Removal of Fe (II) from aqueous solution by Calotropis Procera: Kinetics, isotherm s tudies, and measurement of competitive adsorption with UV-Visible spectrophotometer

Abstract

Iron is essential heavy metal in trace quantities, but its excessive concentration as Fe2+ is present in effluents from steel mills, iron ore mines, and metal processing industries, which pollute the groundwater. Among other conventional methods, sorption by natural biomass is a low-cost alternative for iron sequestration from an aqueous solution. The root of a native weed plant Calotropis Procera was used to optimize the adsorption parameters like pH, contact time, sorbent dose, and initial adsorbate concentration. Competitive adsorption of Fe2+ in the presence of cations (Ni2+, Cd2+, Cr3+, Zn2+, Ca2+, Mg2+, As3+) and anions (Cl-, SO42- , F-) was also studied. Batch adsorption studies were carried out to evaluate adsorption isotherm by Langmuir and Freundlich isotherm models. Leaching of biomass significantly improved iron uptake capacity from 15 mg g-1 to 80 mg g-1. The kinetics of the reaction was fast, with equilibrium conditions attaining in 30 minutes. FTIR study of the biomass revealed the presence of -COOH, -NH groups responsible for the metal binding mechanism. The biomass could be regenerated with 0.1 M HNO3 for further use. Iron removal from simulated acidic water was done under optimum conditions and absorbance was measured by a UV-Visible spectrophotometer.