Abstract: A process for reducing the amount of nitrification-inhibiting sulfur compounds in reaction solutions obtained by the sulfur-compound-catalyzed conversion of &agr;,&bgr;-unsaturated carboxylic acids into the corresponding trans or cis isomer, in which an oxidizing agent is added in molar deficiency up to a maximum of twice the molar amount, based on the catalyst compound, to the reaction mixture obtained after the termination of the isomerization and then isolating the corresponding trans or cis isomer in a known manner and working it up and supplying the resultant process waste waters to a biological cleanup stage.

Abstract: Absorbing polymer consisting of a polymer A which is an optionally modified polyvinyl alcohol or an optionally modified polysaccharide or a mixture of these, and of a polymer B which is a maleic anhydride homo- or copolymer having a hydrolysis time of 5 to 120 minutes, the anhydride groups being open and 0.005 to 5 mol % of the acid functions being esterified with hydroxyl groups of polymer A, and the remaining acid functions being present as free acid groups, as salts or as acid amide groups, an absorbing product containing this polymer and a process for their preparation.