UDC 621.793.3

Precipitation and subsequent regeneration of EDTA from heavy metal complex solution

O. Gyliene·, J. Aikaite·, O. Nivinskiene·

The method of removal of EDTA in form of insoluble Cu₂EDTA·4H₂O from complex solutions containing such heavy metals as Ni(II), Zn(II), Co(II), Cd(II), Ca(II), Mg(II) has been proposed. The formation of insoluble Cu₂EDTA·4H₂O compound proceeds in pH range from 3 to 5,5. In more acidic solutions the precipitate dissolves and in more alkaline it hydrolyzes forming Cu(OH)₂ precipitate. The degree of EDTA removal from solution depends on concentrations of Cu(II), EDTA, the ratio between them and pH. After treatment of Cu₂EDTA·4H₂O formed with water, acidic or alkaline solutions copper from the suspensions formed can be removed by means of electrolysis. In acidic solutions the insoluble H₄EDTA is formed, while in alkaline solutions - the soluble Na₂EDTA, which can be removed from solution by evaporation and crystallization.

Lithuania, Vilnius, Chemistry Institute, CC «Biocentras».