Dual-Responsive Hydrogels for Mercury Ion Detection and Removal from Wastewater

Abstract

This study describes the development of a fast and cost-effective method for the detection and removal of Hg2+ ions from aqueous media, consisting of hydrogels incorporating chelating agents and a rhodamine derivative (to afford a qualitative evaluation of the heavy metal entrapment inside the 3D polymeric matrix). These hydrogels, designed for the simultaneous detection and entrapment of mercury, were obtained through the photopolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and N-vinyl-2-pyrrolidone (NVP), utilizing N,N′-methylenebisacrylamide (MBA) as crosslinker, in the presence of polyvinyl alcohol (PVA), a rhodamine B derivative, and one of the following chelating agents: phytic acid, 1,3-diamino-2-hydroxypropane-tetraacetic acid, triethylenetetramine-hexaacetic acid, or ethylenediaminetetraacetic acid disodium salt. The rhodamine derivative had a dual purpose in this study: firstly, it was incorporated into the hydrogel to allow the qualitative evaluation of mercury entrapment through its fluorogenic switch-off abilities when sensing Hg2+ ions; secondly, it was used to quantitatively evaluate the level of residual mercury from the decontaminated aqueous solutions, via the UV-Vis technique. The ICP-MS analysis of the hydrogels also confirmed the successful entrapment of mercury inside the hydrogels and a good correlation with the UV-Vis method.

Biomedical Trends in Stimuli-Responsive Hydrogels with Emphasis on Chitosan-Based Formulations

“…Designing carriers for chelating agents that are released in response to specific toxic ions may be valuable in industrial settings [64]. Regarding water contamination, there has been research on mercury ion detection and its removal from wastewater with the use of hydrogels containing a rhodamine derivative and four different chelating agents [65]. Regarding anion-responsive formulations, a study by Wang et al highlighted that fluoride (F − ) and chloride (Cl − ) prompt the gel to collapse because of their strong hydrogen atom binding, whereas iodide (I − ) causes a color alteration in the gel without complete degradation [66,67].…”