A comparative study on the performance of different advanced oxidation processes (UV/O3/H2O2) treating linear alkyl benzene (LAB) production plant's wastewater

A detailed investigation on photooxidation of linear alkyl benzene (LAB) industrial wastewater is presented in this study. The process analysis was performed by varying four significant independent variables including two numerical factors (initial pH (3–11) and initial H₂O₂ concentration (0–20 mM)) and two categorical factors (UV irradiation and ozonation). The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). To assess the process performance, two parameters viz. TCOD removal efficiency and BOD₅/COD were measured throughout the experiments. A maximum reduction in TCOD was 58, 53, 51, and 49%, respectively for UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂ processes at the optimum conditions (initial pH of 7, initial H₂O₂ concentration of 100 mM, and reaction time of 180 min). A considerable increase in BOD₅/COD ratio was obtained in the combined processes (0.46, 0.51, 0.53, and 0.55 for UV/H₂O₂, UV/O₃, H₂O₂/O₃ and UV/H₂O₂/O₃, respectively) compared to the single oxidant process (0.35). The results showed that mineralization of the LAB industrial wastewater in neutral pH is more favored than in acidic and basic pH. Gas chromatography–mass spectrometry (GC–MS) was applied to show the fate of organic compounds. In conclusion, the photooxidation process (UV/H₂O₂/O₃, H₂O₂/O₃, UV/O₃ and UV/H₂O₂) could be an appropriate pretreatment method prior to a biological treatment process.     

Effect of H2O2 addition mode on enzymatic removal of phenol from wastewater in the presence of polyethylene glycol

The effect of batch and semi-batch additions of the stoichiometric amount of H₂O₂ on enzymatic removal of phenol has been studied over the phenol concentration range of 1-10 mmol/L. It is found that the ratio between the maximum H₂O₂ concentration during the reaction and the initial horseradish peroxidase concentration ((H₂O₂)_max/(HRP)_o) controls the rate of phenol removal by horseradish peroxidase in the presence of the additive, polyethylene glycol. An optimum range of this ratio is determined to be between 10 and 25 μmol/U. Empirical models are proposed to predict the values of (H₂O₂)_max/(HRP)_o required to treat given phenol concentrations under different modes for adding H₂O₂.     

H2O2与O2协同引发的TiO2/Fe3+光催化降解苯酚

以玻璃纤维为载体,将TiO2/Fe3+负载到其表面制成了空间玻璃纤维反应器。利用该反应器以高压汞灯为光源进行了光催化降解水中苯酚的试验研究,重点考察了H2O2及O2的协同作用对光催化氧化的影响。试验发现,H2O2的加入对HO.的产生有显著的引发作用,同时向溶液中充入O2可明显提高光催化效率,降低H2O2用量。试验结果表明,以UV365-250 W光源照射,在初始pH为3~5,O2通入量为1.0 L/(min.L),上升流速为0.7 m/min,H2O2浓度为0.1 mmol/L等试验条件下,初始质量浓度为30 mg/L的苯酚废水经120 min光催化反应后,其矿化率可达83%左右。     

Studies on biodegradation of phenol using response surface methodology

Biodegradation of phenol was studied using Pseudomonas pictorum (NCIM 2077) immobilized on alginate and activated carbon – alginate beads. Control experiments were also performed using free cells and non‐inoculated activated carbon – alginate beads. The entrapped alginate and activated carbon – alginate beads suffer from a concentration gradient for oxygen in the interior of the beads and hence free cells showed better degradation at lower concentrations of phenol. The results on entrapped alginate beads were modeled using response surface methodology which determines the dependency of the maximum percentage of phenol degraded as a function of the independent variables, namely initial phenol concentration, initial pH, temperature, and diameter of the immobilized beads. The predicted values are in close agreement with the experimental values with the coefficient of correlation equal to 0.9999 and 0.9993 for both P pictorum – alginate beads and activated carbon – P pictorum – alginate beads respectively. © 2002 Society of Chemical Industry     

含La2O3助催化剂的铁酞菁分子筛的微波合成及催化性能的研究

利用微波辐射法在KX分子筛内原位合成了以La2O3为助剂的铁酞菁,用IR、XRD对合成产物进行了表征,比较了加热方式对产率的影响。考察了产物对过氧化氢分解的催化活性。     

微反应器内制备4-（6-羟基己氧基）苯酚工艺

研究了在微反应器中利用Williamson合成法连续高效制备4-（6-羟基己氧基）苯酚的工艺过程。通过响应曲面法中的Box-Behnken模型设计实验,考察了反应温度、催化剂浓度、物料比、停留时间以及因素间的交互作用对目标产物收率的影响,并建立了响应值与影响因素之间的回归模型。根据该模型预测得到的最佳操作工艺参数为：反应温度135℃,NaOH浓度2.35 mol·L^-1,物料摩尔比2.81,停留时间2.70 min。在此条件下产物收率达79.5%,且预测值与实验值吻合良好。此外,建立了一套产物提纯方案,并通过¹H NMR谱图对产物结构进行确认。     

