Stoichiometry of Cu(II) Ion Extraction with di-2-ethylhexylphosphoric acid Dissolved in Waste Palm Cooking Oil

Abstract

This study was aimed to determine the reaction stoichiometry between Cu(II) and di-2-ethylhexylphosphoric acid (D2EHPA) in Waste Palm Cooking Oil (WPCO). The stoichiometry was computed based on the following experimental methods, namely slope analysis, loading test and Job's method. Slope analysis was used to measure the variation of the distribution coefficient to the concentration of Cu(II) ions and D2EHPA. Besides that, the loading test and Job's method are used to determine and confirm the complexation reaction between D2EHPA and Cu(II) ions. It was found that, the reaction stoichiometry for the Cu(II) to D2EHPA was 1:2 in Cu(II) organic complexes. Therefore, the chemical equation can be determined and it will be a useful information in the reaction mechanism of Cu(II) with D2EHPA in WPCO.

Extraction of Cu(II) From Acidic Sulfate Media by Palm Kernel Fatty Acid Distillate: Stoichiometry and Thermodynamic Studies

“…The stoichiometry provides the precise number of moles of each substance required to form one mole of metal-extractant complexes under favorable thermodynamic conditions, while the thermodynamics explains the extraction behavior of a metal ion by the extractant (Choppin and Morgenstern, 2000;Wahab et al, 2016). The stoichiometry of various metal-extractant complexes in different diluents have been reported, for instance, 1:4 and 1:2 for Cu(II)-di-2-ethylhexylphosphoric acid (D2EHPA) complexes in soybean oil (Chang et al, 2011) and waste palm cooking oil (Wahab et al, 2016), respectively; 1:2 for Cu(II)-2-hydroxy-5-nonylacetophenone oxime (active component of LIX 84) complexes in toluene (Elizalde et al, 2019); 1:6 for Nd(III)-D2EHPA complexes in sulfonated kerosene (Yin et al, 2015); 1:3 for Ga(III)-hexaacetato calix(6)arene in xylene (Thakare and Malkhede, 2014); and 1:2 for hydrated Ni(II)-dinonylnaphthalene disulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester complexes in sulfonated kerosene (Hu et al, 2018). The majority of these works used either the equilibrium slope or numerical analysis, or both, to determine the stoichiometry of metal-extractant complexes (Chang et al, 2011;Elizalde et al, 2019;Thakare and Malkhede, 2014;Wahab et al, 2016;Yin et al, 2015).…”

“…The stoichiometry of various metal-extractant complexes in different diluents have been reported, for instance, 1:4 and 1:2 for Cu(II)-di-2-ethylhexylphosphoric acid (D2EHPA) complexes in soybean oil (Chang et al, 2011) and waste palm cooking oil (Wahab et al, 2016), respectively; 1:2 for Cu(II)-2-hydroxy-5-nonylacetophenone oxime (active component of LIX 84) complexes in toluene (Elizalde et al, 2019); 1:6 for Nd(III)-D2EHPA complexes in sulfonated kerosene (Yin et al, 2015); 1:3 for Ga(III)-hexaacetato calix(6)arene in xylene (Thakare and Malkhede, 2014); and 1:2 for hydrated Ni(II)-dinonylnaphthalene disulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester complexes in sulfonated kerosene (Hu et al, 2018). The majority of these works used either the equilibrium slope or numerical analysis, or both, to determine the stoichiometry of metal-extractant complexes (Chang et al, 2011;Elizalde et al, 2019;Thakare and Malkhede, 2014;Wahab et al, 2016;Yin et al, 2015). Other methods like the Job plot (Wahab et al, 2016) and quantitative analysis with FTIR (Chang et al, 2011) (Aidi and Barkat, 2018) and Cu(II)-N-(2 hydroxybenzylidene) aniline (Aidi and Barkat, 2010) complexes, respectively, in cyclohexane; ∆H o of 25.65 kJ•mol -1 , ∆S o of 0.079 kJ•mol -1 •K -1 , and ∆G o of 0.86 kJ•mol -1 for Zn(II)-D2EHPA complexes in kerosene (Jafari et al, 2018); and ∆H o of 17.32 kJ•mol -1 , ∆S o of 0.041 kJ•mol -1 •K -1 , and ∆G o of 5.09 kJ•mol -1 for vanadium(V)-D2EHPA complexes in kerosene (Razavi et al, 2018).…”

“…The majority of these works used either the equilibrium slope or numerical analysis, or both, to determine the stoichiometry of metal-extractant complexes (Chang et al, 2011;Elizalde et al, 2019;Thakare and Malkhede, 2014;Wahab et al, 2016;Yin et al, 2015). Other methods like the Job plot (Wahab et al, 2016) and quantitative analysis with FTIR (Chang et al, 2011) (Aidi and Barkat, 2018) and Cu(II)-N-(2 hydroxybenzylidene) aniline (Aidi and Barkat, 2010) complexes, respectively, in cyclohexane; ∆H o of 25.65 kJ•mol -1 , ∆S o of 0.079 kJ•mol -1 •K -1 , and ∆G o of 0.86 kJ•mol -1 for Zn(II)-D2EHPA complexes in kerosene (Jafari et al, 2018); and ∆H o of 17.32 kJ•mol -1 , ∆S o of 0.041 kJ•mol -1 •K -1 , and ∆G o of 5.09 kJ•mol -1 for vanadium(V)-D2EHPA complexes in kerosene (Razavi et al, 2018).…”