Phosphate removal performance and mechanism of zirconium-doped magnetic gasification slag

Zirconium-modified materials exhibit good adsorption performance, but their large-scale application is limited by the cost of carrier materials and the difficulty of solid–liquid separation of powder adsorbents. Therefore, in this study, we used low-cost gasification slag for zirconium oxide loading to avoid the aforementioned problems and successfully prepared a novel gasification slag–based zirconium-doped magnetic adsorbent material (GS-Z2M). GS-Z2M is a mesoporous adsorbent material with a large specific surface area (188 m2/g); it completely adsorbed phosphate with an initial concentration of 10 mg/L within 3 h. The rate-controlling step of phosphate removal using GS-Z2M was chemisorption. The Langmuir model proved more suitable for describing the adsorption of phosphate on GS-Z2M than the Freundlich and Temkin models, and the maximum phosphate adsorption capacity calculated using the Langmuir model was 26.02 mg/g. GS-Z2M showed good phosphate adsorption selectivity and reusability (can be recycled at least 5 times). GS-Z2M also showed good capacity for treating actual phosphate wastewater under dynamic flow conditions. The mechanism of phosphate adsorption on GS-Z2M mainly involved ligand exchange and inner-sphere complexation. The obtained results suggest that GS-Z2M is a promising adsorbent and vital for the development of phosphate adsorbents and recycling of gasification slag.