Study On Demineralization & Iron Removal Of Coal-based Activated Carbon And Its Decolorization On Xylose

Coal-based activated carbon is widely used in gas and liquid phase adsorption because of its well-developed pore structure,good chemical stability and mechanical strength,and powerful adsorption performance,and the demand is increasing year by year.However,due to the high ash content and iron content,the coal-based activated carbon limits its popularization and application in the high-end fields.This paper applies acid-alkali washing combined with deliming process on the desulfurization of bituminous coal activated charcoal,ultrasonic technology for the first time applied to activated carbon assisted pickling iron removal process research,prepared a low ash,low iron activated carbon,and in the xylose liquid decolorization Applications have been studied.The main findings are as follows:（1）Systematic research has optimized the deashing reaction conditions of bituminous coal activated carbon.The single-factor experiment to obtain the optimum process conditions for the de-ashing of bituminous coal with an initial particle size of 8×30 mesh is:alkali wash concentration 2.0 mol/L,caustic wash temperature 175°C,Alkali wash time 6h,acid wash concentration 3.0mol/L,pickling time 2h,pickling temperature 75°C,liquid to solid ratio 3:1.Under this condition,the ash content of activated carbon was 1.18%,and the deashing rate reached 87.4%.The order of the factors affecting the deliming efficiency was as follows:alkali washing concentration>pickling temperature>caustic washing temperature>pickling concentration The iodine value of activated carbon after desulfurization was1185.2 mg·g^-1,and the adsorption value of methylene blue was 255.0 mg·g^-1.（2）The test analysis and other methods clarified the composition of activated carbon ash and the main performance indicators of activated carbon after deashing.After the ash composition analysis,scanning electron microscopy,BET and adsorption performance tests,it was concluded that acid-alkali combined deashing can effectively remove the main components of activated carbon ash,such as SiO₂,Al₂O₃ and other substances.After the deliming,the activated carbon surface forms a rich pore structure,the specific surface area increases by 22.8%,and the iodine adsorption value increases by 20.1%.（3）A series of experiments determined the best process conditions for removing iron from coal-based activated carbon.Using mixed acid washing and ultrasonic assisted mixed acid washing and removing iron,and through the single factor experiment to determine the best technical conditions for the removal of iron from coal activated carbon:Ultrasonic-assisted ternary mixed acid（hydrochloric acid+sulfuric acid+nitric acid）,in which the mixed acid volume ratio V_HCl:V_H2SO4:V_HNO3=2:2:1,mixed acid concentration V_acid:V_water=1:1,reaction temperature 75°C.,ultrasonic power 240W,treatment time 30min.Under this condition,the iron content in activated carbon dropped from 0.39%to 0.049%,and the removal rate was 87.4%.（4）Explored the relevant mechanism of ultrasonic cleaning mixed iron removal.The investigation shows that the"assimilation effect"occurs in the process of removing iron from ultrasonic and ternary mixed acid,that is,the strong impulse of ultrasonic wave can peel off the iron impurities in activated carbon and enter into the mixed acid solution,making it more easily react with ternary mixed acid,thereby enabling the iron removal rate.Higher,and only ultrasonic or tri-mixed acid can not achieve the same effect.（5）The application effect of coal activated charcoal treated by decalcification and iron removal process was verified.The decolorization experiment of xylose liquor using the best sample coal activated carbon treated by the iron removal process showed that when the pH of the decolorization solution is kept neutral,the amount of activated carbon is 6.0%,the decolorization temperature is 80°C.,and the decoloration time is 40 minutes.The xylose liquid transmittance of 89.4%,to meet the food grade xylose liquid color requirements.