Organic and inorganic polymeric matrix of modified chitosan with algae and coal fly ash for cationic toxic dye removal: Multivariable optimization by Box-Behnken Design

Abstract

In this study, a composite adsorbent of chitosan/algae/coal fly ash (CS/Alg/FA) was synthesized to be an effective and renewable adsorbent for cationic methyl violet 2B dye (MV2B) removal from synthetic wastewater. The optimization of key adsorption variables (A: CS/Alg/FA dosage (0.02-0.1 g/100 mL), B: solution pH (4-10); C: contact time (20-180 min)) was carried out using the Box-Behnken design (BBD). The Langmuir isotherm model (coefficient of determination R² = 0.94) provided a good fit for the empirical data, and the pseudo-second-order model accurately described the kinetic data. The maximum adsorption capacity (q_max) of CS/Alg/FA for MV2B was determined to be 63.4 mg/g at 25 ⁰C. The possible adsorption mechanism of MV2B can be assigned to electrostatic attractions along with n-π, and H-bonding interactions. Thus, this comprehensive study underscores the potential of CS/Alg/FA as a preferable adsorbent for the removal of cationic organic dyes from industrial wastewater.