Perlite, in its expanded form, is very good at absorbing and holding liquids, especially in the finer grades. This makes expanded perlite useful for liquid waste control and bulking, transport, and spill containment. Perlite also has excellent filtration qualities, which makes it useful in storm water management.
Perlite holds onto waste liquids one of three ways: on its frothy exterior, in the many voids and surface nooks, and suspended in between the particles themselves. Fine perlite grades, packed more tightly, provide more surface area and more interspacial gaps, thus are more absorbent and will hold and stabilize more waste liquids.
Liquid Waste Solidification
Tests using expanded perlite fines show water absorption as high as eight times the dry weight of the perlite. Of course, surface tensions and viscosities differ between liquids, but perlite’s ability to hold water provides a useful reference point and make a case for perlite as a lightweight, and highly absorbent media to solidify and stabilize liquid wastes—a process increasingly necessary for transport and/or landfill of liquid waste.
Suitable solidification/stabilization guidelines are established by the EPA and are determined using a simple paint filter test, which specifies that a material is suitably rendered solid if no liquid drips out of a paint filter over a five-minute test period.
Expanded perlite is a key ingredient in many lightweight kitty litters, absorbing and trapping pet waste while providing a significant weight reduction—up to half over standard clay-only products. Perlite is typically used as part of the overall blend—combined with clumping clays and odor-control ingredients.
A couple of perlite’s physical characteristics go to work when used in stormwater management constructs—its aggressive filtration properties and its water holding capacity. The first removes and traps pollutants and other turbidity-causing solids picked up by stormwaters; the second helps control surge as a absorptive component in vegetative roofs and bioswale soils. As an added benefit, perlite in the soil of these ecology constructs will contribute to the hardiness of the vegetative cover by improving the soil tilth and root zone profile.