Modified Fenton reaction for trichlorophenol dechlorination by enzymatically generated H2O2 and gluconic acid chelate

Glucose oxidase is a well-known enzyme that catalyzes the oxidation of β-d-glucose to produce gluconic acid and hydrogen peroxide. Fenton reaction is a powerful oxidation technology used for the oxidation of groundwater pollutants. For the application of Fenton reaction in groundwater remediation, successful operation of Fenton reaction near neutral pH, and on-site generation of both H₂O₂ and chelate will be beneficial. The focus of this experimental study was to couple the glucose oxidation reaction with chelate-based Fenton reaction. The idea was to use the hydrogen peroxide and chelate gluconic acid generated during glucose oxidation for the dechlorination of 2,4,6-trichlorophenol (TCP) by Fenton reaction. The oxidation of glucose was achieved using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for each system, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. In the case of free enzyme reaction, separation of the enzyme was achieved using an ultrafiltration membrane before initiating the Fenton reaction. The oxidation of TCP by Fenton reaction was performed at varying ratios of gluconic acid/Fe, and its effect on the decomposition of TCP and H₂O₂ was studied. TCP degradation was studied both in terms of parent compound degradation and free chloride generation.     

铁铜双金属有机骨架MIL-101(Fe,Cu)活化双氧水降解染料性能

针对非均相芬顿传质效率低和Fe（Ⅲ）Fe（Ⅱ）转化慢导致活性低等问题,采用溶剂热法制备铁铜双金属有机骨架材料[MIL-101（Fe,Cu）],并研究了材料界面性质、催化降解染料（亚甲基蓝）性能以及活化催化机制.结果表明,MIL-101（Fe,Cu）晶体结构完整且呈三维八面体形状;比表面积和平均孔径分别为667.2 m² ·g^-1和1.9 nm,可充分暴露反应活性位点.MIL-101（Fe,Cu）在广谱pH范围可活化H₂ O₂高效降解亚甲基蓝.当pH=5、反应20 min,MIL-101（Fe,Cu）/H₂ O₂对20 mg ·L^-1亚甲基蓝的去除率为100%,较MIL-101（Fe）/H₂O₂和单独H₂ O₂分别提高43.1%和88.9%.自由基猝灭实验与反应前后铁和铜价态变化结果表明,羟基自由基（·OH）是MIL-101（Fe,Cu）/H₂ O₂催化降解亚甲基蓝的主要活性物种;Cu（Ⅱ）掺杂引入新的活性位点,且Cu（Ⅱ）/Cu（Ⅰ）循环和Fe（Ⅲ）/Fe（Ⅱ）循环可协同产生·OH,进而提高催化效率.MIL-101（Fe,Cu）作为新型非均相类芬顿催化剂,无需复杂pH调节即可获得良好催化效果,在工业废水处理上具有较好地应用前景.     

Ca(OH)2解吸并固定混合吸收液中CO2的实验研究

CO₂化学吸收法分离纯度高,技术成熟,但能耗过高及成本是困扰该技术发展的瓶颈.在常压条件下对利用Ca（OH）₂直接矿物碳酸化固定MDEA/PZ混合吸收富液中CO₂进行了一系列实验研究,考察了吸收液负荷、Ca（OH）₂投加量、pH、温度及搅拌速率等因素对解吸率的影响,并利用动态吸收-解吸循环实验研究了其CO₂吸收性能和循环使用稳定性,最后对碳酸化反应产物进行了XRD、TEM分析.结果表明,在常压条件下,Ca（OH）₂可以通过液相直接矿物碳酸化对CO₂进行直接固定,并实现吸收富液的再生;随着负荷的升高及Ca（OH）₂投加量、pH、搅拌速率的增大,解吸率随之增加;随着溶液温度升高,解吸率下降;经过5次动态吸收-解吸循环实验后CO₂吸收量可以达到并保持在0.57 mol·L^-1,显示出了良好的循环稳定性.     

苯醌对聚合硅酸铁多相UV-Fenton体系的增效机制

通过构建苯醌增效聚合硅酸铁多相UV-Fenton体系,讨论了体系中橙Ⅱ的脱色和降解途径.在研究苯醌浓度对聚合硅酸铁铁离子的释放、Fe²⁺与Fe³⁺之间的转化、H₂O₂分解和·OH生成影响的基础上,提出了苯醌对聚合硅酸铁多相UV-Fenton体系的增效机制.结果表明,随苯醌浓度的增加,其紫外光下光解还原聚合硅酸铁并释放Fe²⁺的程度增大、H₂O₂分解速度加快、产生·OH浓度峰值增高且出现的时间提前;苯醌增效体系释放于溶液中的Fe²⁺可以通过Fenton反应转化成Fe³⁺,反应结束后聚合硅酸铁能重新吸附Fe³⁺并使其浓度降低,避免了增效体系铁离子的二次污染.本研究将为多相催化剂催化过程的调控提供新的视角,为多相光助-芬顿反应在有机废水资源化中的应用提供理论依据和技术支持.     

