| Bisphenol S(BPS)is an emerging contaminant of bisphenols with hormonal effects.As a substitute for bisphenol A,it is widely used in various food contact coatings.With the continuous increase in usage,BPS has been widely used into the soil,water bodies and sediments.The adsorption of BPS by soil solid components can significantly affect its soil environmental behavior.In this paper,four soil minerals and humic acid are selected to study the adsorption of BPS by minerals and mineral-humic acid complexes,combined with surface properties X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),to explore the mechanism of minerals and mineral humic acid complexes adsorbing BPS,and the main results obtained are as follows:1.Ca-montmorillonite(Ca Mt)has the largest specific surface area of the four minerals,followed by goethite(Gt),followed by sodium montmorillonite(Na Mt),and kaolinite(Kln)is the smallest.The order of the amount of adsorption of the four minerals on BPS is Ca Mt>Gt>Na Mt>Kln.The fit of the adsorption isotherm model shows that the adsorption of the four minerals on BPS is most in line with the Langmuir model.p H significantly affects the adsorption of BPS.As the p H increases in the range of p H 3-11,the adsorption capacity of the four minerals first increases and then decreases,and the maximum adsorption capacity appears in the range of p H 6-8.With the increase of ionic strength,the adsorption capacity of BPS by minerals increases significantly,which may be attributed to the salting-out effect and the occurrence of cation bridging.The adsorption process is also affected by porosity.The adsorption of BPS with four minerals conforms to the quasi-second-order kinetic model.Except for goethite,the maximum adsorption capacity of the other three minerals-humic acid complexes for BPS is higher than that of pure minerals,but the adsorption capacity of goethite-humic acid complexes is lower than that of pure minerals.2.Comparative analysis of Fourier Transform Infrared Spectroscopy found that after goethite adsorbed BPS,an obvious vibration absorption peak appeared at 1397cm-1,indicating that a C-O-Fe bond was formed.After the two kinds of montmorillonite and kaolinite adsorbed BPS,no new absorption peak or peak shift was found.It shows that montmorillonite and kaolinite mainly adsorb BPS through physical action.When humic acid is present,goethite finds tiny new peak shapes on both sides of 990cm-1and 1397cm-1,which means that after the combination of goethite and humic acid,the surface structure changes,mainly Because the abundant phenolic hydroxyl and carboxyl groups on the surface of humic acid cover part of the Fe-O active sites on the surface of goethite,the adsorption and binding force of the complex and BPS is weakened.3.XRD results show that after BPS is adsorbed,the distance between Ca montmorillonite layers increases by 0.203 nm.When humic acid is present,the distance between Ca montmorillonite layers increases by 0.133 nm,indicating that BPS can enter calcium montmorillonite and calcium montmorillonite-HA Between the layers of the composite,the layer spacing of Na montmorillonite and its composites after adsorbing BPS changed little.XPS results showed that the binding energy of Ca2p1/2and Ca2p3/2 electrons increased after Ca montmorillonite adsorbed BPS,indicating that calcium ions participate in BPS adsorption and may form cation bridges with BPS.The electronic binding energy of Al2 p does not change much after kaolinite adsorbs BPS,indicating that kaolinite mainly adsorbs BPS through weak interaction.The Fe2 p electronic binding energy of goethite adsorbed BPS did not change significantly,combined with infrared,it can be seen that BPS may be combined with minerals mainly through surface coordination,hydrogen bond I and electrostatic attraction. |
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