Inhibition Of Starch And Its Derivatives On A Diaspore

Two non-ionic starches, including soluble starch (SS) and highly branched waxy maize starch (WMS), and three ionic starches with selected charge characteristics including cationic starch (CAS), carboxymethyl starch (CMS) and amphoteric starch (AMS) were investigated as depressants for diaspore in reverse flotation test using cationic collector (dodecylamine, abbreviated as DDA). The microflotation results show that the addition of starches as mentioned above causes the recoveries of diaspore noticeably decreased in the range pH 2～12. The depression performances of starches can be established in the order of WMS>AMS>CAS>SS>CMS. The addition of WMS and AMS (100 mg/L) cause almost no particle flotation of diaspore to be observed in the acidic pH range (pH<6). The effect of starch depressants on the floatability of kaolinite was also investigated for a comparison. The results show that the recovery of kaolinite is more or less activated by the addition of starch reagents, and nearly keeps a constant level with respect to the change of depressant concentration. The microflotation of mixed minerals (mdiaspore:mkaolinite=2:1 and 3:1) were carried out with DDA (6.5×10-4mol/L) as collector and WMS (100 mg/L) as depressant, at pH 9 to avoid flocculation between these two minerals. After flotation, the samples have been greatly upgraded in terms of highly improved A/S (4.26 to 12.73,5.88 to 41.61 respectively) and the recoveries of A12O3 (63.77% and 58.02% respectively) obtained. It is accordingly assumed that WMS is one selective depressant in the diaspore and kaolinite reverse flotation.Adsorption of starches and DDA, Zeta potential measurement, AFM and Fourier transform infrared (FTIR) spectroscopy were used to clarify the role of the surface characteristics of starches in determining the adsorption behavior and depression performance as well as the mineral-starch interaction. The results show that the presence of hydrogen bonds and chemical complexation between mineral and starches in an integrated manner, besides, there also exist electrostatic interaction between ionic starches and diaspore. The adsorption conformation of starch, which influenced by chain structure, electrical properities and density, plays a key role in the cationc flotation. In addition, the experiments also found that the presence of starch can not prevent the adsorption of DDA, but it will also have a facilitating role. In the several starches, there exists a strong adsorption force between CMS and diaspore. Besides, there also exists electrostatic attraction between CMS and collector DDA, so CMS tend to adsorb on the surface of diaspore in lying, forming the polymer-surfactant complex. Therefore the inhibitory effect is not satisfactory, and the higher DS, the poor performance. CAS adsorbs in the form of rings, and the collector DDA will be hold by its thicker adsorption layer, thus show good performance. AMS showing the best inhibitory of the three ionic starches because it has the advantage of CMS and CAS, so it shows better performance than CMS and CAS. WMS, which have large branches, can effective adsorbed on the surface of diaspore by hydrogen bonding. Its multi-branched structure can be well demonstrating its role in covering DDA, so its performance is very prominent.