Electrochemical treatment of Methyl Orange dye wastewater by rotating disc electrode: optimisation using response surface methodology

In the present investigation, a novel rotating disc electrochemical reactor has been developed to treat Methyl Orange dye effluent. Stainless steel and ruthenium oxide‐coated titanium electrodes were used as cathode and anode, respectively. A statistical tool of the Box–Behnken method has been used to design the experimental run and optimisation. The combined effect of the operating parameter on the efficiency of the process has been critically examined. A quadratic model for reduction of chemical oxygen demand has been developed. A maximum of 96% chemical oxygen demand removal was observed under optimum conditions. The degradation mechanism was studied by ultraviolet–visible spectrophotometer, Fourier Transform–infrared and high‐performance liquid chromatography. From the present investigation, it has been observed that dyehouse effluent can be effectively treated using the novel electrochemical reactor.     

Electrochemical oxidation of simple indoles at a PbO2 anode

Simple indoles undergo electrolytic degradation at potentials near +1 V vs the normal hydrogen electrode at a Pb/PbO₂ anode. Oxidation is first order in both current and indole concentration. The reaction is characterized by low CO₂ yields and high TOC values, that is, most of the carbon of the starting material remained in the solution after electrolysis. Monomeric, isolable oxidation products were not found even at high conversion. These results are consistent with the intermediacy of hydroxyl radicals, which are produced at the surface of the Pb/PbO₂ anode by electrolysis of water, initiating the polymerization of the starting materials to water soluble products with high net current efficiency.     

响应曲面法优化电催化降解染料废水工艺的研究

采用中心复合设计的响应曲面法预测电催化降解染料废水的最优条件。具体以Ti/SnO₂-Sb电极作为阳极,应用响应曲面法研究了pH、施加电压值、电极间距对亚甲基蓝溶液脱色效率的影响。研究结果表明模型拟合精度R²=0.9942,初始pH、施加电压值、电极间距及交互作用对脱色率响应值影响大。模型预测最佳反应条件pH为6.98,施加电压6.0 V,电极间距为1.01 cm时,脱色效率预测值达到98.68%。采用实验进一步验证该模型,预测最佳条件下三次实验脱色率平均值98.47%。该方法可用于优化电催化降解染料废水的工艺参数,为实际废水处理提供优化方案。     

Optimizing photocatalytic degradation of phenol by TiO2/GAC using response surface methodology

TiO₂ deposited on granular activated carbon (TiO₂/GAC) was used for photocatalytic degradation of phenol. The effects of photocatalyst loading, initial substrate concentration and addition of an oxidizing agent as H₂O₂ were investigated using a one-factor-at-a-time experiment. Central composite design, an experimental design for response surface methodology (RSM), was used for the modelling and optimization of the phenol degradation. Analysis of variance (ANOVA) indicated that the proposed quadratic model was in agreement with the experimental case with R² and R _adj ² correlation coefficients of 0.9760 and 0.9544, respectively. Accordingly, the optimum conditions for phenol degradation were a photocatalyst loading of two layers, initial phenol concentration of 34.44 mg L^?1 and H₂O₂ concentration of 326.90 mg L^?1. The TiO₂/GAC was used for five cycles with phenol degradation efficiency still higher than 90%. Finally, the phenol that remained adsorbed on GAC was able to migrate to TiO₂ and then photocatalytically be degraded.     

On the performance of Ti/SnO2 and Ti/PbO2 anodesin electrochemical degradation of 2-chlorophenolfor wastewater treatment

Electrochemical oxidation of 2-chlorophenol was studied at Ti/PbO2 and Ti/SnO2 anodes. The performance of the electrodes was evaluated in terms of faradaic yield and fraction of toxic intermediates removed during the electrolysis. Results showed that, although similar average faradaic yields were obtained using Ti/PbO2 or Ti/SnO2 anodes, the latter material is preferred because of its better ability to oxidise toxic compounds. An effective electrochemical treatment (F50%) may be accomplished, in which electrolysis at Ti/SnO2 can be stopped when, in spite of a relatively high COD, only a small amount of easily biodegradable oxalic acid is present in the effluent.     

Optimization and modeling of UV-TiO2 mediated photocatalytic degradation of golden yellow dye through response surface methodology

In this article, heterogeneous photocatalysis of golden yellow (GY) dye by Evonik p25 titanium dioxide (PTD) and UV radiations was optimized by using central composite design of response surface methodology. The GY dye photocatalysis was expressed as the function of amount of PTD loading (X₁), GY dye initial concentration (X₂), and UV irradiance intensity (X₃). The optimization of degradation conditions was done by measuring two different responses, that is, color removal (Y₁) and chemical oxygen demand removal (Y₂). The effect of X₁, X₂, and X₃ were studied in the range 0.5–1.5?g/L, 15–35?W/m², and 10–30?mg/L, respectively. The quadratic model was suggested for Y₁ and Y₂. The numerical optimization of results was done via Design Expert software. The predictive results obtained were verified by performing actual experiments. The photodegradation kinetics, total organic carbon disappearance, effect of inorganic salts, and H₂O₂ concentration on GY dye photodegradation were also studied.     

