Iron nanoparticles derived from rooibos tea extract supported polymer for Cr⁶⁺ removal

Abstract

Deterioration of water quality due to the presence of toxic heavy metals in environmental water resources introduced by industrial pollution is a serious matter of concern today. Only around 20% of the global wastewater was properly treated until 2015. Furthermore, in developing countries, approximately 70% of the industrial wastewater is not properly discharged. Chromium is a common heavy metal contaminant with two major species that is the, trivalent Cr(III) and hexavalent Cr(VI). Due to its higher solubility and mobility in environments, Cr(VI) is highly toxic and carcinogenic while Cr(III) is an essential micronutrient in trace amount for mammals. Therefore, the objective of the study was to synthesize low-cost Fe0 nanoparticles (NPs) supported in polypyrrole (Ppy) to investigate their effectiveness in Cr(VI) removal from aqueous solutions. Moreover, the effect of temperature, contact time, pH, adsorbent dose, and effect of co-existing ions were assessed. Ppy/Fe⁰ nanocomposite (NC) was characterized using various techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), field emission-scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), Braunner-Emmet-Teller (BET) and X-ray diffractometry (XRD). An increase in Cr(VI) removal due to pH was observed when pH was increased, the removal decreased from 73 - 32% and the optimum was at pH 2.0. The kinetic adsorption data ?tted the pseudo-second-order model. The adsorption isotherm followed the Langmuir isotherm model with the maximum sorption capacity of 305.8 mg.g⁻¹ at 25 °C and the adsorption process was endothermic. The specific surface area of the synthesized nanocomposite was calculated to be 80.53 m².g⁻¹ by the BET method. TEM images clearly showed the core/shell structure of the Ppy/Fe⁰ NC. Based on the findings from the study, it is hypothesized that results obtained may assist the wastewater treatment field with easy and safe removal of heavy metals from water.