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Introduction: Phosphate is known to be the main limiting elements in the reuse of wastewater effluents and then it is the key element to outbreak of eutrophication. Therefore the objective of this work was to investigate the adsorption of phosphorous by natural and surface modified pumice with H₂O₂.

Methods: The present work was a fundamental-practical study which done in batch system.  In this work, natural and modified pumice were used for removal of phosphorous from aqueous solution. Several experimental parameters including pH (2-10), adsorbent mass (2-10 g/L), initial phosphorous concentration (5-20 mg/L), ionic strength and contact time were studied. All experiments were conducted in batch system with varying one experimental parameter, while others were constant.

Results: The results show that modification of pumice with H₂O₂ will improve adsorbent sorption capacity without any structural distortion.  In addition, higher removal efficiency was observed at 10 g/L of adsorbent dose, pH 6, 130 min contact time and 20 mg/L of phosphorus concentration. In the optimal conditions, 69% and 97% of phosphorus removal were achieved by natural and modified pumice adsorbents, respectively. In addition, removal efficiency decreased for increasing ionic strength. Pseudo second order kinetic model best describe adsorption of phosphorus onto used adsorbent.

Conclusion: The results of present work well demonstrate that pumice have substantial adsorption capacity for phosphorus and in the case of its modification, its adsorption capacity will be improved.