Lead, copper, cobalt, nickel, iron and zinc ions form monocitrate complexes (negative charge) in citrate solution which is absorbed on the citrate form of anion-exchange resins (citrate as counter ion) y exchange of citrate ion with citrate complexes. These are subsequently recovered from the resin by 0.5M ammonium citrate eluent at pH 2.0. Under optimized conditions, quantitative recovery ...