affordable and efficient removal of direct red 16 from aqueous media based on nano zero-valent iron and nickel bimetallic nanoparticles supported on chitosan

Water pollution by azo dyes that are very toxic for living things is increasing rapidly. thus, it is very important to eliminate these dyes from aqueous media. in this study, bimetallic nano zero-valent iron-nickel (nzvi-ni) supported on biopolymer chitosan (cs-nzvi-ni) were synthesized and characterized by scanning electronic microscopy (sem), energy-dispersive x-ray spectroscopy (edx), x-ray diffraction (xrd), fourier-transform infrared spectroscopy (ftir), brunauer-emmett-teller (bet), and vibrating sample magnetometer (vsm). the synthesized nanocomposite was used as an adsorbent for the removal of direct red 16 (dr16) from the aqueous solution. the effect of ph (4-9), adsorbent dosage (0.08-0.3 g), contact time (5-30 min), and dye concentration (20-40 mg/l) revealed that the ph of 4, the adsorbent dosage of 0.2 g, contact time of 15 min, and initial concentration of 20 mg/l had maximum removal percentage (>96%). two equilibrium models (langmuir and freundlich) were applied to calculate the adsorption parameters. the langmuir model indicated the most suitable model that best fits the equilibrium data and the maximum adsorption capacity (qmax) was 84.74 mg/g with a coefficient of determination (r²) value of 0.9993. the pseudo-second-order kinetic model fitted well for the adsorption of dr16 with r² of 0.9986. thermodynamic parameters were calculated, and the results indicated that the adsorption was spontaneous and exothermic. the proposed adsorbent revealed excellent reusability with the removal efficiency from 88.32% to 60.28% after 5 cycles of adsorption experiments. based on the results obtained from this work, the suggested adsorbent as a promising, simple, cost-effective, and efficient material could effectively be used for the elimination of various dyes from wastewater.