Flow battery electrolyte from carbon black incineration fly ash: A feasibility study of an environment friendly...

Fly ash represents a kind of finely divided solid waste which is derived from industrial or municipal waste incineration and contains various metal elements. In this work, we focus on the waste-to-resource conversion of one fly ash which is generated from the incineration of petroleum coke gasification waste. The leaching behaviors and waste conversion of this fly ash to value-added products under different treatments were investigated. The majority of the identified elements in leachate demonstrated different leaching patterns as the species of leached element from fly ashes depend on the chemical properties of leaching agents. Moreover, A pathway is developed to harvest toxic vanadium from this fly ash, and the vanadium-containing leachate can be further converted into electrolyte for vanadium redox flow battery (VRFB). The vanadium electrolyte was synthesized by using fly ash leachate as the resource materials in two different ways afterwards: reducing vanadium in the leachate directly (electrolyte from leachate) and synthesizing V₂O₅ from leachate as the intermediate product (electrolyte from leachate-derived V₂O₅). The electrochemical behavior and performance of these electrolytes were analyzed to investigate the feasibility of these approaches. The measurement of electrochemical performance proves that the electrolyte from leachate-derived V₂O₅ is comparable to the standard electrolyte in terms of columbic efficiency (CE), energy efficiency (EE) and stability. Based on experimental results, our research provides a potential solution for the establishment of vanadium flow battery plant. Cost-benefit analysis proves that the payback period of electrolyte synthesized from alkaline leachate and leachate-derived V₂O₅ is 2.1 years and 1.0 year, respectively.