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Herein, a natural material including chitosan (CTS) and algae (food-grade algae, FGA) was exploited to attain a bio-adsorbent (CTS/FGA) for enhanced methyl violet 2B dye removal. A study of the FGA loading into CTS matrix showed that the best mixing ratio between CTS and FGA to be used for the MV 2B removal was 50 %:50 % (CTS/FGA; 50:50 w/w). The present study employed the Box-Behnken design (RSM-BBD) to investigate the impact of three processing factors, namely CTS/FGA-(50:50) dose (0.02-0.1 g/100 mL), pH of solution (4-10), and contact time (5-15 min) on the decolorization rate of MV 2B dye. The results obtained from the equilibrium and kinetic experiments indicate that the adsorption of MV 2B dye on CTS/FGA-(50:50) follows the Langmuir and pseudo-second-order models, respectively. The CTS/FGA exhibits an adsorption capacity of 179.8 mg/g. The characterization of CTS/FGA-(50:50) involves the proposed mechanism of MV 2B adsorption, which primarily encompasses various interactions such as electrostatic forces, n-π stacking, and H-bonding. The present study demonstrates that CTS/FGA-(50:50) synthesized material exhibits a distinctive structure and excellent adsorption properties, thereby providing a viable option for the elimination of toxic cationic dyes from polluted water., 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.)

Herein, a highly efficient and sustainable adsorbent of cross-linked chitosan-glyoxal/algae biocomposite (CHT-GLX/ALG) adsorbent was developed through an innovative hydrothermal cross-linking method. The CHT-GLX/ALG biocomposite was characterized using several complementary analytical methods that include CHN-O, XRD, FTIR, SEM-EDX, and pH pzc . This new adsorbent, named CHT-GLX/ALG, was utilized for the adsorption of a cationic dye (methyl violet 2B; MV 2B), from synthetic wastewater. The optimization of the dye adsorption process involved key parameters is listed: CHT-GLX/ALG dosage (from 0.02 to 0.1 g/100 mL), pH (from 4 to 10), and contact time (from 20 to 180 min) that was conducted using the Box-Behnken design (BBD). The optimal adsorption conditions for the highest decolorization efficiency of MV 2B (97.02 %) were estimated using the statistical model of the Box-Behnken design. These conditions include a fixed adsorbent dosage of 0.099 g/100 mL, pH 9.9, and a 179.9 min contact time. The empirical data of MV 2B adsorption by CHT-GLX/ALG exhibited favorable agreement with the Freundlich isotherm model. The kinetic adsorption profile of MV 2B by CHT-GLX/ALG revealed a good fit with the pseudo-second-order model. The maximum adsorption capacity (q max ) for MV 2B by CHT-GLX/ALG was estimated at 110.8 mg/g. The adsorption of MV 2B onto the adsorbent can be attributed to several factors, including electrostatic interactions between the negatively charged surface of CHT-GLX/ALG and the MV 2B cation, as well as n-π and H-bonding. These interactions play a crucial role in facilitating the effective adsorption of MV 2B onto the biocomposite adsorbent. Generally, this study highlights the potential of CHT-GLX/ALG as an efficient and sustainable adsorbent for the effective removal of organic dyes., 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.)