Preparation Of Alginate Fiber Based On Coordination With Lanthanum

In this paper, the interaction of sodium alginate with rare earth metal ion w as mainly investigated. And the wet spinning was used to prepare alginate-lanthanum complex fiber. The different mole of Mannuronic acid unit and guluronic acid unit（M/G） in sodium alginate will result in different physical and chemical properties such as viscosity, gelling performance of alginate, and it has a great impact on the mechanical properties of the fiber prepared. 1HNMR analys is of sodium alginate used in the exper iment showed that FG is 0.38, FM is 0.62. By infrared spectroscopy, ionization degree of alginate at pH 4 was 74%. Above pH 5, alginate is completely ionized. Compared with the COO-, COOH of alginate interact with lanthanum ions is weak.Alginate can coordinate with Al³⁺, Ca²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, La³⁺, Ce³⁺ and other high-priced metal ions to form a three-dimensional network structure of the gel, it has good fiber-forming ability. Preparation of alginate-lanthanum fiber by wet-spinning, when alginate solution extruded from the spinneret orifice there is a significant radial swelling process, the fiber diameter is much larger than the pore size of the spinneret hole. After the fiber is removed from the coagulation bath, the fiber will quickly dehydrate, and have an apparent diameter shrinkage. The surface grooves of alginate-lanthanum fiber is related to rapid dehydration. Dried at room temperature, alginate- lanthanum fiber still contain a lot of water, the water content by TGA is about 15%. Elemental analysis shows that the content of lanthanum element is 16-18% in the alginate-lanthanum fiber.Spinning conditions has a great influence on the mechanical properties of the fiber. With the increase of the coagulation bath concentration, the mechanical properties the fiber is increased. If the concentration of LaCl3 is too high, the elongation at break of fiber will reduce. With increasing pH, break strength and elongation at break of the fiber have increased. When the coagulation bath pH value is too high, La³⁺ will hydrolyze, and the break strength of the fiber will decrease. When coagulation bath at low temperature, fiber has high break strength. With the coagulation bath temperature increasing, the fiber strength decrease. In a certain temperature and different relative humidity conditions, the break strength and elongation at break of fiber are affected. With the humidity increasing, break strength will decrease and elongation at break will increase.Alginate- lanthanum fiber was successfully prepared by wet spinning. Compared with alginate-calcium f iber, the break strength of alginate- lanthanum fiber increase more than 30%, but its elongation at break decrease. Immersed in hydrochloric acid solution p H = 1 for one hour, the break strength of alginate-calcium fibers decrease 40%, while the break strength of alginate- lanthanum f iber decrease only 20%. La³⁺ has a stronger cross-linking ability than Ca2+, and there is a greater compatibility in space when La³⁺ interacts with carboxylate ligands. Alginate-lanthanum fiber has greater stability in an acidic solution.FTIR spectroscopy and conductivity measurement were used to study the interaction between alginate and lanthanum ion, and three different coordination models were put forward. when La³⁺ coordinate with GG segments, form an "egg-box" structure; when La³⁺ coordination with GM segments, form a similar "shell" structure, but it is fragile than the "egg-box" structure; when La³⁺ interact with MM segments or some free COO-, it combines with ionic bonding.