Flocculation of Clays and Soils by Organic Compounds

The effectiveness of 15 substituted benzene ring compounds in flocculating < 2µ Gila clay was evaluated by measuring flocculation percentage and by observation after reaction in water suspension. In general the flocculation percentages were in the order: calcareous clays > noncalcareous, calcium‐saturated clays > noncalcareous sodium‐saturated clays. Effectiveness of organic compounds on carbonate containing clays increases sharply as the pH value drops to about 6.0. In carbonate‐free systems the effect of decreasing pH is not evident until the pH drops to < 4, and is not consistent. Calcium appears necessary for flocculation in all sodium, calcium‐clay systems studied. Interlayer absorption does not insure flocculation, and naturally existing organic matter did not increase flocculation by the organic compounds tested. The effectiveness of the compounds used appeared to depend on the number of active groups, and on the number of unshared electrons. Reactive groups of benzene ring compounds were more effective in the meta than in the ortho or para positions.