| The liquid fluorescent whitening agent was prepared by reaction of Cyanuric Chloride with 4-aminobenzene sulfonate firstly, and then DSD acid and diethanolamine. The optimal technology condition were confirmed by single factors and orthogonal experiments: the first condensation, n(4-aminobenzene sulfonate):n(Cyanuric chloride)=1:1,reaction temperature was 0℃,the volume of ice water was 30.0ml,reaction pH was 6.0,reaction time was 80 minutes, and the conversion rate of amino-group was 99.4%; the second condensation, n(DSD acid): n(Cyanuric Chloride)=0.475:1,reaction pH was 6,reaction temperature was 50℃, reaction time was 100 minutes, and the conversion rate of amino-group was 93.0%, the extinction was 0.731;the third condensation, n(diethanolamine):n(Cyanuric chloride)=1.4:1, reaction pH was 9.0,reaction temperature was 95℃, reaction time was 120 minutes, and the extinction was 0.742.In this study, CA type nanofiltration membranes were used to desalinate and concentrate the aqueous fluorescent whitening agent(FBA). After the six processes under the feeding pressure of 0.3 MPa and 25℃, the concentration of NaCl decreased from 0.31mol/L to 0.0088mol/L and the concentration of fluorescent whitening agent increased from 0.091mol/L to 0.26mol/L,the desalinate rate was 98.2%,the purity of FBA was 99.8%,and the concentration of FBA solution increased 2.9-fold,the time was 640 minutes. The desalinated FBA remained stable under 0℃in 2 months.The enhanced effect of triazine-stilbene fluorescent whitening agents were studied by physical and chemical compounding methods. The results showed that it was useful to enhance the effect of fluorescent whitening agents in paper bleaching take advantage of physical and chemical compounding methods. The whitening rate increased from 14.8% to 16.9% by using the physical compounding methods increased from 13.4% to 21.9% by using the chemical compounding methods.The structures of fluorescent whitening agent were determined by UV-vis and ESI spectra.
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