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ABSTRACT
Owing to its chemical and pharmacological significances, the efficacy of reactive separation of protocatechuic acid (0.001–0.01 kmol m−3) from aqueous stream by means of tri-n-octylamine (TOA), di-2-ethylhexyl phosphoric acid (D2EHPA) as well as tri-n-butyl phosphate (TBP) in octanol has been investigated, in terms of extraction efficiency, loading ratio, equilibrium complexation constants, and distribution coefficients. Extraction ability was obtained in the order TOA (91.2%) > TBP (88.64%) > D2EHPA (86.43%). In all cases, 1:1 protocatechuic acid:extractant complex is obtained. Further, diffusion coefficients, number of stages for extraction systems, and relative basicity model were used for relating the efficacy.
Nomenclature
| [HPA] | = | protocatechuic acid concentration (mol L−1) |
| [H+] | = | H+ ion concentration in aqueous phase (mol L−1) |
| [PA−] | = | concentration of dissociated protocatechuic acid in aqueous phase (mol L−1) |
| Ka | = | ionization constant of protocatechuic acid (mol L−1) |
| P | = | partition coefficient |
| D | = | dimerization constant (L mol−1) |
| KD | = | distribution coefficient of acid in organic phase |
| E% | = | degree of extraction |
| [S] | = | concentration of extractant in organic phase (mol L−1) |
| KE | = | extraction equilibrium constant for (1:1) acid–extractant complex (L mol−1) |
| Z | = | loading ratio |
Subscripts
| aq | = | aqueous phase |
| org | = | organic phase |
| o | = | initial |