Cu/Al2O3催化剂用于H2O2分解生成羟基自由基的效率

非均相Fenton催化反应是降解废水中有机污染物的有效方法。提高H₂O₂分解生成羟基自由基（·OH）的利用率是提升废水处理效率、降低成本的关键。使用溶胶-凝胶法制备了Cu/Al₂O₃催化剂,基于·OH的生成效率,通过单因素实验发现反应温度、反应溶液pH及H₂O₂初始浓度是决定H₂O₂利用率的主要因素。通过响应面法进行实验设计,分析响应面方程,考察了H₂O₂初始浓度、溶液pH及反应温度三个因素之间的交互作用及其对反应过程的影响。以H₂O₂利用率的最大化为目标优化反应条件,当H₂O₂初始浓度、溶液pH及反应温度分别为707 mg·L^-1、5.12及59.4℃时,H₂O₂利用率可高达0.57,与实验结果相对误差仅为3.5%。所得结果对降低废水处理成本、提高降解效率具有重要的指导作用。     

Optimization and analysis of nickel adsorption on microwave irradiated rice husk using response surface methodology (RSM)

BACKGROUND: The removal of heavy metals using adsorption techniques with low cost biosorbents is being extensively investigated. The improved adsorption is essentially due to the pores present in the adsorbent. One way of improving the porosity of the material is by irradiation of the precursor using microwaves. In the present study, the adsorption characteristics of nickel onto microwave‐irradiated rice husks were studied and the process variables were optimized through response surface methodology (RSM). RESULT: The adsorption of nickel onto microwave‐irradiated rice husk (MIRH) was found to be better than that of the raw rice husk (RRH). The kinetics of the adsorption of Ni(II) from aqueous solution onto MIRH was found to follow a pseudo‐second‐order model. Thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were also evaluated. The thermodynamics of Ni(II) adsorption onto MIRH indicates that it is spontaneous and endothermic in nature. The response surface methodology (RSM) was employed to optimize the design parameters for the present process. CONCLUSION: Microwave‐irradiated rice husk was found to be a suitable adsorbent for the removal of nickel(II) ions from aqueous solutions. The adsorption capacity of the rice husk was found to be 1.17 mg g^?1. The optimized parameters for the current process were found as follows: adsorbent loading 2.8 g (100 mL)^?1; Initial adsorbate concentration 6 mg L^?1; adsorption time 210 min.; and adsorption temperature 35 °C. Copyright © 2008 Society of Chemical Industry     

微波/催化剂/H2O2降解酸性红B的研究

以颗粒活性炭为载体,分别负载Fe3+、Cu2+或Fe3+-Cu2+制备出催化剂,采用微波/催化剂/H2O2工艺对酸性红B进行降解研究,并考察了各种因素对酸性红B降解效果的影响。研究结果表明,活性炭负载Fe3+-Cu2+型催化剂对酸性红B的处理效果最好,适宜的Fe3+、Cu2+负载量均为1.0%;对于100 mL初始质量浓度为100 mg/L的酸性红B模拟染料废水,适宜的处理条件为初始pH=3、催化剂投加量0.1 g、H2O20.05 mL、微波功率300 W。在此条件下处理4 min后酸性红B去除率超过99%,说明微波/催化剂/H2O2工艺能够有效去除酸性红B。     

Biodiesel production from Nannochloropsis microalgal biomass-derived oil: An experimental and theoretical study using the RSM-CCD approach

Biodiesel production from Nannochloropsis is investigated in the current study. Based on the extraction studies, the used biomass is composed of 50% saponifiable lipids, which turns this species to a vulnerable feedstock for biodiesel production. It should also be noted that the acidity of the obtained crude bio-oil is higher than 2 mg KOH/g, hence it was attempted to survey the biodiesel production from the obtained oil through the esterification reaction with the aid of response surface methodology (RSM). According to the data, the highest biodiesel yield (99.5%) from the bio-oil is obtained at a reaction temperature of 69°C, a reaction time of 30 min, a methanol to oil molar ratio of 9:1, and an H₂SO₄ concentration of 0.13 wt.%. In the next step, the in-situ extraction and esterification of Nannochloropsis were investigated at the observed optimum reaction conditions. Based on the analysis, biodiesel yield from the dry cell weight of the biomass is considered to be 16%, which accounts for 99% conversion of bio-oil to biodiesel.     