Electrochemical oxidation of polyvinyl alcohol using a RuO2/Ti anode

Polyvinyl alcohol (PVA), known as the dominant contributor of chemical oxygen demand (COD) in textile wastewater, is very difficult to decompose by conventional treatment technologies. In this study, electrochemical oxidation using a RuO₂/Ti anode was applied to treat a PVA solution. The mechanisms of PVA degradation and COD destruction were investigated, while the operating parameters affecting the mechanisms were also studied. The parameters investigated included current density, PVA concentration in waste stream, the rate of electrolyte consumption of sodium chloride, and the feed rate of wastewater. The overall mass transport behavior of electrochemical oxidation of PVA was explained by the mathematical relationship of dimensionless numbers such as the Reynolds, Schmidt and Sherwood numbers.     

N掺杂TiO_2/Ti液膜光催化处理染料废水

以尿素为氮源,采用溶胶-凝胶法制备了N掺杂Ti O2膜电极(N-Ti O2/Ti),并优化了制备条件。结果表明,n(N)∶n(Ti)=0.84∶1、经450℃煅烧2.5 h制得的膜电极光催化性能最佳;与Cu电极组装斜置双极液膜反应器,可见光下考察光催化反应的影响因素。得出最佳降解条件为:初始p H=2.50,废水流量为85 m L/min,Na2SO4质量浓度为0.5 g/L,此条件下处理20 mg/L苋菜红120 min,脱色率可达90.1%;膜电极的重现性与重复性结果表明,6片电极60 min的脱色率为78.1%±4.0%;一片电极经6次循环60 min脱色率比初次减少了7.9%。     

Ti/SnO2+Sb2O3/PbO2电极在硫酸溶液中Cr3+氧化的电化学性能

对用聚合前驱体溶液通过热分解法制备的Ti/SnO2+Sb2O3/PbO2电极在硫酸溶液中Cr3+电化学氧化的电化学性能进行了研究. 分别测定了以Ti/SnO2+Sb2O3/PbO2和PbO2为阳极，硫酸介质中Cr3+电化学氧化过程的极化曲线、抗腐蚀性以及不同操作电流密度、Cr3+浓度、反应温度、硫酸浓度下的电流效率. 实验结果表明，聚合前驱体溶液通过热分解法制备的Ti/SnO2+Sb2O3/PbO2电极与PbO2电极相比具有更高的电催化活性和抗腐蚀性.     

Optimization of sulfamethoxazole degradation by TiO2/hydroxyapatite composite under ultraviolet irradiation using response surface methodology

A titanium dioxide/hydroxyapatite/ultraviolet (TiO₂/HAP/UV-A) system was used to remove sulfamethoxazole (SMX) from water in a second-order response surface methodology (RSM) experiment with a three-level Box-Behnken design (BBD) for optimization. The effects of both the primary and secondary interaction effects of three photocatalytic reaction variables were examined: the concentration of SMX (X₁), dose of TiO₂/HAP composite (X₂), and UV intensity (X₃). The UV intensity and TiO₂/HAP dose significantly influence the SMX and total organic carbon (TOC) removal (p<0.001). However, the SMX and TOC removal are enhanced with increasing TiO₂/HAP dose up to certain levels, and further increases in the TiO₂/HAP dose result in adverse effects due to hydroxyl radical scavenging at higher catalyst concentrations. Complete removal of SMX was achieved upon UV-A irradiation for 180min. Under optimal conditions, 51.2% of the TOC was removed, indicating the formation of intermediate products during SMX degradation. The optimal ratio of SMX (mg L^?1) to TiO₂/HAP (g L^?1) to UV (W/L) was 5.4145 mg L^?1 to 1.4351 g L^?1 to 18W for both SMX and TOC removal. By comparison with actual applications, the experimental results were found to be in good agreement with the model’s predictions, with mean results for SMX and TOC removal of 99.89% and 51.01%, respectively.     

