Green Adsorption-desorption Of Light Rare Earth Elements By Myrtan Tannins Immobilized On Collagen Fiber

The adsorption-desorption property of La³⁺,Pr³⁺ and Nd³⁺ in solution by myrtan tannin immobilized on collagen fiber (IMT) were investigated due to the contradiction of bad pollution, high cost and vast consumption in rare earth industry. The immobilized tannin is a kind of inexpensive, environmental benign and natural absorbent. Some conclusions for experiment results have been drawn as follows.The adsorption capacities of IMT to light rare earth ions(RE³⁺) were related to value of pH, temperature, concentration and molecule sort. It was found that the influence of temperature on adsorption isotherms was not obvious, whilst effect of pH value was significant. Higher pH value of solation led to higher equilibrium adsorption capacity. The highest adsorption capacity of La³⁺ occurred at pH value 4.5, whilst those of Pr³⁺ and Nd³⁺ occurred at pH 5.0. Data of adsorption rate could be well fitted by pseudo-second-order rate model, and it reached the adsorption equilibrium within 2 hours.Under the same condition, the equilibrium adsorption capicities of IMT to RE³⁺ added H2NC2O4NH2 were nearly 3-4 times higher than that of RE³⁺ was not,it was 5-6times higher than that of the last report. When the temperature was at 293 K and the initial concentration of RE³⁺ was 2.50mmol/l, the equilibrium adsorption capacities of La³⁺, Pr³⁺ and Nd³⁺ were 0.94 mmol/g (pH=4.5), 1.02 mmol/g (pH=5.0) and 1.20mmol/g (pH=5.0) respectively. The adsorption column (diameter 10 mm, height 300mm) filled with 2.0g IMT has excellect equilibrium adsorption capacity to RE³⁺ and the RE³⁺ was added with H2NC2O4NH2. The concentration of RE³⁺ in dasorption solution was nearly 15 times higher than that of the RE³⁺ initial solution. When the simulant solution of rare earth mine in which was put H2NC2O4NH2, it was used to the adsorption solution. The excellect selectivity was showed among La³⁺, Pr³⁺ and Nd³⁺. In the course of study, the solutions were collected whose relative concentrations of La³⁺, Pr³⁺ and Nd³⁺ were 96.1%, 32.4% and 90.4% respectively, but the solutions was 1/10 in whole collected desorption solutions.Base on the high selectivity of adsorption-desorption of IMT column to RE³⁺, it can be used to removing RE³⁺ in rare earth industry or from pollutied water. The paper developed a theoretical foundation, so that the novel method of gathered or separated RE³⁺ can be studied next for continuable development of rare earth industry.