Adsorption of textile dye from aqueous solution using coconut husk as adsorbent: Kinetic and equilibrium studies

Abstract

The objective of this study was to investigate the removal of Acid Green 25 (AG25) from synthetic wastewater by the adsorption on coconut husk. This experiment is to compare between untreated coconut husk and pretreated with sulphuric acid, for the removal of Acid Green 25 dyes from water. The operation parameters investigated included initial dye concentrations, pH, agitation speed, particle size, and contact time. Experimental tests were conducted in a batch process. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm models. The analysis found that Freudlich isotherm model fits the data very well for AG25 dyes on adsorbents. The calculated dimensionless separation, RL indicated that the adsorption of the AG25 dyes onto adsorbent were favorable. Pseudo-first order and pseudo-second order kinetic equations were used to examine the experimental data of different initial concentrations. It was found that the pseudo-second order kinetic equation described the data of dyes adsorption on both adsorbents very well. Surface morphology was also examined using Scanning Electron Microscopy (SEM). The results showed that as expected, adsorption capacity of dye increased with the time. The amount adsorption capacity of AG25 is increased with decreasing pH, decreasing of particle size and moderate agitation speed. Similar experiments were carried out with acid treated coconut husk for comparison study. The result revealed that the acid treated coconut husk more tendencies to removal acid dyes in water compared to untreated coconut husk. The results showed that as expected, adsorption capacity of dye increased with the time. The amount adsorption capacity of AG25 is increased with decreasing pH, decreasing of particle size and moderate agitation speed. Similar experiments were carried out with acid treated coconut husk for comparison study. The result revealed that the acid treated coconut husk more tendencies to removal acid dyes in water compared to untreated coconut husk.