Phosphorus Adsorption–Desorption on a Surfactant-Modified Natural Zeolite: A Laboratory Study

Phosphorus adsorption–desorption on a surfactant-modified zeolite (SMZ) was studied with laboratory experiments, in the perspective of using the SMZ for P removal from waters enriched with P. The effects of temperature, pH, and NO3− concentrations on P adsorption on the SMZ were assessed. In addition, P desorption from the SMZ spiked with P at two concentrations (50 and 200 mg kg−1) was investigated. Adsorption data indicated that the SMZ has a high adsorption capacity for P and conformed satisfactorily to the nonlinear forms of Freundlich and Langmuir equations, the latter being slightly superior. Phosphorus adsorption on the SMZ was a fast, exothermic reaction. As the pH of the equilibrium solution increased from the acidic to alkaline range, P adsorption was also increased. In the presence of NO3− in the external solution, P adsorption was reduced only at the highest NO3− concentration studied (50 mg L−1). In both cases of the P-spiked SMZ, P desorption was not affected by P initial concentration and the overall amount of desorbed P reached only the 7.5 mg kg−1. Results showed that SMZ can be an effective adsorbent for P and could be used for P removal from waters enriched with P; however, the latter has to be confirmed by large-scale experiments.