Abstract: A method of adsorbing and separating a heavy metal element by using a tannin adsorbent comprising:(a) adjusting the pH of a solution containing a plurality of heavy metal elements to a predetermined pH;(b) contacting the adsorbent with the solution in which the pH thereof is adjusted;(c) adjusting the pH of the solution contacted with the adsorbent to a pH different from the predetermined pH; and(d) contacting the solution in which the pH thereof is adjusted at the step (d) with the adsorbent prepared at the step (a).According to the inventive method, all of the heavy metal elements can be efficiently separated and adsorbed by using a tannin adsorbent from a solution containing a number of heavy metal elements. A method of regenerating a tannin adsorbent are also disclosed.

Abstract: A method of adsorbing and separating a heavy metal element by using a tannin adsorbent comprising:(a) adjusting the pH of a solution containing a plurality of heavy metal elements to a predetermined pH;(b) contacting the adsorbent with the solution in which the pH thereof is adjusted;(c) adjusting the pH of the solution contacted with the adsorbent to a pH different from the predetermined pH; and(d) contacting the solution in which the pH thereof is adjusted at the step (d) with the adsorbent prepared at the step (a).According to the inventive method, all of the heavy metal elements can be efficiently separated and adsorbed by using a tannin adsorbent from a solution containing a number of heavy metal elements. A method of regenerating a tannin adsorbent are also disclosed.

Abstract: An insoluble hydrolysable tannin is prepared by dissolving a hydrolysable tannin powder in aqueous ammonia; mixing the resulting solution with an aldehyde aqueous solution to form a precipitate; heating the precipitate; mixing the heated precipitate with a mineral acid; and filtering the resulting mixture to leave a residue on a filter. The inventive insoluble tannin exhibits high adsorption properties for heavy metal elements and is insoluble in either water, acid, or alkali. Methods for treating waste liquids and recovering heavy metal elements therefrom using the inventive insoluble tannin are disclosed.

Abstract: An insoluble hydrolysable tannin is prepared by dissolving a hydrolysable tannin powder in aqueous ammonia; mixing the resulting solution with an aldehyde aqueous solution to form a precipitate; heating the precipitate; mixing the heated precipitate with a mineral acid; and filtering the resulting mixture to leave a residue on a filter. The inventive insoluble tannin exhibits high adsorption properties for heavy metal elements and is insoluble in either water, acid, or alkali. Methods for treating waste liquids and recovering heavy metal elements therefrom using the inventive insoluble tannin are disclosed.

Abstract: A process for treating organic phosphates, comprising(a) mixing a waste organic solvent mainly composed of an organic phosphate with an additive mainly composed of at least one of metal salts of aliphatic carboxylic acids represented by formula:(C.sub.n H.sub.2n+1 COO).sub.m MwhereinM is K, Ca or Al, andm is a positive integer of 1, 2 or 3,(b) heating the resulting mixture, and(c) optionally burning the mixture to form stable solid containing phosphor content. The metal salts of aliphatic carboxylic acid are preferably metal salts of acetic acid such as potassium acetate, calcium acetate and aluminum acetate. Typical organic phosphate solvent is tributyl phosphate or a mixed solution of tributyl phosphate and benzene.

Abstract: An insoluble hydrolysable tannin is prepared by dissolving a hydrolysable tannin powder in aqueous ammonia; mixing the resulting solution with an aldehyde aqueous solution to form a precipitate; heating the precipitate; mixing the heated precipitate with a mineral acid; and filtering the resulting mixture to leave a residue on a filter. The inventive insoluble tannin exhibits high adsorption properties for heavy metal elements and is insoluble in either water, acid, or alkali. Methods for treating waste liquids and recovering heavy metal elements therefrom using the inventive insoluble tannin are disclosed.

Abstract: There is disclosed an insoluble tannin preparation process, in which a tannin is first dissolved in an aldehyde aqueous solution. Then, ammonia is added to the solution to produce a precipitate, and the resulting precipitate is subjected to aging. The insoluble tannin thus prepared is employed to treat a waste liquid. Furthermore, there is disclosed an adsorption process in which a tannin is first dissolved in a solution containing a material to be adsorbed. Thereafter, an aldehyde is added to the solution to produce a precipitate having tannin as a principal constituent. The material to be adsorbed is adsorbed to this precipitate.

Abstract: There is disclosed a waste treatment process for alkaline waste liquid in which substances to be removed exist in ionic and colloidal states. In the process, powdered tannin is added to the waste liquid to produce solid substance of the tannin and to capture the substances to be removed on the solid substance. Then, the waste liquid is subjected to filtration to thereby separate the solid substance including the substances to be removed.