Organoclay is a chemically modified type of clay that is used for wastewater and water treatment. It consists of bentonite, which is a clay formed from volcanic ash that contains the mineral montmorillonite. Organoclay also contains artificially added chemical compounds known as quaternary amines, which give the clay its useful industrial properties. The addition of quaternary amines allows the clay to chemically dissolve substances such as oil and grease, removing them from water.
When organoclay is introduced into water, chemical reactions take place that allow the clay to dissolve hydrocarbons — organic chemicals consisting of hydrogen and carbon, such as oil. The clay is able to do this because of the presence of amines, or ammonium compounds, which were added to it during the manufacturing process. It acts as a surfactant, reducing the surface tension of liquids and allowing them to mix with previously incompatible substances. While oil cannot dissolve in water, it can dissolve in the clay due to these chemical properties.
Organoclay is organophilic, meaning that it attracts organic molecules. This makes it useful as a tool for wastewater treatment. When added to the wastewater, the clay acts as a filter, removing organic compounds such as oil, grease, and other substances. It can absorb up to 70% its own weight in hydrocarbons, making it more efficient than other filtration technologies. Carbon filters may be used in conjunction with organoclay as part of a multi-step process in water purification.
Groundwater is also treated with organoclay. For example, when water leaches through a landfill or becomes contaminated at a construction site, it is often environmentally hazardous to allow that water to return to the groundwater without treatment. Organoclay is used for remediation projects in these settings.
The permeable barrier is one example of a technology used to treat groundwater near areas such as landfills. A barrier is constructed around the problem site using organoclay. Since the clay is porous, water is able to seep through the barrier back into the groundwater. Organic compounds and pollutants, however, are trapped and dissolved by the chemical properties of the clay. The barrier prevents contaminants from seeping through while allowing pure water to return to the environment.
Certain types of organoclay have applications outside the water treatment field. Plastics, including plastic bags, may be reinforced with organoclay additives. Certain clay mixtures have been found to increase the strength and flame-retardant properties of plastics when added during the manufacturing process.