Synthesis, Characterization Of Novel Extractants And Studies On Their Extraction Performance Of Heavy Metals

Platinum group metals(PGMs) and rare earth metals are rare and precious metals. Recovery of these metals from secondary resources is significant on sustainable development and recycling economic. Solvent extraction technique has been widely used in the separation and recovery of metals from scrap due to its strong extraction and separation ability. The studies of this technique focus on the selection of novel extractants, research of extraction performance of metals, mastery of extraction mechanism of platinum metals and development of high efficient extraction technique are emphases for the application of solvent extraction technique in the field of recovering and separation metals from scrap. Two kinds of high efficiency extractants, di-sulfoxide and containing thiazolyl substituent extractants, namely bis(noctyl-Sulfinyl-ethyl)ether(L1), bis(isooctyl-Sulfinyl-ethyl)-ether(L2), bis(isooctyl-Sulfinyl-ethoxy)-ethane(L3), N-benzothiazole-butyl-imide (BBI),1-phenyl-3-methyl-4-benzoyl-pyrazolone-5-2-benzothiazole(PMBP-2-ABT) were synthesized successfully. The main contents of this thesis are as follows.L2, L3 was used in the extraction of palladium(Ⅱ) from hydrochloric acid media. The effects of extractant concentration, HCl concentration, temperature, H+ and Cl-concentration on the percentage extraction of Pd(Ⅱ) with L2, L3 had been studied. The percentage extraction of Pd(Ⅱ) increased with increasing [HCl] of aqueous solution when [HC1] was in the range of 0.1～1.0 mol·L-1, while it kept unchange when [HC1] was over 3.0mol·L-1. A "concave valley" extraction curve of Pd(Ⅱ) appeared at where HC1 concentration was within 1.0～3.0mol·L-1. The percentage extraction of Pd(Ⅱ) decreased dramatically with the increase of [Cl-] in 0.1 mol·L-1HCl media. Pd(Ⅱ) was recovered using ammonium chloride-ammonia solution as the stripping agent. L2, L3 has excellent extraction ability to Pd(Ⅱ). The percentage extraction of Pd(Ⅱ) achieved 95.0%,85.0% from 0.1 mol·L-1 HC1 with 0.5 mol·L-1 L2, L3 as extractants respectively. The loading capacity of L2, L3 was over 9.600,9.000 g·L-1 under the experimental conditions respectivly, which was higher than that of 1,6-di(2-ethylhexylsulfinyl)hexane(DEHSOH), 1,6-di(3- methylbutyl-sulfinyl)hexane(DMBSOH) (6.590,7.577g·L-1), The result indicated that ether oxygen group in the central position of the molecule structure could promote the soluble ability of the extracted complex in organic phase and resisted the formation of a third phase because of its active performance and its ability to overcome the steric hindrance to coordinate to the metal ions, which led to a high loading capacity.L2 also has excellent extraction ability to Pt(Ⅳ) in high acidity. The percentage extraction of platinum(Ⅳ) is above 99.0% with 0.5 mol·L-1 L2 in 4.0 mol·L-1 HCl. Furthermore, Pd(Ⅱ) and Pt(Ⅳ) could be extracted and separated by L2 with high efficiency. In the coextraction of Pd(Ⅱ) and Pt(Ⅳ), the separation coefficient is 35.64 in 4.0 mol·L-1 HCl feed, and in extraction of Pd(Ⅱ) from Pt(Ⅳ) the separation coefficient is 1.70×104 in 1.0 mol·L-1 HCl feed. The IR spectrum of L2-Pd(Ⅱ) extraction complex indicated that it was coordination substitution mechanism by bonding O atom at low acidity and ion association extraction at high acidity. The IR spectrum of L2- Pt(Ⅳ) extraction complex indicated that it was ion association extraction at high acidity.BBI has been applied to extraction separation of PGMs from secondary resource. The effects of contact time, phase ratio, extractant concentration, HCl concentration on the percentage extraction of Pd(Ⅱ) with BBI had been studied. Extraction percentage of palladium is 98.5% from the solution of waste wire in 2.0 mol·L-1 HCl using 0.5 mol·L-1 BBI, and the separation coefficient between Pd(Ⅱ) and Cu(Ⅱ) is 21890. Palladium is stripped well by ammonium chloride-ammonia solution with 94.9% percentage of recovery. Thus palladium could be separated from the solution of waste wire containing copper and nickel metals successfully with high selectivity by BBI extractant. The results of IR, UV-visible spectra of BBI-Pd extraction complex indicated that extraction reaction of Pd(Ⅱ) by BBI was ion association extraction. Extractant BBI is easy to synthesized and the purity is high.BBI in chloroform has good extraction ability to Hg2+ at a range of acidity. The stoichiometry of the extracted complex had been found as Hg(BBI)2 by using spectral analysis and slope analysis method. It is possible to separate Hg2+ from heavy metals Fe3+, Cu2+, Ni2+, Zn2+, Pb2+, Cd2+ through one extraction by controling pH=8.0～9.0. The result suggests that BBI has good selectivity to Hg2+, it is a kind of specially good extractant for Hg2+1-Phenyl-3-Methyl-4-Denzoyl-Pyrazolone-5-2-Denzothiazole (PMBP-2-ABT) was used in ionic liquid aqueous two-phase. The system has high extraction efficiency to heavy metals Cu2+, Pb2+, Co2+, Ni2+, Zn2+. The extraction efficiency of heavy metals was affected seriously by pH. The pH was different for different heavy metals to attain equilibrium. Extractant PMBP-2-ABT represented excellent extraction selectivity to these heavy metals in single metal solution or mixture metals solution. The mechanism of extracting metals with PMBP-2-ABT could be determined to be bonded with the central ion by two N atoms of imine group and benzothiazole ring and two O atoms of carbonyl group of pyrazolone and H2O after forming the complex.Synergistic extraction of Lanthanide ions by PMBP-2-ABT with tributyl phosphate (TBP) from ionic liquid aqueous two-phase system had been studied. The influences of the concentrations of co-extraction agent, extractant, value of pH, the amount of K2HPO4 and temperature on the distribution ratio have been discussed. The results of the experiment show that the synergism of PMBP-2-ABT and TBP is obvious. The co-extraction agent is the idealest on the conditions that pH equals 4.3 and the concentration ratio of extractant versus co-extraction agent is 4:1. Determined by slope analysis method, the synergistic extraction compounds is [LaA-HA-TBP]2+. Half extraction pH (pH1/2) of La3+, Pr3+, Nd3+ and Gd3+ is 4.37,4.00,3.74,3.55 respectively. The system could be used to grouping Lanthanide and separating Pr3+, Nd3+.