Study On Preparation Of Fly Ash Composite Filler Based On Wettability Control

Fly ash(FA)is one of the largest solid wastes in China.It is a hot research topic to realize its high value utilization.The research on using fly ash as papermaking filler is one of the hot spots to realize the high value utilization of fly ash.However,the low whiteness of fly ash limits its application in the field of papermaking.Attempts have been made to coat modified fly ash by means of heterogeneous nucleation to improve its whiteness.However,in the process of coating modification,there is a problem that the surface coating effect of fly ash is not good.In response to this problem,this paper uses the method of wetting property regulation to improve the surface properties of fly ash as a substrate,thereby improving the surface coating properties of fly ash.The main research contents are as follows:Using the method of wetting performance regulation,the contact angle of fly ash was used as an indicator to measure the treatment effect.The effects of reaction temperature,reaction time,amount of calcium hydroxide(relative to the amount of dry fly ash),stirring speed and solid-liquid ratio on the wettability control of fly ash were analyzed in detail.Under the optimal process conditions,the fly ash was analyzed and characterized by SEM,XRD,BET and FT-IR to explain the change of wettability.Then,the wettability was controlled during the non-uniform nucleation coating modification of fly ash,and the influence of wettability on the non-uniform nucleation process was further explored.Finally,the paper filling performance of the modified fly ash was evaluated.The main results and conclusions are as follows:After conditioning treatment,the surface wetting angle of fly ash is 64.32°,which is19.47% lower than that of the original fly ash(contact angle is 79.87°).Therefore,the fly ash after the treatment treatment has good surface wetting properties.The microporous structure of the fly ash surface increases,the roughness performance is enhanced;a large amount of hydrophilic silicoaluminophosphate component salts are formed on the surface,and polar hydroxyl groups are increased,which directly cause the surface wetting property of the fly ash to be improved.The optimal control process determined by orthogonal experiment istemperature 85°C,reaction time 5 h,calcium hydroxide dosage 26%(relative to the amount of dry fly ash),reaction liquid to solid ratio 10:1,stirring speed 550 rpm.After the wetting property regulation treatment,the heterogeneous nucleation growth ability of calcium carbonate on the surface of fly ash is enhanced.The effect as a crystalline substrate in the heterogeneous nucleation process is significantly improved.The effect of heterogeneous nucleation coating is enhanced.The average particle size of modified fly ash prepared by wetting control is 14.6?m,which is higher than the average particle size of the original modified fly ash.The whiteness rose to 64.89% ISO,which is more than 5 points higher than the original modified fly ash.The bonding strength of the modified fly ash substrate and the coating layer controlled by the wettability is increased.Compared with paper filled with the original modified fly ash,the optical properties,strength properties,dustiness and retention of the paper filled with the modified fly ash after the wetting control are all improved obviously.