Coal gasification slag secondary resource
Heterogeneous solid residue generated by coal gasification, including source-defined crude/coarse and fine fractions. This processing-derived resource is distinct from coal, coal-beneficiation waste and combustion-derived coal fly ash; it is neither a mineral species nor an aluminium or iron commodity. The accepted experiment concerns one supplied coal gasification crude slag (CGCS) sample and does not establish the same behavior for fine slag or other plants. Laboratory abiotic acid leaching and conversion of the liquors into a mixed flocculant are documented; constituent-element criticality is not inherited.
Microbial & Biochemical Mechanisms (1)
Abiotic acid leaching followed by mixed flocculant preparation
recovery
Separate hydrochloric-acid and acetic-acid treatments of the supplied crude slag produced liquors that were mixed, pH-adjusted, heated, aged and dried into a source-designated poly-aluminum-ferric-acetate-chloride flocculant (PAFAC). Figure 1 and Sections 2.2.1-2.2.3 show parallel leaches on separate slag portions, despite the title calling the approach two-step. The recovered material is a mixed chemical product containing aluminium, iron, calcium and reagent-derived constituents, not isolated elemental metals. No microbial culture, biogenic acid production or industrial recovery operation was tested.
Experimental Context & Analytical Limits:
CGCS was supplied by Yankuang National Engineering Research Center of Coal Water Slurry Gasification and Coal Chemical Industry Co., Ltd., Shandong, China (Section 2.1). The source does not specify its coal feed, gasifier conditions, sampling date, initial particle-size distribution or reaction charge mass. Separate stirred 500 mL beakers contained commercial acid and slag. Section 3.1 and the conclusion select 3.0 mol/L HCl at 40 degrees C for 1.5 h, and 5.0 mol/L acetic acid at 40 degrees C for 2.0 h, each at 15 mL solution per gram slag. Vacuum-filtered residues were water-rinsed, dried and weighed. The two liquors were combined at an HCl-liquor:HAc-liquor volume ratio of 3:2, adjusted to pH 3.5 with NaOH, heated at 70 degrees C for 3 h, aged for 24 h and oven-dried; drying temperature is not specified. Triplicate experiments and averaged results are stated in Section 2.3.1. Preparation of the slag for XRF at 815 degrees C for 1 h is an analytical treatment in Section 2.4, not an established pretreatment of every leaching charge.
CGCS was supplied by Yankuang National Engineering Research Center of Coal Water Slurry Gasification and Coal Chemical Industry Co., Ltd., Shandong, China (Section 2.1). The source does not specify its coal feed, gasifier conditions, sampling date, initial particle-size distribution or reaction charge mass. Separate stirred 500 mL beakers contained commercial acid and slag. Section 3.1 and the conclusion select 3.0 mol/L HCl at 40 degrees C for 1.5 h, and 5.0 mol/L acetic acid at 40 degrees C for 2.0 h, each at 15 mL solution per gram slag. Vacuum-filtered residues were water-rinsed, dried and weighed. The two liquors were combined at an HCl-liquor:HAc-liquor volume ratio of 3:2, adjusted to pH 3.5 with NaOH, heated at 70 degrees C for 3 h, aged for 24 h and oven-dried; drying temperature is not specified. Triplicate experiments and averaged results are stated in Section 2.3.1. Preparation of the slag for XRF at 815 degrees C for 1 h is an analytical treatment in Section 2.4, not an established pretreatment of every leaching charge.
Curated Evidence Points:
Support
Source:
pan_2024
Sections 2.2-2.3.1, 3.1 and 5, Figure 2 and equation 1 report 85.76% for the HCl arm and 44.32% for the acetic-acid arm at the selected conditions. Equation 1 defines these percentages from initial slag mass minus dried residual slag mass divided by initial slag mass. They are separate gravimetric loss endpoints, not measured Al or Fe extraction fractions, not additive stages and not a combined metal-recovery yield. At 50-60 degrees C the reported loss declined from the 40-degree-C maximum; longer contact or more acid did not consistently improve the endpoint.
Support
Source:
pan_2024
Section 3.3, Tables 2-3 and Figures 5 and 11 support preparation of an Al/Fe/Ca-containing mixed product. Table 2 reports the ashed slag on an oxide basis, including SiO2 42.95%, Fe2O3 15.26%, Al2O3 16.47% and CaO 17.26%; Table 3 reports the unashed product on an elemental basis, including Fe 13.95%, Al 7.58%, Ca 11.79%, Na 14.24% and Cl 42.08%. The authors attribute Na to added NaOH and identify crystalline NaCl in Figure 5A alongside material interpreted as amorphous polymer. These are composition measurements on different analytical bases, not evidence of a pure recovered metal or a closed feed-to-product balance.
Support
Source:
pan_2024
Sections 2.3 and 3.4, Figures 6-7 and Table 4 test practical reuse in 200 mL wastewater jar assays, with 250 rpm for 30 s, 60 rpm for 20 min and 15 min settling. At 250 mg/L PAFAC in domestic sewage, Section 3.4.1 reports turbidity, COD and total-phosphorus removals of 89.62%, 58.95% and 76.76%, respectively, while ammonia-nitrogen removal remained below 10% across the tested doses. The separate comparator assay in Section 3.4.2/Figure 7 reports 91.42%, 59.94% and 78.77%, and compares the combined product with products made from each individual acid liquor. These wastewater-concentration changes are not recovered-metal yields, and the two assay summaries are not pooled.
Partial
Source:
pan_2024
The study does not provide dissolved Al/Fe inventories, an isolated product mass yield, residual-carbon or loss-on-ignition correction for the leaching denominator, a complete liquor/residue/product mass balance, or a quantitative trace-contaminant safety assessment of the product. The water-washed residue endpoint can include nonspecific soluble-material losses. No matched water-only slag-leaching blank or acid/reagent-only flocculation blank is reported alongside the accepted outcomes. A supplied industrial feed and laboratory jar tests do not establish a deployed recovery plant or safe use across wastewater types.
Partial
Source:
pan_2024
Source inconsistencies limit detailed mechanistic inference. Section 3.2.1 gives 84.15% turbidity removal at a 2:3 liquor ratio, while Figure 3B places that bar above 90%; the conflicting nonselected ratio is not adopted. Figure 8 caption assigns panels by kinetic equation, whereas Table 5 labels A/C as HCl and B/D as HAc and each plotted panel contains both acids; fitted rates are not imported as uniquely resolved kinetic mechanisms. Section 4.2.1 describes decreasing zeta potential with added PAFAC, while Figure 10 moves from more negative values toward zero up to 250 mg/L. The sign, model fits and proposed adsorption/bridging explanations do not demonstrate a unique causal pathway. Section 2.1 calls the third wastewater aquaculture wastewater but says it came from a cow pasture; no general aquaculture-performance claim is transferred.
Sources & References
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pan_2024: Pan, Sun, Shen, Sun, He, Li and Lu (2024). Coal gasification crude slag based complex flocculants by two-step acid leaching process: synthesis, flocculation and mechanisms. RSC Advances 14:2705-2719. DOI 10.1039/D3RA07232K; complete original, Sections 2-5, Tables 1-5 and Figures 1-14.
https://doi.org/10.1039/D3RA07232K (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T07:16:28.275365Z |
Codex (GPT-6; Codex) | CREATE | Created the distinct gasification-derived resource identity with source-scoped abiotic leaching and mixed-product reuse evidence, preserving gravimetric denominators, analytical-basis differences, negative outcomes and internal source conflicts. |
Record source: data/records/coal-gasification-slag.yaml