Synthesis of Fe3+/Ce3+-doped poly(para-phenylenediamine) adsorbents and their application in the removal of fluorides, arsenites and pathogens from water

Abstract

Herein, we report the synthesis of a novel conjugated polymeric adsorbent for the removal of fluorides, arsenites, and pathogens from water by incorporating Fe³⁺ and Ce³⁺ in the poly(paraphenylenediamine) (pPD) polymer matrix through chemical co-polymerization. Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis and scanning electron microscopy (SEM-EDS) were employed to characterize the adsorbents. The XRD spectrum of pPD changed from amorphous to crystalline after the incorporation of Fe³⁺ and Ce³⁺ in the pPD polymer matrix. The efficiency of the synthesized adsorbent was evaluated using sorption batch experiments for fluorides and arsenites and the well-assay diffusion method for the removal of pathogens. The synthesized adsorbent displayed maximum removal efficiencies of 96.7% (F⁻) and 88.66% (As³⁺) for 10 mg L⁻¹ F⁻ at a dosage of 0.25 g L⁻¹ and 5 mg L⁻¹ As³⁺ at a dosage of 0.35 g L⁻¹. The adsorption kinetic data of both F⁻ and As³⁺ were better described by the pseudo-second-order reaction kinetic model, signifying that the uptake of F⁻ and As³⁺ was influenced by chemisorption. The F⁻ and As³⁺ adsorption isotherms were better described by the Freundlich adsorption isotherm model with the maximum adsorption capacities of 14.75 mg g⁻¹ and 4.71 mg g⁻¹, respectively. The adsorption thermodynamics studies revealed positive values of ΔH°, suggesting that the As³⁺ and F⁻ sorption processes were endothermic in nature. The regeneration studies showed that the Fe/Ce-pPD adsorbent could be reused for up to 4 cycles. The synthesized Fe/Ce-pPD depicted antimicrobial potency toward Staphylococcus aureus, Escherichia coli and Klebsiella pneumonia, showing the minimum zone of inhibition of 9.3, 12 and 10 mm, respectively. Thus, the obtained results showed that Fe/Ce-pPD can remove fluorides and arsenites as well as pathogen contaminants from aqueous solution.