Removal of pararosaniline hydrochloride (basic red 9) from aqueous system with lignocellulose fraction of sugarcane bagasse as adsorbent

The removal of pararosaniline hydrochloride (BR9) from an aqueous system using lignin and holocellulose in extractive-free SCB (eSCB) as a natural and low-cost adsorbent was evaluated. Adsorption experiments were carried out at various initial pH (4−8) and initial dye concentrations (10 mg/L to 500 mg/L) and at different temperatures (303–333 K), to assess its uptake rate and equilibrium uptake. The uptake kinetics were fitted with various models, where the Elovich model and a newly proposed multi-mechanistic model were found to best describe the uptake rate and process. Adsorption of BR9 onto eSCB, involved the simultaneous adsorption at different locations of the eSCB matrix. The adsorption capacity of eSCB for BR9 was found to be 48.98 mg/g at 303 K. From thermodynamic analysis, it was inferred that the adsorption process was exothermic (ΔH = −4.04 kJ/mol), and spontaneous (ΔG = −35.40 to −27.5 kJ/mol). Apart from adsorption, the desorption and subsequent reuse of eSCB for BR9 adsorption were also explored and reported for the first time. The use of acidic aqueous ethanol with HCl as the acid helps the removal of BR9 from eSCB. As an adsorbent for BR9, eSCB could be reused at least 4 times. • Adsorption of basic red 9 (BR9) on extractive-free sugarcane bagasse (eSCB). • High adsorptive capacity (48.98 mg/g) and potentially reusable adsorbent for BR9. • Multi-mechanistic model to describe uptake kinetics of BR9 on multi-layered eSCB.