Raw Materials

The primary raw materials used in the synthesis of silica gel litter are silica precursors, such as tetraethylorthosilicate (TEOS) or sodium silicate (Na2SiO3)[1, 2]. These precursors undergo hydrolysis and condensation reactions to form a network of interconnected silica particles[3]. Other materials, such as ethanol, acetic acid, and water, are also used in the synthesis process as solvents and catalysts[4].

Sol-Gel Process

The sol-gel process is the most common method for synthesizing silica gel litter. It involves the formation of a colloidal suspension (sol) of silica particles, which then undergoes gelation to form a continuous network (gel)[1, 3]. The process can be carried out at room temperature, making it energy-efficient and eco-friendly[1].

sol–gel-synthesis

Figure 3. Flow chart of sol–gel synthesis[5]

The sol-gel process typically involves the following steps:

  1. Hydrolysis: The silica precursor is mixed with water and a catalyst (e.g., acetic acid) to form silanol groups (Si-OH)[2, 4].
  2. Condensation: The silanol groups react with each other to form siloxane bonds (Si-O-Si), leading to the formation of a three-dimensional network of silica particles[2, 3].
  3. Aging: The gel is allowed to age, during which time the network continues to cross-link and strengthen[6].
  4. Drying: The gel is dried to remove the liquid phase, leaving behind a highly porous silica gel[3, 4].

Modifications and Additives

Various modifications and additives can be incorporated into the synthesis process to enhance the properties of silica gel litter. These include:

Surface Modification

The surface of silica gel can be modified to increase its hydrophobicity or hydrophilicity. For example, methylation of the silica surface using methyltriethoxysilane (MTES) can increase its hydrophobicity, improving its moisture resistance[7, 8]. Conversely, the addition of polyether-imide (PEI) or hexadecyl trimethyl ammonium bromide (CTMAB) can increase the hydrophilicity of the silica surface, enhancing its ability to adsorb polar molecules[9].

Additives for Odor Control

Additives such as activated carbon or baking soda can be incorporated into the silica gel litter formulation to enhance its odor control properties[10, 11]. These materials work by adsorbing volatile organic compounds and other odorous substances, keeping the litter box fresh and hygienic.

Antimicrobial Agents

Antimicrobial agents can be added to the silica gel litter to prevent bacterial growth and maintain a hygienic environment for cats[10, 11]. These agents can be incorporated during the synthesis process or applied as a coating on the surface of the silica gel particles.

References

  1. Demirdöğen, R.E. Chemical Synthesis Method for Production of Silica Gel as a Sorbent Material.
  2. Hamawi, M. and N. Trisnaningrum, Modification of The Synthesis of Silica from Litter Ori Bambusa (Bambusa blumeana) Leaves Using Sodium and Potassium With The Hydrothermal Sol-Gel Method As Agricultural Fertilizer.Agroindustrial Technology Journal, 2023.
  3. Salami, S.A., et al., Immobilized Sulfuric Acid on Silica Gel as Highly Efficient and Heterogeneous Catalyst for the One-Pot Synthesis of Novel α-Acyloxycarboxamides in Aqueous Media.Int J Mol Sci, 2022. 23(17).
  4. A’Yuni, Q., et al., Synthesis and characterization of silica gel from Lapindo volcanic mud with ethanol as a cosolvent for desiccant applications.RSC Adv, 2023. 13(4): p. 2692-2699.
  5. Tranquillo, E., et al., Sol–Gel Synthesis of Silica-Based Materials with Different Percentages of PEG or PCL and High Chlorogenic Acid Content.Materials, 2019. 12(1): p. 155.
  6. López, S.F., et al. Effect of microwave heating on the sol-gel process of silica gels. 2020.
  7. Vidal, K., et al., The Synthesis of a Superhydrophobic and Thermal Stable Silica Coating via Sol-Gel Process.Coatings, 2019.
  8. Jiang, C., et al., Synthesis of superhydrophobic fluoro-containing silica sol coatings for cotton textile by one-step sol–gel process.Journal of Sol-Gel Science and Technology, 2018. 87: p. 455-463.
  9. Li, Z., Selective Removal of Phenol from Cigarette Smoke by Silica Gel Additives with Surface Modification.Chinese Journal of Spectroscopy Laboratory, 2011.
  10. Faza, Y., et al., SURFACE MODIFICATION OF ALUMINA-SILICA BY ADDITIVE AGENT USING SOL-GEL METHOD AS FILLER DENTAL COMPOSITE.B-Dent: Jurnal Kedokteran Gigi Universitas Baiturrahmah, 2024.
  11. Borshch, V.N., et al., Low-Temperature Combustion Synthesis and Characterization of Co-Containing Catalysts Based on Modified Silica Gel.International Journal of Self-Propagating High-Temperature Synthesis, 2023. 32: p. 126-138.