Preparation Of Cationic Dyes/Sepiolite Composite Pigments And Study Of The Mechanism

In this study,basic orange 2/sepiolite composite pigments were prepared by atmospheric method and vacuum method using sepiolite(Sep)as the inorganic matrix,basic orange 2(BO2)as the organic dye.The effects of material ratio,sepiolite heating temperature and adsorption times on the structure and properties of the composite pigments were investigated.The cationic organic dyes of different sizes and polarities--BO2,methylene blue(MB),basic red 18(BR18)and basic red 2(BR2)--were selected and the composite pigments were prepared by the negative pressure method with sepiolite,using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,infrared testing,scanning electron microscopy,transmission electron microscopy,infrared testing,thermal analysis,specific surface area and microporous analysis were used to study the effects of the dyes types on the structure of the composite pigments,the loading position,loading amount and properties of the dyes in the composite pigments.The results indicated that.(1)The adsorption rate of sepiolite to the pigment is 94.39%by vacuum method,which is better than the adsorption rate of 88.39%by atmospheric method.The desorption rate of the obtained composite pigment after desorption in HCl,Na OH,Ethanol is lower than atmospheric method,which is 29.23%,11.09%,14.98%.The amount of remaining dye per gram of composite pigment is higher than atmospheric method 5.9%,6.4%,4.4%.Weather resistance performance is:BO2<composite pigment prepared by atmospheric method<pigment prepared by vacuum method.When the material ratio is 8%(m _BO2:m _Sep=8:100),the adsorption rate of the sepiolite composite pigment reaches more than 98%,the desorption rate of acid and ethanol is the smallest,and the weather resistance is stable.The heating temperature of the sepiolite in the negative pressure process has almost no effect on the performance of the sepiolite composite pigment prepared by the negative pressure method.The heat treatment temperature of sepiolite in the negative pressure process has no obvious effect on the performance of the sepiolite composite pigment by negative pressure method.The number of adsorption by negative pressure method(three adsorptions)is positively related to the chemical stability and weather resistance of the composite pigment.(2)The structure of the composite dye obtained from the four cationic organic dyes and sepiolite has no obvious change.The adsorption rate of BO2/Sep,MB/Sep,and BR18/Sep composite pigments are all above 96%,BR2/Sep has a low adsorption rate 87%.Four dye molecules can be adsorbed on the outer surface,grooves and openings of sepiolite.Among them,BO2 and MB can also enter the sepiolite pores,and the absorption performance of MB in the pores to the inner surface is better than that of BO2.Although the BR18 molecule cannot completely enter the sepiolite pores,it has the-NO₂and-N⁺groups so that it can effectively adsorb and accumulate on the outer surface,end face and groove of the sepiolite,thus showing a relatively stable performance.The stability of the composite pigments prepared by the four cationic dyes and sepiolite in this study is:MB/Sep composite pigments,BO2/Sep composite pigments,BR18/Sep composite pigments,BR2/Sep composite pigments.