Adsorptive performance of bentonite-chitosan nanocomposite as a dual antibacterial and reusable adsorbent for Reactive Red 195 and crystal violet removal: kinetic and thermodynamic studies

Abstract

Abstract Herein, bentonite-chitosan nanocomposite (BT-CS nanocomposite) has been synthesized and exploited, for the first time, as a dual adsorbent for the removal of both of an anionic (Reactive Red 195 (RR)) and a cationic (Crystal Violet (CV)) dyes from aqueous solution. The adsorption behavior of the exploited nano-adsorbent towards the dyes under investigation were scrutinized in batch experiments as a function of several factors such as contact time, pH value, adsorbent dose, initial dye concentration, stirring rate, and temperature. The prepared nano-adsorbent achieved superior removal efficiency of 99.4 and 99.8% within 20 min at optimum pH value of 3 and 5 using adsorbent dose of 0.1 g and 0.08 g at room temperature for RR and CV dyes, respectively. Also, the developed nano-adsorbent affords higher removal efficiency of CV dye against broad pH range of 2–9. Moreover, the developed nano-adsorbent achieved significant antibacterial behavior against various pathogenic bacterial and record clear inhibition zone of 21 mm against Escherichia coli (ATCC 8739) . Langmuir adsorption model and pseudo-second order adsorption can fully depict the BT-CS nanocomposite adsorption properties for both of RR and CV dyes. Furthermore, thermodynamic studies showed that the process was spontaneous and endothermic with increased in randomness. The prepared dual adsorbent in this study exhibited reversible dyes adsorption with an excellent regeneration efficiency. Whereas, after 5 successive adsorption–desorption cycles, the adsorption efficiency of the synthesized adsorbent was 99% and 98% for RR and CV dyes, respectively, affirming its capability to economically decontaminate the industrial wastewater comprising RR and CV dyes. Graphical Abstract