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

Abstract

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 16 ) 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 3008C and had a structure that included spherical domains with a mean diameter of 68 lm, uniform porosity, and expected high sorption capability. The sorption properties of the resins were evaluated for applications in water-treatment operations to eliminate Cr 16 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 K 2 Cr 2 O 7 was used to quantify the Cr 16 content by ultraviolet-visible spectroscopy. A remarkable sorption level (94%) of chromate ions (Cr 16 ) was obtained during a 15-h period for the resin with the highest pyridine group content.

Polymers for the Extraction of Chromium—Role of Polymers in the Removal and Recovery of Chromium from Wastewater

“…It is established that the Cr(III) is toxic to fish (3) when present in water above 5.0 mgL −1 . Although Cr(III) is essential in mg levels in human beings, Cr(VI) (in the form of chromate and dichromate) is now established as a carcinogen and a mutagen (2)(3). The chromate enters into mammalian cells through the general anion channel.…”

“…Cr(III) is non toxic and essential species to mammals that helps the body to control blood-sugar levels in trace concentrations, but toxic to fish (1) when present in water about 5.0 mg.L −1 . The Cr(VI) is more hazardous to animals (2)(3) than the Cr(III). The permissible level of Cr(VI) (4) in water is less than 0.05 mg.L −1 .…”

Porous Copolymer Resins: Tuning Pore Structure and Surface Area with Non Reactive Porogens

“…Since their emergence, porous copolymer resins (PCR) have been used in various applications including sorption [ 1 , 2 , 3 ], solid supports in catalysis [ 4 , 5 ], chemical separations [ 6 ], ion-exchange [ 7 , 8 ], chromatography [ 7 , 8 ] and other applications. The usage of PCR materials is related to the unique physicochemical properties and the porous structural features of the polymer resins.…”

“…This review will focus on the phase separation technique where vinyl and acrylic PCR-based materials are synthesized from acrylates, styrene, divinylbenzene, and vinyl pyridine via suspension polymerization, in the presence of single and/or multi-component solvent porogens [ 2 , 4 , 6 , 7 , 10 , 11 , 12 , 13 ]. Suspension polymerization [ 14 ] is a technique where monomer(s), relatively insoluble in water is (are) dispersed as liquid droplets with a steric stabilizer that acts to hinder the coalescence of monomer droplets and the adhesion of partially polymerized particles during polymerization, using vigorous stirring to produce polymer particles as a dispersed phase.…”

“…Suspension polymerization [ 14 ] is a technique where monomer(s), relatively insoluble in water is (are) dispersed as liquid droplets with a steric stabilizer that acts to hinder the coalescence of monomer droplets and the adhesion of partially polymerized particles during polymerization, using vigorous stirring to produce polymer particles as a dispersed phase. A porogen is either a low molecular weight compound [ 1 , 2 , 4 , 5 , 7 , 11 , 12 , 13 , 14 ] or a polymer [ 15 , 16 , 17 ] that is miscible with the monomers. The porogen is inert and can be readily removed, resulting in voids after the reaction with the formation of porous polymeric materials.…”