Adsorption of BEZAKTIV BLAU V3-R and BEZAKTIV BLAU S-2R reactive dyes onto rice husk modified by the circular economy concept

Rice husk, modified with effluent from the alkaline scouring of cotton, employing an inexpensive treatment based on the circular economy concept, is used as a bio-sorbent to study the equilibrium and kinetic on cold brand BEZAKTIV BLAU V3-R (BBV3-R) and medium brand BEZAKTIV BLAU S-2R (BBS2-R) reactive dyes. 10, 20, and 40 g L -1 rice husk is used to follow adsorption of 0.1, 0.2, 0.3, 0.4, and 0.5 g L -1 BBV3-R and BBS2-R in a presence of 60 g L -1 NaCl at pH 10, at the temperature of 25 o C and 40 o C, respectively. Langmuir, Freundlich, and Dubinin-Radushkevic's adsorption models were employed, with the Freundlich model proving the best fit for our data. Activation energy calculated with the Dubinin-Radushkevic model (lower than 8 KJ mol -1 ) confirms the physical sorption of these reactive dyes onto the husk. The obtained maximum experimental absorption capacities of 122.2 mg g -1 for BBV3-R and 171.7 mg g -1 for BBS2-R using 10 g L -1 ERH are the best found in the literature. Pseudo-second-order model determines the adsorption kinetics, while the liquid film diffusion model is rate-determining. This paper demonstrates the applicability of the circular economy concept to obtain an efficient adsorbent for purifying colored effluent enriched with reactive dyes, which are one of the most challenging dyes in the textile industry from the aspect of their effluent purifying.