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铁基材料/过氧化物协同降解水环境中的PAEs研究
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/9/3 9:50:52  

摘要:邻苯二甲酸酯(Phthalates,PAEs)又称酞酸酯,是一类广泛使用的增塑剂和重要的内分泌干扰类污染物。寻求PAEs的高效降解方法并深入研究其降解机理可为PAEs污染治理提供重要的科学依据。本研究采用纳米四氧化三铁(Nano-ferric oxide, nFe3O4)和过氧化钙(Calcium peroxide, CaO2)联用、高铁酸钾(Potassium ferrate,Fe(VI))和过氧化氢(Hydrogen peroxide,H2O2)联用、Fe(VI)和CaO2联用的方法,对水体中的4种PAEs:邻苯二甲酸二甲酯(Dimethyl phthalate, DMP)、邻苯二甲酸二乙酯(Diethyl phthalate, DEP)、邻苯二甲酸二丁酯(Dibutyl phthalate, DBP)和邻苯二甲酸丁苄酯(Butyl benzyl phthalate, BBP)进行处理,研究DMP的降解效果及机理。主要成果有:

(1)     Fe(VI)/H2O2对DMP的降解作用及机理

采用Fe(VI)与H2O2组成类芬顿试剂,研究了Fe(VI)/H2O2体系对DMP的降解效果、反应动力学、降解产物和降解机制。结果表明,DMP的降解速率受到Fe(VI)投加量、H2O2投加量、pH值和共存离子等因素的影响,DMP降解过程符合准一级动力学模型。Mg2+和HCO3-离子显著抑制DMP的降解速率。当Fe(VI)/H2O2/DMP摩尔比为10/2/1、溶液初始pH为7时,DMP降解效率最高。羟基自由基(HO•)是主要的自由基,Fe(VI)和H2O2对DMP降解具有协同效应。DMP及其中间体的降解机制包括单氧化剂氧化、双氧化剂联合芬顿氧化、氧化剂还原产物吸附。

(2)     Fe(VI)/CaO2对DMP的降解作用及机理

研究了Fe(VI)/CaO2单独和联合处理对DMP的降解性能及机理,分析了共存离子的影响。结合响应面方法Box-Behnken实验设计、采用二次多项式和逐步回归法,拟合了DMP去除率与Fe(VI)投加量、CaO2投加量和反应时间之间的关系,对实验条件进行了优化分析。结果表明,当Fe(VI)/CaO2/DMP摩尔比为1.1/4.4/1时,模型预测DMP最大去除率为95.57%,和验证实验得出的去除率90.14%相近,表明该响应面模型能够较准确预测Fe(VI)/CaO2体系对DMP的去除效果。自由基清除实验结果显示,HO•和超氧自由基(O2-•)在氧化体系中发挥重要作用,表明Fe(VI)和CaO2可形成类芬顿试剂协同降解污染物。主要降解途径包括酯基水解、侧链氧化和苯环的羟基化;主要降解产物为邻苯二甲酸单甲酯、2,5-二羟基苯甲酸、间苯二甲酸和草酸等。

(3)     nFe3O4/CaO2处理含PAEs模拟废水

以含DMP、DEP、BBP、DBP等4种PAEs的模拟废水为处理对象,采用nFe3O4与CaO2组成新型非均相类芬顿试剂,研究nFe3O4投加量、CaO2投加量和初始pH值对PAEs去除率的影响,应用响应面法对反应条件进行拟合和优化。结果表明,nFe3O4/CaO2反应体系能有效降解4种PAEs,其中CaO2对DMP和DEP具有较强的降解能力,nFe3O4可以显著强化CaO2对BBP和DBP的降解作用; nFe3O4/CaO2/PAEs摩尔比为2/5/1、溶液初始pH值为5时,DMP、DEP、BBP和DBP的去除率分别为94.6%、95.7%、68.2%和68.7%。

