Recovery of Palladium from Concentrated Nitrate Solutions with N,N 2-Dimethyl-N,N 2-Dioctyltetradecy lmalonamide as New Extractant

Abstract

The new unsymmetrical malonamide namely; N,N2-dimethyl-N,N 2-dioctyltetradecylmalonamide (DMDOT DMA) was prepared and evaluated as agent for the extraction and separation of Pd (II) from nitrate media was studied. N,N 2-dimethyl-N,N 2-dioctylmalonamide (DMDO MA) was synthesized and used for comparison purpose. The effect of various parameters had been studied in details to explain the extraction properties of pd(II) by using DMDOTDMA in mixed diluents (75 vol.% n-dodecane-25 vol.% n-octanol) from nitrate media. The extraction equilibrium of Pd(II) with the investigated maloamides was reached within 10 minutes. Pd(II) showed remarkable extractability by DMDOTDMA and the maximum extraction percentage of Pd(II) is nearly reached at ~ 5 M HNO 3 . Under similar extraction conditions Zn(II), Ni(II), Mn(II) Cu(II) and Pb(II) were found poorly extracted. The dominate extracted species of Pd(II) is Pd(NO 3 ) 2 (MA) 2 . The separation of Pd(II) from other studied metal ions was found to be effective in the range of nitric acid solution used. The stripping of Pd(II) was successfully carried out by single contact with 0.1M thiourea solution.

Palladium Extraction from Nitrate Solutions with the Disulfide of Bis(2,4,4‐trimethylpentyl)dithiophosphinic Acid

“…A similar composition of the extracted compounds during the extraction of palladium from nitric acid solutions with thiacalix [4]arenes was reported by Torgov et al [14] A comparison of the extraction ability of the disulfide of bis (trimethylpentyl)dithiophosphinic acid and the commercially available extractant, triisobutylphosphine sulfide (CYANEX 471X), showed that the disulfide is a better extractant than CYANEX 471X. Thus, when loading the disulfide with palladium, the Pd : L ratio in the extracted complex is 4 : 1, i. e. 4 moles of palladium per one molecule of the extractant, whereas for CYANEX 471X, this ratio is 1 : 2, i. e. two CYANEX 471X molecules per palladium molecule.…”

“…Another option for increasing the extraction rate of palladium with the disulfide is the introduction of catalytic additives into the organic phase. This was shown by the example of palladium extraction with n-tolyl(thiamethyl)calix [4] arene from chloride solutions in the presence of an anionexchange extractant, trioctylammonium chloride (R 3 NHCl), as the additive. [22] The use of catalytic additives in the extraction of palladium from nitric acid media with neutral sulfur-containing extractants has not been previously studied.…”

“…The data on palladium extraction from nitrate solutions with hydroxyoximes, diglycolthioamides, and malonamides have been reported. [2][3][4] Shmidt et al [5] studied the extraction of palladium from nitric acid solutions by tri-n-butyl and triisoamylphosphine oxides and showed that the extraction ability of the phosphine oxides is not very high. It was shown that diphosphine oxides, in their extraction ability, far exceed the monodentate organophosphorus extractants, such as trioctylphosphine oxide and tributyl phosphate.…”

Effect of HNO₃ Concentration on the Pd(II) Extraction Properties using a Thiodiglycolamide Compound

“…Because Pd(II) is a soft acid, extractants containing S-donor atoms tend to have high selectivity for palladium over other hard-acid ions [6]. To date, many studies of Pd(II) separation from highly acidic solutions have been conducted using quaternary amines [7], oximes [8], calixarenes [9], malonamides [10], and sulfur-containing extractants [11][12][13][14]. Among the sulfur-containing extractants, thiodiglycolamide (TDGA) extractants have exhibited both good selectivity and rapid extraction of Pd(II), and they are very durable in strongly acidic environments [15][16][17][18][19].…”