Facile Synthesis of an Organic–Inorganic Nanohybrid Composite of Salicylaldehyde-Based Chitosan Schiff Base/SiO2 for Acid Red 88 Dye Removal: Characterization and Adsorption Modeling

The current study employed the hydrothermal approach to graft chitosan functionalized-SiO2 nanoparticles with an aromatic aldehyde (salicylaldehyde, SA) to obtain an organic–inorganic nanohybrid composite of salicylaldehyde-based chitosan Schiff base/SiO2 (CTS-SA/SiO2) for uptake of an acidic azo dye (acid red 88, AR88) from aqueous media. The effects of A: CTS-SA/SiO2 dose (0.02–0.1 g), B: pH (4–10), and C: time (10–90 min) on the adsorption performance of CTS-SA/SiO2 towards AR88 were studied systematically by the Box–Behnken Design (BBD). The CTS-SA/SiO2 dosage, pH, and contact time resulted in maximum dye elimination (76.46%) of AR88, according to the results of the BBD model. These variables were 0.093 g of CTS-SA/SiO2, pH 4.5, and 87.4 min. The pseudo-second order and Langmuir isotherm provide an account of the experimental results for AR88 adsorption by CTS-SA/SiO2. The calculated maximum Langmuir adsorption capacity for CTS-SA/SiO2 is equal to 184.2 mg/g. The high adsorption of AR88 onto the CTS-SA/SiO2 can be mainly ascribed to electrostatic forces between the protonated CTS-SA/SiO2 and the AR88 anions, along with n–π, π–π, and H-bond interactions. This research demonstrates that CTS-SA/SiO2 has promising potential as an adsorbent for organic dye removal from water systems.