不同形貌二水草酸钙对阴离子表面活性剂AOT的吸附差异

人体尿液中存在大量具有生物表面活性的物质，而这些物质与尿液中不同形貌的草酸钙微晶间的吸附关系并未得到人们广泛关注。挑选了常用的阴离子表面活性剂磺基琥珀酸钠二辛酯(AOT)作为吸附物质，研究了不同形貌的二水草酸钙(COD)晶体对AOT的吸附差异，探究草酸钙结石的形成机理。采用X射线粉末衍射仪(XRD)和傅里叶变换红外光谱仪(FTIR)表征，并通过谱图差异分析了吸附AOT前后棒状、圆钝形、花状、十字形和双锥形COD晶体的组分变化；采用Zeta电位分析仪测定吸附AOT后晶体表面的Zeta电位随AOT浓度的变化；采用比色法通过紫外可见分光光度计测定不同浓度AOT存在下晶体的吸附量变化并绘制吸附曲线。随着AOT浓度的增加，COD的吸附量逐渐上升，最后达到吸附饱和状态，各吸附曲线均呈S型。不同形貌COD对AOT的最大吸附量大小顺序为：棒状COD (41.0 mg·g-1)>圆钝形COD (37.5 mg·g-1)>花状COD (35.0 mg·g-1)>十字形COD (27.2 mg·g-1)>双锥形COD (20.9 mg·g-1)。COD晶体的比表面积越大，表面提供的活性位点也越多，越有利于表面活性剂AOT在晶体表面的吸附；富含Ca2+的(100)晶面更利于阴离子的AOT的优先吸附；此外COD晶体的内能越大，越会抑制AOT在COD表面的吸附，导致吸附量降低。吸附了AOT的COD晶体稳定性显著增加，COD向COM转变的速度明显降低。基于AOT在不同形貌的COD晶体表面的吸附特点，提出了COD晶体吸附AOT的分子模型。COD晶体对AOT的吸附与晶体形貌密切相关。容易吸附AOT的COD晶体形貌更容易粘附在带负电荷受损伤的细胞表面，加大草酸钙结石形成的风险。

Differences in Adsorption of Anionic Surfactant AOT by Calcium Oxalate Dihydrate With Different Morphologies

There are many biosurfactant substances in human urine,and the adsorption relationship between these substances and calcium oxalate crystallites with different morphologies has not received widespread attention.In this study,the commonly used anionic surfactant sodium dioctyl sulfosuccinate(AOT)was selected as the adsorbing substance.The adsorption differences of AOT onto calcium oxalate dihydrate(COD)with different morphologies were studied to calcium oxalate stone’s formation mechanism.The crystalline phase transition of COD with different morphologies(Rod,Blunt,Flower,Cross,Bipyramid)before and after AOT adsorption was analyzed using an X-ray powder diffractometer Fourier-transform infrared spectrometer.Zeta potential changes on crystal surface after AOT adsorption was measured using a Zeta potential analyzer.The adsorption quantity of different AOT concentrations onto various COD crystals was detected using a colorimetric method,and the adsorption curves were drawn.As c(AOT)increases,the number of COD adsorbed increases gradually,and finally reaches saturation,and the adsorption curves are all S-type.The order of maximum adsorption of AOT by different morphologies of COD is:COD(Rod)(41.0 mg·g^-1)>COD(Blunt)(37.5 mg·g^-1)>COD(Flower)(35.0 mg·g^-1)>COD(Cross)(27.2 mg·g^-1)>COD(Bipyramid)(20.9 mg·g-1).The larger the specific surface area of the COD crystal was,and the more active sites were provided,so the stronger the adsorption capacity would be;the(100)surface of COD,which is rich in Ca 2+ions,is beneficial to AOT adsorption;the larger the internal energy of COD crystal was,the lower the adsorption amount would be.COD crystals’stability in suspension adsorbed is obviously increased after AOT adsorption,and the rate of COD transition to COM is obviously reduced.Based on the adsorption characteristics of AOT on the surface of COD crystals with different morphologies,we propose a molecular model for the adsorption of AOT onto COD crystals.The adsorption of AOT by COD crystals is closely related to crystal morphology.The morphology of COD crystal that easily adsorbs AOT is more likely to adhere to injured cells’surface with negative charges,thus leading to an increasing risk of calcium oxalate stone formation.