Yan Zhang

Coke breeze, a solid waste generated during coke production, transportation and utilization, possesses physicochemical properties akin to metallurgical coke except for its finer particle size. Recycling this material offers an effective route to conserve and reuse coal resources, yielding notable environmental and economic benefits. In this study, a composite binder composed of phenolic resin (PR) and coal tar pitch (CTP) was developed for producing high-strength metallurgical coke substitutes from coke breeze. This strategy complementarily combines the excellent binding and curing properties of PR with the superior high-temperature carbonization performance of CTP. Thermal and structural analyses elucidated distinct pyrolysis characteristics and functional group distributions between the two binders, providing a theoretical foundation for their complementary interaction. Systematic investigations into briquette strength, performance, and microstructure established that the optimal composite binder dosage is 15 wt.% of coke breeze, with a CTP-to-PR mass ratio of 7:3. This complementary system substantially enhanced the compressive strength of the formed coke, reaching 37.73 MPa after carbonization at 1000 °C, and improved its thermal stability, as reflected by a Coke Strength after Reaction (CSR) of 41.21%. Compared to the individual binders, the composite binder exhibited superior consolidation efficiency and structural integrity, presenting a promising approach for solid waste valorization and sustainable coke production.

The aluminum industry generates large volumes of highaluminum alkaline wastewater, yet efficient recovery of aluminum from such streams remains a challenge. In this study, we develop a novel crossflow rotary carbonation (CFRC) process that integrates an ultrafine atomizing gas disk with rotational stirring to decouple the mass transfer and crystallization stages, significantly enhancing gasliquid reaction efficiency. Thermodynamic analysis reveals that the optimal conditions for pseudoboehmite (PB) formation are T < 300 K and pH 10.4–13.0. Orthogonal experiments identify the key synthesis parameters: 0.1 mol/L NaAlO₂, caustic ratio of 1.5, endpoint pH of 10.5, CO₂ flow rate of 0.5 L/min, and stirring speed of 350 rpm. Under these conditions, the CFRCderived PB exhibits exceptional textural properties with a specific surface area of 455 m²/g, pore volume of 1.26 cm³/g, and average pore size of 13.86 nm, representing a 94% increase in surface area over conventional batch stirring carbonation. Notably, NaAlO₂ concentration is the dominant factor; concentrations above 0.3 mol/L promote competitive gibbsite formation and deteriorate the pore structure. The process achieves over 98% aluminum recovery and reduces alkaline wastewater discharge by more than 38 tons per ton of PB produced, offering a green and efficient route for resource valorization.

With the increasing depletion of high-quality iron ore resources, the efficient utilization of refractory ores has become a critical challenge in the iron and steel industry. This review systematically examines recent advances in sintering granulation technologies aimed at enhancing the processing of such ores. The study focuses on two main categories: conventional intensification methods, including moisture optimization, binder application, and mixer improvements, and novel sintering processes such as press-briquetting, pelletized sintering, split-stream granulation, composite agglomeration (CAP), and pre-granulation sintering. Key findings indicate that while conventional techniques can partially improve granulation uniformity and sintering bed permeability, they remain inadequate for handling high proportions of ultrafine ores or secondary iron-bearing materials. In contrast, innovative processes like CAP and pre-granulation sintering demonstrate superior adaptability and efficiency by integrating pelletizing and sintering mechanisms, enabling the treatment of complex ores and industrial residues. The adoption of advanced intensification-granulation sintering technologies offers a viable pathway toward sustainable ironmaking, providing the steel industry with essential tools to mitigate raw material constraints, lower production costs, and support green transformation. Future efforts should prioritize intelligent control, process integration, and the scaling of emerging techniques to maximize their industrial potential.

Thiosulfate leaching is considered a promising alternative to cyanidation for gold extraction because it can be achieved at a low cost. However, existing leaching systems struggle to balance leaching efficiency with thiosulfate consumption. Herein, a novel synergistic Cu-CH₃NH₂-NH₃ leaching system was proposed, balancing thiosulfate consumption and gold leaching efficiency through a mixed-ligand strategy. Thermodynamic analysis revealed that the steric hindrance and electron-donating effects of methylamine effectively block the oxidative decomposition pathway of thiosulfate by Cu(II), significantly reducing thiosulfate consumption. However, this also reduced the dissolution rate of gold. By introducing ammonia to adjust the Cu(II) coordination environment, the system achieved a gold leaching rate of 88.6% with a thiosulfate consumption of 14.2 kg/t-ore, significantly outperforming the traditional Cu-NH₃ system. In this system, the gold leaching process mainly is catalyzed by the mixed-ligand complex Cu(NH₃)_x(CH₃NH₂)_4−x²⁺. Within the coordination sphere, the methyl group of CH₃NH₂ inhibits the axial attack of S₂O₃²⁻ on Cu(II) via electron-donating and steric hindrance effects, thereby blocking the redox pathway of S₂O₃²⁻; simultaneously, NH₃ provides active sites to promote the gold oxidation. This study provides a vital theoretical basis and technical support for developing green, low-cost, and high-efficiency gold leaching processes.

Biological oxidation is a low-carbon technology for the treatment of As-containing gold ores, but it causes a large amount of acidic As-containing wastewater that is harmful to the environment. This paper proposed a novel, eco-friendly method to treat this wastewater. Thermodynamic analysis, H₂PO₂⁻ reduction, and wastewater recycling tests were conducted. Thermodynamic analysis indicates the feasibility of the reduction of As(V)/As(III) by H₂PO₂⁻ or H₃PO₂ to As⁰ under acidic conditions. Experimental results confirmed the thermodynamic prediction and showed that H₂PO₂⁻ could efficiently convert the As (i.e., As(V)/As(III)) in the wastewater to high value-added As⁰. Under the optimal conditions, 99.61% of As precipitated out, and the obtained As⁰ had a high purity of 98.5%. Kinetic results showed that the reaction order of H₂PO₂⁻ concentration was 0.6399, and the activation energy of the H₂PO₂⁻ reduction process was 34.33 kJ/mol, which is indicative of a mixed-controlled process (20–40 kJ/mol). Wastewater recycling results showed that after recovering As, the wastewater could be reused as a bacterial culture medium. Based on the thermodynamic analysis and experimental and analytical results, hypophosphite reduction mechanisms for removing and recovering As from its acidic wastewater were proposed. The results presented in this paper suggest the feasibility of this one-step H₂PO₂⁻ reduction approach, which may be promising in treating acidic As-containing wastewater.

It is vital to remove cadmium from wastewater because of its potential harm to the natural environment and human health. It was found that sulfate-reducing bacteria (SRB) had a good fixing effect on Cd under a strict anaerobic environment. However, there are few reports on the immobilization effect and mechanism of SRB on Cd in an anoxic environment. This study revealed the effects of initial Cd²⁺ concentration, initial SO₄²⁻ concentration, temperature, pH, and C/N ratio on the immobilization of Cd²⁺ by SRB in aqueous solution under an anoxic environment. The experimental results showed that under the conditions of initial concentration of Cd²⁺ within 0 mg/L~30 mg/L, initial concentration of SO₄²⁻ within 1200 mg/L, temperature within 25 °C~35 °C, pH neutral, and C/N ratio of 20:1, the immobilization rate of Cd²⁺ by SRB is above 90%. The characterization results showed that bioadsorption and chemical precipitation were the main mechanisms of SRB immobilization of Cd²⁺ in an anoxic environment.