MODELING OF SOLVENT EXTRACTION OF COPPER FROM SULPHATE SOLUTIONS WITH D2EHPA

Transcription

1 MODELING OF SOLVENT EXTRACTION OF COPPER FROM SULPHATE SOLUTIONS WITH DEHPA Clenilson Sousa Junior (IFRJ/EQ-UFRJ) Marisa Nascimento (CETEM) Lídia Yokoyama (EQ-UFRJ) Osvaldo Galvão da Cunha (EQ-UFRJ)

2 SUMMARY 1. INTRODUCTION. THEORETICAL 3. EXPERIMENTAL 4. RESULTS 4.1. Equilibrium constant and metal complex determination 4.. Thermodynamic model 5. CONCLUSIONS

3 1. INTRODUCTION Solvent extraction is an important economical, practical and clean hydrometallurgical process and the technique is one of the most versatile methods used for the removal, separation and concentration of metallic species from aqueous media. In the hydrometallurgy, the organic extractant Di-(-ethylhexyl) phosphoric acid (DEHPA or HA) has been used successfully to extract many divalent metal ions in sulfate media, in the extraction of Cu +, Co + and Ni +, particularly, at equilibrium by DEHPA has been reported. Shibata et al., 198; Owusu, 1998; Gajda et al., 007.

4 1. INTRODUCTION Thermodynamic and kinetics parameters were investigated by Haghshenas Fatmehsari et al. (009), Simonin et al. (003), Zhang et al. (001) and Darvishi et al. (005), that determined parameters such as rate constant, ph, distribution coefficients, equilibrium constant and composition of extracted species in different conditions. In the specific case of this work, the objective was to obtain a thermodynamic model for extraction of Cu(II) in sulfuric acid media by DEHPA in Isoparaffin (17/1).

5 1. INTRODUCTION Table 1: Chemical reaction equilibrium mass and charge balance equations for copper species. Reaction Equilibrium constant H O = H + + OH - K 1 = 1.00 x H + + SO4 - = HSO - 4 K = 9.85 x 10 1 Cu + + SO - 4 = CuSO 4(aq) K 3 = 51. Cu + + HSO 4- = CuHSO 4 + K 4 = 9.1 Cu + + OH - = CuOH + K 5 = 5.01 x 10 7 Cu + + OH - = Cu(OH) K 6 = 1.58 x Equilibrium mass [Cu] i =[Cu + ]+[CuSO 4 ]+[CuHSO 4+ ]+[CuOH + ]+[Cu(OH) ]+(V org /V aq ) [CuH x A +x ] Charge balance [H + ] +[CuHSO 4+ ]+ [CuOH + ] + [Cu + ] = [OH - ] + [HSO 4- ] + [SO - 4 ]

6 . THEORETICAL On account of the dimerization of acid phosphoorganic extractants, it is adopted in scientific reports that in the formation of complexes with Cu + ions. The reaction of extraction with DEHPA can be written as : Cu ( aq) ( 1 x) HA( or) CuH xa x( or) H( aq) The model used the logarithm of activity coefficient of ( i) for a single ion is described and presents validity similar to the model of Pitzer, though with a much simpler mathematical formulation. The Equation is a modification of the Davies s equation. ln i 1 Az i (3x10 10 I ) B I (( 4,17x10 15 ) I ,) Az i I Fu and Golding, 1987; Biswas et al, 000; Swain, et al., 006; Samson et al., 1999.

7 . THEORETICAL For to represent the equilibrium constant for the reaction of extraction (K eq ), we used this equation: D [ CuH x [ Cu A ] x ] ( aq, t) ( or, t) Keq [ CuH [ Cu x A ].[ H x ].[ H (1 A ] ] x) x CuH Cu x A. x H (1 x) H A. LogD CuH x A x H ph (1 x)log[ HA ] log Keq log (1 x). Cu HA. [ H A ] [ HA ] inicial (1 x)[ CuH x A x ] LogD ph (1 x)log{[ H A ] inicial (1 x)[ CuH x A x ]} log K eq

8 3. EXPERIMENTAL M; 0.015M e 0.03M CuSO 4.5H O ph =.5; 3.5 e ml 5 min. 0.05M; 0.10M e 0.0M DEHPA in isoparaffin 5.00 ml 40 min. Org. Aq. ph Reexctracion Atomic Abs.

9 4. Results 4.1. Equilibrium constant and metal complex determination The Quasi-Newton method of non-linear regression estimation was applied and the results of the copper extraction and x (1.31) and K eq (.10x10-1 ) were found, with a correlation coefficient R equal to As a result, the reaction of Cu extraction by DEHPA can finally be represented as: Cu ( aq).h A CuH ( ).4 A H or 4.4( or) ( aq)

10 4. Results 4.. Thermodynamic model For the model the number of solutes in the aqueous phase before extraction, is ten (Cu +, CuSO 4, CuHSO 4+, Cu(OH) +, Cu(OH), H +, OH -, SO - 4, HSO 4- and H O). First, we considered the activity of water equal to 1 as an approximation. Second, the activity of hydrogen was obtained from the initial ph value. The activity of the eight remaining solutes was calculated by solving the six chemical equilibria, one mass balance and one balance of charges.

11 4. Results

12 Percentagem of copper species Percentagem of sulfate species 4. Results CuHSO4(+) HSO4(-) SO4(-) Cu(+) CuSO CuSO CuHSO4(+) 10 CuOH(+) Cu(OH) ,5 1 1,5,5 3 3,5 4 4,5 5 ph 0 0 0,5 1 1,5,5 3 3,5 4 4,5 5 ph Figure 1. Copper metal species. Figure. Sulphate species.

13 4. Results The chemical species after extraction with DEHPA are twelve Cu +, CuSO 4, CuOH +, Cu(OH), H +, OH-, SO 4 -, HSO 4-, H O, H A, Cu.4 A 4.4 and diluent.

14 Log D calc ph calc. 4. Results -0,50-0,70 y = 1,0837x + 0,0761 R² = 0,9855 1,80 1,70 1,60 1,50 y = 1,0617x - 0,0678 R² = 0,9611-0,90 1,40 1,30-1,10 1,0 1,10-1,30-1,30-1,10-0,90-0,70-0,50 Log D exp. Figure 3. Log D calc x Log Dexp. 1,00 1,00 1,0 1,40 1,60 1,80 ph exp. Figure 4. ph calc x ph exp.

15 5. Conclusions The studies show that the copper aqueous species extracted was CuH.4 A 4.4, and the equilibrium constant for the reaction of extraction, obtained by nonlinear regression of experimental data, was.5x10-1. The thermodynamic data calculated by the Cu + proposed model had a satisfactory fit when compared to those obtained experimentally.

16 Acknowledgements Thank You! Obrigado! Muchas Gracias! or