Kinetics, Isotherms and Adsorption-Desorption Behavior of Phosphorus from Aqueous Solution Using Zirconium-Iron and Iron Modified Biosolid Biochars

Excessive discharge of phosphorus (P) to aquatic ecosystems can lead to unpleasant eutrophication phenomenon. Removal and recovery of P is challenging due to low C/N ratios in wastewater, hence the development of efficient removal and recovery of P strategies is essential. In this study, zirconium-iron (Zr-FeBC) and iron modified (Fe-BC) biosolid biochars were examined to investigate their capacity for the removal of P by batch experiments. The influence of solution pH, biochar dose, initial P concentration, ionic strength, interfering ions and temperature were also studied to evaluate the P adsorption performance of biochars. The P experimental data were best described with pseudo-second order kinetics and the Freundlich isotherm model. The maximum P adsorption capacities were reached to 33.33 and 25.71 mg g(-1) for 24 h by Zr-FeBC and Fe-BC at pH 5 and 4, respectively. Desorption studies were performed to investigate the reusability, cost-effectiveness and stability of the adsorbents Zr-FeBC and Fe-BC. The adsorption-desorption study suggests that both examined biochars have considerable potentiality as adsorbent candidates in removing as well as recovery of P from wastewaters. Results also reveal that the regenerated Zr-FeBC and Fe-BC could be utilized repetitively in seven adsorption-desorption cycles using NaOH as a desorbing agent, which greatly reduces the P-removal cost from wastewaters. Thus, P enriched biochar could potentially be used as fertilizer in the agriculture sector.