Mechanism in chlorine-enhanced Pd catalyst for H2O2 in situ synthesis in electro-Fenton system

Palladium-based catalysts have been widely employed in the electro-Fenton process for in situ generation of H₂O₂. However, the process is still far from being practical on a large scale. In this work, a series of Cl_xFePd/γ-Al₂O₃/Al catalysts were prepared by a three-step-impregnation method. They exhibited excellent activity in H₂O₂ in situ synthesis and high efficiency in phenol degradation. The characterization results showed that Cl could assist in increasing the content of Pd⁰ and reducing the isoelectric point of catalysts, which led to the drastic promotion in the synthesis of H₂O₂. Theoretical calculations further demonstrated that Cl doping could facilitate the main reaction in H₂O₂ synthesis, as well as inhibit side reactions such as dissociation of the O O bond. Furthermore, kinetic models were proposed and fitted. A plausible reaction mechanism as well as degradation pathways were elaborated based on electron spin resonance and gas chromatography–mass spectrometry results. These findings illustrate the value of palladium-based Cl_xFePd/γ-Al₂O₃/Al catalysts for their application in the electro-Fenton process.     

响应面法优化电解芬顿协同法深度处理老龄垃圾渗滤液

采用电解芬顿法深度处理老龄垃圾渗滤液,选取电量、进水 pH 值、进水氨氮浓度3个因素为变量,CODCr 去除率为响应值进行 Box-Behnken 中心组合设计。利用响应面法对试验结果进行分析,建立了 CODCr 去除率为响应值的二阶多项式模型并进行了方差分析和显著性检验,通过解模型逆矩阵得到最佳条件：单位面积电量为23．26 Ah／dm2、pH 值为3．58、进水氨氮浓度56．78 mg／L。在最佳条件下,CODCr 去除率为96．5％,与模型预测值偏差为4．45％,吻合度较高。对电解芬顿深度处理前后的渗滤液进行 GC-MS 分析,表明电解芬顿协同处理技术能有效降解垃圾渗滤液中难生化降解的有机物,将有机物种类从42种降低至21种,是较有效的深度处理技术。     

电芬顿体系中铁铈双金属催化剂降解邻苯二甲酸二丁酯研究

以MCM-41为载体,采用水热-焙烧法制备了Al修饰双金属催化剂Fe-Ce/Al-MCM-41并进行了XRD、BET和FT-IR表征;以水体中的邻苯二甲酸二丁酯(DBP)为处理对象,在铂丝-碳毡电芬顿体系中研究了催化氧化降解DBP的效果和影响因素,探讨了降解机理。结果表明,铁、铈双金属催化剂在电芬顿体系降解邻苯二甲酸二丁酯中具有良好的催化活性,铝离子的加入能够提高催化剂的催化性能;最佳实验条件为pH=3、催化剂投加量0.5 g/L、电流强度I=0.15 A、通氧流量0.2 L/min、反应120 min、初始浓度10 mg/L,此时DBP去除率为97.1%,在酸性或中性条件下去除率稳定在92.1%以上,碱性条件下DBP去除率降低,电流强度和通氧量达到饱和后对DBP降解率影响很小,并且催化剂投加过量会导致催化效果降低。此电芬顿体系中·OH的氧化反应是降解DBP的主要途径。     

响应面法优化电Fenton深度处理煤化工废水

为得到电Fenton技术深度处理煤化工废水的最优条件参数,采用电Fenton技术深度处理生物稳定的煤化工废水,利用正交试验、响应面法和中心复合试验设计对影响电Fenton处理效果的主要因素进行优化,建立二次模型,并进行试验结果预测.结果表明:各因素对处理效果影响程度的顺序为p H电流密度Fe2+浓度.根据方差分析,二次模型具有很高的显著性,能够很好地预测试验结果.影响处理效果的3个主要因素的最优值分别为p H 4.13、Fe2+浓度1.56 mmol/L、电流密度14.74 m A/cm2,此时TOC去除率达61.58%.电Fenton可以作为煤化工废水深度处理的一种有效技术.     

