Removal of various dyes from aqueous media onto polymeric gels by adsorption process: Their kinetics and thermodynamics

Adsorptive removal of industrially important dyes namely, bromophenol blue, methylene blue and malachite green from aqueous media onto three novel adsorbents (C0, C2 and C4) has been studied. The effect of different experimental parameters like contact time, concentration of cross-linking agent in the polymeric gel and temperature on adsorption of these dyes was investigated. Adsorption isotherms were found to be of L-type onto three adsorbents at both temperatures of 313 and 323 K. The experimental data for all the dyes on all adsorbents were applied to different adsorption isotherms (Freundlich, Langmuir and Temkin models) and pseudo-first order, pseudo-second order and intraparticle diffusion kinetics models. It was found that the adsorption of all the cases followed the pseudo-second order kinetics. The thermodynamic parameters such as change in free energy (∆G), change in enthalpy (∆H) and change in entropy (∆S) were also calculated. The negative values of ∆G and ∆H indicated that the adsorption process for all the dyes on all adsorbents is spontaneous and exothermic, respectively. The adsorbent C4 was found to be better for the removal of methylene blue and malachite green while C0 for that of bromophenol blue.