Process optimization of Auramine O adsorption by surfactant-modified activated carbon using Box-Behnken design of response surface methodology

Abstract

The present study explores the sorption capacity of anionic surfactant, sodium dodecylsulfate (SDS)-modified activated carbon (PA-AC-SDS) for highly toxic and carcinogenic dye, Auramine O (AO) from aqueous systems. The effects of various process variables such as dye solution pH, adsorbent dose, dye initial concentration and contact time have been explored via Box-Behnken design of response surface methodology. Optimum conditions were found to be solution pH of 6.00, adsorbent dose of 0.110 g, contact time of 240 min and dye initial concentration of 1,000 mg L-1, under which the measured experimental adsorption capacity for AO was 425.060 mg g(-1), which was in close agreement with the predicted value (427.130 mg g(-1)), with relative error of -0.490%. Adsorption kinetics and isotherm data were well described by pseudo-second-order kinetics and Langmuir isotherm model. Intra-particle diffusion and Boyd's models showed that both film diffusion and intra-particle diffusion may occur parallel during the interaction of the AO with PA-ACSDS. Thermodynamic investigations presented spontaneous and endothermic nature of adsorption. In addition, regeneration studies revealed that PA-AC-SDS was effective in removal of AO for five consecutive cycles, showing it to be an efficient technology for textile industries effluents.