Selective Separation Of Molybdenum And Rhenium By Using Chemically Modified Persimmon Tannin

In this thesis, the persimmon tannin which in the skin of persimmon was beprepared as the raw material, and used different amines and a direct and effectivemethod to modified it, finally eight varies kinds of biomass adsorbents were prepared,and then to investigate the adsorption of molybdenum and rhenium, including theadsorption mechanisms、the adsorption properties of thermodynamics and kinetics,the resulting conclusions are as follows:The persimmon tannin was modified and gained NH2-CPT, en-CPT, MA-CPT,all these types of adsorbents for Mo (VI) have showed high adsorption selectivity,especially for NH2-CPT showed that the rate of adsorption of Mo(VI) has reached76.38%at pH=1, but the rate of adsorption of Re(VII) is0, and the other mental ionssuch as Cu(II)、Fe(III)、Zn(II)、Mn(VII) didn’t show the adsorption. So the NH2-CPTcan be used to separate Mo(VI) and Re(VII), the actual experiments in simulatedliquid also found NH2-CPT can be recycled Mo (VII) from the waste solution. The IRspectra of the NH2-CPT gel was taken before and after Mo(VI) adsorption in strongacid medium (1mol/L) and weak acid medium (pH=1), respectively. which indicates–NH2groups especially play a major role in biosorption process. Hence, adsorptionmechanism of Mo(VI)(Mo8O264, MoO42, HMoO4, etc.) onto the gel in weak acidmedium could be expressed by the ion exchange. comparing the spectra of NH2-CPTgel before and after Mo(VI) adsorption in strong acid medium (1mol/L), indicates theformation of N-O bonding in the Mo(VI) loading NH2-CPT gel. Hence, adsorptionmechanism of Mo(VI)(H2MoO4, etc.) onto the gel in strong acid medium could beexpressed by the complexation reactions. The adsorption process fitted Langmuirisotherm model. Additionally, it was the endothermic adsorption process followedpseudo-second order kinetics.The persimmon tannin was modified by DEA, DNBA, DNOA, DIOA, andgained DEA-CPT, DNBA-CPT, DNOA-CPT, DIOA-CPT), all these types ofadsorbents for Mo (VI) have showed high adsorption selectivity than Re(VII), forDEA-CPT showed that the rate of adsorption of Mo(VI) has reached100%at pH=1, but the rate of adsorption of Re(VII) is39.5%, it can separate Mo(VI) and Re(VII),but not the best one. Adsorption mechanism of Mo(VI)(Mo8O264, MoO42, HMoO4,etc.) onto the gel in weak acid medium could be expressed by the ion exchange,because there is not H on the N, so the absorbing capacity is more lower. Theadsorption process fitted Langmuir isotherm model. Additionally, it was theendothermic adsorption process followed pseudo-second order kinetics.The persimmon tannin was modified by TEA, and gained TEA-CPT, TEA-CPTshowed that the rate of adsorption of Mo(VI) has reached97.94%at pH=1, but therate of adsorption of Re(VII) is0. Adsorption mechanism of Mo(VI) and Re(VII)onto the gel in strong acid medium could be expressed by ion exchange and thecomplexation reactions. The adsorption process fitted Langmuir isotherm model.Additionally, it was the endothermic adsorption process followed pseudo-secondorder kinetics, and in the dynamic test proved that DEA-CPT can recycle Mo(VI)from waste liquidmore, and to elute it with the1.0%of ammonium hydroxide, therecovery is more than90%, it can make the resources be reused.