胶结物质去除对[土娄]土纳米颗粒凝聚的影响

Effect of Binding Agent Removal on Aggregation of Lou Soil Nanoparticles

[目的]为探究胶结物质对土壤胶体颗粒凝聚的影响,明确其分别促进土壤团聚体结构形成的微观机理。[方法]采用超声分散结合高速离心法从[土娄]土中提取3种土壤纳米颗粒,分别是[土娄]土提取得到的土壤纳米颗粒(NP-Lou)、去除有机碳[土娄]土中的纳米颗粒(NP-OCR)和去除无机碳[土娄]土中的纳米颗粒(NP-ICR)。采用动态光散射仪测定3种[土娄]土纳米颗粒在Na^(+)、Ca^(2+)和La^(3+)体系中的凝聚动力学过程、临界聚沉浓度(CCC)及表面电位值,结合Derjauin-Landau-Verwey-Overbeek(DLVO)理论计算[土娄]土纳米颗粒的Hamaker常数及相互作用能变化。[结果]在相同溶液化学条件下,与NP-Lou相比,NP-OCR和NP-ICR凝聚速率减小,CCC值增大。NP-OCR和NP-ICR的zeta电位绝对值低于NP-Lou,导致纳米颗粒间静电排斥势能降低。DLVO理论计算表明,NP-OCR和NP-ICR的Hamaker常数也低于NP-Lou;即去除无机碳或有机碳后,土壤纳米颗粒的范德华引力也随之降低。合力计算结果表明,去除无机碳或有机碳后土壤纳米颗粒间相互作用的总势能高于NP-Lou,所以CCC值更大。NP-ICR和NP-Lou的CCC差值大于NP-OCR和NP-Lou的CCC之差,因此土壤无机碳对[土娄]土纳米颗粒凝聚的影响更大。[结论]无机碳和有机碳通过增大[土娄]土土粒间相互作用的Hamaker常数来增强吸引势能,这是胶结物质促进土壤团聚体稳定的重要原因。

[Objective]To investigate the effect of binding agent on the aggregation of soil colloidal particles and to clarify the microscopic mechanism of the formation of soil aggregate structures.[Methods]Soil nanoparticles(NP)were obtained from Lou soil,namely NPs from original Lou soil(NP-Lou),NPs from organic carbon-removed soil(NP-OCR),and NPs from inorganic carbon-removed soil(NP-ICR).The aggregation kinetics,critical coagulation concentrations(CCCs)and surface electricity of three kinds of Lou soil nanoparticles in Na^(+),Ca^(2+)and La^(3+)systems were determined by dynamic light scattering.The Hamaker constant and interaction energy of soil nanoparticles were calculated by Derjauin-Landau-Verwey-Overbeek(DLVO)theory.[Results]In the same solution chemistry condition,the aggregation rate of NP-OCR and NP-ICR decreased and the CCCs value increased compared with NP-Lou.The absolute value of zeta potential of NP-OCR and NP-ICR was lower than that of NP-Lou,which resulted in the decrease of electrostatic repulsive potential energy between nanoparticles.The theoretical calculation of DLVO showed that the Hamaker constant of NP-OCR and NP-ICR was also lower than that of NP-Lou.That was,the attractire van der Waals potential energies of soil nanoparticles also decreased after the removal of inorganic carbon and organic carbon.The combined force calculation results showed that the total potential energy of the interaction between soil nanoparticles after removing inorganic carbon or organic carbon was higher than NP-Lou,so the CCC value was larger.The CCCs difference between NP-ICR and NP-Lou was larger than the CCC difference between NP-OCR and NP-Lou,therefore,soil inorganic carbon affected Lou soil NP aggregation more strongly.[Conclusion]Inorganic carbon and organic carbon enhance the attractive potential energy by increasing the Hamaker constant of the interaction between soil particles,which is important for cementing materials to promote the stability of soil aggregates.