Simultaneous immobilization of arsenic, lead and cadmium by magnesium-aluminum modified biochar in mining soil. (15th May 2022)

• Record Type: Journal Article
• Authors: Li, Qiannan; Liang, Weiyu; Liu, Fang; Wang, Gehui; Wan, Jiang; Zhang, Wei; Peng, Cheng; Yang, Jie
• Is Part Of: Journal of environmental management. Volume 310(2022)
• Publication Date: 2022-05-15
• Subjects: Heavy metals -- Mg–Al modified biochar -- Mining soil -- Remediation mechanisms -- Simultaneous immobilization; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2022.114792
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Owing to the human activities such as smelting and mining, arsenic (As), lead (Pb) and cadmium (Cd) seriously polluted the soil of non-ferrous metal mining areas, thus efficient methods for the simultaneous immobilization of the three heavy metals are urgently needed. In the present study, Mg–Al modified biochars (MABs) were synthesized through a simple one-pot pyrolysis method to immobilize the three heavy metals. According to the BET (Brunauer-Emmett-Teller) test method, MABs had larger specific surface areas than biochar. Compared to the materials obtained at 300 °C and 700 °C, MAB with a pyrolysis temperature of 500 °C (MAB 500) had a significant immobilization effect on As, Pb and Cd in the Gansu mining area. Compared with BC, the removal efficiencies of As, Pb and Cd increased from −62%, 17% and 5% to 52%, 100% and 66%, respectively. And the toxicity characteristic leaching procedure (TCLP) test showed that the leaching concentrations of the three heavy metals in the treated soil were all lower than the standard value. X-ray photoelectron spectroscopy and kinetic experiments showed that there were various mechanisms in the immobilization process of the three heavy metals, and the large specific surface area and the multi-Mg/Al–OH of MABs play an important role in this process. More charges were provided by larger specific surface for ion exchange with heavy metals. In addition, larger specific surface area also provided more adsorption sites. More complex sites were provided by Mg/Al–OH to form Mg/Al–O-M then immobilize the heavy metals. In summary, the immobilization mechanism may involve electrostatic attraction, precipitation/co-precipitation, and surface complexation. Graphical abstract: Image 1 Highlights: Mg–Al modified biochars were obtained through a simple one-pot pyrolysis method. MAB (500 °C) effectively immobilized the three metals in the soil at the same time. After modification, surface area of biochars increased and Mg/Al–OH was introduced. Main mechanism of As was ion exchange, while that of Pb and Cd was complexation.