Fabrication of Biomass-Polymeric Adsorbent for the Removal of Selected Metal Species, Nutrients and Pathogens in Aqueous Solutions

Abstract

Environmental pollution is a major problem that has increased rapidly many decades ago. This has affected the quality of water and has created serious environmental, social, economic, and political issues. Water pollution is mainly caused by chemical species such as chromium and cadmium; nutrients (nitrates and phosphates) and pathogens from natural and anthropogenic activities which cause health problems and in some cases death to both human and aquatic organisms. South Africa is a water-scarce country, and many of the water resources are threatened by human factors. In many cases, most of the water-treatment plants have been abandoned and are in a dire state which often leads to alternative sources of water for domestic activities. The consumption of this untreated water resulted in a lot of diseases and child mortality. In this sense, the biosorption process using a sustainable biomaterial for removing these pollutants has gained prominence due to several advantages it has over other technologies in solving these environmental menaces. The present study successfully developed and evaluated a systemic biomass polymeric adsorbent for the removal of toxic metals such as chromium and cadmium ions, nutrients (nitrate and phosphate ions), and pathogens from aqueous solutions. The bio-sorbent was fabricated by incorporating biomass (grapefruit peels) and algae (diatom) on a polymeric network for improved overall properties towards the selective toxic chemical and microbial pollutants. The structural and morphological properties of the various adsorbents were done by FTIR which show the various functional groups present in the adsorbents responsible for the sorption processes of Cr6+, Cd2+, and PO43-. The SEM-EDS showed different shapes and the elemental compositions that constitute each of the adsorbents. Furthermore, the XRD revealed an amorphous structure for grapefruit peel powder (GFP), diatom biomass, grapefruit peel/diatom (GFP/diatom), while the overall synthesized poly-phenylenediamine based biomass (pPD/GFP/diatom) was crystalline. The batch sorption studies on the uptakes of Cr6+, Cd2+, and PO43- from aqueous solutions by the various adsorbents were investigated as a function of pH, contact time, adsorbent dosage, and initial concentration. The respective adsorption kinetics processes by the GFP, diatom biomass, GFP/diatom, and pPD/GFP/diatom sorbent materials on Cr6+, Cd2+, and PO43- ions revealed that physisorption and chemisorption mechanisms were responsible for the adsorption processes as well governed by intra-particle diffusions. Freundlich and Langmuir adsorption isotherm models proved to be responsible for the sorption of Cr6+, Cd2+, and PO43- ions by the different adsorbents. The thermodynamic data revealed that the adsorption process was spontaneous and feasible in all the adsorbents across all temperatures. Furthermore, the antimicrobial activity of Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae by GFP, diatom biomass, GFP/diatom, and pPD/GFP/diatom showed that they had antimicrobial potency. Overall, these adsorbents present a promising ability to remediate inorganic pollutants in wastewater, allowing for the protection of the environment and living organisms.