Research On Adsorption Of Heavy Metal Ions Of Carbon Aerogels And Their Modified Materials

The environment pollution and human health hazards caused by heavy metal ions have become increasingly serious. Currently, adsorptive process is still the main treatment method of heavy metal ion contamination. Developing efficient, inexpensive and environmentally friendly adsorbents is the imperative of research workers. As a new nano-porous carbon material, carbon aerogels have such kind of characteristics:high porosity, large surface area, and strong adsorption performance. Its value as an adsorbent in the field of environmental protection is increasingly taken serious. Based on this, by using carbon aerogels as research object, relevant research of preparation methods, structural modification, adsorption properties and adsorption mechanism were systematically carried out in this dissertation. The results were as follows:1. Carbon aerogels were synthesized using atmospheric drying method. The adsorption capacity of three heavy metal ions is in the order of Pb2+> Cu2+> Cd2+.The new absorbent carbon aerogels were synthesized using atmospheric drying method, in which resorcinol and formaldehyde as raw material, malonic acid as catalyst, cetyl trimethyl ammonium bromide as dispersing agent, deionized water as solvent. The source controllability of carbon aerogels can be achieved by optimization of reaction conditions, to meet different application requirements. The results of single component system showed that experimental data of three heavy metal ions can be well fitted by the Langmuir adsorption isotherm. The adsorption capacity is in the order of Pb2+> Cu2+> Cd2+, with saturated extent of adsorption of285.35,260.42and137.36mg/g, respectively. The results of two-component system showed the "selective adsorption" of heavy metal ions on carbon aerogels. The competitive adsorption capacity is in the order of Pb2+> Cu2+> Cd2+, consistent with the results of single component system. FTIR results suggested the existence of ion exchange, hydroxyl group, carboxyl group and amide group had played a role.2. Carbon aerogels modified by nitric acid can be used as a rapid, efficient and economical adsorbent to remove Cu2+from aqueous solution.After carbon aerogels modified by nitric acid, microporous little changing, specific surface area reducing, pore volume and pore size enlarging; superficial oxygen-containing groups increasing. Compared with unmodified carbon aerogels, the adsorption capacity of materials after modification to Cu2+improved significantly (299.41mg/g). The adsorption quantity of Cu2+on carbon aerogels before and after modification positively correlates with temperature, initial concentration of ions and pH. The kinetic data of Cu2+on the two adsorbents correlates well with the pseudo-second-order model, indicating that the whole process is mainly controlled by chemical reaction. The adsorption equilibrium amount of Cu2+can be well fitted by the Langmuir adsorption isotherm, futher indicating the monolayer adsorption. The calculated activation energy of adsorption of Cu2+on the modified carbon aerogels can reach15.62kJ/mol. The activation energy is low, proving the existence of both chemical and physical adsorption process in the whole adsorption process.3. Carbon aerogels modified by ethylenediamine can be used as a rapid, efficient and economical adsorbent to remove Pb2+from aqueous solution.The adsorption quantity of Pb2+on carbon aerogels before and after modification positively correlates with pH, temperature, contact time and initial concentration of ions; but negatively with concentration of additional ion Na+. The kinetic data of Pb2+on carbon aerogels after modification correlates well with the pseudo-second-order model, indicating that the whole process is mainly controlled by chemical reaction. The isothermal adsorption data of Pb2+on carbon aerogels after modification can be well fitted by the Langmuir model, the maximum adsorption capacity of321.42mg/g.4. Magnetic nanocomposites with carbon-coated nickel structure (Ni@Cs) can be used as a rapid, efficient and economical adsorbent to remove heavy metal ions from aqueous solution.Three adsorbing materials with different carbon-coating amount (Ni@C-1:5、 Ni@C-l:10> Ni@C-l:20) were prepared by a solid-state method. This kind of material has large specific surface area, and could be magnetically separated. The adsorption quantity of Pb2+and Cu2+on three kinds of magnetic adsorbents positively correlates with reaction time and initial concentration of heavy metal ions. The adsorption capacity of three kinds of magnetic adsorbents is in the order ofNi@C-1:5> Ni@C-l:10> Ni@C-l:20. The adsorption behavior of three magnetic adsorbents correlates well with the pseudo-second-order and Freundlich model (R2＞0.99). Meanwhile, they also could be rapidly separated under the external magnetic field to achieve the thorough elimination of heavy metal ions and recycling.