A large amount of coal gasification slag is produced every year in China. However, most of the current disposal is into landfills, which causes serious harm to the environment. In this research, coal gasification fine slag residual carbon porous material (GFSA) was prepared using gasification fine slag foam flotation obtained carbon residue (GFSF) as raw material and an adsorbent to carry out an adsorption test on waste liquid containing methylene blue (MB). The effects of activation parameters (GFSF/KOH ratio mass ratio, activation temperature, and activation time) on the cation exchange capacity (CEC) of GFSA were investigated. The total specific surface area and pore volume of GSFA with the highest CEC were 574.02 m²/g and 0.467 cm³/g, respectively. The degree of pore formation had an important effect on CEC. The maximum adsorption capacity of GFSA on MB was 19.18 mg/g in the MB adsorption test. The effects of pH, adsorption time, amount of adsorbent, and initial MB concentration on adsorption efficiency were studied. Langmuir isotherm and quasi second-order kinetic model have a good fitting effect on the adsorption isotherm and kinetic model of MB.

There are increasing demands and great potential of coal gasification in China, but there is a lack of studies focused on the disposal and utilization of coal fly ash produced by the gasification process. In this study, a coal fly ash sample derived from a gasifier in Jincheng, China, was utilized as raw material for the synthesis of zeolite by alkali fusion followed by hydrothermal treatments. The effects of operation conditions on the cation exchange capacity (CEC) of synthesized zeolite were investigated. The synthesized zeolite with the highest CEC (270.4 meq/100 g), with abundant zeolite X and small amount of zeolite A, was produced by 1.5 h alkali fusion under 550 °C with NaOH/coal fly ash ratio 1.2 g/g followed by 15 h hydrothermal treatment under 90 °C with liquid/solid ratio 5 mL/g and applied in Ni²⁺ removal from water. The removal rate and the adsorption capacity of Ni²⁺ from water by the synthesized zeolite were determined at the different pH, contact time, adsorbent dose and initial Ni²⁺ concentration. The experimental data of adsorption were interpreted in terms of Freundlich and Langmuir equations. The adsorption of Ni²⁺ by the synthesized zeolite was found to fit sufficient using the Langmuir isotherm. More than 90% of Ni²⁺ in water could be removed by synthesized zeolite under the proper conditions. We show that the coal fly ash produced by the gasification process has great potential to be used as an alternative and cheap source in the production of adsorbents.

Comprehensive utilization of hazardous industrial waste can recover resources but may also transfer residual hazardous constituents into downstream products. Preparing water treatment agents with low environmental risk is an important path towards sustainable development for the sulfuric acid industry. Following the framework of hazard identification, exposure assessment, hazard characterization, and risk characterization in the forthcoming Chinese national standard “General Principles for Environmental Risk Assessment of Products from Comprehensive Utilization of Hazardous Wastes”, this case study evaluated the use-phase human-health and aquatic ecological risks of a liquid polyferric sulfate coagulant produced from waste sulfuric acid. As, Pb, Hg, Cr, Zn, and Ni were reported in the product at 8.6 × 10⁻⁴, 8.6 × 10⁻⁵, 1.5 × 10⁻⁷, 4.78 × 10⁻³, 7.96 × 10⁻³, and 2.10 × 10⁻⁴ mg/L, respectively. Three predefined scenarios were considered: direct worker dermal contact during dosing, indirect dermal contact with receiving water, and aquatic exposure after discharge. Under the case-study parameterization, the total carcinogenic and non-carcinogenic risks were 2.46 × 10⁻⁷ and 3.90 × 10⁻⁴ for occupational exposure and 8.04 × 10⁻¹⁸ and 5.47 × 10⁻¹⁵ for indirect population exposure, respectively. The available ecological-effect dataset supported only a partial Hg-based screening. Thus, the conclusions are limited to the measured product composition, selected scenarios, assumptions, and benchmarks and do not constitute a comprehensive occupational, life-cycle, or multimedia environmental-safety assessment.