Flotation Performance And Mechanism Of Reagents Based On Dodecylamine And 2-Octanol

Iron ore resources are abundant in China,but due to the fine grain size and complex mineral composition,the magnetite concentrate often needs further desilication through reverse flotation to meet the metallurgical needs.At present,the use of reverse flotation process to improve the iron grade and reduce the silicon grade has become an indispensable part of the ore dressing plant.The key technology is the development and application of reverse flotation reagents.Dodecylamine(DDA),a cationic collector often used in reverse flotation of iron ore,has high freezing point and poor water solubility.It is often used industrially as dodecylamine hydrochloride or acetate,and it is difficult to store hydrochloric acid and acetic acid.The inconvenient preparation of the medicine,the sticky foam is difficult to rupture for a long time,causing problems such as increased water consumption and the amount of medicine used,and affecting the pH of the pulp,thereby limiting the application of DDA.In order to simplify the preparation of reagents,eliminate the acidification link of DDA,realize iron ore flotation at room temperature,and save the cost of reagents.According to the technical ideas of compounding and synergizing,DDA and 2-octanol are base reagents,one or more of kerosene and surfactants are auxiliary reagents,and are formulated into mutually miscible multi-component miscible reagents according to a certain ratio.In this paper,the flotation performance of miscible reagents on quartz and magnetite is investigated using mineral flotation tests.The laser particle size analysis,Zeta potential test,freezing point measurement,surface tension and contact angle test,infrared spectrum measurement and molecular dynamics calculation were used to determine the basic properties of miscible reagents,and to explore the mechanism of action of miscible reagents and minerals.The main research work and conclusions of this paper are as follows:DDA and 2-octanol were used as the main reagents to prepare miscible reagents,and the basic physical properties of the miscible reagents were systematically measured,including the freezing point and its dispersibility,charging properties,foamy properties and surface tension in the aqueous solution.The results showed that 2-octanol can improve the properties of the reagent while serving as a solvent for DDA.Compared with kerosene,2-octanol has obvious advantages in reducing the freezing point,improving the dispersibility,improving foam properties and reducing the surface tension of the solution.Within the test range,the freezing points of DDA-2-octanol,DDA-2-octanol-kerosene and DDA microemulsion can be reduced to-15.67?,-4.7? and-12.5?,respectively;the dispersibility of DDA-2-octanol-kerosene and DDA microemulsion in aqueous solution is further improved;DDA-HCl produces a lot of foam and defoaming is difficult,the introduction of 2-octanol can improve the foaming performance of miscible reagents,the foam becomes more brittle,easy to defoaming,the introduction of kerosene can affect the foaming performance of reagents,accelerate the defoaming rate;the miscible reagent is essentially charged positively in an aqueous solution with a pH less than 10;the ability of miscible reagents to decrease air–water interfacial tension:DDA-2-octanol(2:1)>DDA microemulsion D>DDA-2-octanol-kerosene(2:1:1),among which DDA microemulsion D has the best surface activity,at 3.6×10^–3 mol/L(CMC)DDA-2-octanol(2:1),the surface tension reached its minimum(23 m N/m)and remained almost constant despite the increased reagent concentration.The solvation free energy and mixing energy were calculated by molecular dynamics simulation to investigate the solubility and compatibility of the reagents.The results show that the solubility of DDA in aqueous solution is very poor,and it dissolves well in 2-octanol and dodecane,revealing why DDA-2-octanol and DDA-dodecane can be successfully formulated.And the solubility of DDA-2-octanol in water is better than that of DDA-dodecane,which is consistent with the dispersibility of the reagent in water.By calculating the mixing energy of reagent molecules,it can be found that the mixing process of DDA-dodecane can proceed spontaneously,while DDA-2-octanol requires a certain amount of energy to be miscible,such as heating or stirring.The adsorption morphology and synergistic effect of DDA and 2-octanol on the air/water interface were investigated.The results show that there are two main binding forces between d DDA and 2-octanol molecules at the air/water interface:the interaction between polar groups(mainly hydrogen bonds)and the hydrophobic interaction between carbon chains.When the mass ratio of DDA and2-octanol is 2:1,they exhibit a clear synergistic effect at the air/water interface,forming a tight monolayer at the air/water interface,and the results are consistent with the results of the surface tension test of the reagent.The miscible reagents mainly composed of DDA and 2-octanol was used as the collector to investigate its collection performance on quartz.It was found that the components of the miscible collectors had significant synergistic effects in the flotation process,and it has good adaptability to the temperature and pH of the pulp.The recovery of quartz was the worst when DDA-HCl was used alone,the recovery of quartz is