| Due to the rapid development of modern industrialization and the widespread use of copper,Cu(II)pollution is becoming increasingly serious and poses a threat to human and ecological environment.Porous ceramics are a good adsorption carrier,and their adsorption capacity can be improved by loading treatment.In this paper,mullite porous ceramics with composite pore structures combining different pore sizes were prepared by starch solidification molding combined with organic foam impregnation using silica and alumina as the main raw materials.Based on this,chitosan was loaded onto the porous ceramic surface and chitosan/mullite porous ceramic(CTS/MPC)composites were prepared.The adsorption performance of CTS/MPC as adsorbent for Cu(II)in aqueous solution was investigated.The main studies were as follows:Ⅰ.Study of physicochemical properties of starch granules(1)The physicochemical properties of potato,corn,and sweet potato starches were studied to select suitable starches as solidifying agents.According to the results of thermal analysis,all three starches show similar thermal decomposition process and complete decomposition at about 800°C.The morphological changes of starch in the process of water absorption were studied,and the results show that with the increase of solution temperature,the starch granules absorb water and swell until they are broken to complete the gelation process,and the viscosity of starch gels all show a trend of first increasing and then decreasing.In addition,the peak viscosity of potato starch gel is the largest and the peak viscosity of corn starch gel is the smallest.In order to ensure the good strength of the ceramic billets,potato starch was chosen as the solidifying agent.Ⅱ.The study of organic foam pretreatment and ceramic slurry properties(1)Polyurethane foam was selected as the precursor template,and the effects of pretreatment with Na OH solution and CMC-Na solution on the slurry-hanging properties of polyurethane foam were investigated.It is shows that the hydrophilicity and adhesion to the slurry of polyurethane foam are greatly improved when the polyurethane foam was impregnated with 25wt% Na OH solution for 2h at 60℃ and then loaded with 0.75wt%CMC-Na solution for 10 h.(2)Sodium hexametaphosphate,polyethylene glycol and ammonium citrate were selected as dispersants,and the effects of dispersant type and content on the viscosity of ceramic slurry were investigated.The results show that ammonium citrate can effectively reduce the viscosity of ceramic slurry;and the viscosity of ceramic slurry shows a trend of decreasing and then increasing with the increase of ammonium citrate content,and the viscosity of ceramic slurry is the lowest when the content of ammonium citrate was1.5wt%.Ⅲ.Preparation of mullite porous ceramics by starch consolidation molding combined with organic foam impregnation(1)Mullite porous ceramics with composite pore structures of different pore sizes were prepared by starch cementation molding combined with organic foam impregnation using silica and alumina as the main raw materials.The effects of the sintering process on the physical composition,microstructure and physical properties of the specimens were investigated.The results show that mullite porous ceramics with composite pore structures of different pore sizes with open pore porosity of 72.16% and compressive strength of 2.01 MPa could be prepared by holding at 1500 ℃ for 2 h and controlling the starch content at4 wt%.Ⅳ.Preparation of CTS/MPC composites and their adsorption properties(1)Mullite porous ceramics were used as the matrix,which were activated and loaded using 1.5 M nitric acid and 1% chitosan acetate solution,respectively.The loaded specimens were characterized by SEM,EDS,FT-IR and XPS,and the characterization results confirm the successful preparation of CTS/MPC composites.(2)Using copper sulfate pentahydrate as Cu(Ⅱ)source,the adsorption properties of Cu(Ⅱ)wastewater by CTS/MPC composite as adsorbent were studied.The results show that the adsorption properties of the sample increase greatly after crushing.With the increase of p H value of the solution,the adsorption capacity of the sample increased gradually.When the initial concentration range is 20-80mg/g,the adsorption capacity of the sample gradually increases with the increase of the initial solubility of the solution;when the initial concentration range is 80-90mg/g,the adsorption capacity of the sample tends to be saturated with the increase of the initial concentration of the solution.With the increase of adsorption time,the adsorption capacity of the sample first increased and then tended to saturation,and the maximum adsorption capacity was 19.737mg/g.(3)Kinetic and thermodynamic models were used to fit the adsorption data,and XPS and FT-IR were used to characterize the samples.The kinetic and thermodynamic model fitting of the adsorption data shows that the adsorption process of Cu(Ⅱ)by CTS/MPC is a chemisorption based multimolecular layer adsorption.The XPS and FT-IR characterization of the adsorbed samples also confirm the existence of chemisorption in the adsorption process. |
PDF Full Text Request