Removal of heavy metals by homolytically functionalized poly(acrylic acid) with hydroquinone

Poly(acrylic acid) (PAA) was synthesized and chemically modified with hydroquinone (HQ) applying the reaction conditions of Minisci. A degree of modification of as high as 32 % was obtained under optimal conditions: temperature of 70–80 ^0C, time of 5 h, and [p-benzoquinone]/[ acrylic acid)] ratio of 1.25. The synthesized PAA and its modified form HQ-PAA were characterized by UV–visible, FT-IR, XRD, SEM, ^13C NMR spectroscopy, TGA, DSC, and size exclusion chromatography. The study of copper (II) adsorption by the cross-linked PAA and HQPAA resins was undertaken, varying the following parameters: pH, time, temperature, ionic strength, sorbent mass, and initial copper (II) concentration. Optimal copper sorption extents of 5.5 and 20 mg g^-1 for PAA and HQPAA resins, respectively, were found under the following conditions: a pH of 5.4, a time of 3 h, a temperature of 45 ^0C, and an ionic strength of 0. Sorbent resins were achieved by cross-linking poly(acrylic acid) and its modified one through an oxidative decarboxylation process.