Effect of urine hydrolysis degree on the recovery performance of nutrients in magnesium-air fuel cell system

CAI Bohua; WU Di; DENG Yingying; HU Shujie; ZHANG Mengyue; LIU Yuan

doi:10.13205/j.hjgc.202503002

Volume 43 Issue 3

Mar. 2025

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CAI Bohua, WU Di, DENG Yingying, HU Shujie, ZHANG Mengyue, LIU Yuan. Effect of urine hydrolysis degree on the recovery performance of nutrients in magnesium-air fuel cell system[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(3): 11-21. doi: 10.13205/j.hjgc.202503002

Citation:

CAI Bohua, WU Di, DENG Yingying, HU Shujie, ZHANG Mengyue, LIU Yuan. Effect of urine hydrolysis degree on the recovery performance of nutrients in magnesium-air fuel cell system[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(3): 11-21. doi: 10.13205/j.hjgc.202503002

Citation:

CAI Bohua, WU Di, DENG Yingying, HU Shujie, ZHANG Mengyue, LIU Yuan. Effect of urine hydrolysis degree on the recovery performance of nutrients in magnesium-air fuel cell system[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(3): 11-21. doi: 10.13205/j.hjgc.202503002

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Effect of urine hydrolysis degree on the recovery performance of nutrients in magnesium-air fuel cell system

doi: 10.13205/j.hjgc.202503002

1. Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China;
2. Chongqing School, University of Chinese Academy of Science, Chongqing 400714, China

Received Date: 2024-11-20
Accepted Date: 2024-12-23
Rev Recd Date: 2024-12-20

Available Online: 2025-06-07

Publish Date: 2025-03-01

Abstract

Abstract

Recycling resources such as phosphorus （P） and nitrogen （N） from urine is of profound significance in line with the demands of sustainable development. This approach holds great promise in alleviating the imbalance between fertilizer production and mineral reserves that China currently faces. Magnesium-air fuel cells （MAFC） offer a viable means for the efficient removal and recovery of P resources from fully hydrolyzed urine. However， this process unfortunately leads to a waste of valuable urea resources. Urine is highly prone to hydrolysis. Once hydrolyzed， the released NH₄⁺ and OH^- ions will bring about significant changes in urine water quality. This alteration may have a substantial impact on P recovery within the MAFC system. Moreover， excessive hydrolysis is not conducive to the effective utilization of urea resources. In this study， extensive experiments were meticulously conducted by designing simulated urine samples with varying degrees of hydrolysis. The aim was to thoroughly investigate the influence of urine hydrolysis degree on P recovery performance in the MAFC system. The underlying mechanism by which the degree of urine hydrolysis affects the generation of P-containing precipitates in the MAFC was painstakingly revealed. The ultimate objective was to achieve efficient removal and recovery of P while striving to retain as much urea as possible. The research findings demonstrated that urine with a hydrolysis degree of 10% could supply a sufficient amount of NH₄⁺ and create a suitable pH environment. In this case， it could remove 94.42% of the initial PO₄^3- while still retaining 96.81% of the initial urea. Additionally， the degree of urine hydrolysis indeed had a notable influence on the composition of the precipitates. By comprehensively characterizing the precipitates collected from urine with different hydrolysis degrees after 60 minutes of reaction， significant differences in the composition of the generated precipitates were clearly identified. Through the detailed analysis of the recovered precipitates in the urine system with a hydrolysis degree of 10%， it was found that the mass proportion of struvite in the precipitates collected after 40 minutes of reaction could reach an impressive 96%. This study can serve as a valuable reference for recovering high-quality P-containing slow-release fertilizers by carefully controlling the degree of urine hydrolysis. Further research is needed to delve into the impact mechanism of urine hydrolysis degree on electrochemical process of MAFC.
- source-separated urine,
- urine hydrolysis degree,
- resource recovery,
- struvite,
- magnesium-air fuel cell

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References(34)

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