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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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this study, a magnetic chitosan grafted-benzaldehyde (CS-BD/Fe 3 O 4 ) 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/Fe 3 O 4 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 (pH PZC ). The Box-Behnken design (BBD) was adopted to study the role of variables that influence AR88 dye adsorption (A: CS-BD/Fe 3 O 4 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 (q max ) 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/Fe 3 O 4 surface. As a result, this research indicates that CS-BD/Fe 3 O 4 can be utilized as an effective and promising bio-adsorbent for azo dye removal from contaminated wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)