Cleaning Coal with Coal:Coal Humic Acids for Removal of Acid,Iron,Heavy Metals,and Organic Pollutants Associated with Use of Coal as a Fuel.

摘要

Cation exchangers were prepared by surface oxidizing Missouri bituminous coal with 6 M nitric acid through which air was bubbled. This treatment introduces oxygen-containing functional groups on the coal surface producing an ion exchanger with acid-base properties and the capability of chelating metal ions. The sodium form of the ion exchanger removed sulfuric acid from water raising the pH from 1.5to more than 8. Ferrous iron at 25mg/l in pH 1.5sulfuric acid (simulating acid mine water) was removed to less than 0.2mg/l by the sodium form of the ion exchanger. A similar solution of ferric iron was lowered from 100mg/l to about 0.5mg/l by the same treatment. The treated coal was found to chemically reduce some iron (III) to iron (II). When passed over the acid form of the coal ion exchanger,copper and cadmium levels in neutral solution were lowered from 10mg/l to 0.01and 0.00mg/l,respectively,and from 50mg/l to 0.02and 0.01mg/l respectively. The low ion exchange capacity of surface treated coal limits its usefulness in treating water. Base-soluble coal humic acid has a much higher ion exchange capacity,and work is continuing on its use for wastewater treatment.