Binghui Tian

Adsorption of 1,2-dichlorobenzene from water to carbon nanotubes

Abstract The as-grown CNTs and graphitized CNTs were used as adsorbents to remove 1,2-dichlorobenzene from water. The experiments demonstrate that it takes only 40 min for CNTs to attain equilibrium and the adsorption capacity of as-grown and graphitized CNTs is 30.8 and 28.7 mg/g, respectively, from a 20 mg/l solution. CNTs can be used as adsorbents in a wide pH range of 3–10. Thermodynamic calculations indicate that the adsorption reaction is spontaneous with a high affinity and the adsorption is an endothermic reaction.

Characteristics and kinetics of phosphate adsorption on dewatered ferric-alum residuals.

The characteristics and kinetics of phosphate (P) adsorption on dewatered ferric-alum water treatment residuals (Fe-Al-WTRs) have been investigated. The existence of both aluminum (Al) and iron (Fe) in the residuals can result in significantly high P adsorption capacities. The P adsorption kinetics of Fe-Al-WTRs exhibited an initial rapid phase, followed by a slower phase. This could be described by three models, including a pseudo–first-order equation, a pseudo–second-order equation, and a double-constant rate equation. The latter was especially good for those runs with initial P concentrations of 500 and 1000 mg L−1. Both the Langmuir and Freundlich isotherms fit the experimental data well, particularly the Freundlich isotherm, which had a correlation coefficient of 0.9930. The maximum measured P adsorption capacity of Fe-Al-WTRs was 45.42 mg g−1, which is high when compared to those of most WTRs, as well as other reported adsorbents. The results also show that the P adsorption is a spontaneous endothermic process. Highest P adsorption capacities of Fe-Al-WTRs were measured at low pHs and a particle size range of 0.6 to 0.9 mm.

Anammox bacteria community and nitrogen removal in a strip-like wetland in the riparian zone

A strip-like wetland was constructed in the riparian zone for investigation of ammonium nitrogen (NH3-N) removal in the Peach River. An inner zeolite layer was set in the wetland to adsorb NH3-N and further to remove total nitrogen (TN). An oxygen-deficient condition with dissolved oxygen of 0.87–1.60 mg L−1 was observed in the zeolite layer, which benefits anaerobic ammonium oxidation (anammox) bacteria survival. The community structure of anammox bacteria was analyzed in the zeolite layer. The analysis shows that the anammox bacterial sequences are grouped into three known distinct clusters: Candidatus Brocadia fulgida, Candidatus Brocadia anammoxidans and Candidatus Jettenia asiatica. The intensified test driven by artificial pumping shows that average removal rates of NH3-N and TN are 41.6 mg m−3d−1 and 63.2 mg m−3d−1, respectively. The normal test driven by natural hydrodynamics also verifies that NH3-N removal mainly happens in the zeolite layer. Microbial mechanism of TN removal in the wetland involves both the autotrophic and heterotrophic process. These results suggest that the strip-like RW can be a cost-effective approach for NH3-N removal and can potentially be extended to similar rivers as no extra energy is required to maintain the wetland operation.

Zirconia pillared montmorillonite for removal of arsenate from water

Zirconia pillared montmorillonite, a clean adsorbent with increased specific areas of 40.118 m2/g and high basal spacing of 2.20 nm, was prepared for the removal of arsenate from water. Zirconia pillared montmorillonite is effective for the removal of arsenate. Adsorption is favored under acid conditions. Ca2 + and Mg2 + in the solution slightly enhance the adsorption. Over 95% removal was observed under natural pH conditions from 20 mg/L arsenate solutions containing 5.0 mg/L Ca2 + or Mg2 +. High adsorption capacity of over 120 mg/g was observed from arsenate solutions with different Ca2 + concentrations. The Freundlich model can describe the adsorption equilibrium data well. The column test shows that the column allows the passage of the feeding solution for approximately 225 times the bed volume if the removal percentage of arsenate was monitored not to be lower than 98%. The adsorbed arsenate can be desorbed with NaOH and the desorption efficiency reaches 85% and 88% when the concentration of NaOH reaches 0.2 and 0.5 mol/L. Zirconia pillared montmorillonite can be regenerated and the regenerated adsorbents still have good adsorption capacities.

Adsorption of p-Nitrophenol onto PDMDAAC-modified Bentonites

A novel organobentonite was prepared by modifying bentonite with poly(dimethyldiallylammonium chloride) (PDMDAAC), a harmless and cost-effective type of polycation. Zeta potential and X-ray diffraction measurements suggest that PDMDAAC was intercalated into the bentonite interlayer space. PDMDAAC—bentonite has been found to be effective for the removal of p-nitrophenol with a removal rate of 81.4% being achieved. The adsorption process was pH-dependent and was slightly decreased by the Ca2+ and Mg2+ ions co-existing in the solution. A dual-phase adsorption mechanism was suggested for the process. The adsorbents obtained from the regeneration of PDMDAAC—bentonite still exhibit good adsorption capacities.