The commonly used filter aids include diatomite, perlite, cellulose, asbestos, graphite powder, sawdust, magnesium oxide, gypsum, activated carbon, acidic clay, etc. Diatomite has a large specific surface area, which can adsorb colloidal substances and form filter cakes with high porosity. It is the most widely used filter aid. Paper pulp is often used as a pre coating to prevent early clogging of the filter cloth.

The use method of filter aid: one is to mix the filter aid with the suspension to be filtered in a certain proportion, and then filter together; The other is to prepare a suspension containing only filter aid, filter it first, form a pre coating on the filter medium, and then filter the filter slurry. The pre coating of the filter aid can withstand a certain pressure without deformation, and can prevent the filter cloth from increasing resistance due to clogging.