Adsorption of acid red 18 from aqueous solutions by GO-COFe2O4: Adsorption kinetic and isotherms, adsorption mechanism and adsorbent regeneration
Mohammad Reza Zare, Nezamaddin Mengelīzadeh, Ghazaleh Aghdavodian, Fatemeh Zare, Zakieh Ansari, Fatemeh Hashemi, Saeideh Moradalizadeh
Abstract
In the present study, graphene oxide-cobalt ferrite (GO-CoFe2O4) was synthesized by sol-gel method as an adsorbent in the removal of acid red 18 (AR18) dye. The characteristics of the magnetic adsorbent were analyzed through SEM, TEM, XRD, FTIR, N2 adsorption-desorption, and VSM. The findings of the diagnostic analysis showed a surface area of 58.92 m2/g, a pore size of 2 nm, and a magnetic property of 3.82 emu/g for the GO-CoFe2O4 composite. The effect of the operational parameters determined the maximum removal efficiency (100%) at pH of 5, adsorbent dosage of 1 g/L, and AR18 concentration of 25 mg/L. The effect of anions on the removal rate of AR18 by GO-CoFe2O4 composite was evaluated, and the results were its negative effect in reducing the efficiency in the order of NaCl < NaNO3 < Na2SO4 < Na2CO3. Thermodynamic parameters including ΔG°, ΔH°, and ΔS° explained that the adsorption of AR18 on the synthesized composite is favorable, spontaneous, and endothermic. The experimental data was studied by four kinetic equations including pseudo-first-order, pseudo-second-order, Elovich and intraparticle-diffusion and the results based on R2 and qe were consistent with pseudo-second-order kinetics. Eleven isotherm models were selected for adsorption equilibrium data, and the data were fitted with all isotherm models with R2 > 0.95. The results of adsorbent regeneration by peroxymonosulfate (PMS) activation showed that with increasing treatment time and PMS amount (up to 10 mM), the regeneration efficiency increases significantly up to 73.72%.