Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies

Colored effluents are one of the important environment pollution sources since they contain unused dyecompounds which are toxic and less-biodegradable. in this work removal of acid red 14 and acid red 18 azo dyeswas investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions.removal of dye increased with increase in contact time and initial dye concentration, while decreased for incrementin solution temperature and ph. results of the equilibrium study showed that the removal of ar14 and ar18followed freundlich (r2 > 0.99) and langmuir (r2 > 0.99) isotherm models. maximum sorption capacities were 3.1 and29.7 mg/g for ar 14 and ar18, namely significantly higher than those reported in the literature, even for activatedcarbon. fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2 > 0.99)and intra-particle diffusion (r2 > 0.98) models for ar14 and ar18, respectively. for both dyes, the values of externalmass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external masstransfer resistance at solid/liquid layer. desorption experiments confirmed the relevance of pumice stone for dyeremoval, since the ph regeneration method showed 86% and 89% regeneration for ar14 and ar18, respectively.