A comparative study of phosphate removal technologies using adsorption and fluidized bed crystallization process

Abstract

This study compared the two novel technologies “calcium phosphate fluidized-bed crystallization (FBC) process” and “adsorption” which used an amorphous iron oxide BT-1 as the adsorbent for treating an industrial wastewater with high concentration of phosphate (1,000 mg P L–1). In the adsorption process, most of phosphorus was adsorbed rapidly initially and then reached the thermodynamics equilibrium in 24 h. The phosphate adsorptive capacity of BT-1 was 2.03 mmole/g when the PO4 3– equilibrium concentration was conditioned at 8.23 mM. The adsorption process followed the Langmuir and Temkin adsorption isotherm. In the FBC process, the optimum pH range was wider (pH > 5.3) for the total removal of phosphate than that for crystallization (optimum pH = 5.3–5.9). The total removal efficiency and crystallization ratio of phosphate were about 90% and 60%, respectively, in the optimum pH range. The EDS analysis showed that the Ca–P crystal products had an approximate 1:1:6 molar ratio of Ca:P:O. The XRD diagrams ...