One novel composite based on functionalized magnetic peanut husk as adsorbent for efficient sequestration of phosphate and Congo red from solution: Characterization, equilibrium, kinetic and mechanism studies

Abstract

Accessibility to quality and clean water has in recent times been compromised due to the presence of pollutants, thus posing as a threat to the survival of living organisms. The adsorption technique in this regard has been observed to be useful in the remediation process with the material used as the adsorbent playing an integral role. In this study, a novel biocomposite (PN-Fe₃O₄-IDA-Al) based on peanut husk (a low-cost material) was developed by functionalization with aluminum (Al), iminodiacetic acid (IDA) and Fe₃O₄. The efficiency of PN-Fe₃O₄-IDA-Al as an adsorbent for the remediation of wastewater was evaluated using Congo red (CR) and phosphates (PO₄^3-) as model pollutants. The results from the characterization studies confirmed PN-Fe₃O₄-IDA-Al to have superparamagnetic properties which ensures its easy retrieval. Adsorption studies indicated that PN-Fe₃O₄-IDA-Al had a maximum monolayer capacity of 79.0 ± 2.0 and 16.8 ± 2.5 mg g^-1 for CR and PO₄^3- (according to P), respectively, which was significantly dependent on factors such as reaction time, solution pH, temperature and the presence of some common anions. The Freundlich model was observed to better describe both adsorption processes with chemisorption being the principal underlying mechanism. Results from using real water samples confirmed PN-Fe₃O₄-IDA-Al to be highly efficient for practical remediation processes. These results coupled with the synthesis of PN-Fe₃O₄-IDA-Al under benign conditions using low-cost materials help to expound the knowledge on the use of low cost materials as the basis for the development of highly efficient adsorbents for wastewater remediation.

Keywords: Adsorption; Congo red; Modified peanut husk; Phosphate; Water treatment.