A novel heavy metal chelating agent sixthio guanidine acid for in situ remediation of soils contaminated with multielements: its synthesis, solidification, biodegradability, and leachability

Autor: Hao-Tian Hao, Jay Gao, Fan Zhang, Bin Zhao, Feng-He Wang, Shengtian Zhang
Rok vydání: 2015
Předmět:
Zdroj: Journal of Soils and Sediments. 16:371-381
ISSN: 1614-7480
1439-0108
DOI: 10.1007/s11368-015-1236-x
Popis: The main objectives of the study were to (1) develop a one-step facile procedure for synthesizing a new chemical amendment agent with three chelating groups for solidifying multiple heavy metals, called sixthio guanidine acid (SGA), using guanidine hydrochloride and carbon disulfide as raw reactants and (2) assess its biodegradability, solidification effectiveness, and leachability in remedying soils contaminated with multiple heavy metals of various concentrations compared with other traditional amendment agents. Polluted soil samples were collected near a metalliferous mining site of Qixiashan in the southeast of Nanjing, China. Their concentrations were determined at 22.15–320 mg kg−1 for As, 3.30–29.31 mg kg−1 for Cd, 115.66–158.65 mg kg−1 for Ni, 165.04–1677.06 mg kg−1 for Pb, and 355.6–2426.91 mg kg−1 for Zn. Biodegradability of SGA was assessed in accordance with GB/T 21831-2008 and OECD-301D. Total concentration of heavy metals was determined according to ISO11466:1995. A modified three-step sequential Community Bureau of Reference (BCR) extraction procedure was used to examine speciation of heavy metals in the soil sample, and concentrations of heavy metals were measured by using inductively coupling plasma optical emission spectrometry (ICP-OES). Leachate extraction tests were carried out before and after the soil sample was solidified with different amendments in accordance with HJ/T 557-2009. It is found that the optimal conditions for SGA synthesis are a molar ratio of 4:1, a reaction temperature of 40 °C, and a reaction time of 2 h. Under such conditions, SGA yield is achieved as high as 91.5 %. The bioavailability and mobility of As, Cd, Ni, Pb, and Zn in highly contaminated soils can be reduced via using SGA. Our results indicate that SGA is nonbiodegradative and much more effective than other traditional chemical amendment agents in that it is highly effective in comprehensively solidifying As, Cd, Ni, and Pb. SGA has the potential for comprehensive in situ remediation of soils contaminated with several heavy metal elements of various concentration levels, and such findings may be used as a guide to design new chemical amendment agents for rehabilitating soils contaminated with heavy metals.
Databáze: OpenAIRE
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