Nan Bao

Textural properties and surface chemistry of lotus stalk-derived activated carbons prepared using different phosphorus oxyacids: adsorption of trimethoprim.

The preparation of activated carbons (AC-H(x)P(y)O(z)) by four kinds of oxyacids of phosphorus (H(3)PO(4), H(4)P(2)O(7), HPO(3) and H(3)PO(3)) activation of lotus stalk (LS) was studied, with a particular focus on the effect of these H(x)P(y)O(z) on both surface chemistry and porous texture. The XRD analysis of the samples after H(x)P(y)O(z) impregnation showed H(4)P(2)O(7) had the strongest influence on the crystallinity of LS. Thermo gravimetric studies of the pyrolysis of LS-H(x)P(y)O(z) indicated that these H(x)P(y)O(z) had a very different influence on the thermal degradation of LS. The prepared activated carbons were characterized by SEM, N(2) sorption/desorption isotherms, XRD, FTIR and Boehms titration. Batched sorption studies were performed to compare adsorptive properties of the carbons toward trimethoprim (TMP). The surface area and pore volume of AC-H(3)PO(4) and AC-H(4)P(2)O(7) were much higher than AC-HPO(3) and AC-H(3)PO(3). Boehms titration results indicated that AC-H(4)P(2)O(7) and AC-H(3)PO(3) possessed more acidic oxygen functionalities than AC-H(3)PO(4) and AC-HPO(3). The structure of the AC-HPO(3) was kept as its starting material after activation. Activation with H(3)PO(3) would result in the aromatization of the carbon. The sorption affinities of TMP follows an order of AC-H(4)P(2)O(7)>AC-H(3)PO(4)>AC-H(3)PO(3)>AC-HPO(3).

Si-doped mesoporous TiO2 continuous fibers: Preparation by centrifugal spinning and photocatalytic properties

TiO(2) continuous fibers were prepared by a sol-gel method combined with centrifugal spinning without any template or binder polymer. The fibers were characterized using XRD, FT-IR, SEM, N(2) adsorption-desorption, and UV-vis DRS. The addition of silica was a crucial factor for obtaining long fibers because of the formation of Ti-O-Si networks. The effects of dopant contents and heat treatment temperatures were studied. It was found that the proper addition of silica into titania could improve the surface texture and enhance the thermal stability and crystal stability. When Si/Ti molar ratio was 0.15, mesoporous TiO(2) fibers with a BET surface area up to 127.7 m(2)g(-1) were obtained after heat treatment at 700 degrees C. It displayed the highest photoactivity of all, and the degradation rate of X-3B in aqueous solution reached 99.6% after 75 min under UV irradiation. Furthermore, the degradation rate and the mineralization rate of X-3B were 94.7% and 58.9% after 3h under solar irradiation, respectively. In addition, it was worthwhile to mention that the degradation efficiency was also more than 90% after 6 cycles.

Preparation of TiO2 Continuous Fibers with Oxygen Vacancies and Photocatalytic Activity

TiO2 continuous fibers were prepared by a modified sol-gel method combined with centrifugal spinning and different heat treatment processes. The prepared fibers were characterized by TG-DSC, XRD, SEM, N2 adsorption-desorption and XPS. The photocatalytic degradation of X-3B aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The results indicated that heat treatment in steam was conductive to the rapid nucleation of anatase nanocrystal and could effectively suppress the anatase-rutile transformation. Compared with samples calcined in air, products heat treated in steam were long fibers with oxygen vacancies and abundant mesoporous structures, which enhanced their photocatalytic activities. The fibers with a high specific surface area of 87.6 m2·g−1 and the largest pore volume of 0.24 cm3·g−1 were obtained when heat treated at 400°C in steam. The sample exhibited the best photocatalytic activity and the removal rate of X-3B was 99.5% after 90 min under visible light irradiation.