Removal of Arsenite from Water by Ce-Al-Fe Trimetal Oxide Adsorbent: Kinetics, Isotherms, and Thermodynamics

Abstract

Ce-Al-Fe trimetal oxide adsorbent was prepared. The morphology characteristics of the new adsorbent were analysed by the transmission electron microscope (SEM) method. The SEM results implied its ability in the adsorption of As (III). To verify the analyses, bench-scale experiments were performed for the removal of As (III) from water. In the experiments of adsorption, As (III) adsorption capacity of the trimetal oxide adsorbent was presented significantly higher than activated aluminium oxide and activated carbon. As (III) adsorption kinetics resembled pseudo-second-order adsorption mode. When initial As (III) concentration was 3, 8, and 10 mg·L −1 , the maximum adsorption capacity achieved was 1.48, 3.73, and 5.12 mg·g −1 , respectively. In addition, the experimental adsorption data were described well by the Freundlich adsorption isotherm model at 20, 30, and 40°C. The enthalpy change<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mo stretchy="false">(</mml:mo><mml:mi mathvariant="normal">Δ</mml:mi><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>, the standard free energy<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mo stretchy="false">(</mml:mo><mml:mi mathvariant="normal">Δ</mml:mi><mml:mi>G</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>, and entropy change<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mo stretchy="false">(</mml:mo><mml:mi mathvariant="normal">Δ</mml:mi><mml:mi>H</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>indicated that the nature of As (III) adsorption was exothermic and spontaneous with increasing randomness on the interface of solid and liquid. And the adsorption mechanism can be interpreted as chemisorption with As (III) multilayer coverage formation on the adsorbent surface.