US EPA

1577491 

Journal Article 

Separation of Cr(VI) with Aliquat 336: Chemical equilibrium modeling 

Alonso, AI; Galan, B; Irabien, A; Ortiz, I 

1997 

1 

Separation Science and Technology
ISSN: 0149-6395
EISSN: 1520-5754 

32 

9 

1543-1555 

WOS:A1997XB44000005 

The separation of chromium(VI) from industrial wastewaters
is of great interest mostly due to the high toxicity of this metal. Although the extraction of
Cr(VI) with anionic extractants (and among them, quaternary ammonium salts) has been widely
studied using different technologies, a suitable equilibrium model it has not been reported due
to the complex behavior of the organic phase. In this work a general methodology for modeling of
the chemical equilibrium of Cr(VI) is presented, Discrimination between mathematical models that
take account of the nonideal behavior of the organic phase led to the selection of a one-
parameter empirical function of the total extractant concentration, K = K(c)c(0)(n). The
parameter values estimated for this model are the equilibrium constant (Kp = 0.197) and the
fitting parameter (n = 0.661), and they are used in the expression for the description of the
extraction equilibrium: 0.197 = [Cl-](2)[(AQ)(2)CrO4]/[CrO42-][(AQ)Cl](2)c(0)(0.66) This equation
can satisfactorily describe the experimental behavior of chromium(VI) extraction with Aliquat 336
and thus provides a useful expression that could be introduced into mathematical models directed
toward the design and optimization of the separation process.