Biosorption of Phosphorus Using Alginate-Like Exopolymers: Investigation of Removal Mechanism, Kinetic and Thermodynamic Properties

The purpose of this study was to investigate the phosphorus (P) adsorption mechanism, kinetic, isothermal and thermodynamic parameters using alginate-like exopolymer (ALE) beads extracted from residual aerobic granular sludge (AGS). The obtained ALE extraction yield (18.3%) was in line with the current published literature. The pH and initial phosphorus concentration influenced the phosphorus removal mechanism, with precipitation as a co-mechanism involved in adsorption. At 35 °C the maximum adsorption capacity achieved was 9.12 mg g−1. The adsorption isotherms data fitted well to the Langmuir model. The pseudo-first-order kinetics explained the adsorption mechanism, and the adsorption equilibrium was reached in 10 min. The thermodynamic analysis showed that physical mechanisms drive the adsorption process, which is endothermic, non-spontaneous and increases with the temperature. The recovery of this biopolymer from residual biomass, coupled with the recovery of phosphorus from effluents, can be further applied as a secondary phosphorus resource.