Modification Of Municipal Sludge Biochar And Its Adsorption Performance For Phosphorus In Water

With the rapid development of industry and agriculture in China,phosphorus is widely used as an important industrial and agricultural resource;The gradual acceleration of urbanization has also increased the phosphorus content in domestic sewage.These excessive phosphorus enters the river system with the discharge of industrial,agricultural and domestic wastewater,or seeps into the groundwater with the precipitation,polluting the water source and making the phosphorus content in the water exceed the standard.Excessive phosphorus in the water will aggravate the reproduction of algae,seize the nutrients and oxygen in the water,and cause other aquatic plants and animals living in the water to lose their living space and die in large numbers,which is the harm caused by water eutrophication.At present,the use of adsorption to treat water pollution is considered to be a very excellent treatment method because of its high efficiency,low cost and simple operation.Because of its high carbon content and rich sources,municipal sludge is widely used in the preparation of soil improvement,building materials and biochar adsorbent.Although municipal sludge biochar has rich sources and low cost,its adsorption capacity for phosphorus in wastewater is limited,and it must be targeted to improve its adsorption capacity.Therefore,based on the principle of chemical experiments,this paper uses municipal sludge to prepare municipal sludge biochar,and improves its adsorption capacity by modifying it.Then,according to its possible practical application scenarios,it prepares simple,convenient and efficient adsorption materials.This provides a new way for the treatment of water eutrophication and the recycling of municipal sludge.In the first part,municipal sludge biochar(MSBC)was prepared by pyrolysis at different temperatures,and activated by KOH to provide more holes and active sites.In the second part,nano-zero-valent zinc(n ZVZ)was uniformly attached to MSBC using reducing agent to obtain high-efficiency phosphorus-absorbing composite(n ZVZ-MSBC).The characterization results of FT-IR,XPS,XRD and BET showed that n ZVZ was uniformly dispersed on the surface of MSBC.The results show that zinc loading can greatly improve the adsorption performance of MSBC for phosphorus.The adsorption experiment shows that the adsorption process conforms to Langmuir model,and the maximum adsorption amount can reach 186.5 mg/g,which is much higher than other urban sludge biochar.The adsorption process reached 80% of the maximum adsorption capacity at 90 min and gradually stabilized after 240 min.The adsorption equilibrium is reached within 24 h.The optimum p H value for adsorption is 5.The adsorption mechanism is mainly chemical adsorption,including physical adsorption,external diffusion,internal diffusion and surface adsorption.The experiment shows that n ZVZ-MSBC has the application potential as an effective adsorbent for phosphorus in water.In order to apply this material more conveniently to the treatment of actual water bodies,the third part studies the preparation of gel beads that are easy to separate after adsorption by mixing n ZVZ-MSBC with polyvinyl alcohol(PVA)gel,and crosslinking with Ca to prepare Ca/Zn bimetallic modified municipal sludge biological carbon polyvinyl alcohol beads(n ZVZ-MSBC/ Ca@PVA).The characterization results of SEM,FT-IR,XPS and BET showed that there were a lot of pores and gaps on the surface of the sample ball and rich functional groups,which played a positive role in the adsorption of phosphorus;Ca and Zn were successfully loaded in the material,and a series of chemical reactions took place with phosphate in water.By fitting the adsorption process,it is found that it conforms to the pseudo-second-order kinetics and Langmuir isotherm model,indicating that the adsorption process is monolayer adsorption,and mainly chemical adsorption.The optimal adsorption p H is 5,and the optimal addition ratio of PVA and n ZVZ-MSBC is 1:1.The adsorbed material has complete morphology and good mechanical properties,which may be applied in practice.