Fabrication of magnetic chitosan-grafted salicylaldehyde/nanoclay for removal of azo dye: BBD optimization, characterization, and mechanistic study.

Herein, a novel nanohybrid composite of magnetic chitosan-salicylaldehyde/nanoclay (MCH-SAL/NCLA) was hydrothermally synthesized for removal of azo dye (acid red 88, AR88) from simulated wastewater. Response surface methodology combined with the Box-Behnken design (RSM-BBD) was applied with 29 experiments to assess the impact of adsorption variables, that include A: % NCLA loading (0-50), B: MCH-SAL/NCLA dose (0.02-0.1 g/100 mL), C: pH (4-10), and time D: (10-90 min) on AR88 dye adsorption. The highest AR88 removal (75.16 %) as per desirability function was attained at the optimum conditions (NCLA loading = 41.8 %, dosage = 0.06 g/100 mL, solution pH = 4, and time = 86. 17 min). The kinetic and equilibrium adsorption results of AR88 by MCH-SAL/NCLA reveal that the process follows the pseudo-first-order and Temkin models. The MCH-SAL/NCLA composite has a maximum adsorption capacity (173.5 mg/g) with the AR88 dye. The adsorption of AR88 onto the MCH-SAL/NCLA surface is determined by a variety of processes, including electrostatic, hydrogen bonding, n-π, and n-π interactions. This research revealed that MCH-SAL/NCLA can be used as a versatile and efficient bio-adsorbent for azo dye removal from contaminated wastewater.

Design of separable magnetic chitosan grafted-benzaldehyde for azo dye removal via a response surface methodology: Characterization and adsorption mechanism.

In this study, a magnetic chitosan grafted-benzaldehyde (CS-BD/Fe3O4) was hydrothermally prepared using benzaldehyde as a grafting agent to produce a promising adsorbent for the removal of acid red 88 (AR88) dye. The CS-BD/Fe3O4 was characterized by infrared spectroscopy, surface area analysis, scanning electron microscopy-energy dispersive X-ray, vibrating sample magnetometry, powder X-ray diffraction, CHN elemental analysis, and point of zero charge (pHPZC). The Box-Behnken design (BBD) was adopted to study the role of variables that influence AR88 dye adsorption (A: CS-BD/Fe3O4 dose (0.02-0.1 g), B: pH (4-10), and time C: (10-90 min)). The ANOVA results of the BBD model indicated that the F-value for the AR88 removal was 22.19 %, with the corresponding p-value of 0.0002. The adsorption profiles at equilibrium and dynamic conditions reveal that the Temkin model and the pseudo-first-order kinetics model provide an adequate description of the isotherm results, where the maximum adsorption capacity (qmax) with the AR88 dye was 154.1 mg/g. Several mechanisms, including electrostatic attraction, n-π interaction, π-π interaction, and hydrogen bonding, regulate the adsorption of AR88 dyes onto the CS-BD/Fe3O4 surface. As a result, this research indicates that CS-BD/Fe3O4 can be utilized as an effective and promising bio-adsorbent for azo dye removal from contaminated wastewater.