Effect of pH and Ionic Strength on the Removal Phosphorus Efficiency from Aqueous Solution Using Modified Mineral Adsorbents

Abstract

Phosphorus (P) is considered the leading cause of eutrophication in natural waters and has received considerable attention recently from the scientific community. In this study, P removal from aqueous solutions was investigated using bentonite, kaolinite, calcite, and zeolite mineral adsorbents modified with extract of walnut shell and wheat straw, chitosan, sodium carboxymethyl cellulose (CMC), and malic acid. Phosphorus sorption was evaluated using adsorption isotherms equations. Modified adsorbents with chitosan obtained the maximum sorption capacity of P. The results showed that P sorption capacity by Chitosan-adsorbents (bentonite (0.35 mg/g), calcite (2.09 mg/g), kaolinite (0.41 mg/g) and zeolite (0.43 mg/g)) was improved by ~ 129, 102, 128 and 119%, respectively compared to unmodified adsorbents (bentonite (0.27mg/g), calcite (2.04 mg/g), kaolinite (0.32 mg/g) and zeolite (0.36 mg/g). Langmuir and Freundlich models were used to simulate the sorption of P on modified adsorbents. The double layer model (DLM) could predict P adsorption by modified adsorbents over a wide pH range and varying ionic strength. Thermodynamic parameters showed that the nature of P adsorption by these adsorbents was non-spontaneity nature.

Keywords

• adsorption isotherms
• thermodynamic parameters
• maximum sorption capacity
• double layer model