High efficient phosphate removal by lanthanum modified hydroxyapatite with a phase transformation process

It is urgent to develop a cost-efficient phosphorus adsorbent for wastewater treatment. In this study, lanthanum modified hydroxyapatite (La-HAP) has been synthesized as an adsorbent for removing phosphorus in aqueous. The effects of physical and chemical parameters for adsorbent adsorption ability such as initial pH, contact time, initial phosphate concentration, and competing anions were investigated. Phosphate adsorption on La-HAP was fitted well by the Langmuir equation (R-2 = 0.991) and the maximum single-layer adsorption capacity is estimated to be 42.92 mg g(-1) at 298 K. In addition, the kinetic studies showed that the phosphate adsorption data followed a pseudo-secondorder model. The relatively high pH and competing anions have little influence on the adsorption performance. The La-HAP samples were characterized by Brunauer-Emmett-Teller, scanning electron microscopy-mapping, X-ray diffraction, and X-ray photoelectron spectroscopy methods. The analysis revealed that the solid phase transformation is the mechanism of phosphate removal.