期刊
ENVIRONMENTAL POLLUTION
卷 284, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.envpol.2021.117178
关键词
Red mud; Phosphogypsum; Green binders; Stabilization/solidification; Heavy metals; Sustainable remediation
资金
- National Key R&D Program of China [2018YFC1803100, 2020YFC1808201]
- National Natural Science Foundation of China [51978157]
- Fundamental Research Funds for the Central Universities
This study presents a novel approach to recycle industrial by-products as sustainable red mudphosphogypsum-Portland cement binders for stabilizing/solidifying multimetal-contaminated soil. The results demonstrate that RPPC performs competitively in terms of physical strength and metal immobilization ability, but shows poorer performance than PC after freeze-thaw and wetting-drying cycles. Samples treated by RPPC15 and PC10 meet Chinese standards for hazardous wastes in terms of metal leaching concentrations.
Red mud and phosphogypsum are voluminous industrial by-products worldwide. They have long been disposed of in landfills or open storage, leading to a waste of resource and environmental pollution. This study provides a novel approach to recycle these industrial by-products as sustainable red mudphosphogypsum-Portland cement (RPPC) binders for stabilization/solidification (S/S) of multimetal-contaminated soil. The physical strength, metal leachability and microstructure of S/S soil were investigated after 7-day and 28-day curing, as well as freezing-thawing (F-T) cycle and wetting-drying (W-D) cycle. The results show that the strength of soil treated by all binders fulfilled the uniaxial compressive strength requirement (350 kPa) of S/S waste in landfills. Microstructural analyses show that the main hydration products of the RPPC S/S soil are ilmenite, ettringite, anhydrite and hydrated calcium silicate. The 10% and 15% RPPC binders have a competitive metal immobilization ability compared with 10% PC, but the immobilization priority is different: Pb > Zn > Cd in RPPC system and Zn > Cd > Pb in PC system, respectively, probably due to the precipiataion of Pb2+ with the abundant SO42- in phosphogypsum in RPPC system. The strength of RPPC and PC treated soil was still higher than 350 kPa except for RPPC7.5 after 10 freeze-thaw or 10 wetting-drying cycles. The RPPC binder performed worse than PC binder after both freeze-thaw and wetting-drying cycles, especially at a lower dosage. Only the metal leaching concentrations of samples treated by RPPC15 and PC10 could fulfil the Chinese standards for hazardous wastes. (C) 2021 Elsevier Ltd. All rights reserved.
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