Capturing of inorganic and organic pollutants simultaneously from complex wastewater using recyclable magnetically chitosan functionalized with EDTA adsorbent

Herein, we synthesized new and versatile magnetite-doped chitosan−ethylenediaminetetraacetic acid (Fe₃O₄@CS−EDTA) composite for simultaneous capturing of multiple heavy metal ions: Hg²⁺, Cd²⁺, and Ni²⁺, and methyl orange (MO) dye from complex wastewater through adsorption process. We believe that EDTA in the synthesized adsorbent works as a cross-linker as well as a chelating agent for the capturing of heavy metal ions, while the protonated amino groups of CS capture MO through electrostatic interaction. In the monocomponent system, the adsorption followed to Langmuir model and gave the maximum adsorption capacities of 232.70 ± 14.30, 121.40 ± 7.0, 56.50 ± 2.20, and 732.10 ± 72.40 mg g⁻¹ for Hg²⁺, Cd²⁺, Ni²⁺, and MO, respectively. Kinetics data well fitted to the pseudo-second order (PSO) models, confirmed the chemisorption process. Interestingly, in the case of the binary component system containing both metals and MO, the adsorption capacity of the adsorbent for the dye was not affected by metal presence, while the adsorption of metal ions was enhanced with increasing MO concentration. The adsorption mechanism was confirmed by elemental mapping, XPS and FTIR. Moreover, no significant loss in the adsorption efficiency even after the six continuous adsorption-desorption cycles confirms the great stability and potential of the adsorbent in treating the complex wastewater.