Adsorption Of Rare Earths And Heavy Metal Ions By Using Sodium Alginate Gel Resin Immobilized Poly-γ-glutamate

Rare earth elements(REEs)is the general term that includes 17 kinds of elements with similar chemical characters.The special electronic shell structure of 4f gives them unique chemical properties.It leads to more and more applications of REEs in national product.The increasing use of REEs makes rare earth mining scale expanding unceasingly.In this study,based on efficient and environmental biosorption,a novel immobilized biological adsorbent was developed by using immobilized technology.The specific research contents and results are as follows:SA-PGA,one excellent immobilized biological adsorbent,was prepared through crosslinking-embedding method.Poly-γ-glutamic(PGA)is a kind of biological macromolecular material and contains rich carboxyl groups.It had high capacity of removing heavy metal.Sodium alginate(SA)is a kind of ideal immobilized carrier due to its excellent film-forming,ball-forming ability and non-toxic to the environment.Using La3+ and Ce3+ as the main experimental subjects,the effects of ions concentration and p Hs on the adsorption were investigated.Under optimum condition,the adsorption amount of La3+ and Ce3+ on SA-PGA were 172.41mg/g and 158.73 mg/g,respectively.For the low concentration of rare earth ions,the adsorption rate reached 99.99%.The two data of SA were 84.03mg/g and 81.97mg/g,respectively.It indicated that this novel immobilized adsorbent had strong adsorption efficiency and substrate affinity.The pictures,getted from scanning electron microscopy(SEM),showed SA-PGA had a homogeneous porous surface.The surface of SA was harden and compact.After determinating the specific surface of these materials,it found that specific surface of SA-PGA was 40.80m2/g,and SA was 24.86m2/g.The internal structure of SA-PGA had been changed obviously.The results indicated that Pseudo-second order kinetic and Langmuir isotherm model can describe the adsorption behavior very well,through fitting kinetic and thermodynamic model with experimental data.The theoretical adsorption amounts were closest with the actually measured value.Error ±3.91%.Thermodynamic parameters show that the adsorption is a endothermic process and can proceed spontaneously in room temperature,and chemical adsorption plays a key role.Ca2+ will release into solution during the process of adsorption,and acidic condition widd inhibit the adsorption.This showed that H+ would compete adsorption sites with R3+.p H5.0 was the optimum environment.Under this circumstance,there existed competition among of H+,Ca2+ and R3+ in solution.Fourier infrared spectrum analysis showed that after adsorbing rare earth ions,1615cm-1 attribute to carboxylic absorption peak,was transferred to a stronger wave number 1629cm-1.Other absorption peak had no obvious change.This indicated that carboxyl group was the main functional groups.The spectra of SA-PGA showed that before adsorbing R3+ the carboxyl was combined with Ca2+ and a small amount of H+.Therefore,we suggest that the adsorption mechanism is ion exchange between-COOCa and R3+.After 10 adsorption-desorption cycles the adsorption efficience of SA-PGA had no decline.SA-PGA had excellent ability of regeneration.In addition,it also had the same adsorption ability on heavy metal ions.