Adsorption of some cationic and anionic dyes on magnetite nanoparticles-modified activated carbon from aqueous solutions: equilibrium and kinetics study

In this study, magnetite nanoparticles-modified low-cost activated carbon (MMAC) was used as an adsorbent for the removal of the anionic and cationic dyes Congo red, reactive blue 19, thionine, janus green B, methylthymol blue and mordant Blue 29, from aqueous solutions. Batch studies were performed to address various experimental parameters like pH, contact time, temperature and adsorbent dosage for the removal of these dyes. Kinetic studies showed that the adsorption of dyes on MMAC was a rapid process. Quasi equilibrium was reached in 30 min. Pseudo-first order and pseudo-second order models were used to fit the experimental data. Pseudo-second order rate equation was able to provide realistic description of adsorption kinetics. Equilibrium isotherms were analyzed by Freundlich, Langmuir, Redliche-Peterson (R-P) and Sips equations using correlation coefficients and RMS error function. Sips equation is found to best represent the equilibrium data for dye-MMAC system. It was clear that affinity of synthesized adsorbent to cationic dyes is much higher than anionic dyes.