite） were developed to enhance the CWAO of phenol in aqueous solution. The functionalized carbon materials exhibited excellent catalytic activity in the CWAO of phenol. After 60 min reaction,the removal of phenol was nearly100% over the functionalized multi-walled carbon,while it was only 14% over the purified multi-walled carbon under the same reaction conditions. Carboxylic acid groups introduced on the surface of the functionalized carbon materials play an important role in the catalytic activity in CWAO. They can promote the production of free radicals,which act as strong oxidants in CWAO. Based on the analysis of the intermediates produced in the CWAO reactions,a new reaction pathway for the CWAO of phenol was proposed in this study. There are some differences between the proposed reaction pathway and that reported in the literature. First,maleic acid is transformed directly into malonic acid. Second,acetic acid is oxidized into an unknown intermediate,which is then oxidized into CO2 and H2O. Finally,formic acid and oxalic acid can mutually interconvert when conditions are favorable.