Removal of Copper(II) Ions with a Thermoresponsive Cellulose-g-Poly(N-isopropyl acrylamide) Copolymer

Abstract

N-Isopropyl acrylamide monomer was grafted onto cellulose (Cell) with a cerium(IV) ammonium nitrate (CAN)-nitric acid initiator system, and a thermoresponsive Cell-g-poly(N-isopropyl acrylamide) (PNIPAM) copolymer was obtained. The copolymer was characterized with Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy/electron-dispersive spectrometry analysis. The lower critical solution temperature (LCST) of the copolymer was determined by differential scanning calorimetry technique. The swelling capacities and water retention values were determined in distilled water in the temperature range from 10 to 50 degrees C. The adsorption experiments were performed by a solid-phase extraction technique. Sodium dodecyl benzene sulfonate (SDBS) was used as an extractant, and Cu(II) ion was complexed with SDBS before the adsorption process. Then, the adsorption of the Cu(II)-SDBS complexes onto Cell-g-PNIPAM copolymers through hydrophobic interaction was performed at higher temperatures than the LCST of the copolymer. The adsorption capacity (Q) was dependent on the initial pH of the metal-ion solution, and Q decreased at lower pHs. The maximum sorption capacity of the copolymer for the Cu(II) ion was 1.18 mmol/g, and a high amount of sorption equilibrium was attained in 10 h. We found that the adsorption kinetics followed a pseudo-second-order kinetic model. The adsorption experiments showed that the adsorption was S-type according to the Giles classification system. It was also determined that the thermoresponsive Cell copolymer could be used for the removal of Cu(II) ions as an environmentally friendly sorbent. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4440-4448, 2013