Synergistic organic manure treatment with Al/Fe/Ca-based fluoride-fixing agents promote soil formation and utilization of phosphate flotation tailings

Abstract

Soil utilization of phosphate ore flotation tailings (PTs) was achieved using F-fixing agents combined with organic manure treatment to address issues related to inefficient stabilization of P-F, heavy metal solidification/stabilization, poor physicochemical properties, and ecological disruption. The formulation for PTs soil utilization included 1.75 % polyaluminum sulfate (PAS), 1.75 % FeSO₄, and 0.25 % CaO, with PTs content at ≥86.75 %. This approach enhanced water retention and improved nutrient and biochemical conditions. Various nutrient indexes met general planting soil requirements: organic matter 24.93 g/kg, available K 252.26 mg/kg, available Ca 2048.67 mg/kg, available Mg 246.13 mg/kg, and ammonia-nitrogen 42.47 mg/kg. The water-soluble P content of PTs-based soil decreased to 6.96 mg/kg, while available P increased to 677.99 mg/kg. Mn leaching toxicity was less than 0.016 mg/L, with a stabilization efficiency of 96.86 %. Water-soluble F in PTs-based soil was reduced to 11.133 mg/kg. This study maximized phosphorus resource utilization and prevented the migration of water-soluble P, F, and Mn to the surrounding environment. Potting experiments showed PTs-based soil was more effective than red soil and PTs-based raw materials in cabbage plantation, achieving a maximum seedling emergence rate of 98.33 %. Microbial diversity increased, and community structure improved in 40-day soil formation experiments, with PTs-based soils developing microbial communities involved in carbon and nitrogen cycling, enhancing resistance to external environmental disturbances, and promoting ecological utilization. These findings offer practical insights into the ecological utilization of large quantities of PTs and present a cost-effective approach for producing planting soils or ecological mulches from similar solid wastes.