Ammonium adsorption from aqueous solutions by strawberry leaf powder: Equilibrium, kinetics and effects of coexisting ions

The batch experiments were performed to study the equilibrium and kinetics of ammonium adsorption from aqueous solution by strawberry (Fragaia ananassa) leaf powder, a novel bioadsorbent. The effects of pH and strength of coexisting cations and anions were also investigated. The equilibrium data were found to fit well to both the Langmuir Model and Freundlich Model, and the maximum adsorption capacities were 3.93, 6.05 and 7.66 mg/g at 15, 25 and 35 °C, respectively. The increase of temperature was favorable to ammonium adsorption. Kinetics study suggested that the intraparticle diffusion was the rate-controlling step of ammonium adsorption by strawberry leaf powder. The optimum pH for ammonium adsorption was in the range of 5–8. Individual presence of the K+, Na+, Ca2+, Mg2+, Cl−, NO3− or SO42− had no significantly effect on ammonium adsorption, indicating the selectivity of ammonium adsorption by strawberry leaf powder. FTIR analysis indicated that the hydroxyl, phenol and carboxyl groups might be the main active groups for ammonium adsorption.