Evaluation of potential adsorbents for simultaneous adsorption of phosphate and 2024 ammonium at low concentrations

Abass, Olusegun K. and Uzma, Shaheen, and Zhi-Long, Ye and Doaa, Zamel and Abdul, Rehman and Peng, Zhao and Fengming, Huang Evaluation of potential adsorbents for simultaneous adsorption of phosphate and 2024 ammonium at low concentrations. Microporous and Mesoporous Materials.

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Abstract

Evaluation of potential adsorbents to tackle eutrophication caused by low concentrations of phosphate and ammonium are rarely reported in the literature. Besides, the dynamics/mechanisms for removal of these pollutants at low concentration are yet to be explored. In this study we used five different adsorbents, including Lamodified zeolite (LMZ), MgFe-modified biochar (MgFe-BC), phoslock, activated alumina (AA), and diatomaceous earth (DE) to evaluate the removal of these pollutants. Among the selected adsorbents in this study, LMZ and AA both exhibited effective and simultaneous adsorption for phosphate and ammonium and the maximum adsorption capacities were 2.47 mg/g and 3.07 mg/g, respectively. The presence of SO2 4− and CO2 3− negatively impacted phosphate adsorption, while Fe3+ and K+ ions inhibited ammonium adsorption. LMZ adsorption kinetics was over 3 times faster than other adsorbents within 60 min reaction time. Kinetics studies and isotherms revealed that the removal of phosphate and ammonium was primarily driven by chemical interactions and monolayer adsorption and were better fitted by Langmuir isotherm than the Freundlich isotherm and kinetic study was effectively described by Pseudo-second-order kinetic model. FTIR and XPS analysis revealed that the key mechanisms for phosphate adsorption were electrostatic attraction and inner sphere complexation through ligand exchange, whereas ammonium adsorption was mainly governed by ion exchange. Desorption study revealed that LMZ material was stable after three desorption cycles. This study offers vital knowledge on the nature of adsorption and interactions of potential mesoporous adsorbents with eutrophication-causing pollutants in lakes and rivers and proposes effective remedial mean

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