Novel magnetic chitosan Schiff base impregnated with ZnO for removal of malachite green dye from aqueous environment

Contaminated wastewater with malachite green (MG) treated via porous materials with high adsorption function has become a main challenge in achieving the carbon neutrality goal. In this manner, a dual-action novel formulation has been assembled that presents a modified chitosan-Schiff base biopolymer by magnetite and zinc oxide nanoparticles as active centers for selective malachite green adsorption and preventing the growth of microorganisms in the medium. The presented novel porous composite material is characterized by the presence of two cost-effective and efficient surface modifiers (magnetite, zinc oxide nanoparticles) which enhanced the adsorption process rather than the presence of one as reported in the recently reported studies. The dual action of the presented compound as microorganisms' defeater and malachite green adsorbent comprises its novelty among the recently presented compounds. Herin, a novel chitosan-Schiff base (CS-SB) was synthesized by the reaction of Chitosan and (E)-3-(4-hydroxy-3-methoxyphenyl) acryl aldehyde. The prepared Schiff base was modified by magnetite using the co-precipitation method. The magnetic chitosan was impregnated with zinc oxide (ZnO) in the form of nanoparticles to produce Schiff base/ZnO nanocomposite (Mag-CS-SB/ZnO). The prepared compounds were characterized using infrared spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller, zeta potential analyses, and thermal gravimetric analysis, and tested in remediation of MG from aqueous medium. The adsorption parameters: dye concentration (25-100 mg/L), biosorbent dosages (5-60 mg), pH (2-9), and time (10-360 min) were studied. The Maximum adsorption capacity was 34 mg/g after two hours at ambient temperatures. Antibacterial activity of the prepared compounds was scanned for Gram-positive (Bacillus cereus and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The inhibition efficiency was ordered as Mag-CS-SB/ZnO nanocomposite > CS-SB > Chitosan. Mag-CS-SB/ZnO nanocomposite displayed outstanding antibacterial activity as comparable with commercial antibiotics (Streptomycin). The bonding between MG and biosorbent was shown to be predominantly caused by chelation and electrostatic adsorption, as proved by the density functional theory. Throughout five cycles, the biosorbent was effectively regenerated and maintained over 90% of its adsorption capacity, suggesting that it could find a beneficial and promising multi-functional adsorption compound for practical application in water treatment.