Stabilization of Pb, Cd, and Zn in soil by modified-zeolite: Mechanisms and evaluation of effectiveness

Yan Ma; Lu Cheng; Dading Zhang; Fan Zhang; Shengkun Zhou; Yue Ma; Jianda Guo; Yaru Zhang; Baoshan Xing

doi:10.1016/j.scitotenv.2021.152746

Stabilization of Pb, Cd, and Zn in soil by modified-zeolite: Mechanisms and evaluation of effectiveness

Sci Total Environ. 2022 Mar 25:814:152746. doi: 10.1016/j.scitotenv.2021.152746. Epub 2021 Dec 31.

Authors

Yan Ma¹, Lu Cheng², Dading Zhang³, Fan Zhang², Shengkun Zhou⁴, Yue Ma², Jianda Guo², Yaru Zhang², Baoshan Xing⁵

Affiliations

¹ School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA. Electronic address: mayan2202@163.com.
² School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083, China.
³ Center International Group Co., Ltd., Beijing 100176, China.
⁴ Beijing Solid Waste Treatment Co., Ltd., Beijing 100101, China.
⁵ Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.

PMID: 34979223
DOI: 10.1016/j.scitotenv.2021.152746

Abstract

As a type of soil stabilization material, zeolite has good cation exchange ability and synchronous stabilization potential for multiple active heavy metal cations in soil. However, natural zeolite contains relatively high amounts of impurities, and has a single heavy metal stabilization mechanism, which limits its capacity to stabilize heavy metals in soil. To develop a stabilization material that could efficiently stabilize several heavy metals simultaneously, in the present study, modified zeolite (MZEO) was prepared via NaCl pretreatment, chitosan modification, modified chitosan loading, and CaSiO₃ modification to enable Pb, Cd, and Zn stabilization in soil. The aim of the present study was to explore zeolite modification technologies, reveal the stabilization mechanism of polymetallic contaminated soil and evaluate the stabilization effects of MZEO. According to the results, the modification treatment increased the cation exchange capacity of MZEO nearly 8-fold, the specific surface area 3.4-fold, and its internal pore structure was richer, with more adsorption sites. The appearance of a -NH₂ absorption bands confirmed the loading of chitosan successfully, and the modification enhanced the heavy metal stabilization mechanism. Upon the addition of MZEO to Baiyin soil, the chemical morphologies of heavy metals changed, which reduced the weak acid extracted forms of Pb, Cd, and Zn in the soil by 21%, 10%, and 19%, respectively. The potential mechanisms of free heavy metal reduction were ion exchange with Na in MZEO, heavy metal mineral formation by Al replacement in the crystal lattice, and bonding with SiO₃^2- formed by the hydrolysis of MZEO-loaded synaptic CaSiO₃ particles, to form silicate precipitation. MZEO application minimized heavy metal leaching risk in the soil and heavy metal biological/plant accessibility, with potential economic benefits. MZEO has promising applications in polluted soil remediation.

Keywords: Effect evaluation; Modified zeolite; Polymetallic contaminated soil; Stabilization mechanisms.

MeSH terms

Cadmium
Lead
Metals, Heavy* / analysis
Soil
Soil Pollutants* / analysis
Zeolites*
Zinc

Substances

Metals, Heavy
Soil
Soil Pollutants
Cadmium
Zeolites
Lead
Zinc