Citric acid modification in fabrication of composite aerogels from cigarette butts and chitosan for enhancing dye removal efficiency

In this study, recycled cigarette filters were modified with a nontoxic and low-cost citric acid, and chitosan, a biopolymer from crustaceans obtained through food processing waste to fabricate aerogels with highly porous structure, which promisingly illustrates a good sorption ability of the material. The thermal stability of the modified aerogel is higher than 300 °C, which is similar to other cellulose-based adsorbents. The citric acid-modified aerogel then shows a significant result with 50% higher crystal violet (CV) adsorption capacity (17 mg/g) than the original sample (11 mg/g). The maximum adsorption capacity was 166.8 mg/g and reaching the adsorption equilibrium stage took 240 min. The adsorption kinetics was fitted to the pseudo-second-order model with rate constant of 0.01 min⁻¹. The study results of modified aerogel also noticed the mechanism of both monolayer and multilayer adsorption since the isotherm study exhibited a good fit to both Langmuir and Freundlich models. Based on the calculated thermodynamic parameters, the CV adsorption on modified aerogel was exothermic and spontaneous. Based on the Fourier-transform infrared analysis of the modified aerogel after adsorption, the main active sites on the surface of the material that interact with dye molecules are hydroxyl groups and carboxylic groups. Consequently, it can be concluded that the modified aerogel from waste cigarette filters and chitosan is effective, low-cost, and suitable to use in wastewater treatment.