The U.S. Bureau of Mines investigated the application of oxidation- reduction potential (orp) and ph measurements for environmental studies of mining and mineral processing wastes. The methods and techniques for the orp-ph measurements were investigated using known standard solutions made in the laboratory, samples from a ferric oxide waste disposal pond at a rutile production plant, and samples of well water and stream water from a waste site containing lead. Orp values were measured from 5 deg to 80 deg c, from ph 1 to ph 12, and at various ratios of oxidant to reductant. Chemical analyses and orp-ph values can help identify valences and species of most ions present, including those of major, minor, and trace concentrations, and can also indicate possible reactions at various ph values. The orp measurements versus temperature yield data from which estimates can be made of thermodynamic functions. The applications and limitations of these measurements are discussed.
Proc. Western Reg. Symp. on Mining & Mineral Processing Wastes, Berkeley; SME, 1990, PP. 53-59