【作者】 李明；

【导师】 黄丽萍；

【作者基本信息】 大连理工大学 ， 环境科学与工程， 2017， 硕士

【摘要】 稀有金属钨和钼具有良好的物理化学性质,在日常生活和生产领域有着广泛的应用,但钨和钼常共同存在于钨钼工业废水中,回收与分离钨和钼是一技术难题,传统的化学和电化学方法成本高,流程复杂,二次污染严重。而近年来新兴的生物电化学系统(BESs)是一种清洁有效的污水处理新技术,其在回收与分离金属领域已经有很多的报道,其能够在阳极处理有机废水的同时,阴极回收与分离金属,无需任何能量的输入,无二次污染,并且通过改变连接反应器的个数和连接方式,可以改变BESs的阴极电势,同时实现具有不同氧化还原电位的多种金属的回收与分离。因此本次实验将探究耦合型BESs对混合污水中钨和钼的回收与分离。(1)首先探究了9种不同的连接方式,其中单个BES与3个并联BESs串联对钨钼的回收与分离相对于其他连接方式具有更优的效果,实验结果表明:单个BES回收了27.6±1.2%的钨和75.4±2.1%的钼,钨钼分离系数达到8.1±0.2,产氢0.34±0.01m3/m3 d,而3个并联的BESs仅回收了12.3±0.9%的钨和52.6±2.2%的钼,钨钼分离系数7.9±0.5。这归结于在此种连接方式下,串联的单个BES拥有更负的阴极电势和更大的电流密度,而3个并联的BESs充当了电源,其电能有一部分供给了串联的单个BES,因此造成了这两部分的差别。而在不耦合情况下,单个BES仅回收了15.3±1.7%的钨和60.1±1.6%的钼,3个并联BESs回收了12.9±1.3%的钨和56.1±2.0%的钼。与单独钨钼溶液相比,混合情况下,单个BES对钨的回收是单独钨溶液的4.0倍,对钼回收是单独钼溶液的1.2倍,而3个并联BESs分别为3.7倍和1.1倍。(2)耦合系统BES-3-1处理酸性钨钼混合废水的时间过程表明,系统在1~6 h过程中单个BES和3个并联BESs对钨钼的沉积呈现增加的趋势,其中在第6 h达到最高值,单个BES对钨沉积率为34.6±1.0%,对钼沉积率为80.8±0.8%;3个并联BESs对钨沉积率为25.3±1.1%,对钼沉积率为59.1±1.4%。超过6 h后钨和钼的沉积率均呈现降低的趋势,这是由于pH升高导致沉积在电极上的钨钼又溶解所致。耦合系统BES-3-1适合回收和分离含钼低含钨多的酸性废水,其中在W:Mo=1:0.01时能够实现对钼的完全回收,钨钼的完全分离。BES-3-1对pH=2的钨钼混合废水回收分离效果最好,过低的pH会导致不锈钢片电极表面过度的析氢,不利于钨钼的沉积,高pH不利于钨钼得电子发生还原反应,不利于钨钼的沉积。对不同组合电极材料的研究表明,SSS-SSS组合对钨钼的回收分离效果最好,CR-SSS组合更有利于单个BES的产氢,产氢速率能够达到0.82±0.12 m3/m3 d。在钨钼金属浓度达到0.05 mmol/L以下时候能够实现钼的完全回收和钨钼的完全分离。本实验用耦合形式的BESs系统成功实现了钨钼的回收和分离,混合污水钨钼的溶液条件以及反应器的不同连接方式对耦合BESs系统对钨钼的回收和分离以及系统的电化学性能具有重要的作用。更多还原

【Abstract】 Rare metals W and Mo have a good physical and chemical properties,which have been widely used in daily life and production,but W and Mo were common existed in industrial waste water,recycling and separating W and Mo were technical problems,traditional chemical and electrochemical method have a high cost,complex process and secondary pollution.In recent years,bioelectrochemical systems(BESs)was a new technology,which was clean and effective of sewage treatment.Recovery and separation of metals through BESs had a lot of reports,it could deal with organic wastewater at anode and metals could be recycled and separated at cathode,no secondary pollution.Changing the connection number of reactor and the connection mode,the cathode potential of BESs could be changed and many metals of different redox potential could be recycled and separated.So this experiment will explore the coupling system of BESs for W and Mo recycling and separation.(1)At first,this experiment explored nine different connection modes.Stacked bioelectrochemical systems(BESs)of single unit serially matched with three parallel connected units was superior to the other stacked modes and can efficiently deposit and separate W and Mo with simultaneous hydrogen production.The single unit exhibited 27.6 ± 1.2%(W)and 75.4 ± 2.1%(Mo)deposits with separation factor of 8.1 ± 0.2 and hydrogen production of 0.34 ± 0.01 m3/m3 d,compared to 12.3 ± 0.9%(W),52.6 ± 2.2%(Mo)and 7.9 ± 0.5(separation factor)in the adjacent three parallel units.It comes down to under this kind of connection mode,single BES has more negative cathode and larger current density,and 3 parallel BESs acted as the power and part of electricity supply single BES,thus caused the difference between the two parts.In the controls,15.3 ± 1.7%(W)and 60.1 ± 1.6%(Mo)(single unit only),and 12.9 ± 1.3%(W)and 56.1 ± 2.0%(Mo)(three parallel units only)were achieved.These values were also 4.0(W)and 1.2(Mo)times(single unit),and 3.7(W)and 1.1(Mo)times(three parallel units)as those in the absence of Mo(VI)or W(VI).(2)The time process of W and Mo deposition and separation under single unit serially matched with three parallel connected units showed that,in the process of 1 ~ 6 h,single BES and 3 parallel BESs to W and Mo deposit showed increasing trend,in 6th hour,single BES exhibited 34.6±1.0%(W)and 80.8±0.8%(Mo)deposits;compared to 25.3±1.1%(W),59.1±1.4%(Mo)in the adjacent three parallel units.Further improved time,W and Mo deposition rate showed decreasing trend.This was because pH improved led to W and Mo dissolved.The acidic waste water of lower Mo and more W was more suitable for recovery and separation in coupling system,W and Mo could be completely separated under W:Mo=1:0.01.The acidic waste water of pH=2 was more suitable for recovery and separation in coupling system,low pH led to stainless steel electrode surface excess hydrogen evolution,was not conducive to W and Mo deposit,high pH was not suitable for W and Mo redox reaction,was not conducive to W and Mo deposits.Different composite electrode materials showed that,SSS-SSS was more effective for W and Mo recovery and separation,CR-SSS was more effective for hydrogen production,hydrogen production of 0.82±0.12 m3/m3 d was obtained.The Mo was completed removed and W and Mo were completed separated under the concentration of W and Mo were 0.05 mmol/L.This study demonstrates the feasibility of the stacked BESs for W and Mo deposition and separation,and the species of W(VI)and Mo(VI),and location of units were critical for efficient system performance.更多还原