Chitosan-Schiff base nano silica hybrid system for azo acid dye removal: Multivariable optimization, desirability function, and adsorption mechanism

The facile synthesis of cross-linked chitosan-glutaraldehyde/nano silica (CHS-GLA/n-Silica) nanocomposite was accomplished in two steps including the functionalization of a natural biopolymer (CHS) with an inorganic nanomaterial (n-Silica), followed by a cross-linking process with glutaraldehyde (GLA). The ability of CHS-GLA/n-Silica to remove acid red 88 (AR88) dye from an aqueous system was optimized by Box–Behnken design (BBD), taking into consideration the factors affecting adsorption (CHS-GLA/n-Silica dose (0.02-0.1 g/100 mL); time (10-60 min); and pH (4-10). The equilibrium behavior of AR88 by CHS-GLA/n-Silica is clearly illustrated by the Langmuir and Temkin isotherms. The kinetics of AR88 adsorption by CHS-GLA/n-Silica were appropriately described by a pseudo-second-order model. CHS-GLA/n-Silica displays anadsorption capability of 115.9 mg/g. The electrostatic forces between the positively charged CHS-GLA/n-Silica and the AR88 anions, as along with n-π, and H-bond interactions, which accounts for the efficient adsorption of AR88 on the CHS-GLA/n-Silica. This study demonstrates that CHS-GLA/n-Silica has promising potential as an adsorbent for the effective removal of synthetic dyes from wastewater.