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Use of Lignochemicals and Humic Acids to Remove Heavy Metals from Process Waste Streams.
MISSING :9 pages
The Bureau of Mines investigated the feasibility of removing heavy metals from mineral-process waste streams by precipitation with lignochemicals and humic acids. Lignochemicals are byproducts from the paper industry, while humic acids are obtained by caustic treatment of peat, subbituminous coal, and lignite. These high- molecular-weight organic materials have many functional groups, which can coordinate and form innercomplex salts with heavy metals that are crystalline precipitates. Filtering of a humic-acid- or lignochemical-treated solution or waste stream containing these precipitates removes the heavy metal sequestrates. Tests were conducted with two lignochemical samples, three humic acid samples, lime (cao), and sodium hydroxide (naoh) in which increasing amounts of these additives were reacted with 50 ml of solution containing fe3+, al3+, cr3+, pb2+, cu2+, cd2+, zn2+, co2+, ni2+, mn2+, and hg1+. At the appropriate ph, greater than 90- and 99-pct removal was achieved for these 11 heavy metal ions from the 10- and 100-ppm solutions, respectively, using lignochemicals and humic acids. Removal efficiency with these organic materials is better than that with cao, especially for the more toxic ions, hg1+, cd2+, and pb2+. Unlike the precipitates formed with naoh or cao, those with lignochemicals and humic acids are compact and noncolloidal. The volume of their sludge is sharply lower than that of the finely dispersed lime or soda precipitates; thus, their removal in settling tanks or by simple filtration is enhanced.
IH; Report of Investigations;
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division