Immobilization of Bacillus subtilis in biohybrid crosslink chitosan-glutaraldehyde for acid red 88 dye removal: Box–Behnken design optimization and mechanism study

Abstract

Herein, a novel biomaterial of crosslink chitosan-glutaraldehyde combined with Bacillus subtilis biomass (CHS-GLU/BCL) was synthesized via hydrothermal synthesis to effectively remove the anionic dye (Acid red 88; AR88) from synthetic wastewater solution. The features of the CHS-GLU/BCL biomaterial were assessed using SEM-EDX, pH_pzc, BET, and FTIR studies. To optimize the adsorption efficiency of CHS-GLU/BCL to remove AR88 dye a Box-Behnken design (BBD) was utilized. The experiment utilized three independent variables including, the dosage of CHS-GLU/BCL (A: 0.02–0.1 g/100 mL), the contact time (B: 5–30 min), and the pH of the AR88 solution (C: 4–10). The investigation of adsorption kinetics confirms that the AR88 dye adsorption onto the CHS-GLU/BCL biomaterial follows the pseudo second order and pseudo first order kinetics models. Moreover, the isotherm data fits the Langmuir isotherm model. The maximum adsorption capacity (q_max) of AR88 dye onto CHS-GLU/BCL biomaterial was determined to be 148 mg/g in an acidic pH environment (pH = 4). The adsorption mechanism of AR88 and dye onto the biomaterial surface can be related to many connections, such as hydrogen bonding, n-π interactions, and electrostatic attraction. Hence, the biomaterial CHS-GLU/BCL has a good potency affinity for adsorbing anionic dye.