Removal of tartrazine and indigo carmine with layered double hydroxide-modified graphite nanocomposite: Isotherm, kinetics and response surface methodology (RSM) optimization

Abstract

This research in focus investigates the removal of tartrazine (TZ) and indigo carmine (IC) dyes utilizing an AlCuFe-LDH/C nanocomposite as an adsorbent. The composite underwent comprehensive characterization through FE-SEM, EDX, FT-IR, XRD, and BET analyses. To gauge the efficacy of TZ and IC removal with the powdered adsorbent in use, the nanocomposites performance in surface adsorption of dyes species optimized, designed, and tested. Various parameters influencing the dyes adsorption under optimal conditions were considered, with a pH of 6.0 and an adsorption process time of 13 min selected. The concentrations of IC and TZ solutions were set at 11.5 mg/L, while a mass of 0.0143 g of adsorbent was applied. Under these conditions, the adsorbent exhibited impressive capabilities, removing 99.20 % of TZ and 88.5 % of IC. Equilibrium data were fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models, with the Langmuir isotherm model found to be the most fitting. Based on the Langmuir isotherm model, the adsorption capacities were determined to be 26.05 mg g−1 for TZ, 26.56 mg g−1 for IC. Additionally, the kinetic evaluation of experiments conducted at various time intervals revealed that the adsorption processes aligned well with second-order kinetic models. Regeneration studies indicated that the adsorbent could successfully retain dyes even after four cycles, with the adsorption percentage of AlCuFe-LDH/C for dyes remaining at 80 % after four adsorption–desorption cycles.