The Preparation Of Soft Membrance Dust Suppression Agent By Cellulose And Its Application Appraisement

In recent years, serious haze events have taken place in most areas of China, which causes great influence to the transportation and people’s health. The main reason for haze formation is the content of fine particulate matter exceeded in air, the formation of fine particulate matter have diverse factors, for instance, a series of social development and people’s activities like urban demolition, bulk transport, land desertification. With the development of science, the traditional methods(such as canvas cover, spray water, etc.) to prevent the dust is eliminated due to inconvenient use and short dust suppression time. Recently, various chemical dust suppressants are emerged and grew fast. At present, the widely used polymer dust suppressants often formed a shell after spraying, the solidified layer can easily broken by the wind and concussion, then dust suppressants are ineffective, it also has a high costs. Therefore, it is significantly to prepare the dust suppressants which have low prices, film-forming flexible and excellent dust suppression performance.In this paper, the rich resource wheat straw and low price carboxymethylcellulose(CMC) were used as the raw materials, the straw cellulose dust suppressants with soft membrance and the PVA/CMC-g-AM dust suppressants were prepared by aqueous solution polymerization. The extraction process for wheat straw, the synthesis methods for straw cellulose dust suppressant and PVA/CMC-g-AM dust suppressant were investigated in the experiment, the morphology and structure of materials and products were characterized by Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD), thermal gravimetric analysis(TG) and scanning electron microscopy(SEM); the wettability was investigated by static contact angle measuring instrument. Anti-shock property, wind erosion property, water retention property, permesbility and water resistance of these two dust suppressants were investigated in the application by using coal dust as subjects. The main findings were as follows:(1) The optimized extraction technology of straw cellulose were as follows:Straw cellulose was stewing by using mass fraction of 10% sodium hydroxide solution with dilute alkali were 12:1 of liguid-solid ratio for 90 min under 100℃. FT-IR analysis showed that ether bond, ester bond and other characteristics group are in natural straw, and the structure of straw cellulose is simple, which mainly containing hydroxyl group; XRD results show that natural straw has low crystallinity, only 7.59%; after extracted, a large number of OH in cellulose structure is exposed, the crystallinity is 27.04%. The contact angle of natural straw with deionized water is 69.0°, and the contact angle of straw cellulose with deionized water is 15.9°, the results show that the straw cellulose has a rough surface and the contact area is enhanced with reagent.(2) The optimized synthesis technology of straw cellulose dust suppressants were as follows: m(cellulose):m(AA):m(DMDAAC)=6:5:1, the dosage of initiator(KSP) was 1.0% as to the total monomer mass(the same below); the dosage of cross-linking agent(MBA) was 0.5%, the reaction temperature was 65℃ and the reaction time was 5h, the grafting rate of copolymer was 83.2% in this condition. When the dosage of plasticizer(glycerol) was 20% as to the total mass, the crystallinity of dust suppressant film was only 3.80%. The result of TG analysis shows the copolymer has a high thermal stability, thermal decomposition temperature is above 230℃. The dust suppressant with 8% mass fraction of straw cellulose(the solid content is 32.3%) was sprayed on pulverized coal was 5.2%, the loss rate were reduced 17.6% and 46.6% which compared with spraying water.(3) When the m(CMC):m(PVA):m(AM)=3:1:4, the dosage of initiator was 1.2% as to the total monomer mass(the same below), the dosage of cross-linking agent was 0.5%, the reaction temperature was 65℃ and the reaction time was 5.5h, the PVA/CMC-g-AM dust suppressant showed a suitable viscosity in this condition. The result of TG analysis reveals that thermal decomposition temperature of PVA/CMC-g-AM polymer is above 250℃, The PVA/CMC-g-AM polymer was observed by SEM, it had an obvious porous structur. The results of permeability test and contact angle test reveal that the 0.2% surfactant(SDBS) when the 1.0% SDBS was added in 6% dust suppressant(the solid content is 26.7%), the contact angle is 18.9° and the permeate thickness is 3.4cm. The results of application experiment showed that the dust suppressant had good water retention and wind erosion resistance, the water evaporation was 0.2g/cm2 at 50℃and 10 h when the dust suppression solution was sprayed on pulverized coal surface, and the rate of loss on pulverized coal was only 1.8% after 12 h.