Production of macroporous resins for heavy-metal removal. I. Nonfunctionalized polymers

The aim of this work was the synthesis of macroporous resins with large specific surface areas through the use of organic solvents (known as porogens or pore-forming agents) for applications in hexavalent chromium (Cr+6) removal operations. The synthesis of these materials by suspension polymerization allowed the generation of macroporous structures. The comonomers 4-vinylpyridine and divinylbenzene were considered in different ratios. Poly(vinyl alcohol) was used as a suspension agent in a mixture of toluene and hexane. The materials produced were characterized with Fourier transform infrared spectroscopy, elemental analysis, thermogravimetry, nitrogen adsorption, and scanning electron microscopy. The macroporous resin with the largest surface area (130 m(2)/g) was thermally stable up to 300 degrees C and had a structure that included spherical domains with a mean diameter of 68 mu m, uniform porosity, and expected high sorption capability. The sorption properties of the resins were evaluated for applications in water-treatment operations to eliminate Cr+6 ions at a pH near 7. The advantages of these materials were their high removal capability, high selectivity, and fast adsorption kinetics at a pH 6.5. An aqueous solution of 4 ppm K2Cr2O7 was used to quantify the Cr+6 content by ultraviolet-visible spectroscopy. A remarkable sorption level (94%) of chromate ions (Cr+6) was obtained during a 15-h period for the resin with the highest pyridine group content. (c) 2007 Wiley Periodicals, Inc.