Preparation Of The Dewatered Sludge Biochar By Phosphoric Acid Oxidation Modification For Removal Of Heavy Metals Cu(?) And Pb(?) In Water

Dewatered sludge is a biomass waste from municipal wastewater treatment plants.Its main components are organic compounds,inorganic compounds,microorganisms and some trace impurities.The amount of dewatered sludge was produced by urban sewage treatment plants,and it has risen rapidly,the treatment of dehydrated sludge has also become one of the serious environmental problems in today's society.Because the raw materials of the dewatered sludge are very abundant,and the biochar is an environment-friendly green material,the dewatered sludge was used to prepare the dewatered sludge biochar.Meanwhile,biochar is a low-cost adsorbent,the dewatered sludge biochar was used to remove the heavy metal in wastewater,such as Pb²⁺,Cu²⁺,Cr⁶⁺and Cd²⁺.However,there is still possible that the adsorption efficiency of the dewatered sludge biochar for the heavy metals can be improved in wastewater,because on the one hand,the specific surface area of the original dewatered sludge biochar is not large enough,and on the other hand,the original dewatered sludge biochar has fewer oxygen-containing functional groups.In order to improve the removal efficiency of the dewatered sludge biochar on the heavy metal ions,it is essential to modify the original dewatered sludge biochar.In this research,the dewatered sludge was collected from the municipal sewage treatment plant.On the one hand,the dewatered sludge biochar?DSBc?was prepared by the dewatered sludge.On the other hand,10 wt%ZnCl₂ was used to pretreat the raw material of the dewatered sludge,and 20 wt%H₃PO₄ was used to oxidize and modify the raw material of the dewatered sludge,and the oxidized modified dewatered sludge biochar?MDSBc?was further prepared by the vacuum tube furnace.In this experiment,the adsorption characteristics of the Cu²⁺and Pb²⁺were investigated.The addition of H₃PO₄ greatly affected the carbonation degree of the dewatered sludge biochar and the number of oxygen-containing functional groups,which further affected the adsorption mechanism of Cu²⁺and Pb²⁺on the biochar.The characterization results of BET and FTIR indicated that the MDSBc has a larger specific surface area and more oxygen-containing functional groups,such as carboxyl groups?-COOH?and hydroxyl?-OH?,than the DSBc,it further enhances the adsorption of heavy metals Cu²⁺and Pb²⁺by oxidatively modified dewatered sludge biochar.The adsorption capacity of the original dewatered sludge biochar to Cu²⁺and Pb²⁺was 51.59 mg·g^-11 and 39.597 mg·g^-1,respectively,while the adsorption capacity of oxidized modified dewatered sludge biochar to heavy metals Cu²⁺and Pb²⁺was significantly increased to 108.31 mg·g^-11 and 216.2 mg·g^-1,respectively.The adsorption kinetics and thermodynamic studies show that adsorption of heavy metals Cu²⁺and Pb²⁺meet the pseudo-second-order kinetic models both for DSBc and MDSBc.In this study,The adsorption isotherm of Cu²⁺and Pb²⁺meet the Freundlich model for MDSBc.In general,H₃PO₄ modified dewatered sludge biochar was successfully prepared in this study,which confirmed its ability to adsorb heavy metals efficiently,and it provided a useful reference for the treatment of heavy metal pollution in dewatered sludge.