Some problems in the preparation of alum, and the approximate experimental yield of alum

2。Potassium and sulfate.

1。Promotes the hydrolysis of alum (the dissociation constant of aluminum ions increases as the temperature increases).

Stirring increases the contact area and speeds up the reaction rate.

2 It should be sodium ions and sulfate, because the reaction in this step is to generate aluminum hydroxide, sodium sulfate and water!! Potassium ion is an essential element in the product!

AlumThe yield of the preparation experiment is approximately.

Control the concentration of the solution, if the solution is too concentrated, the crystallization rate is too fast, and it is not easy to form crystals with complete crystal shape; If the concentration of the saturated solution is not large, the crystallization rate is too slow, and the small crystals grow slowly.

When preparing small crystals, use a saturated solution 20 -30 above room temperature; The saturated solution added later should be a solution higher than room temperature 15 -20, and the amount of each addition is about 1 10 of the original solution.

Increase the mineral yield of phosphate rock concentrate

Physical properties of phosphate rock.

The change in the physical composition (the actual production compared to the original design) is the result of the yield and the best rate.

The root cause of too low mountain thickness. Due to the change in the physical composition of the ore raw material, the high fine ore content, and the error in the selection of the fine ore separation equipment, the cyclone was caused.

The production and processing capacity is too small, and the tail running phenomenon is serious, which is one of the reasons why the concentrate mineral yield and the first-class teasing rate are too low.

The above content reference: Encyclopedia - potassium aluminum sulfate dodecahydrate.

1. The natural alum stone processing method crushes, roasts, dehydrates, weathers, steam leaching, sedimentation, crystallization and crushing to obtain finished aluminum and potassium sulfate products.

2. The bauxite method uses sulfuric acid to decompose bauxite ore to produce aluminum sulfate solution, and then adds potassium sulfate to react, and then filters, crystallizes, centrifugal dehydration, and drying to obtain aluminum potassium sulfate products.

The finished product of aluminum potassium sulfate was prepared by 3-fold crystallization method of coarse alum with water boiling, evaporation, crystallization, separation and drying.

4. The aluminum hydroxide method dissolves aluminum hydroxide in sulfuric acid, and then adds the metered potassium sulfate solution to heat the reaction, filters, concentrates, crystallizes, centrifuges and separates, and dries to obtain the finished aluminum sulfate potassium sulfate.

5. Dissolve potassium sulfate in 70g100 water, and dissolve aluminum sulfate Al2 (SO4) 318H2O octahydrate in 60g100 water. Mix the two solutions while they are hot and allow the mixture to cool slowly with constant stirring. When the solution is cooled to 20, the crystallization of about 85g of potassium aluminum sulfate dodecahydrate can be obtained.

6. The recrystallization method is adopted. The industrial product potassium aluminum sulfate is dissolved in water, and then purified, impurified, filtered, concentrated, crystallized, centrifugal dehydrated, and dried to obtain potassium aluminum sulfate.

1. Types of alum: potassium alum (potassium aluminum sulfate), ammonium alum (aluminum ammonium sulfate).

2. The function of alum: leavening agent and stabilizer.

3. Regulations on the use of alum (GB2760-2014):

Soy products should be used in an appropriate amount according to production needs.

Batter (e.g. drag batter for fish and poultry), breading, frying powder, and use the appropriate amount according to production needs.

Fried noodle products should be used in an appropriate amount according to production needs.

Shrimp flavor flakes, use in an appropriate amount according to production needs.

Baked goods, use in moderation according to production needs.

Residues of aluminium in the above categories of food 100mg kg (dry sample, calculated as AL).

Pickled aquatic products (jellyfish only), use in appropriate amounts according to production needs; Residual amount of aluminum: 500mg kg (based on AL in ready-to-eat jellyfish).

4. Residue of aluminum in food:

The amount of aluminium residues in food refers to the amount of AL (aluminum) in food (except for ready-to-eat jellyfish) in food (mg kg).

Alum should not be used in water, or it means that alum water (water with alum added) is only used as a food ingredient for the processing of bean products, batter, breading, frying powder, fried flour products, shrimp flaks, baked goods or jellyfish. In the case of aqueous solutions of alum alone, it is somewhat inappropriate to say that the solution "residual amount of aluminum" (food refers to dry samples, except for ready-to-eat jellyfish), but rather as the amount of aluminum in the solution.

Calculation of aluminum content (using potassium alum as an example).

The molecular formula of potassium alum: kal(so4)2·12h2o

Molecular weight of potassium alum: 39 + 27 + (32 + 4 * 16) * 2 + 12 * (2 * 1 + 16) = 474

Purity of potassium alum: 100% assumed

Molecular formula of aluminum: Al

Molecular weight of aluminum: 27

Aluminum as a percentage (%) of alum (100% purity).

The potassium alum is put into 100g of water, and the aluminum content of the solution: (

[Protocol Procedure].

1 Put water 10 20 °C above room temperature in a glass, add alum, stir with chopsticks, until a small number of crystals can no longer be dissolved.

2 When the solution has cooled naturally to slightly higher than room temperature3 5, pour the solution into a clean bowl, cover it with a piece of cardboard, and let it stand overnight.

3 Select 2 3 small crystals with intact shape from the bowl as the nucleus. Gently tie the selected nucleus with a thin wire.

4 Pour the alum solution into a glass and add an appropriate amount of alum to the solution to make it a saturated solution 10 15 above room temperature. When it cools naturally to slightly higher than room temperature3 5, hang the small crystals in the glass**, taking care not to make the crystal nuclei touch the wall of the cup. Cover the glass with a piece of cardboard and let it sit overnight.

5 Gently remove the small crystals that have formed every day and repeat operation 4 until the crystals grow to a certain size.