Cleaning can be defined as the removal of residues from previous batch, other residues, and traces of cleaning agents. There are several mechanisms associated with cleaning of equipment. The mechanisms involved can be mechanical action, chemical action between the residues and the cleaning agent.
The selection of cleaning agent and mechanism involved in cleaning is largely dependant on the process residue to be cleaned.
Cleaning Mechanisms
The cleaning mechanism totally depends on the selection of cleaning agent and type of residue to be cleaned. Following can be the one of the methods involved in cleaning of residues,
- Dissolution
- Saphonification
- Wetting
- Emulsifying
Dissolution
Dissolution is the process by which a solid or liquid forms a homogeneous mixture with a solvent or solution. This can be explained as a breakdown of the crystals into individual ions, atoms or molecules and their transport into the solvent
The mechanism involved in this type of cleaning is solubility of the residue in the cleaning agent or solvent. The monobasic buffers i.e. sodium chloride are soluble in cool and hot WFI.
Ethylene glycol butyl ether is soluble in water as well as oil is also used in solubilizing agent. Chelating agents and builders are added to the formula to keep water hardness from interfering with the cleaning process.
Rate of dissolution is depend on,
- Nature of solvent or residue to be dissolved
- Temperature of solvent
- Presence of mixing
- Area of contact
- Presence of inhibitors
Saphonification
Saponification can be defined as “hydration reaction where free hydroxide breaks the ester bonds between the fatty acids and glycerol of a tri-glyceride, resulting in free fatty acids and glycerol”, which are each soluble in aqueous solutions.
This process specifically involves the chemical degradation of lipids, which are not freely soluble in aqueous solutions. Heat treated lipid residues are difficult to remove than non-heat residues due to polymerization.
Saphonification plays a critical role in cleaning lipids which are present in the areas of process involving cell growth and cell processing i.e. Bacterial fermentation, Cell disruption process
Wetting
Wetting can be defined as a process “involves the lowering of the surface tension of the cleaning solution, thus allowing it to better penetrate residues that are adhered to equipment and piping surfaces”. Wetting agents, or surfactants, are often used in relatively small amounts and they can substantially reduce the quantities of cleaning agent (in this case, alkali) required for residue removal.
Advantages of Wetting
- Lowers the surface tension of the cleaning solution
- Allow better penetrate residues which are adhered to equipment
- Used in small amount
- Sticky residues which are hydrophobic in nature get easily removed
Water acts as a solvent that breaks up soil particles after the surfactants reduce the surface tension and allow the water to penetrate soil (water is commonly referred to as “the universal solvent”).
Emulsifying
Emulsifying and suspending agents are often used to keep residues from precipitating by providing “hydrophobic groups” onto which hydrophobic areas of residues can associate, thus preventing them from associating with other residues and forming larger particles which are likely to leave solution.
These agents also typically have “hydrophilic groups” which keep them very soluble in aqueous solutions of moderate to high ionic concentrations. Emulsifiers increase the capacity of a cleaner to emulsify non-soluble compounds in the cleaner. i.e. anionic soap surfactants, cationic surfactants, neutral surfactants
Advantages of Emulsifying agents,
- Prevent association of residues
- Allow the residue to precipitate and not allow thdse residue to redeposit on surface
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