In-situ fabrication of surfactant modified CNT-based novel bio-composite and its performance evaluation for simultaneous removal of anionic dyes: Optimization by Box-Behnken design

Abstract

• CTAB modified Saccharum munja containing 1% CNT bio-composite was fabricated. • Anionic dyes were removed effectively from single and multi-component systems. • RSM with Box-Behnken design was used for the optimization. • Regeneration of the bio-composite was studied up to 5 cycles. The simultaneous and efficient removal of anionic dyes at neutral pH is a challenging task and is thus attracting considerable attention to remediate wastewater. Herein, cetyltrimethylammonium bromide (CTAB) surfactant was used for the modification of Saccharum munja based bio-composite containing 1% functionalized carbon nanotube (CNT). The as-synthesized bio-composite was characterized and used to study the affinity and efficacy towards the removal of Coomassie Brilliant Blue R-250 (BB), Reactive Red 35 (RR) and Reactive Orange 107 (RO) dyes from the single and multi-component systems. Response surface methodology (RSM), with Box–Behnken design matrix was successfully employed for the optimization of operating parameters i.e., pH, adsorbent dosage and initial concentration of dyes. The proposed models were significant as per the analysis of variance (ANOVA) statistical analysis. Furthermore, the experimental data were well fitted with the pseudo-2nd-order kinetic model and the Langmuir isotherm model with a very high monolayer adsorption capacity for the single-component system, i.e., 1179.39, 109.41 and 22.14 mg/g for BB, RR and RO dyes respectively at neutral pH conditions. The interactive effects between dye molecules in binary and ternary systems were studied using the extended Langmuir model, which revealed competitive as well as synergistic behavior of dyes. Interestingly, the observed affinity trend, BB > RR > RO was explained on the basis of the proposed adsorption mechanism. Regeneration of the exhausted bio-composite depicted excellent reusability even after five adsorption-desorption cycles, which makes CTAB modified SM + CNT a promising candidate adsorbent for treating simulated dyeing effluents and the whole process is cyclic and eco-friendly.