One person has wastewater and another person has treasure. A new study by the university shows that sewage can be mined for valuable materials used in batteries and fertilizers. The analysis shows how to make electrical processes more efficient in order to transform sulfur pollution into clean water.
The senior author of the study said that they are always looking for ways to close the loop on chemical manufacturing processes.
A better solution.
As fresh water supplies dwindle, focus has intensified on developing technologies that convert wastewater to water. Wastewater filters that use an oxygen-free environment are particularly promising because they require relatively little energy. sulfide can be toxic, corrosive and malodorous. Strategies for dealing with that problem, such as chemical oxidation or the use of certain chemicals to convert the sulfur into separable solid, can cause chemical reactions that can cause pipes to break and make it harder to clean the water.
The mechanisms for converting the sulfide to chemicals used in fertilizer and cathode material for batteries are not well understood. Tarpeh and his colleagues set out to find a cost-effective approach that wouldn't create chemical byproducts.
Sulfur oxidation requires low energy input and allows fine-tuned control of final sulfur products. Sulfate can be easily captured and reused, as it can deposit on electrodes and slow down chemical reactions. The process could be powered by renewable energy and adapted to treat wastewater from individual buildings or entire cities.
The researchers quantified the rates of each step of electrochemical sulfur oxidation along with the types and amounts of products formed. They identified the main barriers to sulfur recovery. They found that varying operating parameters, such as the reactor voltage, could facilitate low-energy sulfur recovery from wastewater.
tradeoffs between energy efficiency, sulfide removal, and sulfate production were clarified. The framework was outlined by the researchers to inform the design of future oxidation processes that balance energy input, pollutant removal and resource recovery. The sulfur recovery technology could be combined with other techniques, such as the recovery of nitrogen from wastewater to produce ammonia sulfate. The Codiga Resource Recovery Center is a pilot-scale treatment plant that will likely play a large role in future design and implementation of these approaches.
The lead author of the study said that he hopes the study will help accelerate adoption of technology that mitigates pollution, recovers valuable resources and creates potable water all at the same time.
Tarpeh is an assistant professor of civil and environmental engineering, a center fellow of the Stanford Woods Institute for the Environment, and an affiliated scholar with the Program on Water, Health and Development. At the time of the research, another author was an undergraduate student in chemical engineering.
More information: Xiaohan Shao et al, Quantifying and Characterizing Sulfide Oxidation to Inform Operation of Electrochemical Sulfur Recovery from Wastewater, ACS ES&T Engineering (2022). DOI: 10.1021/acsestengg.1c00376 Citation: Sewer treasure: Engineers reveal how to optimize processes for transforming wastewater sulfur to valuable materials (2022, March 2) retrieved 2 March 2022 from https://phys.org/news/2022-03-sewer-treasure-reveal-optimize-wastewater.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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