Catalytic wet air oxidation of phenol by various CeO2 catalysts

Investigations of various CeO2 catalysts using XRD, 02-TPD, H2-TPR and catalytic wet air oxidation of phenol showed that CeO2 calcined under higher thermal impact (designated as type A) displayed excellent catalytic ability for the redox reaction of organics. Results of the investigations mentioned above showed that type A CeO2 has a less stable structure, more structure oxygen exchangeable and more oxidizing ability for the consumption of H2 and conversion of phenol. At phenol concentrations between 400 and 2,500 mg/L, oxygen pressure in the range of 0.5-1.0 MPa, and temperatures above 160 degrees C phenol conversion stood at > or = 90% after 4 h. Total organic carbon removal increased with the reaction temperature. Under the reaction conditions, CO2 selectivity was about 80% or more after 4 h reaction. The reduced catalytic ability of regenerated CeO2 was caused either by stabilization of CeO2 during the process of regeneration or by the deposition of some reaction residues.     

Catalytic wet oxidation of phenol over a Pt/TiO catalyst

Wet oxidation of phenol by air or oxygen over a Pt/TiO₂ catalyst is studied in a batch reactor in the temperature range 150–200°C, pressure range 34–82 atm, and a catalyst loading range of 0–4 g catalyst L⁻¹. The catalyst was powdered 4.45% Pt/TiO₂ with a maximum particle size of 105 μm. Results show complete oxidation of phenol and almost complete total organic carbon (TOC) removal. Small amounts of stable organic acids are formed in side reactions of the phenol degradation pathway and are not readily degraded. Experimental results show that the reaction rate decreases by increased oxygen concentration. Theoretical rate expressions are derived, based on postulated oxidation and TOC reduction mechanisms.     

Semicontinuous Fenton oxidation of phenol in aqueous solution. A kinetic study

This work investigates the Fenton oxidation of phenol in a semicontinuous reactor where the overall amount of H₂O₂ is distributed as a continuous feed upon the reaction time. The experiments were carried out at 25 °C and atmospheric pressure, with 100 mg/L initial phenol concentration and iron dosages from 1 to 100 mg/L. H₂O₂ aqueous solution was continuously fed during 4 h reaction time up to an overall dose varying within the range of 500-5000 mg/L. The results in terms of evolution of phenol, H₂O₂ and intermediates, as well as TOC abatement were compared with those obtained in conventional batch operation. It was found that the oxidation rates for phenol and intermediates were lower when adding the H₂O₂ continuously. However, a higher abatement of TOC was reached at the end of the 4-h reaction time, in spite of a similar overall H₂O₂ consumption. This is the result of a more efficient OH generation throughout the semicontinuous process, favouring the reaction with the organic species and reducing the occurrence of competitive scavenging reactions involving Fe²⁺, H₂O₂ and OH. Two kinetic models were proposed, one for describing the evolution of phenol, aromatics and H₂O₂ and the other for TOC. The influence of the operating conditions on the kinetic constants was also studied, looking for the optimal conditions in terms of both, environmental and economic points of view.     

Phenol degradation in water through a heterogeneous photo-Fenton process catalyzed by Fe-treated laponite

New photo-Fenton catalysts have been prepared from synthetic layered clay laponite (laponite RD). Two series of Fe-laponite catalysts were synthesised, with or without thermal treatment of the mixture Fe polycations-laponite in the intercalation procedure. In each series, the intercalated solids underwent calcination at four temperatures, 250, 350, 450, and 550 °C. The catalysts were used for photo-assisted Fenton conversion of phenol, analyzing the influence of five operating factors: the wavelength of the light source (254 nm UV-C and 360 UV-A radiation), the amount of the catalyst (between 0 and 2 g/L), the initial phenol concentration (between 0.5 and 1.5 mmol/L), the initial concentration of hydrogen peroxide (between 20 and 100 mmol/L), and the initial pH of the solution (between 2.5 and 3.5). In all experiments, the temperature was kept constant at 30 °C. The results have shown that the almost complete conversion of phenol was possible, after only 5 min, under the following operating conditions: UV-C radiation; a pH of the aqueous solution of 3; a dose of 1 g_catalyst/L, and a hydrogen peroxide concentration of 50 mmol/L for a solution containing 1 mmol/L of phenol. The catalyst prepared under thermal treatment and calcined at 350 °C showed the best catalytic performance. A kinetic model was proposed for the process, testing its validity and estimating the rate constants.     

