Enhancement of PM2.5 Cyclone Separation by Droplet Capture and Particle Sorting.

Fine particulate matter (PM2.5) is one of the most serious environmental pollutants worldwide, and efficient separation technologies are crucial to the control of PM2.5 emission from industrial sources. We developed a novel method to enhance PM2.5 cyclone separation by droplet capture and particle sorting using a vertical reverse rotation cyclone (VRR-C, inlet particle-sorting cyclone). The separation performances of common cyclone (CM-C) without droplets, CM-C with droplets, and VRR-C with droplets were compared in terms of energy consumption, overall separation efficiency, particle grade efficiency, outlet particle concentration, and outlet particle size distribution. The results show that the highest overall separation efficiencies were 51.7%, 89.9%, and 94.5% for CM-C without droplets, CM-C with droplets, and VRR-C with droplets, respectively, when the mean diameter of the inlet particles was 3.2 µm and the inlet particle concentration was 500 mg/m3. The PM2.5 grade efficiency of VRR-C with droplets was as high as 89.8%, which was 6.2% and 49.9% higher than those of CM-C with droplets and CM-C without droplets, respectively. This novel method was first successfully applied to the deep purification of product gas in the methanol-to-olefin (MTO) industry, for which the separation efficiency of fine catalyst particles was considerably improved.

Macroporous materials: microfluidic fabrication, functionalization and applications.

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields.

Highly efficient methyldiethanolamine (MDEA) removal and light naphtha purification via synergistic effect of molecular sieves and fixed adsorption bed.

Light naphtha is an important raw material for the production of benzene, toluene, and xylene from cracking in tubular furnaces for the production of ethylene and propylene. Light naphtha contains MDEA which is left behind after desulfurization. MDEA remaining in light naphtha will cause high alkalinity of light naphtha, which decreases product quality and increases costs. Additionally, MDEA itself is not easy to degrade and is harmful to human skin, so the removal of MDEA is of great significance for the purification of light naphtha and the protection of the environment. In this paper, a molecular sieve (13X) is compared with silica gel and resin (NKA-9) as a means of removing MDEA from light naphtha via synergism with a fixed adsorption bed. The adsorption capacity decreased in the order of 13X > NKA-9 > silica gel, with values of 53.189, 45.889 and 34.863 mg g-1, respectively. Similarly, the effectiveness of steam for 13X regeneration after adsorption saturation was investigated, and the steam regeneration restored 95% of the activity of the fresh 13X. Furthermore, the adsorption mechanism of MDEA in light naphtha by 13X was studied, and it was confirmed that the adsorption process was dominated by chemisorption, supplemented by physisorption. The -OH and -NH2 functional groups were the main groups involved in the chemisorption, and capillary action and hydrogen bond action may be involved in physisorption.

Selective heavy metal removal and water purification by microfluidically-generated chitosan microspheres: Characteristics, modeling and application.

Many industrial wastewater streams contain heavy metals, posing serious and irreversible damage to humans and living organisms, even at low concentrations due to their high toxicity and persistence in the environment. In this study, high-performance monodispersed chitosan (CS) microspheres were prepared using a simple microfluidic method and evaluated for metal removal from contaminated water. Batch experiments were carried out to evaluate the adsorption characteristics for the removal of copper ions, one representative heavy metal, from aqueous solutions. The inherent advantages of microfluidics enabled a precise control of particle size (CV = 2.3%), while exhibiting outstanding selectivity towards target ions (adsorption capacity 75.52 mg g-1) and fair regeneration (re-adsorption efficiency 74% after 5 cycles). An integrated adsorption mechanism analytic system was developed based on different adsorption kinetics and isotherms models, providing an excellent adsorption prediction model with pseudo-second order kinetics (R2 = 0.999), while the isotherm was fitted best to the Langmuir model (R2 = 0.998). The multi-step adsorption process was revealed via quantitative measurements and schematically described. Selective adsorption performance of CS microspheres in the present of other competitive metal ions with different valence states has been demonstrated and studied by both experimental and density functional theory (DFT) analysis.

Fast removal of Co(ii) from aqueous solution using porous carboxymethyl chitosan beads and its adsorption mechanism.

Porous carboxymethyl chitosan (PCMC) beads were synthesized via ionic coacervation/chemical crosslinking, using polyethylene glycol (PEG) as a porogen and calcium chloride and glutaraldehyde as physical and chemical cross-linkers. The as-synthesized PCMC beads were characterized using SEM, EDS, BET, TGA, FTIR and XPS analysis and then tested for the removal of Co(ii) from aqueous solution. The effects of the initial pH, Co(ii) concentration and temperature were investigated. It was found that the adsorption equilibrium is reached within 6 h and the maximum adsorption capacity is 46.25 mg g-1. In addition, the kinetics and equilibrium data are well described by pseudo-second-order kinetics and the Langmuir isotherm model. Moreover, the desorption and re-adsorption performance was also studied, and the results revealed that the prepared new adsorbent still showed good adsorption performance after five cycles of regeneration. Finally, the adsorption mechanism, including chemical and physical adsorption, was proposed on the basis of the microstructure analysis, adsorption kinetics and isotherm results, and chemical adsorption was found to be the main adsorption mechanism during the process of the removal of Co(ii).

Liquid-liquid extraction intensification by micro-droplet rotation in a hydrocyclone.

The previous literature reports that using a hydrocyclone as an extractor intensifies the mass transfer and largely reduces the consumption of extractant from 1800-2000 kg h-1 to 30-90 kg h-1. However, the intensification mechanism has not been clear. This paper presents experimental and numerical methods to study the multi-scale motion of particles in hydrocyclones. In addition to the usually considered translational behavior, the high-speed rotation of dispersed micro-spheres caused by the anisotropic swirling shear flow is determined. The rotation speeds of the tested micro-spheres are above 1000 rad s-1, which are much larger than the instantaneous rotation speed in isotropic turbulence. Due to the conical structure of a hydrocyclone, the rotation speed maintains stability along the axial direction. Numerical results show that the particle Reynolds number of micro-droplets in a hydrocyclone is equal to that in conventional extractors, but the particles have high rotation speeds of up to 10,000 rad s-1 and long mixing lengths of more than 1000 mm. Both the rotation of micro-droplets along the spiral trajectories and the intense eddy diffusion in a hydrocyclone contribute to the extraction intensification.

A redox-mediated chromogenic reaction and application in immunoassay.

A novel redox-mediated chromogenic reaction was demonstrated based on the reaction between HAuCl4 and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), which generate various color responses from red to green in the resulting solutions. Various redox substance could be used to mediate the reaction and trigger a distinct color response. We established a sensitive hydrogen peroxide colorimetric sensor based on the redox-mediated chromogenic reaction and depicted the application both in detection of enzyme and in an immunoassay. Combining the traditional chromogenic reagent with gold nanoparticles, our assay has the advantage in short response time (within three minutes), high sensitivity (10(-12) g mL(-1) for HBsAg) and stability.