Effective adsorption of crystal violet dye on sugarcane bagasse–bentonite/sodium alginate composite aerogel: Characterisation, experiments, and advanced modelling

Abstract

A novel sugarcane bagasse–bentonite/sodium alginate (SCB–Ben/SA) composite aerogel was prepared as an effective green adsorbent via blending–cross-linking for the removal of crystal violet (CV) dye from aqueous solution. The equilibrium adsorption capacity of SCB–Ben/SA for CV was 839.9 mg/g at 0.8 mg/mL adsorbent dosage, temperature 303 K, pH 4, and 800 mg/L initial CV concentration, and presented a removal rate of 85%. Adsorption kinetics studied using the novel pseudo-first-order and pseudo-second-order (PFO–PSO) combined model showed that CV adsorption by SCB–Ben/SA was a complex process and did not include a single mechanism, but involved both chemical and physical adsorption reactions; however, chemisorption was the dominant kinetic mechanism. The dynamic characteristics of CV adsorption process achieved through the liquid film around SCB–Ben/SA and the pores inside SCB–Ben/SA was described satisfactorily and conveniently using the novel film–pore mass transfer (FPMT) model. A multilayer adsorption model was applied to further understand the CV adsorption behaviour of SCB–Ben/SA. The number of linked CV molecules per functional group varied from 0.53 to 0.63 for SCB–Ben/SA. The CV molecules were adsorbed on SCB–Ben/SA via mixed orientation. The adsorption isotherms and thermodynamics revealed that the multilayer adsorption process was endothermic and spontaneous. Overall, SCB–Ben/SA was found to be an efficient, low-cost, green, and recyclable adsorbent for organic dye removal.