| In order to solve the problem in alumina production, it is important to take new collectors for direct flotation to improve the A/S (mass ratio of Al2O3 to SiO2) of diasporic bauxite in China. In this paper, the synthesis of novel alicyclic carboxyl hydroxamic acids and their flotation properties to diaspore, kaolinite and illite have been studied. The adsorption mechanism of the new collectors on the three minerals has been investigated through adsorption amount, zeta potential and IR spectrum measurements.Two carboxyl hydroxamic acids, the MCTB and CETB were synthesized by reaction of hydroxylamine hydrochloride with relevant ester. The molecular structures of synthesized products have been identified by IR spectrum and element analysis.The results of flotation tests for single minerals indicate that the collecting ability of MCTB for diaspore, kaolinite and illite is stronger than that of CETB, and the selectivity of MCTB is better than that of CETB. Using MCTB and CETB as collector in the pH range of 6～7, diaspore have good flotation recovery; however, kaolinite and illite still keep a relatively low flotation recovery. At the dosage of 2×10-4 M, both MCTB and CETB show excellent floatability for diaspore with the recoveries over 90%, but for kaolinite and illite the recoveries were low. The results of flotation separation experiments of artificially mixed ores and diasporic-bauxite ores indicate that MCTB can separate diaspore from the aluminosilicate minerals at pH 6.3 with its concentration 6×10-4 M.The zeta-potential of diaspore change apparently while those of auminosilicates change slightly in the effect of collector. The SEM of single mineral (×20,000) shows the difference flotation power since their different crystal structure. The adsorption measurements indicate that the adsorption amount on diaspore is higher than that on kaolinite or illite, which is generally consistent with the flotation tests. The analysis of interaction mechanism demonstrates that MCTB is adsorbed on the surface of diaspore by a chemical adsorption, while its adsorption on the aluminosilicates is dominated by hydrogen bond; the chemical adsorption of chelator ion on diaspore may take place through-COOH,-NHOH and Al3+to form chemical bond; the adsorption on kaolinite or illite is mainly dominated by hydrogen bond. |
