Chitosan derivative, sequestering agents for heavy metals

Claim 1

A sequestering agent for ions of a heavy metal in an aqueous solution consisting essentially of a chitosan derivative consisting of randomly distributed patterns of the formulae: ##STR4## the proportions of these three patterns being, respectively, 5 to 30% for A, 5 to 40% for B and 30 to 90% for C, R representing a member selected from the group consisting of ##STR5## wherein R 1 represents a member selected from the group consisting of hydrogen and methyl, n is equal to (a) 0, in which case R 2 , R 3 and R 4 , each independently, represent a member selected from the group consisting of hydrogen, methyl, hydroxy, acetoxy, amino, monoalkylamino or dialkylamino wherein the alkyl moiety of each has 1-12 carbon atoms and wherein each is optionally interrupted by one or more nitrogen atoms or substituted by one or more amino, hydroxyl, mercapto, carboxyl, alkylthio wherein the alkyl moiety has 1 to 8 carbon atoms and sulfonic groups, alkylthio wherein the alkyl moiety has 1- 4 carbon atoms and carries an amino residue, and a residue of glutathion, at least one of R 2 , R 3 and R 4 being hydrogen and radicals R 2 and R 3 being able to form together a methylene radical, and (b) 1, in which case R 2 , R 3 and R 4 each represent hydrogen, and the salts formed by this derivative with a base selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonia, lime, magnesia and alkanolamine and an acid selected from the group consisting of hydrochloric, phosphoric, acetic, lactic, tartaric and citric.