Alkali-catalyzed PVA (polyvinyl alcohol) gel bead preparing method

Abstract

The invention relates to an alkali-catalyzed PVA gel bead preparing method. The alkali-catalyzed PVA gel bead preparing method comprises taking PVA as the raw material, NaOH as the catalyst and saturated boric acid and CaCl2 as the crosslinking agent, subjecting the hydroxyl of the molecular chain of the PVA and boric acid molecules to reaction to obtain entangled PVA gel beads with a diameter around 3 mm. The NaOH firstly catalyzes full alcoholysis of the PVA to expand the long-chain molecules of the PVA so that the branch chains of the PVA can be filled with active hydroxyls, and after the saturated boric acid and the CaCl2 solution are dropwise added, the NaOH can further catalyze chemical crosslinking between the hydroxyls of the branch chains of the PVA molecules and the boric acid molecules through ester bonds. The prepared PVA gel beads are low in aqueous swelling property, high in mechanical strength, stable and less prone to adhesion, and meanwhile integrate structural uniformity, good biocompatibility and storage convenience, thereby being applicable as filling materials of biofilm carriers in sewage treatment reactors and high-speed up-flow bioreactors.

Description

technical field [0001] The invention belongs to the field of environmental engineering, and in particular relates to a preparation method of alkali-catalyzed PVA gel beads. Background technique [0002] The polymer materials represented by polyvinyl alcohol (PVA) are conducive to the growth of microorganisms in the wastewater biological treatment reactor, thereby promoting the rapid start-up and high-load stable operation of the reactor. [0003] PVA is one of the common water-soluble polymers. Each repeating unit in its molecular chain contains a hydroxyl group. Due to the small size of the hydroxyl group and strong polarity, PVA has good water solubility, film-forming properties, and cohesive force. Easily cross-linked by hydrogen bonds to form gels. PVA gel has the characteristics of high water content, low toxicity, good biocompatibility, etc., and has wide application prospects in agriculture, biology, medical and health, environmental protection and other fields. How...

AI Technical Summary

Problems solved by technology

The physical cross-linking of PVA is strengthened by cyclic freezing and thawing, which can form hydrogen bonds, microcrystalline regions and intertwined cross-links between macromolecular chains in the molecule, and then form a three-dimensional network structure through hydrophobic interactions. The mechanical strength of the gel, but there is a problem of easy swelling and cracking in water, which shortens its service life

Using saturated boric acid and CaCl 2 The chemical cross-linking method, which is a chemical cross-linking agent, can strengthen the binding force between PVA molecules through ester bonds, and the water resistance and mechanical properties of the gel material obtained by cross-linking are significantly improved, thereby prolonging its service life. However, this method still exists. The problem of incomplete crosslinking, the active groups on the unreacted PVA side chains make the prepared gel materials easy to stick to each other and agglomerate, which is not conducive to the stable storage and application of the product

In recent years, around these problems, scholars have tried to use different cross-linking agents (glutaraldehyde, epichlorohydrin, etc.) to improve the cross-linking of PVA, but obtained PVA with good mechanical strength, low water swelling and stable adhesion. Gel material is still blank