| Currently,heavy metal Hg(Ⅱ)has caused non-negligible threat to the water environment.Adsorption,as a solution for water purification,has been regard as the most promising method,and the design of biologically-derived adsorbents with fast adsorption rate,simple preparation,low cost,and high adsorption capacity has become an important way for the development of new-type adsorbents.As a natural resource with wide sources,low price,biodegradation and regeneration,starch has abundant polysaccharide in its structure,which makes it possible to transform starch into carbonaceous with loose structure after high temperature carbonization.In this thesis,starting from starch carbon,two kinds of composite adsorbent materials based on starch carbon were prepared respectively and their adsorption properties for mercury pollution were studied,which expanded the design road of starch based materials and provided theoretical basis.The main contents of this article include the following two aspects:(1)N-doped carbon materials with 3D porous layered skeleton structure(3D-NC)was synthesized through an one-step co-pyrolysis method,which was fabricated by copyrolysis of natural corn starch and melamine using metal catalysts(Ni(Ⅱ)and Mn(Ⅱ)).The 3D-NC possessed a heterogeneously meso-macroporous surface with a hierarchically connected sheet structure inside.Batch adsorption experiments suggested that highly selective adsorption of Hg(Ⅱ)by the 3D-NC could be completed within 90 min and had maximum adsorption capacities as high as 403.24 mg/g at 293 K,p H = 5.The adsorption mechanism for Hg(Ⅱ)was carefully evaluated and followed the physical adsorption,electrostatic attraction,chelation,and ion exchange.Besides,thermodynamic study demonstrated that the Hg(Ⅱ)adsorption procedure was spontaneous,endothermic,and randomness.More importantly,the 3D-NC could be regenerated and recovered well after adsorption-desorption cycles,showing a promising prospect in the remediation of Hg(Ⅱ)-contaminated wastewater.(2)The Fe-Mn bimetallic system shaped with nano-cluster structure was firstly prepared through mild reaction condition.And it was further composited with corn starchbased carbon,to fabricate Fe-Mn bimetallic doped starch-based porous carbon adsorbents(Fe-Mn@SCAs).Its changes in surface structure,crystalline structure and functional groups in compartment procedure were clarified.Batch adsorption experiments was applied to evaluated the adsorption performance for Hg(Ⅱ)and Fe-Mn@SCAs,which could not only complete its maximum adsorption(324.42 mg/g)within 1.5 h but also had wide range of adsorption p H(4-7).The adsorption mechanism for Hg(Ⅱ)was elucidated carefully and summarized including porous structure,electrostatic attraction,chelation,ion exchange and covalent coordination.Besides,thermodynamic study demonstrated that the Hg(Ⅱ)adsorption procedure was spontaneous,endothermic,and randomness.In addition,its selective adsorbability and regenerability was also excellent,having a promising prospect in the Hg(Ⅱ)sewage purification. |
