A sealant for an oil or geothermal well capable of setting within about 3 to about 6 hours at temperatures less than about 250° F. for shallow wells less than about 10,000 feet and deep wells greater than about 10,000 feet having MgO present in the range of from about 9.9 to about 14.5%, KH2PO4 present in the range of from about 29.7 to about 27.2%, class C fly ash present in the range of from about 19.8 to about 36.3%, class F fly ash present in the range of from about 19.8 to about 0%, boric acid or borax present in the range of from about 0.39 to about 1.45%, and water present in the range of from about 20.3 to about 21.86% by weight of the sealant.

A method of sealing wells is disclosed as are compositions for very high temperature wells is disclosed as is a composition for treating oil field wastes.

A process of washing plastics contaminated with polychlorinated biphenyls (PCBs) is provided to reduce the concentration of the PCBs. A two-step process includes a first washing step using a selected washing solution or solvent, such as, a non-flammable solvent, and followed by a second step using thermal desorption. The two-step process enables reducing the concentration of PCBs in polymers, such as recovered from shredder residue, for example, to as low as 0.253 PPM. One of the preferred solvents is Perchloroethylene.