【作者】 王强；

【导师】 黄丽萍；

【作者基本信息】 大连理工大学 ， 环境工程， 2018， 博士

【摘要】 生物电化学系统(Bioelectrochemical systems,BESs)是近年兴起的、以微生物为催化剂,将阳极有机废水中的化学能转化为电能,用于阴极生产氢气或有价化学产品的装置,包括微生物燃料电池(Microbial fuel cells,MFCs)和微生物电解池(Microbial electrolysis cells,MECs)。由于氧化性金属离子被BESs阴极还原回收的同时可产生电能,回收金属的BESs研究引起了人们的广泛关注。目前,BESs阴极回收金属较多地关注于单一金属,对混合金属如双金属的回收还不多见。同时,沉积在阴极电极上金属的进一步收集与使用也是BESs回收金属领域亟待解决的重要问题。鉴于此,本论文结合电镀冶金和酸矿废水中常见的典型双组分金属,实现了 BES阴极回收典型双金属过程,借助金属间Cu(Ⅱ)对Cd(Ⅱ)的催化作用、Fe(Ⅲ)对Cr(Ⅳ)的促进作用、以及非金属组分02原位生成的H202对W(Ⅳ)和Mo(Ⅳ)的强化作用,进一步提高BESs阴极回收双金属的性能。通过原位利用沉积在阴极电极上的混合金属钨钼,考察其催化降解和矿化难降解有机污染物甲硝唑和甲基橙性能。主要结果如下:(1)利用钛片、碳布或泡沫镍阴极BESs先在MFCs模式回收混合Cu(Ⅱ)和Cd(Ⅱ)中的Cu(Ⅱ),后在MECs模式回收Cd(Ⅱ)同时产氢,并考察MFCs模式沉积于阴极电极上的铜对MECs模式Cd(Ⅱ)回收和产氢的影响。发现MFCs模式下三种材料回收Cu(Ⅱ)的性能相近,约为4.79-4.88mg/L/h,但在MECs模式下,碳布回收Cd(Ⅱ)的回收速率最大(5.86 ± 0.25 mg/L/h),泡沫镍最小(4.96 ± 0.48 mg/L/h)。与未沉积铜的空白电极相比,MFCs模式下沉积的铜能促进MECs模式下Cd(Ⅱ)的回收和产氢,分别提高80-320%和100-600%。阴极电极上沉积的铜可降低Cd(Ⅱ)还原和析氢的过电势。(2)探究MFCs阴极Fe(Ⅲ)存在对Cr(Ⅵ)还原的促进作用。当Fe(Ⅲ)为150mg/L时,Cr(Ⅵ)的去除率达65.6 ± 2.2%,是无Fe(Ⅲ)对照的1.6倍。Fe(Ⅲ)的存在能够降低Cr(Ⅵ)还原的过电势和扩散电阻;Fe(Ⅲ)在Cr(Ⅵ)还原过程中起到电子介体的作用。(3)通过MFCs阴极原位生成的H202,高效回收混合W(Ⅵ)和Mo(Ⅵ)。该系统W(Ⅵ)和Mo(Ⅵ)的回收率分别为67.2 士 3.1%和86.4 ± 1.9%,是无H202对照的2.4和1.3倍,且W(Ⅵ)和Mo(Ⅵ)的回收率随着原位H202生成量的增加而增加。光照可进一步提高W(Ⅵ)和Mo(Ⅵ)的回收率:MECs阴极的光照与原位生成的H202协同提高W(Ⅵ)和Mo(Ⅵ)的回收率至 98.1 ± 0.7%(W)和 100 ± 0.4%(Mo)。(4)原位利用MFCs阴极沉积的钼钨构建光-电-芬顿体系,催化降解和矿化典型抗生素甲硝唑和偶氮染料甲基橙。在厌氧或好氧条件,考察降解和矿化甲硝唑时不同钼/钨沉积量和比例的影响,得到厌氧时钼/钨的最佳沉积量为0.24 mg/cm2、好氧时为0.18 mg/cm2,二者的最佳钼/钨比均为0.17:1.0。在光照和Fe(Ⅲ)浓度为10mg/L的好氧条件下,甲硝唑的降解和矿化分别为94.5 ± 1.4%和89.5 ± 1.1%,是无光、无芬顿对照的1.2、1.1倍和1.3、1.2倍。考察降解和矿化甲基橙时的厌氧和好氧效应,发现厌氧利于甲基橙的脱色而不利于矿化,好氧与Fe(Ⅲ)共存利于甲基橙矿化但不利于脱色。光照下,先厌氧(20 min)后好氧(10 mg/L Fe(Ⅲ)、100 min)可使甲基橙完全脱色,矿化率达96.8±3.5%(9.7mg/L/h),分别是完全厌氧、完全好氧、完全好氧与Fe(Ⅲ)共存对照的2.9、1.9和1.3倍。本论文研究结果为混合金属在BESs阴极的回收提供了清洁有效的新方法,丰富了BESs回收金属的阴极作用理论,拓展了 BESs回收金属的应用领域和使用范围,为回收金属的BESs的进一步应用提供了新思路。更多还原