Phthalates (PAEs) is a widely used class of plasticizers and important endocrine disrupting contaminants. Seeking efficient degradation method for phthalate and in-depth study of its degradation mechanism can provide an important scientific basis for phthalate pollution control. In this study, nano-ferric oxide (nFe3O4) and calcium peroxide (Calcium peroxide, CaO2), potassium ferrite (Fe(VI)), hydrogen peroxide (H2O2) were applied to remove PAE-type plasticizers including dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP). Concrete work consists of the following three aspects:

(1) Remediation efficiency and mechanism of dimethyl phthalate (DMP) contaminated wastewater by combined Fe(VI)and H2O2 based Fenton-like system was evaluated. The reaction kinetics, reaction products and degradation pathways were investigated. Experimental results indicated that the degradation rate of DMP depended on H2O2 dosage, Fe(VI)dosage, pH and co-existing ions concentration. The kinetics of DMP degradation was pseudo <SPAN style="FONT-FAMILY: " Gothic?? ?MS mso-bidi-font-family: Gothic?; MS>first-order. The optimal reaction conditions was pH 7 and molar ratios of Fe(VI)/H2O2/DMP:10/2/1. HO• was con<SPAN style="FONT-FAMILY: " Gothic?? ?MS mso-bidi-font-family: Gothic?; MS>firmed to be account for the DMP degradation in the system. Infrared spectroscopy analysis of DMP in aqueous solutions and filter residue indicated that flocculation occurred during the reaction. Plausible mechanisms in the system were hydroxylation and oxidation of the benzene ring and the ester bond.

(2) The degradation efficiency and mechanism of ferrite (Fe(VI))/calcium oxide (CaO2) combined treatment on dimethyl phthalate (DMP) were studied. Multi-factor experiments were carried out based on the Box-Behnken experimental design in Response Surface Method. Relationships between the removal rate of DMP and Fe(VI)dosage, CaO2 dosage and reaction time were fitted by quadratic polynomial and stepwise regression method, and the experimental conditions were optimized. The results showed that the degradation process conformed to the pseudo-second-order kinetic model. The maximum degradation rate of DMP predicted by the model reached 95.57% when the molar ratio of Fe(VI)/CaO2/DMP was 1.1/4.4/1, which was close to 90.14% obtained by verification experiments, indicating that the model possessed a good simulation and predictive performance. The results of free radical scavenging experiments revealed that hydroxyl radical (HO•) and superoxide radical (O2-•) made significant contributions to the degradation of DMP, demonstrating that Fe(VI)and CaO2 could form Fenton-like reagents to synergistically degrade pollutants. The main degradation pathways of DMP included hydrolysis of ester group, oxidation of side chain and hydroxylation of benzene rings. The main degradation products were monomethyl phthalate, 2, 5-dihydroxybenzoic acid, isophthalic acid, oxalic acid, etc. In summary, Fe(VI)/CaO2 technology can effectively remove organic pollutants in water environment and has high potential application value.

(3) The nFe3O4 and CaO2 were used as Fenton-like reagent in the treatment of model solutions containing PAEs (DMP, DEP, BBP and DBP). Three factors selected in the research were dosage of nFe3O4, dosage of CaO2 and initial pH, and the removal rates of DMP, DEP, BBP and DBP were selected as response values. The Response Surface Method (RSM) was used to design experiment treatments and optimize the operational conditions. The results indicated that CaO2 was the key factor of the degradation of DMP and DEP. Introduction of nFe3O4 could significantly enhance the removal rates of BBP and DBP. nFe3O4 and CaO2 system could efficiently degrade the 4 PAEs at neutral pH. The optimal conditions were as follows: the molar ratio of dosage of nFe3O4 was 2, the molar ratio of dosage of CaO2 was 5, and initial pH was 5, the removal rates of DMP, DEP, BBP and DBP were 98.7%, 98.3%, 74.2% and 78.4%, respectively.

关键词:邻苯二甲酸酯;铁基材料;过氧化物;降解机理

PAEs; iron-based Materials; Peroxides; degradation mechanism

上一篇:环境水质现场监测技术研究     下一篇:石墨烯基尖晶石型金属氧化物复合物的制备及其催化过硫酸盐降解双酚A的研究
 
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