Removal and recovery of phosphate by modified oyster shell and its fertilizer application

The resource utilization of oyster shell (OS) is essential for environmental and human health because its random disposal can induce the environmental pollution and disease spread. Herein, MnFe₂O₄ loaded-oyster shell (OMF_s) was prepared by co-precipitation method for phosphate removal and recovery. The salt etching and MnFe₂O₄ (MF) loading improved the adsorption performance of OS, and the maximum adsorption capacity of OMF_0.02 reached 87.39 mg P/g. Phosphate adsorption was dominated by chemisorption and its rate was limited by membrane diffusion and intra-particle diffusion. Phosphate adsorption by OMF_0.02 was involved with electrostatic attraction, surface precipitation and ligand exchange. 98.95 % phosphate on saturated adsorbent could be desorbed by 0.1 mol/L malic acid and 92.31 % adsorbed phosphate was released by 0.5 mol/L NaHCO₃. Furthermore, phosphate adsorbed on OMF_0.02 was plant-available basing on the results of water spinach growth trial. All the results implied the bright prospect of OMF_0.02 in phosphate removal and recovery from wastewater.