Preparation And Property Studies On Recyclable Ditopic Ligand Extractants Which Simultaneously Extract Cation And Anions Of Metal Salts

Metal recovery via solvent extraction in hydrometallurgical process is essentially an ion-exchange process in which the desired metal cation exchanges with protons from an extractant. However, the anions of the metal salt are not extracted and they may cause hazard to environment; large volume of organic solvents used during the solvent extraction process also causes environmental issues. Similarly, cationic ion-exchange resins used for the treatment of waste water containing heavy metal salts only absorb metal ions whereas the anionic ions still cause environmental pollution. In order to solve this problem, in this paper use two salicylaldehyde derivatives to synthesiz Salen-type Schiff base containing a secondary amine backbone. Which then graft onto the modified silica gel for preparation of new solid extractant of metal salt. The new type of extractant can simultaneously combined with the cationic and anionic of metal salts. Upon complexation of the ligand with metal ions, the phenolic hydroxyl protons transfer onto the ortho-pendant tertiary amine group,thus creating positively charged environment wherein the anions of the metal salt are bound via a combination of favourable hydrogen bonding and electrostatic interactions. The coordinating extraction efficiency and selectivity for heavy metal salt ions and the regeration and recycling property of the extractants will be investigated by changing steric and electronic structure of the coordinating ligands and pH conditions of the extracting system; the effect of coexisting ions on the coordinating absorption processes will be analysized; the thermodynamics and kinetics model for the co-operative extraction of the cation and anion will be established; the factors and mechanism which control the simultaneous bindingN co-operativityN recongnition and transport of cation and anions will be explored; the structure-function relationship will be revealed; and the theory for optimal ligand design will be further clarified. The more detailed novelty of this research call be categorized as following: (1)5-bromo-3-methylene morpholine salicylaldehyde and triethylene tetramine reaction synthesis Schiff-base, and by using the NaBH4will Schiff-base of imide group (-HC=N-) reduction into saturation secondary amine group (-H2C-NH-). Schiff-base reduction after get compound soft will improve, and metal ion coordination will have greater freedom. The compounds were characterised by NMR, IR and MS.(2) In order to grafting ditopic ligand, modify the silica gel with3-Chloropropyltrimethoxysilane and trimethylchlorosilane, and then grafted Schiff-base and reducing Schiff-base ditopic ligand onto the modified silica gel for preparation of new solid-phase extractant SD-D, SD-E.The compounds were characterised by Fourier transform-infrared spectroscopy (FTIR), elemental analysis, thermogravimetric analysis(TG) and wide-angle X-ray diffraction. The elemental analysis results suggested that the macrocycle content of the modified silica gel(SD-D,SD-E) is0.32mmol/g and0.29mmol/g of silica, strllctures. The TG results indicated that the thermal stability of the adsorbents was favorable. The decomposition temperature of the adsorbents were all about200℃.(3) Static adsorption results showed that the extraction efficiency of metal salts of cation(Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Mn2+) and anion(SO42-, NO3-,Cl-) of SD-E is better than SD-D.(4) Effects of pH value on the adsorptive properties of adsorbents suggested that extraction of sulfate quantity is reduced, and the extraction of copper ion ratio increases with the increase of ph value.(5) Thermodynamic studies showed that the Langmuir model fitted the adsorption process for Cu2+in the range of the experiment.(6) Through the study of solid extractants on copper sulfate extraction/stripping and extraction solvent regeneration experiment, suggest that both a variety of solid extractants possess well desorption and regeneration capacities. When the lmol/L H2SO4and1mol/L NH3H2O was used, the adsorbed Cu(Ⅱ) and SO42-could be completely eluted and the adsorption capacities of two adsorption materials remain approximately the same via5adsorption-desorption cycles.The above data shows different ligands of space and electron configuration of extractant have different extract efficiency and Selective for extract cation and anion of metal salts.