| Activated carbon has a wide range of applications due to its developed pore structure,large specific surface area,unique surface active functional groups,good thermal stability and chemical stability.Activated carbon preparation materials are usually composed of carbon-based materials.At present,research work on the preparation of activated carbon using renewable and inexpensive and readily available biomass resources has attracted much attention.The distiller's grains are rich in cellulose and hemicellulose and can be used to prepare activated carbon.In this paper,the effects of temperature,pressure and residence time on the adsorption performance of activated carbon were investigated by using the method of sub-and supercritical water treatment.At the same time,the effect of carbonization temperature,activation temperature and steam flow rate on the adsorption performance of activated carbon was investigated by traditional steam activation method,and the optimum process conditions were determined.The target activated carbon was characterized by scanning electron microscopy?SEM?,specific surface area measurement?BET?and X-ray diffractometry?XRD?to explore the activation mechanism of sub-and supercritical water and compare it with the traditional steam activation method.The advantages and disadvantages of the activated carbon were used to study the adsorption properties of methyl orange molecules in simulated wastewater.The effects of adsorbent dosage,solution p H,adsorption time and initial solution concentration on the adsorption performance were investigated.Finally,the adsorption power was combined.The adsorption and adsorption isotherms explored the adsorption mechanism.?1?The results show that the optimum process conditions for the preparation of activated carbon by sub-and supercritical water treatment method are as follows:The iodine adsorption value was 624 mg·g-1 and the methylene blue adsorption value was 120 mg·g-1when the reaction temperature was 450?,the reaction pressure was 25 Mpa,and the residence time was 10 min.After nitrogen adsorption analysis,the specific surface area is 201 m2·g-1,pore volume is 0.105 cm3·g-1,and average pore diameter is 2.82 nm.?2?The results show that the optimum process conditions for the preparation of activated carbon by conventional steam activation method are as follows:The iodine adsorption value was 575 mg·g-1 and the methylene blue adsorption value was 100 mg·g-1 when the carbonization temperature was 450?,the activation temperature was 800?and the stean flow rate was 2.5 L·min-1.After nitrogen adsorption analysis,the specific surface area is 368 m2·g-1,the pore volume is 0.241 cm3·g-1,and the average pore diameter is 2.63 nm.?3?The adsorption experiment of the dye molecule methyl orange shows that the activated carbon prepared by the above two methods can be used as an adsorbent for adsorbing dye wastewater.The adsorption rate of activated carbon to methyl orange decreased with the increase of p H,and increased with the increase of the amount of activated carbon.The adsorption conforms to the Langmuir adsorption isotherm,and the adsorption kinetics can be described by a quasi-secondary kinetic model,which is mainly controlled by chemical adsorption.In summary,the use of sub-and supercritical water treatment of distiller's grains can be used to prepare activated carbon,the temperature influence is greater,the pressure and time are less affected,and the pore structure is mainly microporous.The sub-and supercritical water has a low reaction temperature and a fast reaction speed,and the carbonization activation is completed in one step,and the deposited tar can be dissolved,but the equipment is required to be high and the yield is low.The activated carbon prepared by the traditional steam activation method is mainly microporous,and the operation is simple,but the temperature requirement is high,and it needs to be carried out in two steps,and tar deposits during the reaction. |
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