Which material is most likely used as a pre-coat in a plate and frame press for dewatering industrial sludge?

The use of diatomaceous earth as a pre-coat in a plate and frame press for dewatering industrial sludge is well-established due to its unique physical properties. Diatomaceous earth is composed of the fossilized remains of tiny aquatic organisms known as diatoms, which have a high surface area and porous structure. This allows it to effectively filter and capture solids during the dewatering process, enhancing the efficiency of the operation.

When applied as a pre-coat, diatomaceous earth forms a thin layer on the filter plates, creating a barrier that improves the separation of solids from liquids. This pre-coating process not only helps in capturing finer particles, which might otherwise pass through the filter, but it also aids in reducing the cake moisture content, leading to a more effective dewatering process.

Other materials listed, such as activated carbon, sanding grit, and polymer resin, do not serve the same function as a pre-coat. Activated carbon is primarily utilized for its adsorption properties in applications involving chemical removal, sanding grit is more commonly used as an abrasive material, and polymer resin can be employed for flocculation but does not provide the filtration properties that diatomaceous earth does. Therefore, diatomaceous earth stands out as the most suitable choice