IC反应器在微氧条件下的运行特性研究

采用人工合成废水对IC反应器在微氧和厌氧条件下去除COD的效果、沼气产量、出水VFA、颗粒污泥粒径分布及颗粒污泥浓度等进行对比试验研究.结果表明:在进水COD分别为1 000、2 000、2 600、3 300、4 000 mg/L时,与厌氧相比,微氧时(溶解氧控制在0.5～1.0 mg/L)对COD的去除率分别增长了4.0%、4.0%、2.6%、1.5%、0.9%,沼气产量分别增长了160.0%、137.0%、78.0%、90.5%、50.9%;两种条件下的出水VFA均在200 mg/L以下,但与厌氧相比,微氧的出水VFA值更低、波动更小、变化更平稳;微氧时颗粒污泥的MLSS减少了3.6%,而MLVSS/MLSS值增长了0.6%,表明颗粒污泥的活性增强.     

A/O除磷工艺丝状菌污泥膨胀的研究

丝状菌污泥膨胀是影响活性污泥法高效、稳定运行的重要因素。采用A/O生物除磷工艺中试装置处理实际生活污水,分析了污泥膨胀发生的原因及恢复系统性能的方法。结果显示,长期曝气不均匀是导致丝状菌污泥膨胀的重要原因,通过调控系统运行参数可以有效控制由低DO值或者高负荷引起的丝状菌污泥膨胀。当发生污泥膨胀后,首先降低负荷至0.45 kgCOD/(kgMLSS.d),调节回流比为83%,同时控制好氧池各段的DO分别为1.5、1.0、1.0 mg/L以淘汰丝状菌,在SVI值降至200 mL/g以下后继续降低回流比至53%,同时降低曝气量以形成1.0、0.5、0.5 mg/L的DO浓度梯度。采取上述调控措施后,SVI值由569.8 mL/g降至150 mL/g以下,污泥性状得以恢复;同时出水COD和TP分别在50、0.5 mg/L以下,去除率分别约为85%、95%。     

ZnO/O3工艺降解水中微量有机物的研究

以实验室制备的粉末氧化锌(ZnO)为催化剂,考察了ZnO/O3工艺去除水中有机物的效能.采用总有机碳(TOC)指标反映水中有机污染物的含量.结果表明:臭氧投量为1 mg/L、ZnO投量为300 mg/L时,反应60 min后ZnO-O3工艺对TOC的去除率为46%,比单独臭氧化提高了1倍;反应温度明显影响该工艺对有机物的降解效果,在水温为5,10,20和25 ℃时,TOC的去除率分别为17.5%,31.5%,45.9%和51.3%.臭氧浓度和催化剂投量的增加,可以提高TOC的氧化降解效率.     

Treatment of 2-chlorophenol aqueous solutions by wet oxidation

In the present work, the wet oxidation (WO) of 2-chlorophenol (2-CP) was studied in aqueous solutions, in a high-pressure agitated autoclave reactor. Specifically, the effect of temperature (160-190 degrees C), oxygen partial pressure (5-40 bar) and 2-CP initial concentration (250-1500 mg L(-1)) was examined. The process was attended via total organic carbon (TOC), 2-CP, chloride ion, acetic acid, formic acid and pH measurements. Significant rates of 2-CP disappearance and TOC removal were achieved above 170 degrees C. A decrease in 2-CP initial concentration below 1000 mg L(-1) resulted in a dramatic decrease in the TOC removal achieved, whereas an increase in oxygen partial pressure enhanced greatly the decontamination of the 2-CP aqueous solution, especially from 10 to 20 bar. Much attention was given on the chloride ion removal from the phenolic ring in order to attend the dechlorination of 2-CP during WO. In the WO process, the majority of chloride ions were detached from organic compounds. Finally, a parallel and in series reaction scheme has been proposed for the interpretation of the experimental results.     

饮用水深度处理中膜清洗方式的研究

通过研究连续微滤装置运行及清洗后的跨膜压差(TMP),对装置的物理及化学清洗工艺进行了优化.结果表明:在完成物理清洗后的最初几个水力清洗周期内,采用1.0 min+0.5min和1.5 min+0.5 min这两种清洗方式的效果相差不大,但在6个水力清洗周期后.1.5 min+0.5 min反冲洗方式下的TMP明显低于1.0 min+0.5 min的,前者运行期间的TMP平均为110kPa,而后者为112 kPa,比前者高出约1.8%.采用小化学清洗时,建议采用先碱洗后酸洗的方式,周期为24 h,清洗液的浓度均为300～400 mg/L,在水质较好的情况下,可以适当延长酸洗周期.     

