Adsorb And Recovery Of Gold And Palladium In Secondary Resource By Persimmon Powder-Formaldehyde Gel

Using green persimmon powder as raw material, the persimmon powder-formaldehyde gel was prepared through formaldehyde(37%) cross-linking reaction and then was analysed. As a novel adsorbent, its ability of removing or recovering Au(III) and Pd(Ⅱ) from aqueous solutions was studied. The pH, initial ion concentration, initial persimmon powder-formaldehyde gel concentration, adsorption isotherms and adsorption kinetics of Au(Ⅲ) and Pd(Ⅱ) on the persimmon powder-formaldehyde gel was investigated. In addition, the adsorption selectivity of the gel to Au(Ⅲ) and Pd(Ⅱ) in the mixture solutions of metal ions and the actual industry solution was also investigated. Finaly, taken the adsorption of Au(Ⅲ) for example, the conceivable mechanism of persimmon powder-formaldehyde gel to precious metals was educed through analysing the research data and results above.The main results are as follows:1. The adsorption capacity of the persimmon powder-formaldehyde gel to Au(III) and Pd(Ⅱ) were 1033.33mg/g and 111.49mg/g respectively when initial concentration were 310mg/L and 40mg/L, pH were 2.0 and 5.0 at 50℃.2. The adsorption capacity of the persimmon powder-formaldehyde gel to Au(Ⅲ) and Pd(Ⅱ) decreased and increased respectively with the raise of pH. In addition, with the raise of temperature, the adsorption capacity of the persimmon powder-formaldehyde gel to Au(Ⅲ) and Pd(Ⅱ) were both increased. These results mean the pH and temperature played an important role on adsorption capacity.3. The adsorption equilibrium data was analyzed by the Langmuir and the Freundlich equations further, from which we found that the adsorption of both Au(III) and Pd(Ⅱ) could be described by the Langmuir equation. This indicated the adsorption mechanism of Au(Ⅲ) and Pd(Ⅱ) might be the same. The adsorption kinetics investigation of Au(Ⅲ) and Pd(Ⅱ) revealed that, the adsorption kinetics could be well described by the pseudo-second-order rate model, by which the adsorption capacity calculated inosculated with those determined by actual measurements.4. Au(Ⅲ) and Pd(Ⅱ) could be selectively adsorbed by persimmon powder -formaldehyde gel in mixture solution and actual industry solution, especially for Au(Ⅲ). The adsorption rate to Au(Ⅲ) was far above to Cu(Ⅱ), Fe(Ⅲ), Zn(Ⅱ), which practically reached 100% in the mixture solutions of Au(Ⅲ), Pd(Ⅱ), Cu(Ⅱ), Fe(Ⅲ), Zn(Ⅱ) and actual industry solution. This meaned Cu(Ⅱ), Fe(Ⅲ), Zn(Ⅱ) almost had no effect on adsorption rate and the adsorption selectivity to Au(Ⅲ)was distinct. Meanwhile, the adsorption rate of persimmon powder-formaldehyde gel to Pd(Ⅱ) increased with decline of other ions concentration. In addition, the adsorption capacity of the persimmon powder-formaldehyde gel to Au(Ⅲ) and Pd(Ⅱ) was different when the pH of the solution different. So persimmon powder-formaldehyde gel could be used in selective adsorption of Au(Ⅲ)Pd(Ⅱ) and reached the motive of separation, purification and enrichment of the precious metals through controlled the ions concentration and the pH of the solution, which had great value of practical application.5. The adsorption mechanism research indicated that a redox reaction happened in the adsorption process of Au(Ⅲ) on the persimmon powder-formaldehyde gel. That meaned Au(Ⅲ) was reduced into Au(0) firstly by persimmon tannin, and then Au(0) was adsorbed by the persimmon powder-formaldehyde gel.These results showed that the adsorption capacity of the persimmon powder-formaldehyde gel to Au(Ⅲ) and Pd(Ⅱ) were very high when initial pH were 2.0 and 5.0 respectively. With the raise of temperature, the adsorption capacity to Au(Ⅲ) and Pd(Ⅱ) were increased and could reach 1033.33mg/g and 111.49mg/g respectively. Au(Ⅲ) and Pd(Ⅱ) could be selectively adsorbed by persimmon powder -formaldehyde gel and Au(Ⅲ) was reduced into Au(0).That meaned the persimmon powder-formaldehyde gel had more great value of practical application.