Research on the Application of Diatomite Filter Aid in Enzyme Preparations, Citric Acid, Alginate, Gelatin and Titanium Dioxide Industries

1. Introduction
Diatomite filter aid is a porous filtration medium processed from natural diatom fossils, featuring high porosity, chemical inertness and excellent adsorption capacity. It is widely used in food, chemical, pharmaceutical and other industries. In the production processes of enzyme preparations, citric acid, alginate, gelatin and titanium dioxide, diatomite filter aid plays a crucial role in solid-liquid separation, clarification and purification. This paper will systematically analyze the application principles, process optimization and future development trends of diatomite filter aid in these industries.

2. Characteristics and Advantages of Diatomite Filter Aid
The microstructure of diatomite filter aid is composed of numerous micrometer-sized pores, endowing it with the following core advantages:
High filtration precision: It can retain particles ranging from 0.1 to 50 μm, suitable for filtering liquids of different viscosities.
Chemical stability: Resistant to acids and alkalis, it does not react with the target products, ensuring product quality.
High permeability: Low filtration resistance reduces energy consumption and enhances production efficiency.
Regenerability: In some industries, diatomite filter aid can be regenerated through calcination or acid washing, reducing waste treatment costs.
These characteristics make it an indispensable filtration material in enzyme preparations, citric acid, alginate, gelatin and titanium dioxide industries.

3. Application of Diatomite Filter Aid in Various Industries
3.1 Application in Enzyme Preparation Production
Enzyme preparation production involves microbial fermentation, cell disruption and protein purification. The fermentation broth contains a large amount of microorganisms, cell debris and colloidal impurities. The application of diatomite filter aid in enzyme liquid filtration mainly includes:
Microbial cell removal: Through pre-coating and dynamic filtration techniques, it efficiently retains microbial cells, improving the clarity of the enzyme liquid.
Protein stability: It avoids enzyme protein denaturation caused by traditional filtration media (such as filter cloth), maintaining enzyme activity.
Increased yield: Compared with centrifugation or membrane filtration, diatomite filter aid can reduce product loss and increase the recovery rate of enzyme preparations.
3.2 Application in Citric Acid Extraction Process
Citric acid is mainly produced through Aspergillus niger fermentation, and the fermentation broth contains mycelium, proteins and pigments. The role of diatomite filter aid in citric acid filtration includes:
Mycelium separation: As a pre-coating filter aid, it effectively removes mycelium from the fermentation broth, reducing the contamination of subsequent ion exchange resins.
Assisted decolorization: When used in conjunction with activated carbon, it improves the light transmittance of citric acid liquid, meeting food-grade standards.
Reduced energy consumption: Compared with plate and frame filtration, diatomite filter aid can reduce filtration time by more than 30%, enhancing production efficiency.
3.3 Application in Alginate Refining
The extraction of alginate (such as carrageenan, agar) involves soaking, alkaline treatment and filtration. The liquid contains a large amount of seaweed residue and colloidal particles. The application advantages of diatomite filter aid include:
Efficient solid-liquid separation: In the hot-soluble gel filtration stage, it can remove fine suspended solids, improving the purity of the gel.
Improved fluidity: It reduces the impact of gel liquid viscosity on filtration and avoids filter membrane clogging.
Increased transparency: It ensures that the final product meets the high transparency requirements of the food and pharmaceutical industries.
3.4 Application in Gelatin Production
Gelatin is produced by hydrolyzing animal collagen, and the liquid contains fat, protein fragments and impurities. The functions of diatomite filter aid include:
Fat and particle removal: In the gelatin liquid filtration stage, it can adsorb fats and retain fine particles, enhancing product purity.
Improved gel strength: It reduces the impact of impurities on the molecular structure of gelatin, ensuring the gel properties of the final product.
Extended filter membrane lifespan: Compared with direct use of filter cloth or filter cartridges, diatomite filter aid reduces membrane contamination and lowers maintenance costs.
3.5 Application in Titanium Dioxide (TiO2) Production The preparation of titanium dioxide involves the sulfuric acid method or the chloride method, and the reaction liquid contains unreacted titanium ore particles and by-products. The application of diatomite filter aids includes:
Purification of titanium sulfate solution: Removing solid impurities before the hydrolysis of titanium solution to improve the whiteness and purity of titanium dioxide.
Wastewater treatment: Used for the adsorption of heavy metals and the removal of suspended solids in titanium dioxide production wastewater, meeting environmental protection requirements.
Replacement of traditional filter media: Compared with traditional filter cloth, which is easily corroded by strong acids, diatomite has strong acid resistance and a longer service life.

4. Comparison of diatomite filter aids with other filtration technologies
Although membrane filtration (such as ultrafiltration and nanofiltration) and centrifugal separation technologies are applied in some industries, diatomite filter aids still have irreplaceable advantages:
| Comparison item | Diatomite filter aid | Membrane filtration | Centrifugal separation |
| Filtration precision | 0.1~50μm | 0.001~0.1μm | 1~100μm |
| Applicable viscosity | Applicable to high viscosity | Applicable to low viscosity | Applicable to medium viscosity |
| Operating cost | Lower | Higher | Higher |
| Maintenance difficulty | Low | High (prone to contamination) | Medium (requires regular cleaning) |
In the enzyme preparation, citric acid and other biological fermentation industries, diatomite filter aids still dominate due to their economy and high adaptability.

5. Future development trends
With the strictening of environmental regulations and process upgrades, the future development directions of diatomite filter aids include:
Nanometer diatomite: Increasing the specific surface area to enhance adsorption capacity, suitable for high-purity products (such as pharmaceutical-grade enzyme preparations).
Composite filter aids: Combining with activated carbon, perlite, etc., to improve decolorization and impurity removal efficiency.
Green regeneration technology: Developing low-energy regeneration processes to reduce the discharge of waste diatomite.

6. Conclusion
Diatomite filter aids, with their excellent filtration performance and economy, play a key role in enzyme preparations, citric acid, alginate, gelatin, and titanium dioxide industries. In the future, through technological innovation and process optimization, the application scope of diatomite filter aids will further expand, providing more efficient solutions for the production of high-purity products.