乙酰甲胺磷UV-TiO_2/类Fenton光催化降解过程的响应面法优化

为提高乙酰甲胺磷农药残留降解效率,在单因素实验的基础上,应用响应面法对乙酰甲胺磷纳米TiO2-UV/类Fenton光催化降解过程中纳米TiO2添加量、农药初始浓度、添加类Fenton试剂及反应时间等因素进行了优化,建立并验证了所得到的预测模型。结果表明,乙酰甲胺磷纳米TiO2-UV/类Fenton光催化降解过程可应用所建立的二次多项回归拟合方程进行预测,模型拟合良好;同时,除类Fenton组成比例与乙酰甲胺磷初始浓度之间无交互作用外,其他各因素之间均存在显著交互作用;计算得到的优化工艺条件为:纳米TiO2添加量0.1 g/L,H2O2∶Cu2+添加比例26.34,乙酰甲胺磷初始浓度23.09 mg/L,光照时间25.42 min,在此条件下,乙酰甲胺磷降解率预测值为100.414%,验证值为99.99%。说明响应面法对筛选光催化降解工艺条件,提高光催化降解效率是十分有效的。     

新型钛基PbO2阳极电氧化降解 有机污染物的特性研究

用电沉积法制备了PbO2/SnO2+Sb2O3/Ti、Bi-PbO2/SnO2+Sb2O3/Ti、PbO2（超声）/SnO2+Sb2O3/Ti、Bi-PbO2（超声）/SnO2+Sb2O3/Ti等4种二氧化铅电极,用稳态极化曲线表征了它们的电催化性和选择性,分析了电解苯酚废水的处理效果,用加速寿命实验测定了电极寿命,用电子扫描电镜表征了沉积层晶相和形貌。结果表明：掺Bi可以提高电极的电催化性和电氧化苯酚的选择性,超声电沉积可以增大电极比表面积,提高电极的表观催化活性,显著增长电极加速寿命。     

Ag掺杂Ti/PbO2电极的制备及其在苯酚降解中的应用

使用化学还原和电沉积的方法制备了单质银（Ag）掺杂的Ti/PbO₂电极（Ti/Ag-PbO₂）。在保持镀银液浓度一定的条件下,通过改变镀银的时长制备出三种银含量的钛基体二氧化铅电极（Ti/Ag1-PbO₂、Ti/Ag2-PbO₂、Ti/Ag3-PbO₂）。利用X射线光电子能谱（XPS）和X射线荧光光谱分析（XRF）确定了PbO₂电极中Ag的价态和掺杂量。扫描电子显微镜（SEM）和X射线衍射（XRD）结果表明,Ag掺杂未明显改变电极的表面形态和晶型。根据涂层附着力测试试验发现,掺银PbO₂电极与基底之间有更好的结合力,电极使用寿命提高了约2.5倍。电化学交流阻抗谱（EIS）和循环伏安法（CV）测试结果表明,Ag的掺杂大幅降低了PbO₂电极的电荷转移电阻,提高了电极的电催化活性。利用掺银量2.7%（质量分数）的Ti/PbO₂电极降解100mg/L的苯酚水溶液,相较常规Ti/PbO₂电极,完全降解时间缩短了33.3%,降解能耗下降了34%。     

Electrochemical degradation of azo dye C.I. Reactive Red 195 by anodic oxidation on Ti/SnO2-Sb/PbO2 electrodes

This study investigated the electrochemical degradation of C.I. Reactive Red 195 (RR195) in aqueous solution on a Ti/SnO₂-Sb/PbO₂ electrode. The influence of operating variables on the mineralization efficiency was studied as a function of the current density, the initial pH, the initial concentration of the dye and the addition of NaCl. The efficiency of RR195 mineralization decreased with increased initial concentration, from 100 mg L⁻¹ to 400 mg L⁻¹. The current density had both a positive and a negative effect on degradation rates, and no significant effect of initial pH on RR195 mineralization was observed. Measurement of absorbance was used to discriminate the effect of NaCl in the electro-oxidation process. We found that the decolouring efficiency increased whereas the mineralization efficiency decreased with the increasing concentration of NaCl. The intermediates formed during the degradation were detected by gas chromatography-mass spectrometry, and the major aromatic intermediates identified were 1-(3,6,8-trihydroxy-1-naphthyl)urea, nitrobenzene, benzo-1,4-quinone, (3,6,8-trihydroxy-1-naphthyl)carbamic acid and phthalic acid. Quantitative measurement of organic and inorganic ions was done by ion chromatography. On the basis of the reaction products identified, a possible degradation pathway for the anodic oxidation of RR195 in aqueous solution is proposed.     

