Preparation And Characterization Of Hydroxyl-Fe-Al Pillared Montmorillonites And Adsorption Of PPCPs In Water Environment

Pharmaceuticals and personal care products(PPCPs),as emerging pollutants,have a potential impacts on the safety of drinking water,the ecological environment and human health,and how to solve the pollution problems of PPCPs effectively has attracted great attention of scientists in many countries.In this study,a series of organic and inorganic montmorillonites were prepared by using environment-friendly materials montmorillonite as raw material,meanwhile hydroxy iron-aluminum polymer,TDAB or TTAB as a pillar reagent.Many analysis methods were used to characterize the pillared montmorillonites,such as XRD,BET,FT-IR,EDX,XPS,TG-DTA and SEM.Systematic study on formation mechanism of intercalated montmorillonite composites,adsorption capacity and adsorption mechanism of both GEN and ZEA was carried out,and the removal of PPCPs in the process of livestock wastewater treatment was studied by using montmorillonite.The main conclusions are listed as follows:Effect of modified condition on structures and properties of modified montmorillonite:(1)The interlayer spacing(d(001))of hydroxyl Fe pillared montmorillonites increases with the increase of OH/Fe molar ratio,whereas to hydroxyl iron aluminum pillared montmorillonite that decrease with the increase of Fe/Al molar ratio,by the impact of different polymer produced in hydroxyl iron and hydroxyl aluminum's different hydrolysis phases and the hydroxyl polymer aluminum Keggin structure.When the molar ratio of Fe/Al>1.5,the d(001)value of both hydroxyl iron and aluminum pillared montmorillonite tends to be consistent.(2)Compared with raw montmorillonite,the surface area of hydroxyl Fe pillared montmorillonite increases significantly,which is consistent with the change of d(001),while the surface area of hydroxyl aluminum dominant pillared montmorillonite(with a molar ratio of Fe/Al?0.5)decreases.The adsorption isotherms of pillared montmorillonite are typical porous media multilayer adsorption type,and the most probable pore size value is 3.59 ± 0.04nm.The most probable pore volume value significantly increases,and the maximum can reach 1.5 times of the raw montmorillonite.(3)The contents of Fe and Al in the pillared montmorillonite increase significantly,and the binding energy of Fe and Al also changes in different degrees.With the increase of thermal stability,the new NO3-ions in the pillared montmorillonites give them the anion exchange function.Study on adsorption behavior of GEN on intercalated montmorillonite:(1)The adsorption capacity of pillared montmorillonite to Gen increases significantly and the maximum adsorption capacity is 2 times of the raw montmorillonite.When the value of pH is 9,the adsorption capacity reaches the maximum.The adsorption isotherms can be well described by Freundlich equation.The kinetic data of Gen adsorption can be well described by the pseudo second-order rate equation.The adsorption capacity of quaternary ammonium salt pillared montmorillonite to Gen decreases significantly.Competitive adsorption phenomenon can be found in the adsorption of multiple components,but the total of adsorption is increased.(2)XRD analysis shows that inter layer spacing amplification in both hydroxyl-Fe and hydroxyl-Al(with a molar ratio of molar ratio of Fe/Al?0.5)dominant pillared montmorillonite is the main reason for the increase of adsorption capacity to GEN.Surface area and pore volume value of hydroxyl Fe pillared montmorillonite have a strong correlation with the adsorption capacity of GEN.Cationic exchange is the dominant mechanism which can explain Gen,hydroxyl-Fe and hydroxyl-Al enter montmorillonite interlayer,and at the same time the auxiliary mechanism is chemical adsorption of surface coordination.Study on adsorption behavior of ZEA on intercalated montmorillonite:(1)The adsorption capacity of pillared montmorillonites to ZEA significantly increases,in which both 0.5Fe/Al-Mont and OH/Al-Mont reaches maximum adsorption capacity(approximately 10 times that of raw montmorillonite)and 1.50H/Fe-Mont attains 5 times that of raw montmorillonite.Adsorption isotherm study reveals that Freundlich adsorption isotherms best represents the experimental data.The kinetic data for ZEA adsorption can be best described using the pseudo second-order rate equation.The optimum value of pH for ZEA adsorption is 8,and the optimum temperature is approximately 35?.The adsorption capacity of ZEA in organic pillared montmorillonite is significantly higher than that in the hydroxyl-Fe-Al pillared montmorillonite.(2)Affected by the structure of pillared reagent,the amplification of d(001)in hydroxyl-Fe dominant pillared montmorillonite is the main reason for the increase of the adsorption capacity to ZEA,whereas hydroxyl aluminum iron pillared montmorillonite does not has similar mechanism.The change of surface element binding energy shows the difference adsorption mechanism in hydroxyl-Fe dominant pillared montmorillonites and hydroxyl aluminum iron pillared montmorillonites.(3)There is not obvious competitive adsorption phenomenon in the adsorption of multiple components,and the order is AFB1>OTA>ZEA.Study on PPCPs removal from swine wastewater:(1)After treatment by ABR +coagulation sedimentation + SBR treatment process,both CODcr and NH4+-N of wastewater reach the standard discharge.The total removal rate of GEN,TC,OTC,AMP,AFB1 and ZEA is higher than 76%.(2)GEN,TC,OTC,AMP and AFB1 in the wastewater are almost removed by adsorption in pillared montmorillonite,but ZEA has a certain residual.The hydroxy 1-Fe dominant pillared montmorillonite has a superior adsorption effect than that of raw montmorillonite.