The Utilization of Alkali-Activated Lead–Zinc Smelting Slag for Chromite Ore Processing Residue Solidification/Stabilization

Abstract

Lead–zinc smelting slag (LZSS) is regarded as a hazardous waste containing heavy metals that poses a significant threat to the environment. LZSS is rich in aluminosilicate, which has the potential to prepare alkali-activated materials and solidify hazardous waste, realizing hazardous waste cotreatment. In this study, the experiment included two parts; i.e., the preparation of alkali-activated LZSS (pure smelting slag) and chromite ore processing residue (COPR) solidification/stabilization. Single-factor and orthogonal experiments were carried out that aimed to explore the effects of various parameters (alkali solid content, water glass modulus, liquid–solid ratio, and initial curing temperature) for alkali-activated LZSS. Additionally, compressive strength and leaching toxicity were the indexes used to evaluate the performance of the solidified bodies containing COPR. As a result, the highest compressive strength of alkali-activated LZSS reached 84.49 MPa, and when 40% COPR was added, the strength decreased to 1.42 MPa. However, the leaching concentrations of Zn and Cr from all the solidified bodies were far below the critical limits (US EPA Method 1311 and China GB5085.3-2007). Heavy-metal ions in LZSS and COPR were immobilized successfully by chemical and physical means, which was detected by analyses including environmental scanning electron microscopy with energy-dispersive spectrometry, Fourier transform infrared spectrometry, and X-ray diffraction.

Sustainable Management Strategy for Solidification/Stabilization of Zinc Plant Residues (ZPR) by Fly Ash/Clay-Based Geopolymers

“…The visual appearance of both acid wastes is shown in Figure 1. In this way, recent investigations on the use of geopolymer matrices to solidify/stabilize different hazardous waste-containing heavy metals have been reported: electric arc furnace dust [29][30][31], municipal solid waste incineration fly ash (MSWI) [26], lead-zinc smelting slag [14,[32][33][34], chromite ore processing residues [35,36], hexavalent chromium [37,38], or galvanic solid waste [39], among others. Immobilization efficiency is measured mainly by the mechanical strength and the leaching reduction as indicators of solidification and stabilization, respectively.…”

Research on the environmental stability performance of chromite ore processing residue solidified products

“…23 Many researchers have been focusing on the immobilization of chromium in COPR. 7,9,20 Muhammad et al 2020 (ref. 20) used composite-based geopolymer (BFS and metakaolin) and green tea synthesized nanoscale zerovalent iron (GT-NZVI) to solidify COPR, and they found that the compressive strength of the cured body with GT-NZVI particles was not greatly reduced, but the leaching toxicity was far below the safety limit (5 mg L −1 ), indicating that COPR was effectively solidified in the composite-based geopolymer.…”

“…Technologies dealing with COPR could be divided into ve main categories: (I) Solidication/stabilization (S/S) technology, [7][8][9] which means that the chromium in COPR is transformed into states and forms that are insoluble, migratory or less toxic by physical and chemical means using some materials such as ordinary Portland cement or alkali-activated cementitious material; (II) chemical reduction technology, including dry-detoxication (utilizing some reducing gases, such as CO) and wet-detoxication (reduction of Cr(VI) to Cr(III) in the liquid phase); [10][11][12] (III) microbial techniques, [13][14][15] i.e. the reduction of Cr(VI) in COPR by microorganisms; (IV) resource utilization methods, 16,17 in which COPR is used as an alternative material to produce certain products, transforming it into useful substances that promote the recycling of waste, such as sintered iron and glass colorants; (V) compound treatment technology, [18][19][20] which refers to using multiple technologies at the same time.…”

“…Yu et al 2021 (ref. 9 ) conducted solidification/stabilization of alkali-activated lead-zinc smelting slag (LZSS) and COPR, and found that the highest compressive strength of alkali-activated LZSS was 84.49 MPa, and the compressive strength was reduced to 1.42 MPa when the COPR content was 40%. However, the leaching concentrations of Zn and Cr in all cured bodies were well below the critical limits.…”

Structural and Chemical Properties of Geopolymer Gels Incorporated with Neodymium and Samarium

“…Despite that, some metal cations can even participate in the geopolymerization reaction [ 2 , 3 ]. Research to date has shown a lot of results in field of toxic heavy metals treatment by immobilization into alkali activated structure [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ].…”