M.A. Habib

Kinetics of backward extraction of Mn(II) from Mn-D2EHP complex in kerosene to hydrochloric acid medium using single drop technique

Abstract The extraction equilibrium constant, K ex for the extraction of Mn(II) from hydrochloric acid medium by di-2-ethylhexylphosphoric acid (D2EHPA or H 2 A 2 ) in kerosene (mostly aliphatic) has been determined to be 10 −2.16 . The rate of backward extraction of Mn(II) from Mn-D2EHP complex dissolved in kerosene by hydrochloric acid has been measured by the single rising drop technique and it is found that the flux equation at 30 ± 1°C is: J (kmol/m 2 s) = 10 −4.08 [Mn-D2EHP] (o) (1 + 0.011[H + ] −1 ) −1 (1 + [H 2 A 2 ] (o) 0.5 ) −1 . Analysis of this rate equation suggests that the process is almost chemically controlled at lower aqueous acidity and higher free D2EHPA concentration regions; whereas it is almost diffusion controlled at higher aqueous acidity and lower free D2EHPA concentration regions. In the investigated D2EHPA concentration (0.04-0.50 kmol/m 3 ) and aqueous acidity (pH = 1.0–3.0) regions, the process is intermediate controlled. The activation energy depends on the back-extraction parameters and is of the order of ∼ 20–∼ 40 kJ/mol. This low value of activation energy supports the conclusion that the process is intermediate controlled. Temperature dependence data give ΔH ± and ΔS ± values of 20–40 kJ/mol and (−180)–(−250) J/K mol, respectively. The high negative value of ΔS ± suggests that the chemical controlling step occurs via S N 2 mechanism.

Recovery of manganese and zinc from waste Zn-C cell powder: Mutual separation of Mn(II) and Zn(II) from leach liquor by solvent extraction technique.

Acidic organophosphorous extractants were screened for the mutual separation of Mn(II) and Zn(II), in a leach solution of waste Zn-C cell powder. This was done using a 2mol/L H2SO4 solution containing 2g/L glucose. Extraction characteristics of both metal ions in this mixture have been examined as functions of equilibrium pH. Although tech. and anal. grade D2EHPA are not so effective for the separation, PC88A, Cyanex 272, Cyanex 302 and Cyanex 301 are all promising for this purpose. Strippings of Mn(II) and Zn(II) from the extracted organic phases have been examined, using 0.25, 0.50 and 1mol/L H2SO4; and 1mol/L HCl, HNO3 and HClO4 at different phase ratios. H2SO4 appears to be the best stripping agent. A 1mol/L H2SO4 solution strips almost 100% of target metal ions in 10min, regardless of the extractant used. As ΔpH1/2=2.75 and as the max. separation factor (β)=1793 for Cyanex 302 at pH(eq)=4.0, a flow sheet has been developed for their mutual separations. Finally, classical precipitation methods have been adopted to obtain MnS and ZnS, which can be easily oxidized to MnO2 and ZnO, respectively.

Kinetics of Solvent Extraction of Iron(III) from Sulfate Medium by Purified Cyanex 272 using a Lewis Cell

Abstract The kinetics of the forward and backward extraction of the title process have been investigated using a Lewis cell operated at 3 Hz and flux or (F) – method of data treatment. The dependences of (F) in the forward extraction on [Fe3+], [H2A2](o), pH, and [HSO4 −] are 1, 0.5, 1, and −1, respectively. The value of the forward extraction rate constant (k f ) has been estimated to be 10−7.37 kmol3/2 m−7/2 s−1. The analysis of the experimentally found flux equation gives the following simple equation: F f =100.13 [FeHSO4 2+] [A−], on considering the monomeric model of BTMPPA and the stability constants of Fe(III)‐HSO4 − complexes. This indicates the following elementary reaction occurring in the aqueous film of the interface as rate determining: [FeHSO4]2++A−→[FeHSO4.A]+. The very high activation energy of 91 kJ mol−1 supports this chemical reaction step as rate-determining. The negative value of the entropy change of activation (−94 J mol−1 K−1) indicates that the slow chemical reaction step occurs via the SN2 mechanism. The backward extraction rate can be expressed by the equation: F b =10−5.13 [[FeHSO4A2]](o) [H+] [H2A2](o) −0.5. An analysis of this equation leads to the following chemical reaction step as rate-determining: [FeHSO4A2](int)→[FeHSO4A]+A(i) −. However, the activation energy of 24 kJ mol−1 suggests that the backward extraction process is intermediate controlled with greater contribution of the diffusion of one or the other species as a slow process. The equilibrium constant obtained from the rate study matches well with that obtained from the equilibrium study.

Processing of ilmenite through salt-water vapour roasting and leaching

Abstract The ilmenite fraction of beach sand has been processed through salt (NaCl, NaNO3 and Na2SO4)-water vapour roasting, followed by hydrochloric acid leaching. The optimum conditions for roasting are: 800°C (885°C for Na2SO4): 90 min (75 min for NaCl); ilmenite to salt (wt) ratio 1.70 for NaNO3, 2.00 for Na2SO4 and 0.67 for NaCl; N2 flow rate 84 ml/cm2 min; and water vapour pressure 0.0042 bar. For the optimum leaching of ore, with a solid to liquid phase ratio ( S L ) of 0.02 kg/l, a HCl concentration of 6 M (2 M for Na2SO4), a temperature of ∼ 110°C, and a pulp agitation speed of ∼ 350 min−1 are required. Under the above conditions 72.5%, 44.50% and 86.5% titanium and 96.0%, 55.9% and 71.0% iron are dissolved from ilmenite for NaCl, Na2SO4 and NaNO3 systems, respectively.