Electrolysis designed for clean production of selective iron products from coal fly ash leachate

With the development of society, solid waste, such as coal fly ash has caused serious environmental problems. Extraction of high value metals from coal fly ash is vital for sustainable development and maintenance of social economy. This work aimed to present a nonhazardous and efficient electrolysis method to extract selective iron products from coal fly ash leachate. Compared with current precipitation, biological, and organic extraction processes, this electrolysis method can selectively prepare different iron products. No chemicals or expensive membranes were used to prevent the introduction of pollutant and membrane limitations. Moreover, no waste was produced enabling realization of zero pollution discharge. Batch experiments indicated that the degree of reduction of iron can be controlled during the electrolysis process, thereby allowing for the production of different types of iron products. The purity of iron electrolytic product was 98.30 wt% Fe2O3, 1.35 wt% SO3, and 0.09 wt% Al2O3, and current efficiency reached 60.3% under the optimal conditions: c (Fe2+) = 0.1 M, t = 4.0 h, and J = 2500 A/m(2). Different iron products like Fe3O4, FeOOH and Fe can be prepared sequentially during electrolysis process. Moreover, O-2 is generated on anode, and H-2 is generated on cathode as clean energy, which increases economic benefits. The wastewater (containing H2SO4) is widely used as a leaching reagent during leaching of coal fly ash, which can return to leaching process enabling zero hazardous substance discharge. This study would provide an alternative clean and efficient method for extracting selective iron products from coal fly ash leachate.