加轴压卸围压条件下北山花岗岩破坏特征

为了研究开挖扰动对花岗岩的破坏机理,对北山花岗岩进行了加轴压卸围压的三轴试验,试验中设置0.1,0.5,1.0,1.5,2.0 MPa/min五种卸围压速率,轴压加载速率是卸载速率的10倍,每一种卸载速率设置5,10,15,20,30 MPa五个围压,并在试验过程中记录声发射事件。分析了声发射事件数随卸载速率的变化规律,使用层次聚类的方法将声发射事件分为张拉破坏和剪切破坏,研究了卸载速率、围压和卸载时间对张剪比(张拉破坏与剪切破坏的比值)的影响,研究表明:(1)随着卸载速率的增加,声发射事件数呈幂函数下降,且围压越高,声发射事件数下降越明显;(2)裂纹的张剪比随着卸载速率的增加而增加,随着围压的增加减小,随着卸载时间增加降低;(3)围压卸载速率增加,岩石声发射b值降低,初始围压升高,对应的b值增加,且卸载速率和围压对张拉b值的影响比对剪切b值影响更明显;(4)基于Maxwell模型分析岩石内局部应力状态,并进一步研究了岩石破坏过程中张剪比变化的力学机理。     

Nitrification with high nitrite accumulation for the treatment of wastewater with high ammonia concentration

The objective of this paper was to determine the best conditions for partial nitrification with nitrite accumulation of simulated industrial wastewater with high ammonia concentration, lowering the total oxygen needed in the nitrification step, which may mean great saving in aeration. Dissolved oxygen (DO) concentration and pH were selected as operational parameters to study the possibility of nitrite accumulation not affecting overall ammonia removal. A 2.5L activated sludge reactor was operated in nitrification mode, feeding a synthetic wastewater simulating an industrial wastewater with high ammonia concentration. During the start-up a pH of 7.85 and a DO of 5.5mg/L were used. The reactor was operated until stable operation was achieved at final nitrogen loading rate (NLR) of 3.3kgN- NH(4)(+)/m(3)d with an influent ammonia concentration of 610mg N-NH(4)(+)/L.The influence of pH was studied in continuous operation in the range of 6.15-9.05, changing the reactor pH in steps until ammonia accumulation (complete nitrification inhibition) took place. The influence of DO was studied in the same mode, changing the DO in steps from 5.5 to 0.5mg/L.The pH was not a useful operational parameter in order to accumulate nitrite, because in the range of pH 6.45-8.95 complete nitrification to nitrate occurs. At pH lower than 6.45 and higher than 8.95 complete inhibition of nitrification takes place. Setting DO concentration in the reactor at 0.7mg/L, it was possible to accumulate more than 65% of the loaded ammonia nitrogen as nitrite with a 98% ammonia conversion. Below 0.5mg/L of DO ammonia was accumulated and over a DO of 1.7mg/L complete nitrification to nitrate was achieved.In conclusion, it is possible under the conditions of this study, to treat high ammonia synthetic wastewater achieving an accumulation of at least 65% of the loaded nitrogen as nitrite, operating at a DO around 0.7mg/L. This represents a reduction close to 20% in the oxygen necessary, and therefore a considerable saving in aeration.     

Wet air oxidation of table olive processing wastewater: determination of key operating parameters by factorial design

The wet air oxidation of an effluent from edible olive processing was investigated. Semibatch experiments were conducted with 0.3L of effluent loaded into an autoclave and pure oxygen fed continuously to maintain an oxygen partial pressure of 2.5MPa. The effect of operating conditions, such as initial organic loading (from 1240 to 5150mg/L COD), reaction time (from 30 to 120min), temperature (from 140 to 180 degrees C), initial pH (from 3 to 7) and the use of 500mg/L H(2)O(2) as an additional oxidant, on treatment efficiency was assessed implementing a factorial experimental design. All five parameters had a statistically considerable effect on COD removal, alongside second order interactions of COD with reaction temperature, contact time and effluent pH. In most cases, high levels of phenols degradation (up to 100%) and decolorization (up to 90%) were achieved followed by low to moderate mineralization (up to 70%). The oxidation of phenols was affected to a considerable level by the initial COD, reaction temperature and contact time, as well as the second order interaction between COD and temperature, while all other effects were insignificant.     

