Removal of crystal violet by clay/PNIPAm nanocomposite hydrogels with various clay contents

Abstract

The clay/poly(N-isopropylacrylamide) (PNIPAm) nanocomposite (CPN) hydrogels, using lithium magnesium silicate hydrate (LMSH) as a clay mineral physical cross-linker, with the mass ratio of NIPAm/LMSH ranging from 5 to 30wt.% were prepared to remove crystal violet (CV) from aqueous solution. Morphology and temperature-sensitivity of hydrogels were investigated by SEM and DSC. Adsorption capacity and kinetic under different times, pH values and concentrations were evaluated by using UV/vis spectroscopy. The pore sizes of CPN hydrogels range from 30 to 50μm, and volume phase transition temperature (VPTT) were 33–36°C. The adsorption capacity (Qt) of CV onto CPN hydrogels at 25°C increased quickly at initial 12h, with a maximum value of 4.71mg/g. At 37°C, the Qt values are not more than 2mg/g. The Qt values of CPN hydrogels increase 2–4 times when CV concentration was added from 10 to 30mg/L, and increase 1–1.5 times as pH value increases from 3.0 to 8.9.