| Carbonaceous material derived from biomass using hydrothermal fabrication method is a promising material. It includes C, N, O, H elements, which can be incroduced by hydrothermal treatment of biomass. It has excellent physical and chemical properties and has extensive application in energy and environmental field. When used as adsorbents, the surface functional groups, such as –OH,-NH2-,-COOH and-SO3 H can serve as active sites for selective removing harmful pollutants.Chitosan, with plentiful amino and hydroxyl groups is abundant in the world, which can obtain from the deacetylation of chitin. However, the application in fabrication of carbonaceous materials with hydrothermal method is limited due to its poor dissolution property in water. Herein, we made an attempt to obtain carbonaceous materials by hydrothermal method, which use chitosan as carbon source. Further, we have studied their selective adsorption capacity toward heavy metal ions.(1)Sphere-shaped carbonaceous based materials have been successfully synthesized for the first time by a facile hydrothermal process and using chitosan as carbon resouce. The carbonaceous content is about 80%. Amount of chitosan is crucial for formation of final sphere structure. Without chitosan, irregular polyhedron α-Fe2O3 produced. With the dosage increased from 0.15 to 1.00 g, the etching effect could be enhanced on the produced product and last developed sphere-shaped carbonaceous based product. However, when the dosage of chitosan further increased to 1.50 g, only irregular sphere with more exposed α-Fe2O3 was obtained. Further, it was found that the synthetic process was related to α-Fe2O3 formation and subsequent α-Fe2O3-ecthing induced by chitosan carbonization process.More importantly, after adjusting the pH value, the as-obtained product is suitable for adsorption and exhibits selective adsorption performance toward Cr(VI) and Cu(II). As p H value of the mixed solution is 2, the adsorption of Cr(VI) can highly reach 1.90mmol/g and the adsorption of Cu(II) is limited at 0.022 mmol/g. It means that can selectively adsorb Cr(VI) in mixed solution. When adjusting the pH value from 3 to 5, the adsorbent increases the adsorption of Cu(II) until a high value at 1.32 mmol/g. However, The adsorption of Cr(VI) decrease from 1.90 to 1.32 mmol. At high pH value, the adsorbent do not show selective adsorption of Cr(VI).(2)Hollow α-Fe2O3 spheres have been successfully fabricated by a simple templatefree hydrothermal process, in which chitosan and glucose were employed as dispersion and morphology-controling reagent. The carbonaceous content is about 6.5%. The results showed the as-prepared α-Fe2O3 hollow spheres possessed good dispersion and exhibited plentiful functional groups on their surface. The time-dependent experiments reveal that the hollow structure was developed from an Ostwald ripening process and the recrystallization of α-Fe2O3 spheres occurred during the reaction. Furthermore, the effect of chitosan and glucose were also investigated. The result showed that chitosan played a key role on hollow structure development, while the glucose promoted formation of the hollow structure. When α-Fe2O3 hollow spheres used as adsorbent to remove trace As(Ⅴ)( 156.2μg/L), they showed a high removal efficiency(98%).(3)We have utilized urea as precipitant and chitosan as carbon resource to prepare magnetic carbonaceous material. The carbonaceous content is about 20.65%.With plentiful carboxyl group,the surface of the as-prepared product performed strong negative charged-COO- in aqueous solution. When used as absorbent,the magnetic carbonaceous material had a good selective adsorption toward MB in MB and MO mixed solution. |
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