混合捕收剂在锂云母表面吸附行为的分子动力学模拟研究
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摘要
采用Materials Studio中Forcite模块,对十二胺和油酸钠两种捕收剂分子在锂云母表面的吸附过程进行了分子动力学模拟研究,分析了水分子在吸附前后相应的排布变化。吸附形貌的结果表明,十二胺与油酸钠用量在2∶1时吸附效果最好。通过对捕收剂头基以及碳原子分布函数的分析,其协同作用的机理可能是十二胺首先在锂云母表面进行有效吸附,油酸钠"间接"地通过头基间的静电吸引或是碳链之间的疏水作用,从而增加表面碳链密度和高度并使得吸附层更加稳定。表面水分子自扩散系数的分析也显示,吸附了单层DDA和混合捕收剂的自扩散系数相较纯云母表面的值分别下降了20%和25%左右,表明混合捕收剂的吸附使得锂云母表面更加疏水,从而有利于浮选的进行。
Molecular dynamics simulations of adsorption of mixed DDA and NaOL collectors on lepidolite surface as well as the arrangement of water molecules are investigated by Forcite module in Materials Studio.The results of adsorption configurations show the best DDA/NaOL ratio is 2∶1.Distributions of head groups of collectors and C atoms density profiles reveal that DDA prior adsorbs on the lepidolite.And NaOL co-adsorb on the surface by electrical static attraction between opposite-charged head groups or the interaction between the hydrophobic chains,leading to a higher and more stable adsorption layer.The analysis of the self-diffusion coefficient of surface water molecules also showed that the self-diffusion coefficient of the single-layer DDA and the mixed collector was reduced by 20% and 25%,respectively,compared with the pure mica surface.All of the above results indicate that the adsorption of the mixed collector makes the surface of the lithium mica more hydrophobic,which is beneficial to the flotation.
Molecular dynamics simulations of adsorption of mixed DDA and NaOL collectors on lepidolite surface as well as the arrangement of water molecules are investigated by Forcite module in Materials Studio.The results of adsorption configurations show the best DDA/NaOL ratio is 2∶1.Distributions of head groups of collectors and C atoms density profiles reveal that DDA prior adsorbs on the lepidolite.And NaOL co-adsorb on the surface by electrical static attraction between opposite-charged head groups or the interaction between the hydrophobic chains,leading to a higher and more stable adsorption layer.The analysis of the self-diffusion coefficient of surface water molecules also showed that the self-diffusion coefficient of the single-layer DDA and the mixed collector was reduced by 20% and 25%,respectively,compared with the pure mica surface.All of the above results indicate that the adsorption of the mixed collector makes the surface of the lithium mica more hydrophobic,which is beneficial to the flotation.
引文
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[25]ASH L A,EVANS S,HIORNS A G.Cation ordering in lepidolite and biotite studied by X-ray photoelectron diffraction[J].Clay Minerals,1987,22(4):375-386.
[2]何桂春,冯金妮,毛美心,等.组合捕收剂在锂云母浮选中的应用研究[J].非金属矿,2013(4):29-31.
[3]吕子虎,赵登魁,沙惠雨,等.阴阳离子组合捕收剂浮选锂云母的试验研究[J].矿产保护与利用,2017(2):81-84.
[4]XU L,HU Y,TIAN J,et al.Synergistic effect of mixed cationic/anionic collectors on flotation and adsorption of muscovite[J].Colloids and Surfaces A:Physicochemical and Engineering Aspects,2016,492(Supplement C):181-189.
[5]ROSEN M J,GU B.Synergism in binary mixtures of surfactants.6.interfacial tension reduction efficiency at the liquid/hydrophobic solid interface[J].Colloids&Surfaces,1987,23(1/2):119-135.
[6]PARIA S,KHILAR K C.A review on experimental studies of surfactant adsorption at the hydrophilic solidwater interface[J].Advance Colloid Interface Science,2004,110(3):75-95.
[7]TOMLINSON E,DAVIS S S,MUKHAYER G I.Ionic interaction and phase stability[M].Springer New York,1979:3-43.
[8]WANG L,SUN W,HU Y H,et al.Adsorption mechanism of mixed anionic/cationic collectors in muscovite-quartz flotation system[J].Minerals Engineering,2014,64:44-50.
[9]VIDYADHAR A,KUMARI N,BHAGAT R P.Adsorption mechanism of mixed collector systems on hematite flotation[J].Minerals Engineering,2012,26:102-104.
[10]HANUMANTHA RAO K,FORSSBERG K S E.Mixed collector systems in flotation[J].International Journal of Mineral Processing,1997,51(1-4):67-79.
[11]HEINZ H,KOERNER H,ANDERSON K L,et al.Force field for mica-type silicates and dynamics of octadecylammonium chains grafted to montmorillonite[J].Chemistry of Materials,2005,17(23):5658-5669
[12]HEINZ H,VAIA R A,KRISHNAMOORTI R,et al.Self-assembly of alkylammonium chains on montmorillonite:Effect of chain length,head group structure,and cation exchange capacity[J].Chemistry of Materials,2007,19(1):59-68.
[13]刘跃龙,徐尧,刘够生.硅酸盐矿物浮选过程的理论模拟.有色金属(选矿部分),2015(5):92-97.
[14]徐尧,刘跃龙,刘够生.水分子在白云母表面吸附的分子动力学模拟[J].化工学报,2014(12):4814-4822.
[15]XU Y,LIU Y L,HE D D,et al.Adsorption of cationic collectors and water on muscovite(001)surface:Amolecular dynamics simulation study[J].Minerals Engineering,2013,53:101-107.
[16]XU Y,LIU Y L,GAO S,et al.Monolayer adsorption of dodecylamine surfactants at the mica/water interface[J].Chemical Engineering Science,2014,114:58-69.
[17]石玉翔,王林林,刘跃龙,等.相同链长伯铵盐和季铵盐对云母表面润湿性的影响.有色金属(选矿部分),2017(4):93-98.
[18]WANG L,LIU R,HU Y,et al.Adsorption of mixed DDA/NaOL surfactants at the air/water interface by molecular dynamics simulations[J].Chemical Engineering Science,2016,155:167-174.
[19]LOEWENSTEIN W.The Distribution of aluminum in the tetrahedra of silicates and aluminates[J].American Mineralogist,1954,39(1-2):92-96.
[20]BELLAICHE L,VANDERBILT D.The virtual crystal approximation revisited:Application to dielectric and piezoelectric properties of perovskites[J].Physical Review B Condensed Matter,1999,61(12):7877-7882.
[21]TIAN J,XU L,DENG W,et al.Adsorption mechanism of new mixed anionic/cationic collectors in a spodumene-feldspar flotation system[J].Chemical Engineering Science,2017,164:99-107.
[22]VIDYADHAR A,HANUMANTHA R K.Adsorption mechanism of mixed cationic/anionic collectors in feldspar-quartz flotation system[J].Journal of Colloid Interface Science,2007,306(2):195-204.
[23]WANG J,KALINICHEV A G,KIRKPATRICK R J,et al.Structure,energetics,and dynamics of water adsorbed on the muscovite(001)surface:A molecular dynamics simulation[J].The Journal of Physical Chemistry B,2005,109(33):15893-15905.
[24]MIRANDA P B,XU L,SHEN Y R,et al.Icelike water monolayer adsorbed on mica at room temperature[J].Physical Review Letters,1998,81(26):5876-5879.
[25]ASH L A,EVANS S,HIORNS A G.Cation ordering in lepidolite and biotite studied by X-ray photoelectron diffraction[J].Clay Minerals,1987,22(4):375-386.