Modeling of Reactive Black 5 azo dye adsorption from aqueous solution on activated carbon prepared from poplar sawdust using response surface methodology

Abstract

ABSTRACT The objective of this study was to use activated carbon produced from poplar sawdust (ACPSD) as an adsorbent to remove Reactive Black 5 dye from aqueous solution. Investigation of the properties of the prepared activated carbon by scanning electron microscopy showed that it has a porous structure. Adsorption experiments were carried out according to the Box–Behnken design and base on response surface methodology (RSM) under different operational parameters including pH, initial dye concentration, adsorbent dose, and contact time. The maximum dye removal of 80.19% was obtained under optimum conditions pH 3, dye concentration 4 mg/L, contact time 109 min, and the adsorbent dose 4 g/L. The maximum experimental dye removal was close to the predicted value of 78.32% which confirms the suitability of the selected statistical model. The findings showed the data were fitted well with the pseudo-second-order kinetic model (R2 = 0.992), and the equilibrium data were in agreement with the Langmuir isotherm (R2 = 0.999). In the thermodynamic studies of the adsorption process, negative value ΔG and positive value of ΔH showed that the process was spontaneous and endothermic. Also based on the results of the regeneration process, the ACPSD as an efficient adsorbent could be used for four adsorption cycles with high dye removal efficiency.