Effect of formaldehyde on Cu(II) removal from synthetic complexed solutions by solvent extraction.
The effect of formaldehyde (HCHO) on the extraction of Cu(II) from an equimolar EDTA (ethylenediaminetetraacetic acid, H4L) solution with Aliquat 336 in kerosene (a quaternary amine) was examined. Experiments were carried out at different initial concentrations of Cu(II) (1.57-5 mol/m3), solution pH (3.0-8.0), HCHO concentrations (0-3 vol.%), Aliquat 336 concentrations (80-400 mol/m3), and temperatures (15-35 degrees C). It was shown that the distribution ratios (D) of Cu(II), which exists in the form of complexed anions CuL2-, increased with increasing equilibrium pH (pHeq), but reached a plateau at pHeq>4 for the system without HCHO and at pHeq>4.5 for the system with 1 vol.% HCHO. The D values increased with increasing HCHO concentration, likely due to the reduction of Cu(II) to Cu(I) by HCHO in solution. A semi-empirical two-parameter model was proposed to describe the extraction equilibrium, in which the non-ideality in organic phases was considered. The thermodynamic parameters were also evaluated and discussed.
Lin
Su-Hsia
SH
Department of Chemical Engineering, Nanya Institute of Technology, Chung-Li 320, Taiwan, ROC.
Kao
Hsiang-Chien
HC
Su
Hsiu-Ning
HN
Juang
Ruey-Shin
RS
D002614:Chelating Agents / Q000737:chemistry; D003300:Copper / Q000737:chemistry* / Q000302:isolation & purification*; D004492:Edetic Acid / Q000737:chemistry; D004581:Electronics; D005557:Formaldehyde / Q000737:chemistry*; D011210:Power Plants; D012997:Solvents; D013816:Thermodynamics; D018508:Water Purification / Q000379:methods*
D002614:Chelating Agents; D012997:Solvents; D005557:Formaldehyde; D003300:Copper; D004492:Edetic Acid