Fengling Liu

Adsorption of Pharmaceutical Antibiotics on Template-Synthesized Ordered Micro- and Mesoporous Carbons

The presence of pharmaceutical antibiotics in aquatic environments poses potential human health and ecological risks. We synthesized ordered micro- and mesoporous carbons, and further conducted batch experiments to systematically examine their adsorption properties toward three antibiotics, sulfamethoxazole, tetracycline, and tylosin, in aqueous solution. In comparison, nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were included as additional adsorbents. Adsorption of low-sized sulfamethoxazole was stronger on the activated carbons than on other carbonaceous adsorbents resulting from the pore-filling effect; in contrast, due to the size-exclusion effect adsorption of bulky tetracycline and tylosin was much lower on the activated carbons, especially for the more microporous one, than on the synthesized carbons. After normalizing for adsorbent surface area, adsorption of tetracycline and tylosin on the synthesized carbons was similar to that on nonporous graphite, reflecting complete accessibility of the adsorbent surface area in adsorption. Additionally, compared with other porous adsorbents the synthesized carbons showed faster adsorption kinetics of tetracycline and tylosin, which was attributed to their regular-shaped, open and interconnected three-dimensional pore structure. The findings indicate that template-synthesized micro- and mesoporous carbons are promising adsorbents for the removal of antibiotics, particularly, the bulky and flexible-structured compounds, from aqueous solution.

Zeolite-templated microporous carbon as a superior adsorbent for removal of monoaromatic compounds from aqueous solution.

A microporous carbon with very high specific surface area and narrow pore size distribution was synthesized using Y zeolite as a template. The structural, porosity, and surface characteristics of the material were investigated by elemental analysis, N2 adsorption, powder X-ray diffraction, and Raman spectroscopy. The batch adsorption technique was performed to assess adsorption of three monoaromatic compounds, phenol, 1,3-dichlorobenzene, and 1,3-dinitrobenzene, on the synthesized carbon. Nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were also included as comparative adsorbents. The synthesized microporous carbon showed extraordinarily high adsorption affinity (comparable or higher than activated carbons and carbon nanotubes) for the three adsorbates, and very fast adsorption/ desorption kinetics (equilibrium reached less than 3 h) and complete adsorption reversibility for phenol. These adsorption properties were attributed to the large hydrophobic surface area and the regular-shaped, open and interconnected three-dimensional pore structure of the synthesized microporous carbon. Additionally, with normalization of adsorbent surface area adsorption of a bulky solute, 1,2,4,5-tetrachlorobenzene, was prominently higher on the synthesized carbon than on the activated carbons, due to alleviated size exclusion effect. Findings of the present work highlight the potential of using zeolite-templated carbons as effective adsorbents for removal of hydrophobic organic contaminants in water treatment.

Influence of ZrO2 properties on catalytic hydrodechlorination of chlorobenzene over Pd/ZrO2 catalysts

Pd/ZrO(2) catalysts using different ZrO(2) as supports were prepared using the deposition-precipitation method and were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N(2) adsorption, temperature programmed reduction, H(2) chemisorption and measurement of surface hydroxyl group. Catalytic hydrodechlorination (HDC) of chlorobenzene was used to evaluate the activity and stability of the catalyst. The results showed that ZrO(2) support calcined at 300 degrees C was amorphous in nature, whereas ZrO(2) supports calcined at 500 and 600 degrees C consisted of both monoclinic and tetragonal phases. In addition, increasing calcination temperature led to the decrease of specific surface area and surface hydroxyl group content of the ZrO(2) support. For temperature programmed reduction of PdO/ZrO(2) samples, two H(2) consumption peaks with varied reduction temperature were distinctly observed, implying the existence of different Pd species in Pd/ZrO(2) catalysts. In addition, Pd/ZrO(2) catalyst with ZrO(2) calcined at 500 degrees C had a relatively higher content of Pd species with strong metal-support interaction than other catalysts. For catalytic HDC of chlorobenzene, Pd/ZrO(2) catalyst with ZrO(2) support calcined at 500 degrees C exhibited a higher initial activity and stability as compared to other catalysts, indicative of a strong dependence of the catalytic behavior of the Pd/ZrO(2) catalyst on the support properties for catalytic HDC of chlorobenzene.

Enhanced adsorption of humic acids on ordered mesoporous carbon compared with microporous activated carbon

Humic acids are ubiquitous in surface and underground waters and may pose potential risk to human health when present in drinking water sources. In this study, ordered mesoporous carbon was synthesized by means of a hard template method and further characterized by X-ray diffraction, N2 adsorption, transition electron microscopy, elemental analysis, and zeta-potential measurement. Batch experiments were conducted to evaluate adsorption of two humic acids from coal and soil, respectively, on the synthesized carbon. For comparison, a commercial microporous activated carbon and nonporous graphite were included as additional adsorbents; moreover, phenol was adopted as a small probe adsorbate. Pore size distribution characterization showed that the synthesized carbon had ordered mesoporous structure, whereas the activated carbon was composed mainly of micropores with a much broader pore size distribution. Accordingly, adsorption of the two humic acids was substantially lower on the activated carbon than on the synthesized carbon, because of the size-exclusion effect. In contrast, the synthesized carbon and activated carbon showed comparable adsorption for phenol when the size-exclusion effect was not in operation. Additionally, we verified by size-exclusion chromatography studies that the synthesized carbon exhibited greater adsorption for the large humic acid fraction than the activated carbon. The pH dependence of adsorption on the three carbonaceous adsorbents was also compared between the two test humic acids. The findings highlight the potential of using ordered mesoporous carbon as a superior adsorbent for the removal of humic acids.