APAM在水/高岭石界面吸附行为的试验和分子模拟研究

Experimental and molecular simulation study of the adsorption behavior of APAM at water/kaolinite interface

微细高岭石对煤泥浮选与煤泥水处理会产生不利影响,为深入了解水溶液中阴离子聚丙烯酰胺(APAM)与高岭石的作用机理,通过APAM在高岭石颗粒上的吸附量及残留量、絮凝沉降后上清液的浊度、絮团的Zeta电位和尺寸分布等分析了APAM对微细高岭石悬浮液的吸附现象和沉降规律,借用数量密度分布、水密度分布和自扩散系数等分子动力学参数计算研究其中的吸附作用和桥连机制.结果表明:除浊效果与APAM的吸附性能和残留量相关,絮团尺寸主要与残留量相关.随着APAM质量浓度的增加,APAM与高岭石表面的吸附能力和非键作用增-强,其以水分子为“纽带”间接吸附在高岭石(001)面,通过氢键直接吸附在高岭石(001)面.APAM与高岭石表面的吸附是形成桥连机制的前提,APAM的扩散范围和扩散速度共同决定桥连机制的强弱,扩散范围对桥连机制的影响效果更大.APAM分子链越多,扩散范围越大,桥连性能越强,有利于絮团的生长变大;APAM过量导致溶液黏度增大,扩散速度降低,桥连机制减弱,阻碍颗粒的沉降.大量水分子与APAM在高岭石表面存在强烈地竞争吸附,阻碍了氢键作用的形成.

Fine kaolinite hurts slime flotation and slime water treatment.To understand the interaction mechanism of anionic polyacrylamide(APAM)and kaolinite in aqueous solution,the adsorption phenomenon and the sedimentation law of APAM with the fine kaolinite suspension were studied by the adsorption amount and residual amount of APAM on kaolinite particles,supernatant turbidity,floc Zeta potential,and size distribution of the flocculation sedimentation.The adsorption interaction and bridging mechanism were studied via calculation of molecular dynamics parameters such as number density distribution,water density distribution,and self-diffusion coefficient.The results show that the effect of turbidity removal is dependent on both adsorption performance and residual amount of APAM,whereas the floc size is mostly dependent on the residual amount.With the increase of mass concentration of APAM,the adsorption capacity and non-bonding interaction between APAM and kaolinite surface are enhanced,and APAM is adsorbed on the kaolinite(001)surface with water molecules as a“link”,-and it is adsorbed by hydrogen bond on kaolinite(001)surface.The adsorption of APAM and kaolinite surface is the premise of forming the bridging mechanism.The strength of the bridging mechanism is determined by the diffusion range and diffusion speed of APAM,with the diffusion range having a bigger impact.The greater the number of APAM molecular chains,the greater the diffusion range and the stronger the bridging performance,which is beneficial for floc growth.However,excessive APAM increases the viscosity of the solution,decreases the diffusion rate,and weakens the bridging mechanism,which inhibits particle sedimentation.A large number of water molecules and APAM strongly compete for adsorption on the surface of kaolinite,which hinders the formation of hydrogen bonds.