Xin Lin,Chaoyi Chen,Junqi Li,Gangan Wang,Deyang Ning
Brown corundum dust ash(BCFA) is an industrial solid waste from the brown corundum production process. The alkali metal is a key factor limiting its comprehensive use. Currently, BCFA is mainly stockpiled and occupies a large amount of land. Its fine particles are easy to cause air pollution. The addition of NH4HSO4 allows for the effective extraction of K from BCFA and the efficient use of BCFA. Under optimum conditions: NH4HSO4 to BCFA mass ratio of 1.2:1, the roasting temperature of 240 °C, roasting time of 2 h, water leaching time of 90 min, water leaching temperature of 65 °C water leaching liquid to solid ratio of 3:1, the leaching rate of K from BCFA reached 97%. The leachate was crystallised by evaporation to obtain K, N compound fertiliser for agricultural use. The leaching residue is mainly Al and Si, which can be used for the preparation of refractory materials, aluminium and silicon molecular sieves, construction materials and other raw materials.
Alkali-catalyzed hydrolysis effectively depolymerizes waste polyesters and recovers high-purity monomers. Nonetheless, the conventional acid-based neutralization process (ABNP) for polyesters recycling faces economic and efficiency challenges due to substantial alkali consumption. To address these challenges, this study developed an electrochemical recovery and separation system (ERSS), a three-chamber electrolyzer separated by cation exchange membranes (CEM), with an ion separation module (ISM) situated between the anode and cathode of a water electrolysis system. Through water electrolysis, the system can efficiently recover excess KOH from polyester hydrolysates by leveraging directed ion migration under an electric field. Experimentally, the system achieves outstanding performance in real PET hydrolysates, with a KOH Faraday efficiency of 96.4%, yielding 88.4% for ethylene glycol (EG) and 89.3% for p-phthalic acid (PTA). The system operates stably and continuously for 100 h, processing ≈6 liters of hydrolysate. Additionally, it has exceptional KOH recovery across multiple polyester hydrolysates. A techno-economic analysis (TEA) shows that compared to the traditional ABNP, the ERSS significantly reduces chemical input costs in the hydrolysis unit, achieving savings of up to 62.5%. This study provides an efficient and cost-effective solution for the alkaline hydrolysis recycling of waste polyesters, effectively mitigating the economic drawbacks of excessive KOH usage.
危险品化学品经营许可证（带存储）