Poly (N-vinyl Imidazole)/Nitrogen-Doped Graphene Quantum Dot Hydrogel Adsorbent With Remarkable Capability for Metal Ion Removal From Aqueous Systems

Abstract

The present work studies the adsorptive removal of cadmium, nickel and chromium ions from an aqueous solution using a highly efficient nanocomposite adsorbent hydrogel. pH-sensitive nanocomposite hydrogels prepared easily by the free radical polymerization of N‑vinyl imidazole (VI) monomer using N, N′- methylene-bis-acrylamide (MBA) and dicationic imidazolium-based (DIL) cross-linkers with molar ratios of monomer/cross-linker in the presence of 0.0, 0.9 and 4.0 wt.% nitrogen doped graphene quantum dots (NGQD). The prepared hydrogel (PVI/NGQD) with higher swelling degree (V-D-G1) with molar ratio of VI/DIL=24 and 4.0 wt.% NGQD was a prominent candidate for adsorption study of three elements (Cd, Ni, and Cr) from the solution. FT-IR, DSC, XRD, SEM, and EDS analysis were used to characterize the structure and the surface morphology of adsorbent before and after the metal ions adsorption. The effects of pH, initial concentration of ions and contact time on the adsorption capacity of the hydrogel were also studied. Adsorption of ions were investigated at pH 1.0, 7.0 and 9.0 and maximum removal efficiencies for Cd(II), Ni(II) and Cr(VI) ions (75%, 94.6% and 70.9%) were achieved at pH=7.0 and optimum ions concentration and contact time of 1000 mg/L, and 40, 40 and 150 min, respectively. The maximum adsorption capacity values of V-D-G1 is found to be 5000, 5000 and 370.370 mg/g for Cd(II), Ni(II) and Cr(VI), respectively. The adsorption data were used to study the adsorption kinetic and isotherm models in which Langmuir model and pseudo-first order model showed the better applicability.

Frontier Materials for Adsorption of Antimony and Arsenic in Aqueous Environments: A Review

“…Hydrogels are widely used in the delivery of genetically engineered drugs [ 118 ], adsorption [ 119 ], sensors [ 120 ], and many other fields. Specific functional groups in hydrogels, such as −OH, −NH 2 , −COOH, −CONH 2 , are beneficial for removing metal ions from water [ 121 ]. It is worth mentioning that the hydrogels can be modified or composited with other materials to deal with different heavy metals or metalloids according to actual needs [ 122 ], and the adsorption effect of the synthesized composite hydrogel is better than that of the natural hydrogel [ 75 ].…”