[Phosphorus Enrichment Efficiency of CaO@FA Composites and the Effect of Its Recovered Material on Soil Improvement].

To explore the resource utilization of phosphorus (P) in wastewater and industrial waste fly ash, we used an efficient composite material (CaO@FA) for phosphorus removal by loading nano-CaO on the surface of fly ash as well as in the pores using the surface precipitation method. The results showed that the material had a larger specific surface area and porosity after loading CaO on the fly ash surface. The specific surface area increased to 4.641 m·g, and the total pore volume was up to 0.025 cm·g. The adsorption process of CaO@FA on P could be described using the Langmuir isothermal adsorption model, and its maximum adsorption capacity was 185.776 mg·g(20℃). The adsorption mechanism was attributed to chemical precipitation, mainly the formation of calcium hydroxyphosphate. The enrichment efficiency of CaO@FA composites on P was significantly higher than that of fly ash, and the efficiency was increasing with the increase in the dosage added. HCO and CO in the coexisting ions had a negative effect on P adsorption by the composites. The enrichment rate of P in domestic wastewater was up to 93% when the dosage of CaO@FA composites was 2.0 g·L. The content of biological P in the recovered precipitates reached 1.658 mg·g. The soil improvement test showed that the biological P content in soil increased by 102.9% when the recovered precipitates were added into the soil. This indicated that the operating cost of recovering 100 mg of P by this composite was as low as 0.76 yuan.