An optimization and modeling approach for H2O2/UV‐C oxidation of a commercial non‐ionic textile surfactant using central composite design

BACKGROUND: Industrial surfactants are biologically complex organics that are difficult to degrade and may cause ecotoxicological risks in the environment. Until now, many scientific reports have been devoted to the effective treatment of surfactants employing advanced oxidation processes, but there is no available experimental study dealing with the optimization and statistical design of surfactant oxidation with the well‐established H₂O₂/UV‐C process. RESULTS: Considering the major factors influencing H₂O₂/UV‐C performance as well as their interactions, the reaction conditions required for the complete oxidation of a commercial non‐ionic textile surfactant, an alkyl ethoxylate, were modeled and optimized using central composite design‐response surface methodology (CCD‐RSM). Experimental results revealed that for an aqueous non‐ionic surfactant solution at an initial chemical oxygen demand (COD) of 450 mg L^?1, the most appropriate H₂O₂/UV‐C treatment conditions to achieve full mineralization at an initial pH of 10.5 were 47 mmol L^?1 H₂O₂ and a reaction time of 86 min (corresponding to a UV dose of 30 kWh m^?3). CONCLUSION: CCD allowed the development of empirical polynomial equations (quadratic models) that successfully predicted COD and TOC removal efficiencies under all experimental conditions employed in the present work. The process variable treatment time, followed by the initial COD content of the aqueous surfactant solution were found to be the main parameters affecting treatment performance, whereas the initial H₂O₂ concentration had the least influence on advanced oxidation efficiencies. The H₂O₂ concentration and surfactant COD were found to be more important for TOC abatement compared with COD abatement. Copyright © 2009 Society of Chemical Industry     

Response surface methodology as a tool to study the lipase‐catalyzed synthesis of betulinic acid ester

BACKGROUND: The synthesis of betulinic acid ester using betulinic acid and oleyl alcohol catalyzed by Novozym 435 (immobilized Candida antarctica lipase) was carried out. Response surface methodology (RSM) based on a five‐level, three‐variable, central composite rotatable design (CCRD) was employed to evaluate the interactive effects of various parameters. The parameters were reaction time (8–16 h), temperature (20–60 °C) and enzyme amount (120–160 mg). RESULTS: Simultaneously increasing reaction time, temperature and amount of enzyme increased the yields of betulinic acid ester produced. CONCLUSION: The optimum conditions derived via RSM for the reaction were reaction time of 10.2 h, temperature of 53.1 °C and enzyme amount of 138 mg. The actual experimental yield was 48.5% under optimum conditions, which compared well with the maximum predicted value of 47.6%. Copyright © 2008 Society of Chemical Industry     

Response Surface Optimization of the Critical Media Components for the Production of Surfactin

Optimization of the fermentation media for maximization of surfactin production was carried out. The carbon source (glucose), the nitrogen source (ammonium nitrate) and the mineral salts ferrous and manganous sulphates were the critical components of the medium optimized. A 2⁴ full factorial central composite experimental design followed by multi-stage Monte-Carlo optimization was used in the design of experiments and in the analysis of results. This procedure limited the number of actual experiments performed while allowing for possible interactions between the four components. The optimum values for the tested variables for the maximal production of surfactin were (in g dm⁻³): glucose = 36·5; NH₄NO₃ = 4·5; FeSO₄ = 4×10⁻³ and MnSO₄ = 27·5 ×10⁻². Relative surfactant concentrations were expressed as the reciprocal of the critical micelle concentration (CMC⁻¹) and the maximum predicted yield of surfactin in terms of CMC⁻¹ was 45·5. © 1997 SCI.     

微波辐射条件下H2O2氧化蒽合成蒽醌的研究

研究了微波辐射条件下H2O2氧化蒽的反应，考察了时间、H2O2用量、催化剂和溶剂对葸醌收率的影响。结果表明．CH3COOH浓度对蒽醌的收率影响很大，以适量的(CH3COO)3Fe作为催化剂可以增加蒽醌的收率和缩短反应时间。     

响应面法优化油菜秸秆真空热解液化工艺及生物油分析1

以油菜秸秆为原料,采用真空热解系统进行了制取生物油的中心组合实验研究,以热解终温、体系压力和升温速率为实验因子,生物油产率为实验指标,利用响应面法(RSM)对制备生物油的工艺参数进行了优化,并对在最优条件下制取的生物油进行了理化特性和化学组成分析。研究结果表明,热解终温、体系压力和升温速率对生物油产率有显著影响,热解终温和升温速率之间的交互作用显著;获得最佳热解液化工艺条件为:热解终温490.0℃、体系压力5.0 k Pa、升温速率20.0℃·min-1,在此条件下,生物油产率可达41.65%。与预测值42.00%较为接近。油菜秸秆真空热解所得生物油的含水量为33.85%,热值为18.65 MJ·kg-1,常温下的运动黏度为4.16 mm2·s-1,密度和p H值分别为1.14g·cm·3和2.32;生物油成分较为复杂,其中多种有机物可被进一步提取用作化工原料;生物油中羧酸、醛、酮类等腐蚀性和不稳定组分含量较高,需对其进一步精制,以提高其稳定性。     

