Efficient Synergistic Stabilization/Solidification of Phosphogypsum and Copper Smelter Slag

Abstract

Abstract: Phosphogypsum (PG) and copper smelter slag (CSS) are solid wastes produced from phosphorus chemical industries and nonferrous metal smelting industries. PG mainly consists of CaSO₄·2H₂O with harmful impurities such as residual acids, phosphate, fluorides, and trace metals (e.g., Cr, As and Cd). CSS contains large amounts of heavy metals such as lead and zinc. The soluble portions of the harmful substances in PG and CSS may enter the environment and cause serious pollution problems. In this study, NaOH and CaO were added as activators and additional calcium sources in mixed slag of PG and CSS with water to produce cemented blocks (named PG-S). Unconfined compressive strength (UCS) test and leaching test show that the compressive strength of PG-S reaches 14.8 MPa, and the stabilization efficiency of $PO^{3-}_{4}$ and F^- in PG are 99.87% and 92.13%, respectively. The concentrations of heavy metal zinc, lead and other harmful substances in the leaching solution meet the requirements of "integrated wastewater discharge standard" (GB 8978—1996) of China. The stabilization/solidification (S/S) of PG and CSS using the proposed method shows high efficiency and feasibility. Through XRD and SEM analysis, the stabilized wastes show structures similar to C-S-H, ettringite, Zn₃(PO₄)₂(H₂O)₄, Pb₁₀(PO₄)₆(OH)₂ and CaF₂. On this basis, the possible mechanism of the stabilization/solidification process is: the harmful substances in PG and CSS may be stabilized/solidified by formation of insoluble substances and adsorption of cementitious substances.

Key words: phosphogypsum, copper smelter slag, immobilization, waste treatment, activation

CLC Number:

X705

WANG Wei, XU Xiangqun, LI Jie, GUO Li, CHEN Rongsheng, DU Dongyun. Efficient Synergistic Stabilization/Solidification of Phosphogypsum and Copper Smelter Slag[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(5): 1601-1609.

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