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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2024 Vol.25 No.1 P.36-46
Biotreatment of incinerated bottom ash and biocementation of sand blocks using soybean urease
Abstract: Because of the high cost of cultivating urease-producing bacteria (UPB), this paper proposes soybean-urease-induced carbonate precipitation (SUICP) as a novel biocement for treatment of nickel contaminants and cementation of sandy soil. We found the optimal soaking time and soybean-powder content to be 30 min and 130 g/L, respectively, based on a standard of 5 U of urease activity. The most efficient removal of nickel ions is obtained with an ideal mass ratio of urea to nickel ions to soybean-powder filtrate (SPF) of 1׃2.4׃20. The removal efficiency of nickel ions can reach 89.42% when treating 1 L of nickel-ion solution (1200 mg/L with the optimal mass ratio). In incinerated bottom ash (IBA), the removal efficiency of nickel ions is 99.33% with the optimal mass ratio. In biocemented sandy soil, the average unconfined compressive strength (UCS) of sand blocks cemented with soybean urease-based biocement can reach 118.89 kPa when the cementation level is 3. Currently, the average content of CaCO3 in sand blocks is 2.52%. As a result, the SUICP process can be applied to remove heavy metal ions in wastewater or solid waste and improve the mechanical properties of soft soil foundations.
Key words: Biocement; Soybean-powder filtrate (SPF); Removal efficiency; Sandy soil; Unconfined compressive strength (UCS)
机构：1东南大学，江苏省土木工程材料重点实验室，中国南京，211189；2浙大宁波理工学院，土木建筑工程学院，中国宁波，315100
目的：大豆脲酶基生物水泥与脲酶菌基生物水泥功能相同，其同样可被应用于环境和土木工程中。由于培养脲酶菌的过程复杂且成本较高，本文提出使用简单且成本相对较低的大豆脲酶，其可诱导碳酸盐沉淀，是一类新型生物水泥。它可被应用于污染物中重金属处理和软土地基加固。在处理后的重金属污染物中，可有效降低游离重金属的浓度至安全阀值以下；在胶结后的砂土中，可显著提高其力学性能。
创新点：1.大豆脲酶可采用水浸泡法提取；2.根据最佳脲酶活性，确定大豆粉末的最佳浸泡时间和用量；3.根据最佳去除率，确定最佳去除镍离子的配方；4.根据脲酶水解机理和矿物形成的生物化学反应机制，讨论大豆脲酶基生物水泥矿化固结镍离子和胶结砂土的机理和过程。
方法：1.通过浸泡大豆粉末，根据最佳脲酶活性确定最佳浸泡时间和掺量（图S3和S4）；2.通过调节尿素掺量、大豆粉末滤液含量和矿化时间，在溶液中镍离子最佳去除率下，确定尿素、镍离子与大豆粉末滤液的最佳质量比（图5a~5c）；3.通过应用最佳质量比下的尿素和大豆粉末滤液，可以有效去除垃圾焚烧底灰中镍离子和提升胶结砂土的力学性能（图6和7）；4.通过大豆脲酶矿化固结镍和钙离子的示意图，揭示大豆脲酶基生物水泥的形成机制和胶结机理（图8）。
结论：1.大豆粉末与水混合可以释放大豆脲酶，并溶于水中，可催化分解尿素，引起电导率变化，从而确定脲酶活性；2.大豆粉末的最佳浸泡时间和掺量需要根据不同浸泡时间和掺量与脲酶活性的关系确定；3.尿素、镍离子与大豆粉末滤液的最佳质量比需要根据不同尿素掺量、大豆粉末滤液含量和矿化时间与镍离子去除率关系确定；4.通过应用最佳质量比下的尿素和大豆粉末滤液，可以获得不同镍离子浓度下的去除率和不同胶结次数下的砂土的碳酸钙含量和无侧限抗压强度。
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DOI:
10.1631/jzus.A2300006
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On-line Access:
2024-01-15
Received:
2023-01-05
Revision Accepted:
2023-04-14
Crosschecked:
2024-01-15