铁掺杂PbO2/Ti电极电催化氧化苯酚的实验研究

以苯酚为目标化合物,研究了新型铁掺杂PbO2/Ti阳极电催化氧化有机污染物的特性,结果表明,该电极对苯酚的降解显示了良好的电催化活性,有较好的环保应用前景。同时,初步探讨了反应的动力学和氧化机理。     

利用响应面法对L-2菌株降解石油烃进行优化

从石油烃污染土壤中分离得到菌株L-2,对石油烃（TPH）的降解进行研究。通过16S rRNA鉴定L-2为肠杆菌属。采用基于Box-Behnken设计（BBD）的响应面方法（RSM）,考察温度、pH和TPH质量浓度3个自变量对TPH降解率的交互效应,建立二次回归方程预测模型,确定3个实验因素的最佳组合,通过方差分析验证该二次模型的有效性。确定系数R²=0.9943,表明二次模型与实验数据吻合较好。响应面优化得到最佳降解条件：温度为30℃,pH为7.13和TPH质量浓度为3.93g/L,TPH降解率为87.79%。结果表明,温度对TPH降解速率的影响（P<0.0001）较其他两个参数更显著。GC/MS结果表明菌株L-2可降解十六烷(C₁₆)至二十五烷(C₂₅)范围内的TPH组分。     

微流控反应器中苯酚在Ti/SnO2-Sb2O5电极上的阳极氧化分析

目前在电化学氧化处理法降解苯酚废水的研究过程中,研究者多将重心放在活性电极的探索及制备上,而对于反应器的开发鲜有报道。就这一问题,本文研究了新型微流控反应器中苯酚的电化学降解效果。电化学氧化实验在装有Ti/SnO₂-Sb₂O₅阳极的微型流通池中操作进行,实验对循环体系的体积流率Φ_V、电极间距h的影响进行了考察。结果表明,当流通电解槽中的阴阳极间距采用微米级尺寸时,苯酚的阳极氧化反应取得了较快的氧化速度。在 em= 20 mA/cm²、Φ_V= 0.54 mL/min的电解条件下,电解2~3h苯酚去除率即可达到90%以上,相同流速下电极间距h越小降解速率越快。且由数据回归得到了苯酚的一系列随h的减小而增大的准一级反应的反应速率常数。这一结论表明微流控电解槽内的苯酚降解过程主要传质控制过程。     

脉冲电镀制备钛基二氧化铅电极

应用脉冲电镀技术制备钛基二氧化铅电极，考察了制备电极在1mol／L的硫酸溶液中的电化学特性．对制备电极进行SEM研究，测定了电极的电化学动力学参数，并与直流电镀制备的电极进行了比较．结果表明，脉冲电镀电沉积可以降低晶粒大小，改善镀层的物理性能，增高电极的析氧电位．     

Optimization of aqueous p-aminophenol degradation by external-loop airlift sonophotoreactor using response surface methodology

The combination of sonolysis and photolysis in the presence of hydrogen peroxide (H₂O₂) in a 7-L external-loop airlift sonophotoreactor was used to treat the aqueous solution of p-aminophenol. The central composite design (CCD) and response surface methodology (RSM) were employed to evaluate the interaction effects of the initial H₂O₂ concentration (x₁ = 100–900 mg/L), the ultrasonic power (x₂ = 25–65 W), the air flow rate (x₃ = 1–5 L/min), and the initial concentration of p-aminophenol (x₄ = 10–50 mg/L) on the p-aminophenol degradation and total organic carbon (TOC) reduction efficiencies as well as to optimize operating conditions. The coefficients of determination (R²) and adjusted-R² obtained from the analysis of variance (ANOVA) were 0.9900 and 0.9812 for the p-aminophenol degradation; and 0.9742 and 0.9516 for the TOC removal, respectively, ensuring a satisfactory adjustment of the quadratic regression model with experimental results. The linear, square, and interaction effects of x₁, x₂, x₃, and x₄ were also calculated. Genetic algorithm optimization was employed to maximize the mineralization efficiency. 79% TOC reduction efficiency after 90 min and 86.5% p-aminophenol removal efficiency after 30 min were achieved under recirculating batch mode at operating conditions of x₁ = 740 mg/L, x₂ = 65 W, x₃ = 5 L/min, and x₄ = 24 mg/L.     

斜板液膜反应器光电催化降解罗丹明B

采用溶胶-凝胶法制备了TiO2/Ti电极,进行光电催化降解罗丹明B(RhB)试验。确定了最佳降解条件:外加偏压+0.8 V、废水流量7.7 L/h、初始pH=2.5和电解质质量浓度2.0 g/L。在最佳条件下,处理20 mg/L的RhB溶液1.5 h,脱色率和TOC去除率分别达到97.3%和76.2%。结果表明,由于同时强化了激发光源的利用率和溶液的传质效率,斜板液膜反应器可高效降解RhB。