【Abstract】 Bioelectrochemical systems(BESs)that use microorganisms as catalysts are promising technologies to capture the energy in organic wastewaters for the prodcuction of electricity,hydrogen or value-added chemicals,including microbial fuel cells(MFCs)and microbial electrolysis cells(MECs).Based on the oxidative characteristic of heavy metal ions,recovery of single metals in the cathodes of BESs has been extensively studied along with critical parameters including cathode matterial,solution chemistry,cathodic electrode potential,current and so forth.However,the recovery of dimetals is rarely researched,and the performance of dimetal recovery in BESs is poor due to the competition resulting from simultaneous reduction of metal ions.Therefore,in this paper,considering the fact of co-existence of Cu(II)and Cd(II),Fe(Ⅲ)and Cr(Ⅵ),W(Ⅵ)and Mo(Ⅵ)in electroplating,metallurgy and acid mine wastewaters,the performances of recovery of these typical dimetals in cathodes of BESs were systematically investigated,including the catalysis of copper on Cd(Ⅱ)recovery,the mediator role of Fe(Ⅲ)in Cr(Ⅵ)reduction,and the effect of in-situ generated H2O2 and light irradiation on W(Ⅵ)and Mo(Ⅵ)deposition.In addition,further collection and application of these metals deposited on the cathode of BESs have not yet been previously reported.Mo/W deposits on the cathodes of BESs were in-situ utilized for catalyzing degradation and mineralizaiton of metronidazole(MNZ)and methly orange(MO).The detailed results are as follows:(1)BESs were first operated in a MFC mode for Cu(Ⅱ)recovery from mixed Cu(Ⅱ)and Cd(Ⅱ),and then shifted to a MEC mode for simultaneous Cd(Ⅱ)recovery and hydrogen production.Cathode electrodes including Titanium sheet,nickel foam,and carbon cloth were explored for system performance.Insignificant Cu(Ⅱ)recovery(4.79-4.88 mg/L/h)was observed for all materials whereas carbon cloth exhibited the highest Cd(Ⅱ)recovery(5.86 ±0.25 mg/L/h),compared to the lowest(4.96 ± 0.48 mg/L/h)for nickel foam.This Cd(II)recovery was 1.8-4.2 times and hydrogen generation was 2.0-7.0 folds as high as those on no Cu controls.Cyclic voltammetry analysis verified the catalysis of in-situ deposited Cu in MFC mode for subsequent enhanced Cd(II)recovery and hydrogen generation in MEC mode.(2)The impact of Fe(III)as an electron-shuttle mediator for enhanced Cr(VI)reduction in MFCs was investigated.The presence of 150 mg/L Fe(III)achieved Cr(VI)reduciton of 65.6 ±2.2%,1.6 times as that in the absence of Fe(Ⅲ).Linear sweep voltammetry and tafel plot tests implied that Fe(Ⅲ)played a critical role in decreasing both the diffusional resistance of Cr(Ⅵ)species and the overpotential for Cr(Ⅵ)reduction.Cyclic voltammetry analysis confirmed the mediator role of Fe(Ⅲ)in Cr(Ⅵ)reduction in this system.(3)W(VI)and Mo(VI)was efficiently recovered in cathode of MFCs through the formation of more easily deposited peroxo-tungstate or peroxo-molybdate with the in-situ generated H2O2.Deposition of 67.2 ± 3.1%(W)was 2.4 times and 86.4 ± 1.9%(Mo)was 1.3 folds higher than those in the absence of H2O2.In addition,W(VI)and Mo(VI)recovery increased with the increase in the in-situ generated H2O2.The cooperative light irradiation and in-situ generated H2O2 achieved recovery of 98.1 ± 0.7%(W)and 100 ± 0.4%(Mo)in MECs.(4)The Mo/W deposits on the cathodes of BESs can be in-situ employed to establish a photo-electro-Fenton system for degradation and mineralization of MNZ and MO.The effect of Mo/W catalyst loading and ratio on degradation and mineralization of MNZ was investigated.The optimum loadings were 0.24 mg/cm2 for anaerobic conditions and 0.18 mg/cm2 for aerobic conditions.Under both anaerobic and aerobic conditions,the Mo/W molar ratio of 0.17:1.0 invariably achieved the highest rates of MNZ degradation and mineralization.Under aerobic conditions and in the co-presence of 10 mg/L Fe(Ⅲ)and light,MNZ degradation of 94.5 ± 1.4%and mineralization of 89.5 士 1.1%were obtained,1.2 and 1.3 folds as those in no light control,and 1.1 and 1.2 folds as those in no Fenton control,respectively.The impact of anaerobic and aerobic conditions on decolorization and mineralization of MO was explored.Anaerobic conditions favored MO decolorization,but were unsuitable for the subsequent mineralization.Conversely,aerobic conditions favored MO mineralization but were disadvantageous for its decolorization.Complete decolorization and mineralization of 96.8 ± 3.5%(9.7 mg/L/h)were achieved with a sequential operational strategy of first anaerobic conditions(20 min)and then aerobic conditions with addition of 10 mg/L Fe(III)(100 min).This mineralizaiton rate was 2.9 times as that under entirely anaerobic conditions,1.9 times as that under entirely aerobic conditions and 1.3 times as that under entirely aerobic conditions with addition of Fe(Ⅲ).These results provide alternative methods for efficiently recovering typical multiple metals in wastewaters,not only enriching the conceptual metal recovery in BESs,and expanding the applicable metal recovery in BESs,but also deepening the further application of the cathodes of BESs with deposited metals.更多还原