Study On Preparation And Performance Of Activated Carbon From High Humidity Chinese Herbal Medicine Wastes

Large amounts of Chinese herbal medicine wastes(CHMWs)produced as by-products in pharmaceutical process of traditional Chinese crude medicines and it cause serious solid waste disposal problems in China.Due to absence of proper disposal methods,CHMWs are mainly landfilled or optionally disposed as solid wastes.So,it is deadly required to provide a cost-eff ective,high value-added,and innovative solution of the problems caused by CHMWs.For CHMWs,a possible utilization is converting it into activated carbon(AC).The conventional method of transformation CHMWs into AC usually contains drying,carbonization and activation.However,CHMWs has a high humidity content that cause quantity energy consumption during drying.If high humidity CHMWs(HH-CHMWs)can directly transform into AC,it will reduce the energy consumption and promote efficiency.HH-CHMWs was prepared for AC by using the physical-chemical two-step activation.Firstly,HH-CHMWs was heated and its inner water was evaporated at hot temperatures,the steam will react with CHMWs(the procedure is defined as firstly physical activation),and the primary activated material was gained.Secondly,primary activated material was chemically activated by KOH activation and CHMWs-AC prepared.By using this innovative method it can avoid the drying process of traditional method and save energy.Single factor experiment and orthogonal experiment was applied in experiment.In physical activation step,the preparation condition contains moisture content of HH-CHMWs,carbonization temperature and carbonization time.In chemical activation step,the preparation condition contains impregnation ratio of KOH,activation temperature and activation time.Then it researches the character of AC by using TGA,SEM and Physisorption.The single factor experiment shows that:when the condition of moisture content is 50~90%,carbonized temperature is 500~700°C,carbonization time is 30~150min,the best preparation conditions are moisture content is 50%,carbonization temperature is 700°C,carbonization time is 150min.In this condition,the carbonized material’s performance is:the surface area is 307 m~2/g.the orthogonal experiment shows those conclusion:in the condition of moisture content is 50~80%,carbonization temperature is 700~850°C,carbonization time is 90~180min,the significance level of three conditions is activation temperature,moisture content,activation time.The best preparation conditions are moisture content is 50%,carbonization temperature is 850°C,carbonization time is 180 min,the carbonized material’s performance is:the surface area is 998 m~2/g.In chemical activation step,the single factor experiment shows that:in the condition of activation temperature is 650~850°C,activation time is 30~150min,impregnation ratio is 0.5~2.5.The best preparation conditions are activation temperature is 700°C,activation time is 60 min,impregnation ratio is 1.0.the AC’s performance is:surface area is 1841m~2/g.The orthogonal experiment shows those conclusion:the significance level of three conditions is activation temperature,activation time,immersion ratio.The best preparation conditions of AC are activation temperature is 750°C,activation time is 90min,impregnation ratio is 2.0.The performance of the AC is:surface area is 2131m~2/g.