Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP

Microbial-induced carbonate precipitation (MICP) is an effective technology for repairing sites contaminated by heavy metals. In this work, <i>Sporosarcina pasteurii</i> was cultured and mixed with a cementing fluid as a binder to remediate Pb-contaminated silt. The effects of varying ex...

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Autores principales:	Fusheng Zha, Hao Wang, Bo Kang, Congmin Liu, Long Xu, Xiaohui Tan
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	MICP heavy metal contaminate silt <i>Sporosarcina pasteurii</i> Pb toxicity dry density Crystallography QD901-999
Acceso en línea:	https://doaj.org/article/e7d0d5b231bd449894440131d244c4d1
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spelling	oai:doaj.org-article:e7d0d5b231bd449894440131d244c4d12021-11-25T17:17:57ZImproving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP10.3390/cryst111113032073-4352https://doaj.org/article/e7d0d5b231bd449894440131d244c4d12021-10-01T00:00:00Zhttps://www.mdpi.com/2073-4352/11/11/1303https://doaj.org/toc/2073-4352Microbial-induced carbonate precipitation (MICP) is an effective technology for repairing sites contaminated by heavy metals. In this work, <i>Sporosarcina pasteurii</i> was cultured and mixed with a cementing fluid as a binder to remediate Pb-contaminated silt. The effects of varying experimental parameters, including Pb concentration and dry density, were also tested and analyzed. The leaching and strength characteristics and the MICP improvement mechanism of the Pb-contaminated silt were studied. Samples with dry densities of 1.50 g/cm<sup>3</sup> and 1.55 g/cm<sup>3</sup> exhibited the highest unconfined compression strengths (UCS). Scanning electron microscopy showed that not all CaCO<sub>3</sub> crystals produced a cementation effect, with some filling pores in an invalid cementation form. The results showed that MICP remediation of low Pb<sup>2+</sup> concentration-contaminated silt could meet the relevant Chinese environmental safety standards. Low Pb concentrations helped improve MICP-treated, Pb-contaminated silt strength, whereas high Pb concentrations significantly reduced this strength. Testing to determine the tolerance of an active microbe, <i>Sporosarcina pasteurii</i>, showed that trace amounts of Pb promoted its growth, thus improving the MICP effect, whereas excessive Pb had a toxic effect, which reduced MICP effectiveness. Mercury injection experiments showed that MICP produced CaCO<sub>3</sub>; this mainly filled soil mesopores and macropores and, thus, improved the soil UCS. Scanning electron microscopy showed that not all CaCO<sub>3</sub> crystals produced a cementation effect, with some filling pores in an invalid cementation form. MICP was innovatively applied to silt sites with heavy metal pollutants while considering the soil compaction in actual construction, thus broadening the application scope of MICP, optimizing the construction process, and reducing the construction cost.Fusheng ZhaHao WangBo KangCongmin LiuLong XuXiaohui TanMDPI AGarticleMICPheavy metal contaminate silt<i>Sporosarcina pasteurii</i>Pb toxicitydry densityCrystallographyQD901-999ENCrystals, Vol 11, Iss 1303, p 1303 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	MICP heavy metal contaminate silt <i>Sporosarcina pasteurii</i> Pb toxicity dry density Crystallography QD901-999
spellingShingle	MICP heavy metal contaminate silt <i>Sporosarcina pasteurii</i> Pb toxicity dry density Crystallography QD901-999 Fusheng Zha Hao Wang Bo Kang Congmin Liu Long Xu Xiaohui Tan Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP
description	Microbial-induced carbonate precipitation (MICP) is an effective technology for repairing sites contaminated by heavy metals. In this work, <i>Sporosarcina pasteurii</i> was cultured and mixed with a cementing fluid as a binder to remediate Pb-contaminated silt. The effects of varying experimental parameters, including Pb concentration and dry density, were also tested and analyzed. The leaching and strength characteristics and the MICP improvement mechanism of the Pb-contaminated silt were studied. Samples with dry densities of 1.50 g/cm<sup>3</sup> and 1.55 g/cm<sup>3</sup> exhibited the highest unconfined compression strengths (UCS). Scanning electron microscopy showed that not all CaCO<sub>3</sub> crystals produced a cementation effect, with some filling pores in an invalid cementation form. The results showed that MICP remediation of low Pb<sup>2+</sup> concentration-contaminated silt could meet the relevant Chinese environmental safety standards. Low Pb concentrations helped improve MICP-treated, Pb-contaminated silt strength, whereas high Pb concentrations significantly reduced this strength. Testing to determine the tolerance of an active microbe, <i>Sporosarcina pasteurii</i>, showed that trace amounts of Pb promoted its growth, thus improving the MICP effect, whereas excessive Pb had a toxic effect, which reduced MICP effectiveness. Mercury injection experiments showed that MICP produced CaCO<sub>3</sub>; this mainly filled soil mesopores and macropores and, thus, improved the soil UCS. Scanning electron microscopy showed that not all CaCO<sub>3</sub> crystals produced a cementation effect, with some filling pores in an invalid cementation form. MICP was innovatively applied to silt sites with heavy metal pollutants while considering the soil compaction in actual construction, thus broadening the application scope of MICP, optimizing the construction process, and reducing the construction cost.
format	article
author	Fusheng Zha Hao Wang Bo Kang Congmin Liu Long Xu Xiaohui Tan
author_facet	Fusheng Zha Hao Wang Bo Kang Congmin Liu Long Xu Xiaohui Tan
author_sort	Fusheng Zha
title	Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP
title_short	Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP
title_full	Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP
title_fullStr	Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP
title_full_unstemmed	Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP
title_sort	improving the strength and leaching characteristics of pb-contaminated silt through micp
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/e7d0d5b231bd449894440131d244c4d1
work_keys_str_mv	AT fushengzha improvingthestrengthandleachingcharacteristicsofpbcontaminatedsiltthroughmicp AT haowang improvingthestrengthandleachingcharacteristicsofpbcontaminatedsiltthroughmicp AT bokang improvingthestrengthandleachingcharacteristicsofpbcontaminatedsiltthroughmicp AT congminliu improvingthestrengthandleachingcharacteristicsofpbcontaminatedsiltthroughmicp AT longxu improvingthestrengthandleachingcharacteristicsofpbcontaminatedsiltthroughmicp AT xiaohuitan improvingthestrengthandleachingcharacteristicsofpbcontaminatedsiltthroughmicp
_version_	1718412565458976768

Improving the Strength and Leaching Characteristics of Pb-Contaminated Silt through MICP

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