greatly improved when used in combination with 2-octanol.DDA-2-octanol can completely replace DDA-HCl+2-octanol without affecting the flotation effect and eliminating the acidification of DDA,and HCl has no effect in the flotation process and only acts as a solvent in the preparation of DDA-HCl.The 2-octanol in DDA-2-octanol ensures the foaming property of the miscible reagent,while saving the amount of DDA and reducing the cost of the reagent.And DDA-2-octanol is simple and convenient to prepare,environmentally friendly,low freezing point and easy to use.The adaptability of miscible reagents to the temperature of the pulp is consistent with their freezing points.DDA-2-octanol-kerosene and DDA microemulsion can achieve normal temperature or even low temperature floatation of quartz without acidification of DDA.The pH range of DDA-HCl,DDA-2-octanol,DDA-2-octanol-kerosene and DDA microemulsion D suitable for quartz flotation are basically the same(pH=5.0?9.0).However,the collection capacity of miscible reagents under weak acid(pH=5.0)and weak alkali(pH=9.0)is significantly better than DDA-HCl,and the recovery of quartz is above 95%.In order to further explore the mechanism of action of miscible reagents and minerals,the infrared spectrum,integrated heat of adsorption,contact angle and Zeta potential of the quartz surface after the action of the reagents were tested.It was found that the miscible reagents all act on the quartz surface through physical adsorption,and the contact angle of the quartz surface increases significantly after the interaction with the reagents.There is an interaction between the components of the miscible reagents,which promotes the adsorption of DDA on the quartz surface other components and DDA co-attach to the surface of quartz in some form.Among them,2-octanol and DDA will co-adsorb on the surface of quartz,thereby improve the hydrophobicity of the quartz surface;kerosene does not adsorb on the quartz surface,but it can reduce the adsorption equilibrium time.Using molecular dynamics calculations,the adsorption model of miscible reagents on the solid-liquid interface was constructed to investigate the adsorption morphology and synergistic effects of the reagents on the quartz surface with the single or mixtures of DDA and 2-octanol.It was found that DDA and 2-octanol have a significant synergistic effect at the solid-liquid interface,and DDA and 2-octanol are co-adsorbed on the quartz surface.Compared with the single reagent system,the mixtures of DDA and 2-octanol has the largest binding energy on the quartz surface.The addition of reagent molecules does not fundamentally displace the water molecules on the quartz surface,but through this layer of water molecules to adsorb to the quartz surface,and use its own long hydrocarbon chain to improve the hydrophobicity of the quartz surface.And when DDA and 2-octanol are miscible,the concentration of water molecules near the quartz surface is the lowest,and the hydrophobicity of the quartz surface is the strongest.By investigating the flotation effect of quartz and iron ore after the compounding of different auxiliary reagents with DDA-2-octanol,it was found that the addition of auxiliary reagents significantly improves the recovery of quartz,DDA-2-octanol-esters have poor stability,DDA-2-octanol-AEO series of surfactants have no significant effect on the flotation results of iron ore.Under the action of DDA-2-octanol-kerosene,the flotation effect of Jianshan magnetite is the best,a concentrate with 69.10%TFe and 2.26%SiO₂ of iron concentrates were obtained,the recovery rates of TFe and SiO₂ were 81.88%and 80.17%,and the separation efficiency of TFe and SiO₂ were 52.05%and 61.29%,respectively.The BBD experimental results show that the experimental data has a good agreement with the proposed model.A concentrate with 70.08%TFe and 3.56%SiO₂ was obtained,at a yield of 83.29%.Backward regression analysis was used to eliminate the insignificant effect on the flotation results of magnetite and clarify the relationship between the amounts of the three reagents and the flotation results of magnetite.The results show that the increase in the amount of DDA and 2-octanol is beneficial to the separation of magnetite and quartz.When the amount of the main component of DDA and 2-octanol is large,the beneficiation efficiency decreases as the amount of the auxiliary kerosene increases.Effect of kerosene on the flotation of magnetite is related to the amount of DDA:when the dosage of DDA is less than 30 g/t,increasing the kerosene dosage is beneficial to the flotation of magnetite.And when the amount of 2-octanol is less than 26.67 g/t,the separation efficiency of TFe increased as the amount of kerosene increases,otherwise the separation efficiency of TFe decreased.The Jianshan magnetite was used as the original ore sample for the reverse flotation test of the open-circuit process,it was found that the open-circuit process test of the Jianshan magnetite with one roughing,one cleaning and three stages scavenging,and without adding any reagents during the scavenging process,can sort iron ore more thoroughly,and DDA-2-octanol-kerosene has the best flotation effect on Jianshan magnetite.Compared with DDA-HCl as collector,the concentrate with higher TFe content and lower SiO₂ content can be obtained by using the miscible agent based on DDA and 2-octanol as collector at the same recovery rate.