Comparative study of hydrogen peroxide electro-generation on gas-diffusion electrodes in undivided and membrane cells

The generation of hydrogen peroxide by means of the cathodic reduction of oxygen at gas-diffusion electrodes with a near 100% current efficiency was achieved in concentrations sufficient for the mineralization of refractory organics in Fenton treatment. A decrease in current efficiency over time at high temperatures and high current densities was observed. The polarization study carried out in potentiostatic, potentiodynamic and galvanostatic modes in 0.5 M Na₂SO₄ solution at pH 3 showed that the destruction of hydrogen peroxide at the cathode of the electrochemical reactor, as well as its chemical decomposition in the bulk solution, takes place at a significantly lower rate than the oxidation of H₂O₂ at the Ti–IrO₂ anode. Preparative electrolysis in the membrane reactor showed much higher current efficiencies for H₂O₂ electro-generation in comparison with tests carried out in an undivided cell. The performance of different proton-exchange membrane in this process was studied and a membrane cell with a heterogeneous MK-40 type PEM was found to be suitable. An optimized cell design, the appropriate selection of electrodes, supporting electrolytes, and a membrane resulted in a lower voltage in the membrane cell in comparison with the undivided cell.     

电Fenton方法在甲基橙染料废水中的试验研究

考察了均相EF-Feox法(牺牲阳极法)、均相EF-Fere法和非均相电Fenton(Fe2(MoO4)3-kaolin-450)法3种电Fenton法对甲基橙偶氮染料废水的降解效果,对比了各反应体系的优缺点。与均相EF-Feox体系和均相EF-Fere体系相比,非均相电Fenton-Fe2(MoO4)3-kaolin-450体系对甲基橙的降解效果最好。当电流密度为65 mA/cm2、Fe2(MoO4)3-kaolin-450催化剂的加入量为6.6 g/L、初始pH为4.34、50 mmol/L的Na2SO4作为电解质、甲基橙的初始质量浓度为100 mg/L,甲基橙的COD去除率和脱色率分别可以达到92.48%和99.3%。将此方法应用于铬蓝黑R、橙黄Ⅱ、以及吩噻嗪类物质亚甲基蓝等染料废水体系中,同样条件下电解10 min,3者的脱色率均可以达到93%以上,说明此方法在染料废水处理中具有普遍适用性。     

几种电化学法处理苯酚废水对比试验研究

以苯酚模拟废水为研究对象,对几种电化学法处理苯酚废水的效果进行对比研究,采用正交试验对pH值、电解电压、电解质浓度,电解时间等4个因素对苯酚去除率的影响进行分析,并确定最佳反应条件。试验结果表明,电催化氧化法处理苯酚废水的最佳反应条件为:pH值为6,电解电压为9 V,电解质的质量浓度为20 g/L,电解时间为120 min;电-Fenton法处理苯酚废水的最佳反应条件为:pH值为3,电解电压为9 V,电解质的质量浓度为20 g/L,电解时间为120 min;在此基础上,三维电极法最佳活性炭投加量为150 g/L。4种电化学法处理苯酚废水效果的优劣顺序依次为:三维电极与电-Fenton耦合法三维电极法电-Fenton法电催化氧化法。     

电-Fenton预处理兰炭废水

采用电-Fenton法预处理煤低温干馏兰炭废水,考察了阴极材料、反应时间、反应p H值、电流密度和极板间距对电-Fenton反应的影响。最后选择不锈钢板作为阳极,石墨板作为阴极,最佳试验条件为电反应p H值为4.0,反应时间为150 min,极板间距为3 cm,电流密度为5.0 m A/cm2。在此最佳条件下,CODCr去除率达到57.30%,该方法为治理兰炭废水提供了借鉴思路。     

光敏电芬顿法处理高盐分硝基苯废水

利用光敏电芬顿法降解高浓度、高盐分的有机废水(以硝基苯为例),考察FeSO4浓度、草酸钾浓度、电流强度、初始pH对硝基苯降解效果的影响。结果表明:采用紫外光光敏电芬顿法处理硝基苯废水时,盐分耐受度高,降解速度快。最佳降解条件为FeSO4浓度4.5 mmol/L,草酸钾浓度3.0 mmol/L,电流强度1.5 A,初始pH为2,处理1.5 h后,硝基苯的去除率可达93%。     

Fenton氧化法在废水处理中的研究进展

阐述了Fenton试剂的氧化机理,在此基础上重点介绍了光Fenton技术、电Fenton技术、超声波Fenton技术在废水处理中的机理与研究现状,展望了未来Fenton氧化技术的发展方向.