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.
Highlights
Lead–zinc smelting slag (LZSS) is a nonferrous metal smelting residue that belongs toChina’s national hazardous waste list
Alkali solid content (7%, 8%, 9%), water glass modulus (1.3, 1.4, 1.5), and liquid–solid ratio (0.18, 0.19, and 0.20) were selected for the orthogonal experiment based on the single-factor experiment
More and Si contributing to aluminoformation produced alkali solid increased, the aluminosilicate gel could silicate gel was formation wasasproduced as content alkali solid contentand increased, and the aluminosilimprove the compressive by hardening the alkali-activated binder
Summary
Lead–zinc smelting slag (LZSS) is a nonferrous metal smelting residue that belongs to. Solidification/stabilization is a relatively mature technology for harmless pretreatment and waste reuse, and is widely used in waste-material disposal [8,9,10] It converts pollutants into a less-soluble form and immobilizes pollutants by creating a persistent matrix to encapsulate them [11]. The compressive strength of solidified products reached 96.14 MPa with a removal rate of heavy metals above 90%, indicating that LZSS had a good self-cementing effect. Alkali-activated LZSS could solidify/stabilize hazardous waste due to the excellent performance in compressive strength and heavy-metal-leaching toxicity. COPR addition had effective solidification (compressive strength was 18.52 MPa, and hexavalent chromium leaching concentration was 1.553 mg/L). The heavy-metal extraction toxicity and compressive strength of the solidified bodies with different content of COPR (LZC) were investigated.
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