Starch based depressors for selective flotation of metal sulfide ores

When starch blends with various biogenic L-alpha-amino acids are heated for 6 h in an open vessel, starch esterifies the amino acids and dextrinizes. The water solubility of the dextrins depends on the acid used in the reacti on. Because of the poor solubility of dextrins produced on heating starch w ith either cysteine, arginine, proline, aspartic acid or glutamic acid, cro sslinking of the polysaccharide is postulated. Healing produces free radica ls, which possesses unpaired electron localized either on the C, N or S ato m depending on the amino acid and thermolysis conditions.