Biosorption and retention of orthophosphate onto Ca(OH)2-pretreated biomass of Phragmites sp.

The biosorption of phosphorus in the form of orthophosphate (Po) from wastewater using biomass as the sorbent is of potential importance because the Po-loaded biomass could be applied in the agricultural sector as fertilizer and soil conditioner. However, biomass generally displays a very low affinity for Po sorption and therefore biomass surface modification is required. In the present study, the biomass (as model grinded leaves of Phragmites sp. were used) was pretreated with Ca(OH)2 to enhance Po biosorption capacity (qe). The results indicate that the alkaline pretreatment resulted in a modification of surface functional groups. It was concluded that the main sorption mechanisms were ligand exchange and electrostatic attraction. A series of experiments were conducted to investigate the performance of the pretreated biomass for Po uptake under various conditions. Isotherm and thermodynamic studies were also applied and analyzed. The biosorption process was best described by the pseudo-second order kinetic model and Langmuir isotherm, which gave a qmax of 12.27 mg P/g at 25°C and pH 7. The Ca(OH)2 treated Phragmites biomass applied in this study for Po recovery may present some potential advantages in terms of costs and environmental impact.

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