Removal of dye from iron-coated activated carbon and aqueous solutions

Coprecipitation method of Fe+2 and Fe+3 salts is one of the most preferred methods for magnetite synthesis. In this study activated carbon was obtained by the activation of chestnut shells with ZnCl2 primarily. Then Fe3O4-AK (magnetic activated carbon) adsorbent was synthesized with coprecipitation method. The characteristics of synthesized Fe3O4-AK were identified with SEM, FTIR and XRD examinations. The malachite green (MG) was removed from water solution over Fe3O4-AK. In the study the effects of the parameters such as initial pH (1-10), initial dyestuff concentration (25-300 mg/L), adsorbent amount (0,05-1,00 g/100 ml), temperature (298-318 K) and contact time (5-120 min) MG adsorption with Fe3O4-AK were examined. Optimum conditions for maximum adsorption were identified as pH=6, time 60 min, adsorbent amount 0,1 g and time 45 C. It was identified that the equilibrium isotherm was complied with Langmuir Isotherm according to the obtained experimental data. When all conditions were provided in the study, maximum adsorption capacity was determination as 312,50 mg/g for Fe3O4-AC sorbents and as 136,25 mg/g for AC sorbents. During the kinetic study it was identified that the adsorption was complied with pseudo second degree kinetic model. When the adsorption thermodynamics was examined, it was found as ∆H=36,15 kj/mol and ∆S=140,76 j/mol.K. In the consequences of what have been obtained, the values of Standart Gibbs Free Energy it has been pointed out as negative for AK, 298, 308 and at 318K by the line (-2,40; -2,77 and -3,25 kj/mol) for Fe3O4-AK, 298, 308 and at 318K by the line (-5,40; -6,50 and -8,05 kj/mol). For the recycle of the MG, desorption study was conducted with water, acetone, methanol and methanol+acid containing desorbents. The highest D % was found in the study conducted with methanol: acid (95:5) study and cycle study was conducted with this solution mixture for 7 times. All experimental results has shown that Fe3O4-AK that has synthesized with coprecipitation method, is natural, low-cost and easy-applicable adsorbent for the removal of MG which is a cationic dyestuff from water solution.