Study On Preparation Of Straw-Sludge Activated Carbon And Adsorption Performance

In recent years,the overall situation of "sedimentation of water and mud" and "heavy water and light mud" have been improved in China.However,with the implementation of the Water Pollution Prevention Action Plan,therefore,the development of the municipal sludge treatment methods and technologies with decentralized and small-scale feature is highly urgent and desired.The conversion of sludge into activated carbon is an environmentally friendly disposal of waste resources.In this paper,municipal sludge and rice straw were selected as raw materials for fabrication of straw-sludge-based activated carbon using zinc chloride?ZnCl₂?or potassium hydroxide?KOH?as activators.Single-factor experiments and response surface methodology were used to investigate the effect of various influencing factors on straw-sludge-based activated carbon and then confirm the optimal preparation conditions.Based on this,the study on the adsorption performance of Pb²⁺ in aqueous solution and the preliminary design of industrial preparation equipment were performed.The main conclusions obtained are as follows:?1?The optimum preparation conditions for preparation of straw-sludge-based activated carbon using ZnCl₂ activation method are:activation temperature 510?,mass ratio 1:2,activation time 1h,and liquid-solid ratio 1.5:1.The characterization results show that the specific surface area of the activated carbon prepared under this condition is as high as 669.29 m2/g;and the surface functional groups are mainly acidic functional groups,mainly including specifically olefins,alcohols and phenols,etc.The experimental results show that the iodine adsorption value of straw-sludge-based activated carbon is 833 mg/g.?2?The optimal preparation conditions for preparation of straw-sludge-based activated carbon using KOH as activating agent were:activation temperature 750 ?,mass ratio 1:1,activation time 62 min,activator mass fraction 30%,and solid-liquid ratio 1.5:1.The characterization results show that the specific surface area of activated carbon prepared under this conditions is as high as 902.60 m2/g,and the carbon content is 82.74%.The experimental results show that the iodine adsorption value of this type of straw-sludge-based activated carbon is 938 mg/g.?3?The straw-sludge-based activated carbon was used to study the behavior of adsorbing Pb²⁺ in aqueous solution.The effects of various factors on the adsorption capacity were investigated,and the best adsorption conditions were obtained.Adsorption experiments demonstrated that the dosage of 6 g/L of straw-sludge-based activated carbon,adsorption time of 200 minutes,pH of 6,and Pb²⁺ solution initial concentration of 60 mg/g,and the removal and adsorption of Pb²⁺ in aqueous solution were determined to be 71%and 42.56 mg/g,respectively.According to the adsorption kinetics and isothermal adsorption experiments,the Langmuir isotherm equation model can better fit the practical adsorption behavior of Pb²⁺ of the straw-sludge-based activated carbon.The adsorption process of Pb²⁺for straw-sludge-based activated carbon conforms to the pseudo-second-order kinetic model and is a typically chemical adsorption process.Based on the above research results,we successfully designed a set of conversion device for the preparation of rice straw-sludge-based activated carbon.