Study on a highly sensitive determination of toxic metals in waste water with high matrix contents using coprecipitation separation techniques

Abstract

Selective coprecipitations of selenium species and arsenic species in complex high-salts wastewater, followed by graphite-furnace AAS, were developed. Selective separations of selenium species were based on the reductive coprecipitations on tellurium and palladium collector using hydrazinium sulfate, L-ascorbic acid and tin (II) chloride as reducing agents. In particular, the selective reductive coprecipitation of selenite in the presence of selenate was achieved on a 50∼500 μg amount of tellurium collector under 1 M HCl for 15 min boiling using L-ascorbic acid and tin (II) chloride, and was achieved on a palladium collector under 0.2 M HCl for 30 min boilng by using hydrazinium sulfate. On the other hand, the selective coprecipitation of inorganic arsenic (III,V) in the presence of organic arsenics was achieved by lanthanum hydroxide coprecipitation at pH 12 or more. Moreover, organic arsenics (dimethylarsinic acid, monometylarsonic acid and p-aminophenylarsonic acid) were quantitatively distilled as chloroarsine compounds under 0.2 M SnCl₂, 2.75 M H₂SO₄ and 4 M HCl. The developed selective determinations of selenium species and arsenic species were satisfactorily applied to real waste water containing ppb levels of selenium and arsenic.