Dispersion-free solvent extraction of Cr(VI) from acidic solutions using hollow fiber contactor

Environ Sci Technol. 2009 Oct 15;43(20):7718-22. doi: 10.1021/es9012273.

Abstract

The use of dispersión-free solvent extraction, through microporous hydrophobic membrane has been investigated. The hollow fiber contactor, with surface area of 1.4 m2 was used to extract Cr(VI) (0.005-0.12 g/L from aqueous sulphuric acidic media (pH 2.5-4.2 +/- 0.05). Several parameters such as extractant concentration, feed acidity and metal concentration in the initial aqueous solution were investigated. Results revealed that 15% v/v Cyanex 923 in Exxsol D-100 as organic phase and feed in the 2.5 pH range, gave optimum extraction (exceeding 95%) of Cr(VI) and it was possible to strip using 10 g/L hydrazine sulfate (also with recoveries exceeding 95%). In this step, Cr(VI) is immediately reduced to the less hazardous Cr(III) state. Results also showed that under the various experimental conditions, chromium(VI) extraction was rate-controlled by the interfacial reaction on the membrane surface. Typical overall mass transfer coefficients values are 4.2 x 10(-5) and 3.6 x 10(-6) cm/s for extraction and stripping operations, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chemical Fractionation / methods
  • Chromium / isolation & purification*
  • Hydrazines / chemistry
  • Hydrogen-Ion Concentration
  • Osmolar Concentration
  • Oxidation-Reduction

Substances

  • Hydrazines
  • Chromium
  • chromium hexavalent ion
  • hydrazine