Tapping the potential of a glucosamine polysaccharide-diatomaceous earth hybrid adsorbent in the solid phase extraction of a persistent organic pollutant and toxic pesticide 4,4′-DDT from water

Abstract

A chitosan (a glucosamine polysaccharide)-diatomaceous earth hybrid was studied for the adsorption of 4,4′-dichloro-diphenyl-trichloroethane (4,4′-DDT), a persistent organic pollutant and organochlorine pesticide compound from water. The diverse adsorption process parameters were studied and the modified adsorbent was characterized through XRD, SEM-EDX, FT-IR, XRF, BET and TGA analysis. The concentration of 4,4′-DDT was measured using gas chromatography-tandem mass spectrometry (GC-MS/MS) by adopting a validated analytical procedure. The Langmuir and Freundlich isotherms ascertained the adsorption capacity. The optimum pH and temperature for 4,4′-DDT adsorption were found to be between 5.0 and 7.0 and 20 and 30 °C respectively. Thermodynamic parameters confirmed that the adsorption of DDT on chitosan modified with diatomaceous earth was an exothermic process. The data obtained from kinetics and intra-particle diffusion showed that the composite material is able to sequester 4,4′-DDT and this is reflected in the Langmuir adsorption capacity of 0.968 mg g⁻¹. The adsorbed 4,4′-DDT was successfully eluted with ethyl acetate and recycling studies showed that the modified chitosan can be used for three cycles with significant adsorption performance and this adsorbent proved its efficacy in removing 4,4′-DDT from farm water.