改良型氧化沟污泥膨胀原因的分析与控制

为了有效控制低负荷改良型氧化沟工艺的污泥膨胀现象,对该工艺的运行参数进行了系统的分析。结果表明,工艺发生污泥膨胀的主要原因是由于氧化沟循环廊道内的溶解氧浓度分级不明显。针对污泥膨胀原因及相关的膨胀机理,采用在循环廊道内加设插板来保证缺氧区、好氧区溶解氧浓度的合理分布。确定了试验装置的最佳运行条件为：好氧区溶解氧含量为1．5—2．0mg／L,缺氧区溶解氧含量小于0．5mg／L,污泥指数为120～150mL／g,污泥质量浓度为3．5-4．0g／L。     

CAST工艺处理城市污水的强化脱氮研究

介绍了镇江征润州污水处理厂CAST工艺的运行情况，结合该厂实际运行状况开展了强化脱氮效果的生产性试验研究。结果表明，该工艺对COD、SS和TP的去除率均能维持在80％以上，但对氨氮的去除效果较差；在该厂运行模式下，控制进水／曝气前30min的DO〈0．5mg／L、进水／曝气后30min的DO浓度在1．0-3．0mg／L、纯曝气DO浓度在2．0-3．0mg／L，可以实现同步硝化反硝化和硝化／反硝化作用下的共同脱氮，使脱氮效率提高了57％左右；在控制进水／曝气后DO〈0．5mg／L、纯曝气DO浓度在1．0-3．0mg／L的条件下，可以实现同步硝化反硝化作用下的脱氮，但较难实现理想的脱氮效果。     

Optimization of phenol removal from wastewater by activation of persulfate and ultrasonic waves in the presence of biochar catalyst modified by lanthanum chloride

In this paper, the effects of phenol concentration, pH, catalyst dose, persulfate concentration, temperature and contact time on the phenol removal from wastewater by activation of persulfate (S₂O₈^?2) in the presence of biochar modified by lanthanum chloride and ultrasonic waves (US) are optimized. Experimental design and optimization were carried out by response surface methodology. The optimum conditions for the maximum phenol removal were obtained pH of 4, phenol concentration of 86 mg/L, catalyst dose of 43 mg/L, persulfate concentration of 86 mg/L, temperature of 41 °C and contact time of 63 min. The optimum phenol removal from synthetic wastewater was attained 97.68%. Phenol removal by the mentioned system was fitted with the first‐order kinetic model. The combination of the ingredients of ‘S₂O₈^?2/US/Biochar‐LaCl₃’ system had a synergistic effect on the phenol removal.     

Evaluation of cycling patterns of dissolved oxygen in a tropical lake as an indicator of biodegradable organic pollution.

Dissolved oxygen cycling patterns in a tropical lake (Weija Lake) were shown to be useful as a potential indicator of biodegradable organic pollution, by dosing with liquid malt to give an additional organic burden of 2.5 and 5.0 mg l-1 TOC, and monitoring the DO values continuously for 140 h. These loadings were added to water columns (in tubes) suspended from a raft in a lake in south-east Ghana. The addition of organic pollution burden to the lake water produced two main effects: the mean DO value was lowered, and the amplitude of the DO cycle decreased as organic loading increased from 2.5 to 5.0 mg l-1 TOC. There was also an indication of heterotrophic respiration associated with organic inputs for the 5.0 mg l-1 added TOC suggesting a P/R ratio of well below 1.0. Taking the results of a DO cycling computer model together with those from the lake raft experiments, it can be concluded that dissolved oxygen cycles can be a good indicator of biodegradable organic pollution load.     

