Insight into the Influence of the Integrated Chitosan on the Adsorption Properties of Chitosan/Al-MCM-41 Composite for As (V) Metal Ions: Characterization and Advanced Equilibrium Studies

Abstract

Ecofriendly chitosan/Al-MCM-48 (CH/Al-MCM) was synthesized from natural microcline and assessed as a potential adsorbent of As (V) ions with enhanced capacity. The As (V) adsorption properties of CH/Al-MCM were assessed in comparison with Al-MCM-41 as a single phase. The studied CH/Al-MCM exhibits 178.6 mg/g as As (V) adsorption capacity which is higher than Al-MCM-41 (124 mg/g). The adsorption properties were illustrated based on the pseudo-first-order kinetic, Langmuir isotherm, and monolayer model with one energy site. Based on the recognized steric parameters, CH/Al-MCM displays significant enhancement in the active sites density (Nm = 88.8 mg/g (20°C)) as compared to Al-MCM (Nm = 61.5 mg/g). This signifies the role of the chitosan integration process in enhancing the adsorption capacity by increasing the availability of the present active sites. The number of adsorbed arsenic ions (2.01 to 2.66) suggests the uptake of 2 or 3 ions per free site by a multi-ionic and physical mechanism considering the adsorption energy (−16.3 to −16.9 kJ/mol). The thermodynamic functions of entropy, internal energy, and free enthalpy reflect the spontaneous and exothermic properties of the studied As (V) adsorption system by CH/Al-MCM. Moreover, the composite displays significant As (V) adsorption capacity in the existence of other dissolved ions.