Removal of basic and acidic dyes from aqueous solution by adsorption on a low cost activated carbon:Kinetic and thermodynamic study

摘要

Batch experiments were carried out for the sorption of Congo red(CR),Malachite green(MG),Rhodamine B(RDB)and Rose Bengal(RB)dyes onto acid activated carbon prepared from a plant material,Aloe barbadensis Mill.The operating variables studied were initial dye concentration,pH,temperature and contact time.Equilibrium data were fitted to the Langmuir and Freundlich isotherm equations.From this,adsorption efficiency,adsorption energy,adsorption capacity,intensity of adsorption and dimensionless separation factor were calculated.The amounts of CR,MG,RDB and RB removed from a 60 mg L~(-1)of the dye solution at 30°C are 21.17,26.19,8.50 and 3.62 mg g~(-1),respectively.The results of these studies indicate that the adsorption is favourable.From the kinetic studies,the rate constant values for the adsorption process were calculated.The thermodynamic parameters like DELTA G°,DELTA H°,and DELTA S° indicate that the adsorption process is endothermic and spontaneous in nature.The mechanism of the adsorption of dyes onto the adsorbent has been investigated by using the experimental results and confirmed by FT IR,XRD and SEM images.