Study On The Preparation Of Acid Pretreated Sawdust Activated Carbon And Its Adsorption Properties Of Dyes

As energy crisis and environmental pollution become more and more serious,seeking biomass resources with abundant resources,low cost,safe and renewable as raw materials for the preparation of activated carbon has become a hot research topic both domestic and overseas.In this paper,sawdust as the raw material,activated carbon was prepared by two carbonization technology of hydrothermal and pyrolysis in presence of four different acids(phosphoric acid,tartaric acid,citric acid and formic acid)pretreatment solution.The adsorption mechanism of the adsorption of anionic dye acid red 18 and cationic dye methylene blue on activated carbon was investigated by adsorption isotherm model,adsorption kinetic model and adsorption thermodynamic model,and the practicability of the activated carbon sample was investigated.The conclusions were shown as follows:(1)It can be seen from a series of characterizations that the sawdust fiber structure is destroyed during the acid pretreatment.Different types of acid pretreatment were confirmed to influence the final formation and adsorptive properties of activated carbon.There are hydroxyl,carbonyl and other functional groups in the presence of acid pretreatment sawdust activated carbon surface.Among them,the activated carbon pretreatment by phosphoric acid with the largest specific surface area was 1785.35 m~2/g,and it had the strongest adsorption capacity for acid red 18 and methylene blue.(2)Adsorption of acid red 18 and methylene blue with sawdust activated carbon by phosphoric acid pretreatment showed that the adsorption of the two dyes was monolayer,and the maximum adsorption capacity was 400 mg/g and 344.83 mg/g respectively.The adsorption of both dyes on activated carbon was mainly chemical adsorption,and the adsorption rate of acid red 18 was greater than that of methylene blue.The adsorption process of both dyes was spontaneous and Endothermic.(3)From the practical research,it was found that in the case of reusability,the acid red 18 adsorbed on the activated carbon with the phosphoric acid pretreatment can be reused three times,the methylene blue can be reused twice,while both dyes adsorbed on activated carbon pretreated by other acid can be reused twice.From the desorption performance,it is found that the adsorption of both dyes by activated carbon with Phosphoric acid and Tartaric acid pretreatment is mainly by chemical adsorption.The adsorption process of both dyes adsorbed by activated carbon with Formic acid pretreatment is physical adsorption;the adsorption process of acid red 18 adsorbed by activated carbon with Citric acid pretreatment may be the main physical adsorption,with chemisorption,the process of adsorption of methylene blue by chemical adsorption.