Synthesis And Extraction Palladium Properties And Mechanism Of New Palladium Extractants

This dissertation provides a new method for solvent extraction and separation of palladium with new heterocyclic compounds as extraction agents. In addition, the extraction and stripping mechanism is also studied, which enrich and develop the theory of extraction chemistry.Seven kinds of new thiadiazole extractants 2-(heptylthio)-5-methyl-1,3,4-thiad-iazole(HPTMT),2-methyl-5-(octylthio)-1,3,4-thiadiazole(MOTT),2-(hexylsulfinyl)--5-methyl-1,3,4-thiadiazolesulfide(HSMT),2-methyl-5-(octylsulfmyl)-1,3,4-thiadiazo-le(MOST),2,5-bis(hexylsulfinyl)-1,3,4-thiadiazole(BHXST),2,5-bis(heptylsulfinyl)--1,3,4-thiadiazole(BHPST),2,5-bis(octylsulfinyl)-1,3,4-thiadiazole(BOST), Methylbu-tylbenzoxazole(MBBX) and a new benzoxazole extractant, were synthesized and their structures were characterized.Four new systems of solution extraction of Pd(II) were established with thiadiazole and benzoxazole heterocyclic compounds as extractants. Various parameters such as the type of diluent, extractant concentration, hydrochloric acid concentration, phase ratio, extraction time, saturation capacity, stripping condition, modifier content, reusability etc., were investigated.Comparing with three kinds of thiadiazole,2-(hexylthio)-5-methyl-1,3,4-thiad-iazole(HXTMT),2,5-bis(hexylthio)-1,3,4-thiadiazole(BHXTT),2-(hexylsulfiny-l)-5--methyl-1,3,4-thiadiazolesulfide(HSMT), all the thiadiazole compounds with different structures show excellent extraction capability on Pd(II) in the medium of hydrochloric acid of 0.1 mol/L. The contact times for all of them are 10 minutes, phase ratios are 1.0 and extraction rates are more than 98.0%. Acidic thiourea is the effective stripping agent and stripping rates are over 96.0%. The separation coefficient of Pd(Ⅱ) and Pt(Ⅳ)、Fe3+, Cu2+、Ni2+ and Rh(Ⅲ) reached 103, respectively. Pd(II) can be separated efficiently by thiadiazole extractants from leaching solution of automotive waste catalyst.The result showed that extraction rate of Pd(Ⅱ) is with over 99.0% with MBBX as extractants in the medium of hydrochloric acid of 0.1 mol/L. However, stripping of Pd(II) from organic phase is difficult.The mechanism of extracting palladium(Ⅱ) with thiadiazole or benzoxazole extractant was determined to be coordination replacing by ultraviolet visible spectrum, infrared absorption spectrum and slope method. The X-ray crystal structures of the MBBX-Pd(II) and thiourea-Pd(II), which were not reported previously were obtained. The mechanism of extraction and stripping of Pd(II) was explained from the level of molecule structure. The crystal structure showed that the whole complex of PdCl2(MBBX)2 was in completely symmetric plane square structure with palladium atom as the symmetric center, in which MBBX coordinated with palladium(II) via the benzoxazole N atom. The molar ratio of Pd(II) to MBBX was 1:2.