Adsorptive Removal of Heavy Metals and Organic Dye Simultaneously from Complex Wastewater Using Recyclable Magnetically Chitosan Functionalized EDTA Adsorbent

The existence of more than one class of pollutants in wastewater is a challenging task to treat via one-step process due to significant differences in physicochemical properties. Here, we prepared a new and effective adsorbent magnetite-doped chitosan-ethylenediaminetetraacetic acid (Fe₃O₄@CS-EDTA) for the simultaneous removal of multiple heavy metals: Hg²⁺, Cd²⁺, and Ni²⁺, and methyl orange (MO) dye from complex wastewater through adsorption process. In this adsorbent, we believe that EDTA in the synthesized adsorbent work as a cross-linker as well as a chelating agent for the capturing of heavy metal ions, while the protonated amino groups of CS adsorb MO through electrostatic interaction. In the single component system, the isotherm data followed to Langmuir model and gave the maximum adsorption capacities (q_m) 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 strongly 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 heavy metals was increased with increasing MO concentration. elemental mapping, XPS and FTIR confirmed the adsorption mechanism via complexation and electrostatic interactions. 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.