Textile wastewater treatment by agro-industrial waste: Equilibrium modelling, thermodynamics and mass transfer mechanisms of cationic dyes adsorption onto low-cost lignocellulosic adsorbent

Abstract

Abstract The present paper aims to develop a low cost, efficient and environment-friendly process by the use of an agro-industrial waste to purify dye-contaminated aqueous solutions. The ability of palm-date stones to adsorb basic violet 3 (BV3) and basic red 2 (BR2) from wastewaters is assessed through kinetic, thermodynamic and equilibrium investigations. FTIR spectra indicated that hydroxyl and carbonyl groups are the possible functional groups involved on dyes uptake. Kinetic and dynamic studies showed that 77 and 93% of BR2 and BV3 were removed within a contact time of 15 min, which proves the applicability of the process at an industrial scale. Kinetic data were extracted using pseudo-first-order, pseudo-second-order, Elovich and Brouers–Sotolongo models. Calculations gave that the rate sorption was simultaneously controlled by film and intra-particle diffusion models, which was confirmed by Biot numbers. Using a non-linear regressive method, the equilibrium isotherm data were evaluated by six different three-parameter models which were compared to two-parameter isotherm models. Error analysis showed that Hill and Koble–Corrigan models best described the uptake of BR2, whereas Toth, Khan and Redlich–Peterson fit better BV3 removal. Thermodynamic study showed that, for both pollutants, the adsorption was endothermic, spontaneous, according physisorption mechanism and involving probably hydrogen bonds.