酸碱不平衡电解回收酸性矿山排水中金属及产氢研究

Metal recovery and hydrogen production from acid mine drainage by acid-base imbalance electrolytic cell

  • 摘要: 针对微生物电解和光电化学技术处理酸性矿山排水(AMD)时存在反应速率慢、氢气(H2)产量低等问题,设计了一种酸碱不平衡电解池(AB-EC)。以单一Fe2+的煤矿型AMD为模型体系,系统优化电极间距、电压、尿素浓度及pH等关键参数,确立AB-EC的基础运行条件;进而将优化体系扩展至含Fe2+、Al3+、Mn2+和Ni2+的冻融型硫铁矿AMD处理,深入探究多金属离子竞争下的反应机制;最后提出两级AB-EC协同产氢且分级回收金属的策略。结果表明:通过系统优化试验确定AB-EC最佳运行条件,电极间距为2.5 cm,施加8 V恒压,阳极电解液采用pH为13的0.5 mol/L尿素溶液。该条件下处理230 mL煤矿型AMD运行50 min后,Fe2+去除率达70.10%±3.87%,H2产量为(54±2)mL,其去除金属和产氢性能显著优于微生物电解与光电化学技术。处理230 mL冻融型硫铁矿AMD,AB-EC运行100 min后,出水Fe2+、Al3+、Mn2+、Ni2+平均浓度分别为0.71、0.01、2.81、0.23 mg/L,去除率均超过97%。此时H2产量达(116±3)mL,阳极尿素和NaOH的平均消耗量分别为0.21和0.18 g。进一步研究结果表明,构建序批式两级AB-EC工艺能同步实现生产H2与Al(OH)3/Fe3O4的选择性分离回收。

     

    Abstract: An acid-base unbalanced electrolytic cell (AB-EC) was designed to overcome the limitations of slow reaction rate and low hydrogen (H2) production in the treatment of acid mine drainage (AMD) by microbial electrolysis and photoelectrochemical technology. Taking the coal mine type AMD with a single Fe2+ as the model system, the key parameters such as electrode spacing, voltage, urea concentration and pH were systematically optimized to establish the basic operating conditions of AB-EC. Furthermore, the optimization system was extended to the AMD treatment of freeze-thaw pyrite containing Fe2+, Al3+, Mn2+ and Ni2+, and the reaction mechanism under the competition of polymetallic ions was deeply explored. Finally, a strategy of two-stage AB-EC collaborative hydrogen production and staged metal recovery is proposed.The results showed that the optimal operating conditions of AB-EC were determined by system optimization tests as follows: electrode spacing of 2.5 cm, applied voltage of 8 V, and 0.5 mol/L urea solution with pH 13 for the anode electrolyte. After treating 230 mL of coal-type AMD for 50 min under these conditions, the Fe2+ removal rate reached 70.10%±3.87% and the H2 production was (54±2)mL, which was significantly better than microbial electrolysis and photoelectrochemical technology in terms of metal removal and H2 production. For the 230 mL freeze-thawed sulfuric iron pyrite AMD, the average concentrations of Fe2+, Al3+, Mn2+, Ni2+ in the effluent were 0.71, 0.01, 2.81, 0.23 mg/L, respectively, and the removal rate was more than 97% after the AB-EC was operated for 100 min. Simultaneously, the H2 production amounted to (116±3)mL, and the anode urea and NaOH average consumption were measured at 0.21 and 0.18 g, respectively. Further results showed that the construction of sequential batch two-stage AB-EC process could simultaneously achieve the H2 production and the selective separation and recovery of Al(OH)3 and Fe3O4.

     

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