Simultaneous trapping of Cr(III) and organic dyes by a pH-responsive resin containing zwitterionic aminomethylphosphonate ligands and hydrophobic pendants

A novel functionalized resin containing hydrophilic motifs of aminomethylphosphonate and hydrophobic pendant of 6-(biphenyl-4-yloxy)hexyl has been synthesized. The resin has been utilized as a sorbent for the simultaneous removal of Cr(III) as well as several organic dyes from aqueous solutions. At an initial Cr(III) concentration of 1.0 ppm, the metal uptake was almost ≈100% in 20 min at pH 5 and 25 °C. The experimental results were evaluated by Langmuir, Freundlich, and Temkin isotherm models. By using 0.1 M HNO₃ solution, the adsorbed Cr(III) ions were desorbed effectively. Interestingly, the resin demonstrated remarkable efficacy in simultaneous and complete removal of Cr(III) and several dyes including methyl orange, eriochrome black T, rhodamine B, methyl red and methylene blue from their mixture. The resin has also been remarkably effective in the removal of several toxic metal ions from a real industrial wastewater. As such, the resin may have applications for international environmental management in the water technology.