Adsorption behaviour of As(III) onto synthetic iron-based minerals: a comparative study of akaganeite, goethite and magnetite

The present study compares the adsorption capacity of iron-based minerals in removing As(III) from aqueous solutions. The work contains the results of studies carried out on a laboratory scale. The synthetic material was used in three forms as akaganeite, goethite and magnetite. To characterise the minerals before and after adsorption of As(III), specific surface area, particle size distribution, density, and zeta potential were determined. Additionally, digital and optical micrographs, SEM, and FTIR analyses were performed. In the experimental part, the influence of the main parameters on the adsorption efficiency was investigated (pH, initial concentration, contact time, and amount of adsorbent). Adsorption isotherms were fitted by Freundlich, Langmuir, and DubininRadushkevich models. Pseudo-first-order (PFO), pseudo-second-order (PSO), and intraparticle diffusion (IPD) models were used to fit the kinetics data. Linear regression was used to estimate the parameters of isotherm and kinetic models. FTIR measurements gave helpful information on the synthesised minerals and the As(III) removal process. Results show that As(III) adsorption is related to the iron-based adsorbents, and adsorption efficiency increases in the following order: goethite < magnetite < akaganeite.