Preparation And Functional Modification Of Cellulose-based Flocculating Materials From Flax Waste Yarn

Most of the textile wastes are landfilled or burned as waste.The caused environmental problems are receiving increasing attention.It is urgent to increase its recycling degree.Flocculation is the first step of industrial wastewater treatment,in which the quality and cost of flocculant are the key factors to operating efficiency.In comparison to traditional synthetic flocculant as polyacrylamide(PAM),bio-based flocculant holds the significant advantages as abundant materials and environmental friendliness.With the development of technical research and reduction of production cost,it becomes possible to replace synthesized flocculant using bio-based flocculant.Flax waste yarn belongs to textile waste.Due to its high content of cellulose,flax waste yarn can be used to prepare eco-friendly bio-based flocculant,which is employed to treat industrial wastewater to cut back operating cost,improve flocculation efficiency,reduce flocculation sludge.Therefore,in this work,FC-g-PAM,FC-g-PAM-g-TMPS and CFC-g-PAM-g-TMPS were prepared based on the cellulose from flax waste yarn.Their morphologies and structures were characterized.They were employed to treat dying,papermaking and mechanical processing wastewater repectively to evaluate their flocculation performance.1.Preparation of FC-g-PAM and its flocculation performanceIn order to improve the flocculation performance and environmental friendliness of PAM,FC-g-PAM was prepared based on the cellulose from flax waste yarn(FC).The optimal preparation process was obtained as: reaction temperature at 80?,ammonium persulfate dosage at 0.30 g/g,PAM dosage at 0.25 g/g,FC concentration at 6%.The graft ratio and degree of substitution of the FC-g-PAM were 52% and 1.61,respectively.Its turbidity removal rate was 98.8% to simulated wastewater and 90 d biodegradation rate was 68.5% which was obviously better than that of PAM.The FC-g-PAM was employed to treat dyeing,papermaking and mechanical processing wastewaters,respectively.The positive results showed that the FC-g-PAM held excellent flocculation performance to the three kind of typical industrial wastewaters.Its flocculation performance was better than that of PAM.The flocculation mechanism of the FC-g-PAM mainly presented as electric neutral and bonded bridge as well as net catching sweep when it was employed to treat negative electric pollutants in water.2.Hydrophobic modification of FC-g-PAM and its flocculation performanceIn order to reduce sludge moisture content and filtering energy consumption,the FC-g-PAM was hydrophobically modified with propyltrimethoxysilane(TMPS)to prepare FC-g-PAM-g-TMPS.The optimal preparation process was obtained as: pH at 9,TMPS dosage at 0.80 g/g,reaction temperature at 80?,reaction time at 10 h.Its water contact angle was 112°and turbidity removal rate was 99.2% to simulated wastewater.The FC-g-PAM-g-TMPS was employed to treat dyeing,papermaking and mechanical processing wastewaters,respectively.The positive results showed that the FC-g-PAM-g-TMPS held excellent flocculation and sludge reduction performance to the three kind of typical industrial wastewaters.The amplification test results from factory indicated that the sludge production and filtering energy consumption of the FC-g-PAM-g-TMPS flocculation declined 22.9% and 16.7% respectively in comparison to those of PAM.The flocculation mechanism of the FC-g-PAM-g-TMPS mainly presented as electric neutral and bonded bridge as well as net catching sweep when it was employed to treat negative electric pollutants in water.3.Preparation of CFC-g-PAM-g-TMPS and its flocculation performanceIn order to reduce coagulant dosage and sludge production,the FC-g-PAM-g-TMPS was cation modified with 3-chloro-2-hydroxypropyl-trimethylammonium chloride(CTA)to prepare CFC-g-PAM-g-TMPS.The optimal preparation process was obtained as: reaction time at 8 h,reaction temperature at 70?,NaOH concentration at 6%,stirring speed at 100 r/min.Its turbidity removal rate was 99.5% without the assistance of coagulant to simulated wastewater.The CFC-g-PAM-g-TMPS was employed to treat dyeing,papermaking and mechanical processing wastewaters,respectively.The positive results showed that the CFC-g-PAM-g-TMPS still held excellent flocculation performance without the assistance of coagulant to the three kind of typical industrial wastewaters.Meanwhile,its flocculation sludge and operating cost were also reduced.The flocculation mechanism of the CFC-g-PAM-g-TMPS mainly presented as electrostatic cluster and bonded bridge as well as net catching sweep when it was employed to treat negative electric pollutants in water.