METHOD FOR MANUFACTURING INSOLUBLE TANNIN AND METHOD FOR ADSORBING HEXA-VALENT CHROMIUM USING THE TANNIN

摘要

PROBLEM TO BE SOLVED: To obtain a gelatinous insoluble tannin capable of controlling a gel to 5-90% water content which is the wider content than that of a conventional adsorbent and increasing adsorption capacity of a metal by varying a net structure and a molecular space in accordance with a size of the metal ion to be adsorbed, and at the same time, to obtain the gelatinous insoluble tannin having a desired particle size and the water content not necessitating crush at the time of using the tannin as the adsorbent. SOLUTION: This method for manufacturing insoluble tannin comprises steps of: (a) dissolving condensed tanning powder into an alkaline aqueous solution; (b) adding and mixing an aldehyde aqueous solution into the aqueous solution obtained in the step (a); (c) adding and dispersing the solution obtained in the step (b) in a shape of liquid drops into a hydrophobic solvent containing a polyether based non ionic surfactant while stirring the solvent at a heated temperature and (d) forming spherical and gelatinous insoluble tannin by evaporating water from the liquid drops.