ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Extraction equilibrium of chromium(III) from sulphate medium by Cyanex 272 dissolved in kerosene

Aneek Krishna Karmakar, Ranjit Kumar Biswas, and Most. Naima Khatun

Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Rajshahi, Bangladesh

E-mail: aneek007@gmail.com

Received: 8 October 2020  Accepted: 24 February 2021

Abstract:

The solvent extraction of Cr(III) from SO₄²⁻ medium by Cyanex 272 (bis 2,4,4-trimethyl pentyl phosphinic acid) dissolved in kerosene has been studied as a function of equilibration time, pH, [Cr(III)], [Cyanex 272], [SO₄²⁻] and temperature. Over 55% extraction occurs with the favourable parameters used. Experimental study of the pH variation shows that the hydrolysis of the extractant to a certain extent occurs during the phase contact period. One dimeric molecule of Cyanex 272 is required for each Cr(III) to form the extractable species. The co-existing anion (sulphate ion) suggests the formation of Cr(H₂O)₃SO₄OH or Cr₂(H₂O)₄(OH)₂(SO₄)₂ in the aqueous phase. The positive ΔH value (~ 12.73 kJ/mol) indicates that the system under investigation is endothermic. The measured loading capacity is 4.40 g Cr(III)/100 g of Cyanex 272. The stripping is difficult, and after two stages, only 8.13% of Cr(III) is stripped by 3 mol/L H₂SO₄. Selectivity of Fe(III)/Cr(III) separation by Cyanex 272 is high.

Keywords: Cr(III); Cyanex 272; Equilibrium; Sulphate medium; Extraction; Kerosene

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01575-1

Chemical Papers 75 (8) 3739–3749 (2021)