Insight into the adsorption properties of a β-cyclodextrin/phillipsite organophilic composite for effective removal of toxic organophosphorus pesticides: kinetic and advanced equilibrium studies

Abstract

Natural phillipsite zeolites were functionalized with β-cyclodextrin chains and assessed as a potential organophilic and multifunctional adsorbent (CD/Ph) for three types of organophosphorus pesticides (methyl parathion (MPn), omethoate (OM), and acephate (AC)). The CD/Ph structure achieved significant efficiencies and the estimated Q_sat values are 360 mg g⁻¹ (MPn), 321.6 mg g⁻¹ (OM), and 434.5 mg g⁻¹ (AC) at 313 K. The classic equilibrium studies of the MPn, OM, and AC adsorption systems reflect their agreement with the Langmuir isotherm and pseudo-first order kinetics. The steric and energetic parameters of the addressed advanced isotherm model (monolayer model of one energy site) were estimated to illustrate the uptake mechanisms. Each active site on the surface of CD/Ph can adsorb up to 2 molecules of the AC pesticide and up to 3 molecules of MPn and OM pesticides in a vertical orientation by effective multi-molecular mechanisms. The estimated values of the effective site densities (199.18 mg g⁻¹ (MPn), 175.89 mg g⁻¹ (OM), and 314.9 mg g⁻¹ (AC)) illustrate the determined higher AC uptake efficiency. The findings of Gaussian energies (<8 kJ mol⁻¹), kinetic and isotherm studies and adsorption energies (<40 kJ mol⁻¹) validate the physisorption of MPn, OM, and AC pesticides by the synthetic CD/Ph structure. This might involve van der Waals, hydrogen bonding, and dipole bonding forces. The thermodynamic functions validate the spontaneous and endothermic behaviors of the adsorption systems.