SEPARATION OF CR(VI) WITH ALIQUAT-336 - CHEMICAL-EQUILIBRIUM MODELING

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, quatern ary ammonium salts) has been widely studied using different technologi es, a suitable equilibrium model it has not been reported due to the c omplex behavior of the organic phase. In this work a general methodolo gy for modeling of the chemical equilibrium of Cr(VI) is presented, Di scrimination between mathematical models that take account of the noni deal behavior of the organic phase led to the selection of a one-param eter empirical function of the total extractant concentration, K = K(c )c(0)(n). The parameter values estimated for this model are the equili brium 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)(0.6 6) This equation can satisfactorily describe the experimental behavior of chromium(VI) extraction with Aliquat 336 and thus provides a usefu l expression that could be introduced into mathematical models directe d toward the design and optimization of the separation process.