The Physicochemical And Adsorption Copper Properties Of Different Sources Sludge Biochar

Biochar has received increasing interest due to its special properties and potential in environmental application.Wastewater treatment plants produce a large amounts of sludge,and excert big pressure to the environment every year,which has caused a big problem in the treatment of wastewaters.Pyrolysis technology can relize the transformation of sludge to biochar,which may greatly reduce volume of the sludge,decompose organic components and stabilization heavy metals in sludge.This study made different biochars with the sludges from municipal,pharmaceutical and steel works wastewater treatment plant at different temperatures using prolysis methods.Physico-chemical properties of the biochars were characterisized and adsoption performances of copper on the biochars were detected.Trough the adroption kinetics and isotherm of copper on biochars,combined with SEM,EDS,FTIR and XRD,mechanism of the adsorption of copper on the sludge biochars was explored.The main results of his stydy are as follows:（1）Biochars with different sources were made at 500,600 and 700℃.With the increase of temperature,the yieds of biochar decreased,while ash contents and the overall trends of thee specific surface area increased.C content is relatively low and C,H,O,N and S contents decreased;Surface functional groups decreased gradually,H/C,O/C,and O+N/C decreased;mineral composition increased.（2）Inorganic components play a key role in the properties of sludge biochar,which accounts for more than 60%of the total weight of the biochar.The high content of the inorganic minerasl make the surface of sludge biochar relatively smooth and there is no obvious pore structures in the biochar.The mass loss was relatively small during the pyrolysis.In the process of sludge pyrolysis,special inorganic compounds was produced,e.g.,magnetic ferric oxide formed during the pyrolysis of steelworks sludge.（3）The adsorption of Cu²⁺on the biochar increased with the increase of temperature,which is related to the increase of inorganic mineral compositions.The adsorption of Cu²⁺by sludge biochar was more in line with the second order kinetic equation.The adsorption experienced two stages,first fast and then slow.The fast stage is mainly carried out within 12h,associated with active sites（oxygen-containing function groups）and mineral constituents on the biochar surface.The slow stage was after 12h,in which adsorption is carried out through particle diffusion.（4）With the increase of initial pH,the adsorption capacities of Cu2⁺on the three biochar sludges increased first and then decreased,which shows that too high or too low initial pH would both hinder Cu2+adsorption.The amount of Cu²⁺adsorpted by the biochar from pharmaceutical factory sludge is higher than that form municipal sludge and steelworks sludge.The adsorption isotherms fitted well with Freundlich model.