Y.C. Lu

Determination of dynamic interfacial tension and its effect on droplet formation in the T-shaped microdispersion process.

Interfacial tension is an important physical property affecting the droplet formation process in microfluidic devices. This work presents the variation of dynamic interfacial tension caused by slow adsorption of surfactant, as well as its influence on the liquid/liquid microdispersion process in a T-shaped microchannel. Using hexane/water-Tween 20 as the working system, it was observed that the droplet size changed with the variation of surfactant concentration when the concentration of Tween 20 was lower than 10 mmol/L, but hardly changed at higher concentrations, which was caused by the unsaturated adsorption and saturated adsorption of surfactant, respectively. The saturated interfacial tension was measured with an interfacial tension meter, and the relationship between the interfacial tension and the droplet diameter was established. Accordingly, the dynamic interfacial tension with unsaturated adsorption of surfactant was determined. The main factors affecting the dynamic interfacial tension were discussed, and a semiempirical equation was established to characterize those effects.

Development of a multi-criteria index ranking system for urban runoff best management practices (BMPs) selection

Low impact development best management practices (LID-BMPs) are considered to be cost-effective measures for mitigating the water quantity and quality impact of urban runoff. Currently, there are many types of LID-BMPs, and each type has its own intrinsic technical and/or economical characteristics and limitations for implementation. The selection of the most appropriate BMP type(s) for a specific installation site is therefore a very important planning step. In the present study, a multi-criteria selection index system (MCIS) for LID-BMP planning was developed. The selection indexes include 12 first-level indices and 26 second-level indices which reflect the specific installation site characteristics pertaining to site suitability, runoff control performance, and economics of implementation. A mechanism for ranking the BMPs was devised. First, each individual second-level index was assigned a numeric value that was based on site characteristics and information on LID-BMPs. The quantified indices were normalized and then integrated to obtain the score for each of the first-level index. The final evaluation scores of each LID-BMP were then calculated based on the scores for the first-level indices. Finally, the appropriate BMP types for a specific installation site were determined according to the rank of the final evaluation scores. In order to facilitate the application of the MCIS BMP ranking system, the computational process has been coded into a software program, BMPSELEC. A case study demonstrating the MCIS methodology, using an LID-BMP implementation planning at a college campus in Foshan, Guangdong Province, is presented.

Porous glass beads as a new adsorbent to remove sulfur-containing compounds

This paper explores porous glass beads as a pollutant-free-prepared, low-cost, and recyclable adsorbent for desulfurization. Porous glass beads with a specific surface area, pore volume, and mean pore diameter of 162.6 m2 g−1, 0.26 cm3 g−1, and 6.34 nm, respectively, were obtained by subcritical water treatment. The effects of the surface chemistry of the adsorbent and the structure of the organosulfur molecules on adsorption capacity were studied; the software, Materials Studio, was used to calculate the interactions between the surface of the glass beads and the sulfur-containing compounds. Compared with these porous glass beads, two other kinds of porous glass beads modified by hexamethyldisilazane and hydrochloric acid, respectively, showed much lower adsorptive capacity for dibenzothiophene, indicating the metal ions contained in the glass played an important role during the adsorption; the capacities of the porous glass beads for benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene were 6.47 ± 0.09, 8.58 ± 0.09, and 11.20 ± 0.08 mg(S) gadsorbent−1, respectively, corresponding to the simulation results. The adsorptive capacity for dibenzothiophene decreased with the increase of temperature but increased with the increase of initial concentration, the highest capacity of 10.29 ± 0.11 mg(S) gadsorbent−1 was obtained at 303 K with the initial concentration of 565 ppmw(S). Spent adsorbent can be regenerated by heating at high temperature, and the adsorptive capacity only decreased about 3.38% after five cycles. Experimental results and the computer simulations indicate that polar interactions between the surface and sulfur-containing compounds dominated the adsorption.

Two-phase electrophoresis separation of dyestuffs from dilute solution

Abstract Dyestuffs are not efficiently removed by biological treatment or by conventional dye treatment techniques. New separation techniques are required. Two-phase electrophoresis, a coupled separation technique of solvent extraction with electrophoresis, can be used to remove dyestuffs from dye effluents. A study on the characteristics of the separation technique has been carried out with n -butanol–acid-chrome blue K–water, n -butanol–methyl blue–water and n -butanol–methyl red–water as working systems. Continuous separation equipment has been designed and used in this work. The influences of the two-phase flow rate, field strength and feed concentration on the recovery are studied. The results show that a high recovery with less solvent consumption can be achieved using this technique, especially for the separation of dilute solutions. As the field strength is increased, the recovery and mass flux increase. When the feed flow rate and the initial solute concentration in the feed are increased, the recovery decreases and the mass flux increases.

Fast flow synthesis of highly reactive polyisobutylene co-initiated by an AlCl3/isopropyl ether complex

In this work, with AlCl3 addition in the range from 4 to 10 mmol L−1 and enough isopropyl ether (iPr2O) addition, we successfully synthesized highly reactive polyisobutylene (HRPIB) using a microflow system within 12 s or less. The temperature window was extended from −20 °C to 50 °C, and the molecular weight (Mn) was adjustable between 500 and 15 000. The evolutions of HRPIBs and the effects of reaction conditions were carefully investigated, revealing multiple effects of an excess of iPr2O over AlCl3 including: (1) decreasing the intensive isomerization co-initiated by free AlCl3; (2) inhibiting the chain termination to present chain transfer dominated kinetics; (3) weakening the temperature sensitivity of Mn as a restriction on temperature elevation; (4) retarding the chain propagation to slow the reaction and increase the probability of isomerization. Key access to fast synthesis of high quality HRPIB is proposed to make a compromise of these effects by properly selecting iPr2O : AlCl3.