Synthesis And Flotation Performance Of High Selective Cationic Collector For Hematite Reverse Flotation

In recent years,with extension exploitation of mine,the high-grade and easy-beneficiation ores have been decreasing year by year.Traditional physical sorting methods,for example,gravity separation and magnetic separation are losing their superiority in obtaining high-grade useful minerals.Forth flotation,however,with its unique advantages in separation of low-grade,complex,fine-grained and refractory ores,has attracted more and more attention of researchers.The development and application of flotation reagents is the key and core factor for flotation technology.Recently,with the policy development of intensive economy,cost-saving,and energy consumption reducing,cationic flotation process has been reemphasized as a research focus.Cationic flotation process has many special merits,such as simple reagent system,easy operation and low-temperature resistance.Unluckily,there are only few available cationic collectors applied in dressing plant and suffering from poor selectivity in the flotation process,which seriously hamper the popularization and application of the technology.Therefore,the research and development of highly selective cationic collectors are of great significance to improve the comprehensive utilization efficiency of resources,and also to the green and sustainable development of mines.In this paper,with the aid of hematite reverse flotation desilication system,five new cationic collectors with high flotation selectivity were designed based on molecular simulation,taking selectivity index derived from adsorption energy as a criterion in the solvation model of quartz and hematite.Then,N-(2-hydroxy-1,1-dimethylethyl)dodecylamine(HDMEA),N-(2,3-dihydroxypropyl)-dodecylamine(PDDA),N,N-dimethyl-N'-dodecyl-1,3-propyl diamine(DPDA),N-(2-hydroxyethyl)-N-dodecyl-1.2-ethyl diamine(NHDE),and N,N-dimethyl-N'-(2-hydroxyethyl)-N-dodecyl-1.3-propyl diamine(DMPDA)were synthesized and characterized in laboratory.The activity and flotation performance of these cationic collectors were systematically studied by surface tension tests,flotation of single mineral,and separation of artificially mixed minerals.Then,the adsorption mechanism of the new cationic collectors was studied by zeta potential tests,Fourier infrared spectrum(FTIR)analysis and X-ray photoelectron spectroscopy(XPS)measurements.Firstly,combining with molecular simulation,the quartz(101)surface(lO1-lO1…1Si3-1Si3)and hematite(001)surface(1Fe3-3O3…3O3-1Fe3)were chosen as the initial model under the suitable compass ? force field.Then,the influence of solvation effect on quartz and hematite surface was introduced through the construction of quartz and hematite solvation model.Based on these,the adsorption characteristics of dodecylamine(DDA)on mineral surface were investigated.As a result,the quartz(101)surface and hematite(001)surface constructed under neutral condition were selected as the receptor mineral model for subsequent design and selection of new cationic collectors.The relationship between molecular configuration and the selectivity of several common cationic collectors was studied using the molecular simulation technology.According to the results,the selectivity index based on calculation of the adsorption energy between reagents and mineral surfaces was determined as the criterion of selectivity characterization for collectors.Combined with molecular structure design theory of flotation reagents,substituents containing more electronegative active atoms(N atom and O atom)were introduced into polar group(-CH2NH2)of DDA,and then a variety of novel highly selective cationic collectors with multiple active sites and larger polar group size were designed in the solvation model of receptor minerals.In laboratory,five collectors were synthesized by the nucleophilic substitution reaction.The products were characterized by elemental content analysis,mass spectrometry,1H nuclear magnetic resonance spectrum,and FTIR.The results of surface tension tests showed that the five collectors had superior surface activity than DDA.Flotation results of single mineral demonstrated that all five cationic collectors showed a similarly good collection effect on quartz,but diverse collection ability on hematite.Compared with DDA,under the same flotation conditions,the order of collection ability of tested cationic collectors on quartz is NHDE>DPDA>DMPDA>PDDA>HDMEA>DDA,and the order of the collection ability on hematite is NHDE>DDA>DPDA>DMPDA>PDDA>HDMEA.There were two different flotation behaviors for quartz and hematite after adding starch.When a proper amount of starch(less than 10.0 mg/L)was added,the flotation recovery of quartz was about 90.0%,while the flotation recovery of hematite was less than 5.0%,which laid the foundation for flotation separation of quartz and hematite.In laboratory,the artificially mixed minerals composed of hematite and quartz with a mass ratio of 2:3,were used to investigate the flotation separation performance of five synthetic cationic collectors.The results showed that these five cationic collectors possessed a good separation performance within a wide pH range(7.0-10.0),and the separation of artificially mixed minerals could be realized under natural slurry pH.Separation performance of cationic collectors is in accordance with the following rule:HDMEA>DMPDA>DPDA>PDDA>NHDE>DDA,which was consistent with the order of selectivity index.The results indicated that the design thought and method based on selectivity index has good reliability and applicability.The results of zeta potential tests,FTIR analyses,and XPS analyses showed that physical adsorption was dominated between the new cationic collectors and the mineral surfaces,which mainly depended on electrostatic attraction and hydrogen bonding.Meanwhile,the oxygen elements on quartz surface were involved in adsorption process.