Abstract
Azo dye removal from polluted water is vital from a sustainable viewpoint. In this study, we investigated the influence of chitosan molecular weight on the adsorption of basic blue 41. Nanocomposite (NC(M)) was prepared using magnetite nanoparticles modified by amino-silica, medium-molecular weight chitosan, diethylenetriaminepentaacetic acid and graphene oxide. FT-IR, XRD, FESEM, TEM, EDX, elemental mapping, TGA/DTG, VSM and N2 adsorption/desorption isotherm were applied to characterize NC(M). Its effectiveness for the dye adsorption was compared with the adsorbent having low-molecular weight chitosan (NC(L)) (Asadabadi 2021). In this regard, the effect of initial pH, temperature and adsorbent concentration on the dye removal was investigated by Central Composite Design. The maximum percentage of dye removal was 31% for NC(M) at optimum conditions. An increase in the monomer number of chitosan caused to increase in the contact angle and decrease in the hydrophilic property of NC(M). Thus, it had a very low dye adsorption. However, NC(L) led to dye removal of 95%. It was proposed that NC(L) adsorbed dye by coulumbic attraction, π-stacking interactions and H-bonding. The NC(L) kinetics data were satisfactorily fitted by the modified pseudo-n-order model. About 30 min necessitated reaching the equilibrium and the rate-limiting steps changed from the film diffusion to intra-particle diffusion as time passed. The modified Langmuir–Freundlich isotherm was the best model to reproduce equilibrium data and the maximum adsorption capacity was equal to 55.87 mg·g−1. Besides, NC(L) was recovered seven times without dramatic changes in its adsorption efficiency.Graphic Abstract
Highlights
Remarkable increase of the demand for treated water is resulted from the fast growth of population and industrial development [1, 2]
The silica-modified magnetite nanoparticles were treated with medium-molecular weight chitosan, graphene oxide and diethylenetriaminepentaacetic acid
Techniques including FT-IR, XRD, FESEM, thermal gravimetric analysis (TGA)/DTG, VSM and nitrogen adsorption/desorption isotherm were applied for characterization of adsorbent (NC(M))
Summary
Remarkable increase of the demand for treated water is resulted from the fast growth of population and industrial development [1, 2]. Azo dye molecules have a conjugated system of aromatic rings and nitrogen double bonds with strong π→π* transitions in the UV-Vis region [5]. Aromatic amines can be formed because of azo bond cleavage and reduction creating severe environmental problems. Different techniques such as reverse osmosis, chemical oxidation, adsorption, coagulation, electrochemical methods and their combinations can be used for treatment of the industrial azo dyes [6,7,8]. Developing a cost-effective, biodegradable and efficient adsorbent has been a big challenge for researchers to remove dangerous azo dyes [10, 11]. Graphene-based materials, hydrogels and bio-polymers can be utilized for dye adsorption [12, 13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
