Jonovan Van Yken

Redox flow batteries (RFBs) are known for their exceptional attributes, including remarkable energy efficiency of up to 80%, an extended lifespan, safe operation, low environmental contamination concerns, sustainable recyclability, and easy scalability. One of their standout characteristics is the separation of electrolytes into two distinct tanks, isolating them from the electrochemical stack. This unique design allows for the separate design of energy capacity and power, offering a significantly higher level of adaptability and modularity compared to traditional technologies like lithium batteries. RFBs are also an improved technology for storing renewable energy in small or remote communities, benefiting from larger storage capacity, lower maintenance requirements, longer life, and more flexibility in scaling the battery system. However, flow batteries also have disadvantages compared to other energy storage technologies, including a lower energy density and the potential use of expensive or scarce materials. Despite these limitations, the potential benefits of flow batteries in terms of scalability, long cycle life, and cost effectiveness make them a key strategic technology for progressing to net zero. Specifically, in Australia, RFBs are good candidates for storing the increasingly large amount of energy generated from green sources such as photovoltaic panels and wind turbines. Additionally, the geographical distribution of the population around Australia makes large central energy storage economically and logistically difficult, but RFBs can offer a more locally tailored approach to overcome this. This review examines the status of RFBs and the viability of this technology for use in Australia.

Electronic waste, or e-waste, represents one of the rapidly expanding categories of waste worldwide. By 2019, the global production of e-waste had surged to 53.6 million tons. Due to its substantial metal content, e-waste holds significant financial value, estimated at US$57 billion globally in 2019, predominantly concentrated in printed circuit boards (PCBs). Previous studies have explored hydrometallurgy techniques to extract base metals from PCBs, but effectively recovering these solubilized metals remained a challenge. This research sought to assess metal recovery from PCB waste leachate by utilizing hydrogen sulfide generated through a consortium of sulfate-reducing bacteria (SRB) in a fluidized bed reactor (FBR). Both lactate and glycerol were examined as potential organic electron donors for the sulfate reduction. With lactate (1 g L−1) as the electron donor, the FBR achieved an average sulfate reduction efficiency of 62%, with a hydrogen sulfide (H2S) production rate of 250 mg H2S-S L−1 d−1 and H2S-S concentration of 300 mg L−1 in the effluent. When glycerol was the organic electron donor, the average sulfate reduction efficiency was 49%, H2S production rate was 210 mg H2S-S L−1 d−1 and H2S-S concentration was 260 mg L−1. Desulfovibrio, Desulfococcus and Desulfomicrobium were the dominant sulfate reducers in the FBR. The resulting dissolved hydrogen sulfide was employed to recover metals from e-waste leach liquor. Utilizing biogenic sulfide and NaOH, a notably high precipitation efficiency (>99%) was attained for aluminum, nickel, copper, and zinc. Additionally, iron, utilized in the e-waste leaching process, was also recovered with an efficiency exceeding 99%. The precipitation of metals occurred within a pH range from 1.5 to 8.5. Overall, this process facilitated the formation of valuable mixed-metal precipitates from waste PCB-derived leachate. These precipitates could undergo further purification or serve as raw material for subsequent processes.
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