Co-pyrolysis Of Municipal Sewage Sludge And Bamboo Sawdust For Producing And Adsorption Characteristics Study

In recent years,the large-scale construction of sewage treatment plants and the improvement of treatment rate have produced a large amount of waste activated sludge,and the output has also increased year by year.In terms of sludge disposal policies,sludge disposal is included in social costs,and it is particularly urgent to effectively and reasonably dispose of solid waste sludge.Bamboo has the characteristics of fast growth,strong reproduction and renewal ability,and the yield of bamboo in China ranks the first in the world.The purpose of this paper is to study the method of producing biochar by co-pyrolysis of waste activated sludge and bamboo chips.The main research content is the pyrolysis preparation of biochar and the experiment of character characterization.The response surface optimization experiment was used to determine the best preparation conditions and enhance its application value.By using biochar as adsorbent,methylene blue was adsorbed into common dye wastewater,and its adsorption characteristics were studied,providing effective reference data for the industrial application of biochar.Biochar was prepared by co-pyrolysis of waste activated sludge and bamboo chips under the action of chemical activator ZnCl2.The optimum process conditions were selected by single factor variable experiment:chemical activator ZnCl2 concentration is 3mol/L,bamboo chip addition rate is 30%,pyrolysis time is 90min,pyrolysis final temperature is 500℃,iodine adsorption is up to 855.41mg/g.The action mechanism of ZnCl2 as an activator:dehydration and condensation of pyrolysis reaction substances,which makes the raw material molecules carbonized and stable,and then forms condensed carbon,which becomes a carbon skeleton structure with developed pores and enhances the adsorption capacity of biochar.The organic components of raw materials are pyrolyzed to form inorganic components and crystal structure.The parameters of biochar prepared by co-pyrolysis of waste activated sludge and bamboo chips were optimized by response surface method,and it was concluded that the influence of various factors on the iodine adsorption value of biochar was as follows:bamboo chips addition rate>final pyrolysis temperature>ZnCl2 concentration>pyrolysis time,and there was interaction among all factors in the reaction.The optimal immersion conditions are as follows:the concentration of activator ZnCl2 is 4.06 mol/L,the final pyrolysis temperature is 445.01℃,the addition rate of bamboo chips is 50%,the pyrolysis time is 37.64 min,and the iodine adsorption value theory can reach 898.57mg/g.Methylene blue from common dye wastewater was adsorbed by the prepared biochar as adsorbent,and its adsorption characteristics were studied.It was concluded that the adsorption time,the amount of biochar and the pH value of the solution had significant effects on the adsorption value of methylene blue.With the increase of concussion adsorption time,the rate of methylene blue adsorption increased from fast to slow,and the adsorption capacity reached saturation around 120min.With the increase of the amount of biochar,the increase of adsorption rate gradually became slower,and with the increase of pH value,the adsorption efficiency and adsorption capacity also increased.The Redlich-Peterson and Langmuir adsorption isotherm model fits this experiment well.According to the calculation of the equation,the maximum adsorption capacity is 163.77mg/g.