新型除磷填料的制备及除磷吸附床运行参数的优化

为解决现有除磷吸附剂粒径小造成的材料易流失和系统压降过大等问题,以实现吸附除磷工艺在实际工程中的应用,以聚氨酯填料为载体,水溶性聚氨酯为介质,将水化硅酸钙负载到聚氨酯填料上制成负载型除磷填料。研究了制备条件对除磷填料除磷效果的影响,采用扫描电子显微镜（SEM）和傅里叶变换红外光谱仪（FTIR）观察分析了负载前后水化硅酸钙微观结构及化学基团的变化;利用除磷填料作为除磷吸附床的滤料,研究了运行条件对吸附床除磷效果的影响。在此基础上,利用响应曲面法研究了除磷吸附床磷酸盐去除率和各变量之间的关系,并对工艺参数进行了优化。结果表明,水性聚氨酯溶液的浓度和用量分别为100 g/L和50 ml,水化硅酸钙的质量为12 g的条件下所制备的除磷填料除磷效果最好;SEM和FTIR分析结果显示,水化硅酸钙负载前后其孔隙结构和化学基团没有明显的变化;预测模型的方差分析结果表明,HRT(X ₁)、进水ρ(PO₄ ^3--P)(X ₂)、温度(X ₃)、初始pH(X ₄)以及X ₁ X ₂,X ₁ X ₄,X ₂ X ₃,X ₂ X ₄的交互作用均对磷酸盐的去除具有显著影响 (P＜0.05),但X ₁ X ₃的交互作用对磷酸盐的去除影响不显著。通过预测模型获得的最佳运行条件为：HRT为79.77 min,进水ρ(PO₄ ^3--P)为1.70 mg/L, 温度为34.04℃,pH为9.68。在该条件下,反应器对磷酸盐的去除率可以达到93.46%。     

响应面法优化竹材热裂解制备生物油的工艺研究

为了提高竹材生物质流化床快速热裂解制备生物油产率,利用响应面法优化其最佳工艺条件.试验选择热裂解温度(450～550℃)、气相停留时间(1.5～2.5 s)和物料粒径(0.18 ～0.22 mm)三因素作为独立变量,采用中心组合设计建立模型和考察上述因素对生物油收率的影响.结果表明三因素对生物油收率具有显著影响而它们之间的交互作用均不显著.依据所得到的模型,在各因素设定范围内获得的最佳工艺条件为:热裂解温度519.0℃、气相停留时间2.1s、物料粒径0.18mm,生物油理论收率为58.17％.在该条件下进行的三次重复试验,竹材生物油的实际平均收率为57.85％,与模型预测值58.17％无显著差异.响应面法简便、高效,优化结果能给生物质流化床快速热裂解制备生物油制备工艺提供一定的参考.     

Photocatalytic oxidation of treated municipal wastewaters for the removal of phenolic compounds: optimization and modeling using response surface methodology (RSM) and artificial neural networks (ANNs)

BACKGROUND: TiO₂ heterogeneous photocatalysis should be optimized before application for the removal of pollutants in treated wastewaters. The response surface methodology (RSM) and artificial neural networks (ANNs) were applied to model and optimize the photocatalytic degradation of total phenolic (TPh) compounds in real secondary and tertiary treated municipal wastewaters. RESULTS: RSM was developed by considering a central composite design (CCD) with three input variables, i.e. TiO₂ mass, initial concentration of TPh and irradiation intensity. At the same time a feed‐forward multilayered perceptron ANN trained using back propagation algorithms was used and compared with RSM. Under the optimum conditions established in experiments ([TPh]₀ = 3 mg L^?1; [TiO₂] = 300 mg L^?1; I = 600 W m^?2) the degradation for both TPh and total organic carbon (TOC) followed pseudo‐first‐order kinetic model. Complete degradation of TPh took place in 180 min and reduction of TOC reached 80%. A significant abatement of the overall toxicity was accomplished as revealed by Microtox bioassay. CONCLUSIONS: It was found that the variables considered have important effects on TPh removal efficiency. The results demonstrated that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process and that ANNs gave better modelling capability than RSM. Copyright © 2012 Society of Chemical Industry