Removal of As3+, As5+, Sb3+, and Hg2+ ions from aqueous solutions by pure and co-precipitated akaganeite nanoparticles: adsorption kinetics studies

Abstract

Adsorption kinetics models have been used to evaluate the adsorption behaviour of pollutants on different materials but there are no reports for the adsorption of As⁵⁺, As³⁺, Sb³⁺ and Hg²⁺ on co-precipitated akaganeite nanoparticles which were previously formed in the presence of these ions. In this research, the performance of pure and co-precipitated akaganeite nanoparticles as adsorbents of As³⁺, As⁵⁺, Sb³⁺ and Hg²⁺ in aqueous solutions was evaluated using the nonlinear kinetics models of Langmuir, Lagergren, Ho–McKay, Bangham, Elovich and simplified Elovich. In addition, transmission ⁵⁷Fe Mössbauer spectrometry was used for the first time to compare the physico-chemical properties of akaganeite before and after the adsorption processes. The results showed that co-precipitated akaganeites had much better adsorption capacities than pure akaganeites. On the other hand, the Sb³⁺ and Hg²⁺ were the fastest and slowest pollutants respectively adsorbed on all akaganeites. The kinetics models that best described the experimental data for As³⁺, As⁵⁺ and Sb³⁺ were those of Elovich and simplified Elovich. For Hg²⁺, the kinetic model that best described the experimental data was that of Bangham. The 300 K and 77 K Mössbauer spectrometry showed only slight variations in some of the hyperfine parameters for the akaganeites after adsorption.