Synthetic method of Sodium gluconate and its role in concrete. What are its functions as a water reducing agent, retarder and cleaning agent?
In industry, substances containing glucose (such as grains) are generally used as raw materials, and gluconic acid is obtained from glucose by fermentation, and then neutralized by sodium hydroxide to obtain sodium gluconate. Electrolysis and oxidation can also be used. synthesis. Most of our country adopts chemical oxidation method-hypobromide oxidation method to produce and synthesize.
According to the different types of fermentation enzymes used, the fermentation method can be divided into two phases, one is to use Aspergillus Niger enzyme and the other is acid. The latter method uses glucose dehydrogenation to form lactones and then decomposes the esters.
Sodium gluconate can also be obtained directly from glucose fermentation. At this time, the composition of the fermentation base can be: glucose 250~350g/L, magnesium sulfate heptahydrate 0.2~0.3g/L, diammonium phosphate or urea 0.4~0.5g/L. This substrate must be sterilized. During the fermentation process, the temperature is controlled at 30-32 degrees, the pH is controlled at 5.5-6.5 with 30%-50% sodium hydroxide, and the fermentation process lasts 40-100h. Then, the microorganisms are removed by filtration and washing, the activated carbon is decolorized, and then filtered, and the result is concentrated or spray-dried to obtain the finished product.
Sodium gluconate can be used as an admixture in concrete. Its functions in concrete are as follows: water reducer and retarder
Sodium gluconate is generally used alone, but it can also be used in combination with other retarders such as carbohydrates and phosphates. Sodium gluconate is a crystalline powder. It is produced under properly regulated and controlled conditions. This compound is chemically pure and non-corrosive. The quality is constant. These features can ensure that it has reliable and reproducible results in the application.
Sodium gluconate as water reducer
By adding a water reducing agent, the water-cement ratio (W/C) can be reduced. The following effects can be obtained by adding sodium gluconate:
1. Improve workability.
When the water-cement ratio (W/C) remains unchanged, adding sodium gluconate can improve workability. At this time, sodium gluconate acts as a plasticizer. When the addition amount of sodium gluconate is below 0.1%, the degree of improvement in workability is proportional to the addition amount.
2. Improve strength.
When the cement content remains the same, the water content in the concrete can be reduced (that is, W/C is reduced). When the amount of sodium gluconate added is 0.1%, the amount of water added can be reduced by 10%.
3. Reduce cement content.
The water and cement content is reduced in the same proportion, and the W/C ratio remains unchanged.
Sodium gluconate as retarder
Sodium gluconate can significantly delay the setting time of concrete. When the dosage is less than 0.15%, the logarithm of the initial setting time is directly proportional to the dosage, that is, the dosage is doubled, and the initial setting time is delayed to ten times, which makes the working time from very few The hours are extended to a few days without compromising the strength. This is an important advantage especially in hot weather and when it needs to be placed for a long time.
Used as a special cleaning agent for glass bottles
The beverage industry, food industry, and brewing industry have hundreds of millions of glass bottles per day, such as soda bottles, beer bottles, milk bottles, canned bottles, soy sauce bottles, wine bottles, etc. The cleaning work is a very important thing. The formulation of medicaments is a difficult technical task. An ideal medicine has not yet appeared in China. The main problems are: poor detergency, easy to block the nozzle and pipeline of the bottle washer; unsatisfactory de-staining power to bottle stickers and bottleneck rust; the trace residue after washing is not ideal for food safety (such as phosphate Residue); the washing water is discharged into a public hazard (not meeting the standards set by the country). If sodium gluconate is used as the main body in the formulation of the glass bottle cleaning agent, the above problems can be solved. (In the 1980s, large-scale experiments were carried out at the Shanghai Soda Plant and Shanghai Brewery, and the appraisal proved.) This application has not yet been developed in China. If a market is formed, the potential is great.