A magnetically recyclable chitosan composite adsorbent functionalized with EDTA for simultaneous capture of anionic dye and heavy metals in complex wastewater

Ascribing to their significant differences in physicochemical properties, it is extremely challenging to treat complex wastewater containing more than one class of pollutants via one-step treatment. Here, we focused on disposal of complex wastewater bearing organic dye and heavy metal by using adsorptive method. Thus, we successfully fabricated a novel and versatile EDTA functionalized magnetic chitosan composite adsorbent (Fe3O4-CS/EDTA) for simultaneous removal of methyl blue(MB) and heavy metal (Pb(II) and Cu(II)) from complex wastewater. In this setting, EDTA chelating groups are mainly responsible for the binding of heavy metals, while the protonated amino groups of CS adsorb anionic dyes through electrostatic interaction, thus enabling the simultaneous capture of these two classes of pollutants. In monopollutant system, the resulting material showed prominent uptake ability toward MB, Pb(II), and Cu(II) with uptake characteristics of pseudo-second-order model and Langmuir isotherm equation. The maximum monolayer uptake capacities were determined to be 225.0 mg g(-1) of Cu(II), 220.0 mg g(-1) of Pb(II), and 459.9 mg g(-1) of MB at 303 K, respectively. More interestingly, in metal-MB binary system, uptake of MB was almost not affected by coexisting metal. While the uptake capacity of Cu(II) or Pb(II) was enhanced with increasing of MB concentration. These results demonstrated the synergetic removal performance of as-designed adsorbent toward cationic metal ions and anionic dye. Moreover, as-resulting adsorbent showed no significant adsorption capacity loss even after 8 runs of sorption-desorption cycle, manifesting that it is of great stability and could be regarded as a promising candidate adsorbent for treating complex wastewater. This study provides some insights into the design of highly efficient adsorbents with spatially separated sorption sites for disposing complex wastewater bearing organic and metallic contaminants.