Numerical Simulations of Combined Dielectrophoresis and Alternating Current Electrothermal Flow for High-Efficient Separation of (Bio)Microparticles.

High-efficient separation of (bio)microparticles has important applications in chemical analysis, environmental monitoring, drug screening, and disease diagnosis and treatment. As a label-free and high-precision separation scheme, dielectrophoresis (DEP) has become a research hotspot in microparticle separation, especially for biological cells. When processing cells with DEP, relatively high electric conductivities of suspending media are sometimes required to maintain the biological activities of the biosample, which results in high temperature rises within the system caused by Joule heating. The induced temperature gradient generates a localized alternating current electrothermal (ACET) flow disturbance, which seriously impacts the DEP manipulation of cells. Based on this, we propose a novel design of the (bio)microparticle separator by combining DEP with ACET flow to intensify the separation process. A coupling model that incorporates electric, fluid flow, and temperature fields as well as particle tracking is established to predict (bio)microparticle trajectories within the separator. Numerical simulations reveal that both ACET flow and DEP motion act in the same plane but in different directions to achieve high-precision separation between particles. This work provides new design ideas for solving the very tricky Joule heating interference in the DEP separation process, which paves the way for further improving the throughput of the DEP-based (bio)microparticle separation system.

Improvement of SO2 Resistance of Low-Temperature Mn-Based Denitration Catalysts by Fe Doping.

The influence of vapor and SO2 in coal firing flue gas on the selective catalytic reduction activity of Mn/γ-Al2O3 and Mn-Fe/γ-Al2O3 catalysts was investigated at 150-275 °C. Denitration experiments and detailed characterization of catalysts were conducted. Vapor had no chemical effects on denitration, and the mechanism of SO2 deactivating the Mn/γ-Al2O3 catalysts was investigated in detail. This is due to the reaction between MnO2 and SO2 and the ammonium sulfate deposits forming on the surface. Sulfation of the Mn-active component was significantly reduced by doping the Mn/γ-Al2O3 catalyst with Fe. Iron doping also lowered the stability of the ammonium sulfate surface deposits, forcing them to rapidly decompose. Thus, iron doping significantly improved SO2 resistance and the denitration efficiency of Mn-Fe/γ-Al2O3 catalysts was not clearly decreased.