Caustic solutions (either sodium hydroxide or potassium hydroxide) are widely used in the cleaning of process equipment, piping, storage tanks, etc. Typically the caustic concentration is about 2 - 4% but varies from < 1% to > 5% caustic. The caustic used may or may not contain additives like surfactants, chelating agents, buffers, etc in food and beverage industry, where hygiene is of paramount importance. The equipment cleaned with caustic solutions includes: centrifuges, juicing equipments, evaporators, drying equipments, storage tanks, piping, etc. The dirty caustic typically contains both suspended/ colloidal and dissolved contaminants.

The primary justifications for caustic recovery are: (1) reduction in purchase costs for fresh caustic; (2) reduction in waste treatment costs; and (3) achieve or maintain regulatory compliance on plant discharges.

In the bottle wash process, hot caustic solution - typically 2% concentration and 80 - 85°C, is sprinkled on the used bottles to maintain high hygienic standards and to remove residual labels and tint. Additives, such as surfactants and chelates, are frequently included in the cleaning solution for enhancing the washing efficiency.

Taking advantage of the pore size and charge on the membranes surface, caustic is recovered by rejecting proteins, sucrose, and suspended solids resulting in reduction of more than 90% of dispersed and soluble organic contaminants and 80% of the carbonates.

Published on: 24 Sept. 2019 Uploaded on: 10 July 2020
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