Adsorption studies of ammonia and phosphate ions onto calcium alginate beads

Abstract

This study aims to utilize the calcium alginate (Ca-Alg) beads for ammonia and phosphate ions adsorption. The alginate beads were characterized using the scanning electron microscope (SEM) with Energy Dispersive X-Ray (EDX) spectroscopy. The alginate beads showed relatively high removal efficiencies for ammonia ions (94.94%) and phosphate ions (88.31%). For the ammonia ions adsorption, the optimum condition was at the original pH (6.0), alginate beads amount of 5 g/L, ammonia ions concentration of 50 mg/L, and a contact time of 60 min. The optimum conditions for the phosphate adsorption occurred at the original pH, adsorbent amount of 5 g/L, initial concentration of 10 mg/L, and a contact time of 60 min. The adsorptions of ammonia and phosphate ions onto the alginate beads were found to follow Langmuir isotherm and the pseudo-second-order model. The thermodynamic experiments showed that the adsorptions of ammonia and phosphate were feasible and naturally spontaneous. The ammonia and phosphate removal efficiencies from real wastewater reached 40.70% and 10.52%, respectively. The adsorption of ammonia and phosphate ions onto the calcium alginate beads can be used as a fertilizer since the alginate can be biodegraded naturally.