The Process Optimization And Properties Modification Of The Granular Activated Carbon Prepared From Walnut Shell By Phosphoric Acid

In this paper,the activated carbon is prepared from walnut shell by phosphoric acid.The effects of material’s water content,impregnation time and temperature,impregnation methods,additives,TiO2 and heating rate on the properties of activated carbon have been studied.The SEM and Multifunctional physical adsorption analyzer are used to observe the microstructure and pore’s structure of activated carbon.It has been found that dry walnut shell should be choice of preparing activated carbon.Most of the pores in activated carbon are micropores.The best parameters of impregnation temperature and time are 37℃ and 8h,in which the iodine value,methylene blue value,surface area,total pore volue,micropores volume and mesopores volume are 798mg/g、203mg/g,685m2/2,0.5826ml/g,0.313 ml/g and 0.2696 ml/g,respectively.Stirring during impregnation process for 8h,the microporous activated carbon was prepared with the iodine adsorption value and methylene blue adsorption value are 834mg/g and 158mg/g,respectively.When citric acid is used as the additive,considering the microspore adsorption,adding proportion 1%is the best choice for activated carbon performance,the iodine adsorption value of 885mg/g,10.9%higher than that without adding reference samples.If consider both micropore and mesopore,it is better to add 16%citric acid into phosphoric acid solution,and the iodine adsorption value and methylene blue adsorption value are 874mg/g and 203mg/g,respectively.Compared with citric acid,the greater the proportion of sodium citrate is,the worse the adsorption performance is.Reducing the heating rate is favorable to the strength of activated carbon,and heat preservation before carbonizating makes activated carbon’s strength reach 95%,the iodine adsorption value and methylene blue adsorption value are 700mg/g and 128mg/g,respectively.To increase the strength of activated carbon with colloid titanium dioxide,the adding proportion of 0.02%of titanium dioxide is the best choice,The strength,the iodine adsorption value and methylene blue adsorption value of activated carbon were 93.7%,731mg/g and 180mg/g.