Effect of substituents in hydroxyl radical-mediated degradation of azo pyridone dyes: Theoretical approaches on the reaction mechanism

Understanding the degradation behavior of azo dyes in photocatalytic wastewater treatment is of fundamental and practical importance for their application in textile-processing and other coloration industries. In this study, quantum chemistry, as density functional theory, was used to elucidate different degradation pathways of azo pyridone dyes in a hydroxyl radical (HO^?)-initiated photocatalytic system. A series of substituted azo pyridone dyes were synthesized by changing the substituent group in the para position of the benzene moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The effect of dye molecular structure on the photocatalytic degradation reaction mechanism was analyzed and quantification of substituent effects on the thermodynamic and kinetics parameters was performed. Potential energy surface analysis revealed the most susceptible reaction site for the HO^? attack. The calculated reaction barriers are found to be strongly affected by the nature of substituent group with a good correlation using Hammett σ_p constants and experimentally determined reaction rates. The stability of pre-reaction complexes and transition state complexes were analyzed applying the distortion-interaction model. The increased stability of the transition state complexes with the distancing from the substituent group has been established.     

新型Fe3O4@α-MnO2活化过一硫酸盐降解水中偶氮染料

采用两步水热法制备了新型磁性纳米Fe₃O₄@α-MnO₂复合材料作为催化剂,用于活化过一硫酸盐（PMS）产生强氧化性的硫酸根自由基（SO₄^-·）氧化降解偶氮染料活性黑5（RBK5）.采用透射电子显微镜（TEM）,X射线粉末衍射仪（XRD）和振动样品磁强计（VSM）对制备的催化剂进行表征,证明成功合成了纳米α-MnO₂包覆Fe₃O₄形态的Fe₃O₄@α-MnO₂催化剂,催化剂的饱和磁化强度为39.89emu/g.Fe₃O₄@α-MnO₂催化剂活化PMS与单一的Fe₃O₄和α-MnO₂活化PMS相比,具有更高的催化效率,说明铁锰双金属存在协同作用.同时研究了催化剂的投加量、PMS的浓度和初始pH值等各种因素对RBK5的降解效率以及反应动力学的影响.实验结果表明,Fe₃O₄@α-MnO₂催化剂活化PMS降解RBK5的过程符合准一级反应动力学,在催化剂投加量为1.2g/L,PMS的浓度为4mmol/L,初始pH值为7.0,反应时间为60min的情况下,浓度为30mg/L的RBK5的降解效率可达到91%,此时RBK5的降解速率常数也达到最高值0.023min^-1.此外,通过加入自由基淬灭剂甲醇、叔丁醇和硝基苯判断了Fe₃O₄@α-MnO₂/PMS体系中起主要氧化降解作用的活性物种为SO₄^-·.     

活性氧的化学发光测定法

以作者近年来的研究结果为中心 ,综合地介绍过氧化氢 (H2 O2 )、单线态氧 ( 1O2 )、超氧阴离子自由基 ( .O-2 )以及羟自由基 ( .OH)等活性氧化学发光研究的最新动态 .侧重介绍活性氧的鲁米诺、光泽精、甲壳动物荧光素化学发光测定体系 ,比较了这几种方法的各自特点和应用情况     

硝酸银滴定法与硫氰酸汞分光光度法测定水中氯化物（Cl^-）的方法比对

用硝酸银滴定法、硫氰酸汞分光光度法分别测定高浓度的考核已知样及低浓度的考核未知样，均合格。说明两种方法都能满足水和废水中氯化物（Cl^-）测定的需要。     

Fe(Ⅱ)/K_2S_2O_8对水体中As(Ⅲ)的氧化研究

研究了Fe(Ⅱ)/K2S2O8对水体中As(Ⅲ)的氧化作用,以及pH值、Fe(Ⅱ)初始浓度等因素对氧化As(Ⅲ)的影响,并且采用分子探针法的竞争性实验鉴定了体系中产生的活性中间体,探讨了K2S2O8在Fe(Ⅱ)存在的条件下对As(Ⅲ)的氧化机理。     

电晕氧化结合化学吸收脱除烟气中NO2实验研究

实验研究了直流电晕湿空气自由基簇射结合25%的NaOH溶液吸收的NOx脱除过程．结果表明：通过调节流过喷嘴电极中的空气流量,可以得到稳定的流光电晕;空气中水蒸汽对NOx脱除效率有影响;在反应器内同时有HNO2和HNO3生成;实验工况下,反应器NOx转化率45％以上,经吸收液吸收后系统总脱氮效率可达70％．