Free sharing of sodium alginate extraction methods

　　As we all know, sodium alginate is made from kelp, and then processed by professional sodium alginate manufacturers into finished products of sodium alginate required by food-grade and printing and dyeing industries. So how is sodium alginate extracted? Today, Nanshan Biotechnology Sodium Alginate Factory will share with you the methods of extracting sodium alginate for free:
　

　　1 Extraction method of sodium alginate: acid coagulation-acidification method.

　　The raw material kelp is soaked to remove mechanical impurities, fucoidan, inorganic salts and other water-soluble components, and then the kelp is taken out, washed and cut into uniform blocks. At 25℃, it is treated with dilute hydrochloric acid or dilute sulfuric acid below 0.01 mol/L. Then sodium carbonate is added, and the reaction is carried out for 1-1.5h under stirring at 55-5 DEG C, so as to convert polyvalent metal ion type alginic acid into sodium type. The reaction equation is as follows: 2M (Alg)n+ nNa2CO3→ 2nNaAlg+ M2 (CO3) (1)( M is metal ions such as Ca and Fe, and Alg stands for alginate)

　　Firstly, the raw material digestive juice is filtered to remove coarse particles, then the filtered feed liquid is diluted with water, and then dilute salt acid is slowly added to the feed liquid until flocculent precipitation begins, and then it is allowed to stand for 8-12h. Finally, dilute hydrochloric acid is slowly added to the standing liquid to adjust the PH to about 1-2, and alginic acid is condensed into acid clots. The reaction formula is as follows:

　　NaAlg + HCI→ Halg↓ +NaCI (2)

　　2NaAlg + H2SO4→ 2HAlg↓ +Na2SO4 (3)

　　Collecting acid blocks, washing, dewatering, pulverizing, and mixing with powdered sodium carbonate. Generally, the amount of alkali added is about 8%, which is evenly mixed under stirring, and then allowed to stand for 4-6 hours to complete the transformation process and generate sodium alginate. The water content of the neutralized product is 65~75%, and the pH is 6.0~7.5, which is solid phase neutralization. Liquid phase neutralization can also be carried out: after alginic acid is crushed, it is dispersed in an alkaline ethanol solution with gel content of 40% or more, and mixed and reacted with stirring to obtain sodium alginate, until the pH is 7.5. After neutralization, it is filtered, dried and crushed to obtain the product.

　　2. Extraction method of sodium alginate: calcium coagulation-acidification method.

　　The processes of raw material treatment, soaking, digestion and clarification are the same as the "acid coagulation-acidification method", but the later coagulation processes are different: after the digestive juice is filtered, a quantitative 10% calcium chloride solution is added under the condition of pH 6.0~7.0, and it is coagulated under stirring. The calcium alginate obtained by calcium coagulation was washed with water to remove the residual inorganic salts, and then acidified with 10% dilute acid for 30 minutes to transform it into alginate clots. Then sodium carbonate solution is converted into sodium alginate by liquid phase method or solid phase method, filtered, dried and crushed to obtain the product.

　　3. Extraction method of sodium alginate: calcium coagulation-ion exchange method.

　　The raw material treatment, soaking, digestion, pre-neutralization and dilution, filtration and calcium coagulation of this method are the same as those of "calcium coagulation-acidification method". After calcium coagulation, 10% sodium chloride solution is used as eluent, which can be exchanged by column chromatography, or can be reacted intermittently in a container. The sodium alginate generated by the reaction is dried and crushed to obtain the product.