Enhanced decontamination of pefloxacin and chlorpyrifos as organic pollutants using chitosan/diatomite composite as a multifunctional adsorbent; equilibrium studies

Chitosan/diatomite composite (CH/D) was synthesized at potential multifunctional adsorbent of enhanced uptake capacities for different species of organic water pollutants. The synthetic CH/D composite was characterized and applied in batch adsorption studies for pefloxacin (PF) as pharmaceutical residual and chlorpyrifos (CF) as pesticide residual from water. The CH/D composite is of enhanced uptake capacities for both PF (310.7 mg/g) and CF (392.2 mg/g) as compared to diatomite and chitosan and single components. The PF and CF uptake reactions follow the Langmuir model as an equilibrium model which demonstrates their adsorption in monolayer and homogenous form. The PF uptake process is of Pseudo-First order kinetic while the CF uptake process is of Pseudo-Second order kinetics. The Gaussian energies (6.74 KJ/mol (PF) and 7.76 KJ/mol (CF)) and thermodynamic parameters suggest PF and CF adsorption reactions of physical, feasible, exothermic, and spontaneous properties. The CH/D composite exhibits strong selectivity for PF and CF molecules in the existence of PO43−, SO42−, and NO3− anions and considerable selectivity for them in the coexistence of Zn2+, Cd2+, and Pb2+ metal cations. The CH/D composite is of remarkable recyclability and reused in the removal of PF and CF for five cycles with removal percentages higher than 86% and 89%, respectively.