Fenton oxidation of cork cooking wastewater--overall kinetic analysis

In the present work, the possibility of using chemical oxidation through Fenton's reagent for the pre-treatment of cork cooking wastewaters was exploited. Aiming both the selection of the best operating conditions (pH, Fe2+:H2O2 ratio and initial H2O2 concentration) and the evaluation of the overall reaction kinetics, trials were performed in a batch reactor. Operating at pH = 3.2, H2O2 concentration = 10.6 g/L and Fe2+:H2O2 ratio = 1:5 (by weight), about 66.4% of total organic carbon (TOC), 87.3% of chemical oxygen demand (COD) and 70.2% of biochemical oxygen demand (BOD5) were removed and an increase of the BOD5/COD ratio from 0.27 to 0.63 was achieved. In the temperature range 20-50 degrees C, the best performance was obtained at 30 degrees C. The kinetic study was undertaken at different initial TOC concentrations and temperatures. Overall kinetics can be described by a second-order followed by a zero-order rate equation and the apparent kinetic constants at 30 degrees C are k = 2.3 x 10(-4) L/mg min and k0 = 26.0 mg/L min, respectively. The experiments performed at different temperatures confirmed the global kinetic model and allowed to calculate the global activation energy for the second-order reaction (70.7 kJ/mol).     

围压与温度共同作用下盐岩的SHPB实验及数值分析

 在自主研制的可进行围压和温度共同加载的分离式Hopkinson压杆(SHPB)实验装置TSCPT-SHPB基础上,对盐岩在5～25 MPa围压作用下的轴向动力性能以及盐岩在40 ℃～80 ℃,0.0～0.5 MPa围压下进行实验研究,分析围压和应变率对盐岩在围压作用下轴向抗压强度动力增长系数(DIF)的影响,以及温度和围压对盐岩动态力学性能的影响。结果表明：在动态作用下,围压对盐岩延性的提高有显著影响;盐岩属率敏感性和温度敏感性材料,其峰值强度随应变率的提高而提高,在低围压下的提高幅度比高围压下显著,并得到实验范围内盐岩材料动力增长系数(DIF)与围压和应变率关系的表达式;在高应变率(400 s－1)条件下,盐岩的动态峰值强度随温度的升高而降低,并依据实验数据,拟合得到峰值强度在各实验温度下随围压变化的计算公式。为考虑应变软化效应,对ABAQUS有限元软件中的Drucker-Prager模型进行改进,并基于单向动态围压下的实验数据拟合的计算参数,对盐岩TSCP-SHPB实验进行数值模拟,模拟结果与实验结果吻合较好。     

Degradation of natural organic matter by TiO2 photocatalytic oxidation and its effect on fouling of low-pressure membranes

Natural organic matter (NOM) fouling continues to be the major barrier to efficient application of microfiltration (MF) and ultrafiltration (UF) in drinking water treatment. In this study, the potential of TiO2/UV photocatalytic oxidation to control fouling of membranes by NOM was evaluated. Decomposition kinetics of NOM was investigated using a commercial TiO2 catalyst, and the effect of various experimental parameters including TiO2 dosage and initial total organic carbon (TOC) concentration were also determined. The reaction kinetics was found to increase with increasing TiO2 dosage, but decrease with increasing initial TOC concentration. Even though the rate of TOC removal was relatively low, the TiO2/UV process was very effective in controlling membrane fouling by NOM. At a TiO2 concentration of 0.5 g/L, fouling of both an MF and a UF membrane was completely eliminated after 20 min of treatment. Careful analyses of specific UV absorbance (SUVA) and molecular weight (MW) distribution of NOM revealed that the effectiveness in membrane fouling control is the result of the changes in NOM molecular characteristics, namely MW and SUVA due to the preferential removal and transformation of large, hydrophobic NOM compounds. Results from this study show that TiO2/UV photocatalytic oxidation is a promising pretreatment method for MF and UF systems.     

Catalytic wet oxidation of o-chlorophenol at mild temperatures under alkaline conditions

Wet oxidation of a 100 ppm aqueous solution of o-chlorophenol (o-CP) was performed in a lab-scale batch reactor using 3% Ru/TiO(2) catalyst at 373 and 413 K, and a partial oxygen pressure of 0.1 MPa. The experiments were conducted by varying the initial pH values of o-CP solution from pH 6.3 to 9.8 and 11.8. From the results, it was revealed that the catalytic decomposition of o-CP occurred most effectively at 413 K and at the initial pH of 9.8. Complete decomposition and dechlorination of o-CP were almost achieved within 1h, and about 85% of TOC was removed in 3.0 h. On the other hand, the catalytic wet oxidation of o-CP at a higher pH value of 11.8 was not effective in the removal of TOC. The incomplete removal of TOC at the initial pH of 11.8 is likely attributed to a low pK(a) of carboxylic acids formed during the wet oxidation of o-CP.