The Theoretical Study On The Efficiencies Of2-[Tris(Hyroxycarbamoyl)Methyl] Carboxylic Acids As Chelating Agents In Flotation Separation Of Diaspore And Aluminosilicates

Due to the character of higher A/S in most of the diasporic bauxite in China, a class of novel carboxyl hydroxamic acid anionic surfactants was used as direct flotation collector for the de-silication of bauxite ores, based on the invesgations of structure-activity relationship between the anionic collectors and their collecting ability. The flotation results were also explained by density functional theory (DFT) and molecular dynamics simulation (MD). And the results in this work have an important theory meaning and an actual application value.2-[tris(hyroxycarbamoyl) methyl] carboxylic acids, namely THDA, THCA, and THTA were synthesized using hydroxylamine hydrochloride, sodium chloroacetate, straight alkyl bromides, and other relevant esters as raw materials. They were tested as collectors for the direct flotation of diaspore, kaolinite and illite and artificially mixed minerals. The results showed that the recovery of three single minerals presents similar trend though using different collectors. At the beginning, the recovery of diaspore, kaolinite and illite increases gradually with the increase of pH; however, the recovery declines in alkaline solution. Diaspore shows better floatability than kaolinite and illite though they all exhibit better flotation at pH7, the collecting capacity of the three compounds are in the order of THCA> THDA> THTA. The results of artificially mixed mineral samples indicate that THCA has better selectivity and higher floatability and is perhaps more suitable for separating against kaolinite and illite under the condition of pH7and2×10-4mol/L THCA.Some quantum-chemical parameters, such as Frontier molecular orbitals energy and atom charges were calculated and analysised by DFT method, which predicted reaction activity of the compounds is in the order of THCA> THDA> THTA, which agrees well with the flotation experiments. Large negative charges are located at the O atoms in the polar group of these collectors, which can easily donate electrons to the unoccupied orbital of Al atoms on the mineral surfaces as active centers. The MD simulation gave the configuration of THDA, THCA and THTA adsorbed and the binding energy of the three collectors on diaspore (010), kaolinite (001), and illite (001) surface. An analysis of these results indicates that THCA has better selectivity in flotation of diaspore than kaolinite. So THCA can be used to float and separate diaspore against aluminosilicates as a commendable collector. The theoretically obtained results are consistent with the flotation tests.