Lab- and pilot-scale wet scrubber study on the redox-mediated simultaneous removal of NOx and SO2 using a CaCO3-based slurry with KI as a redox catalyst.

This study presents a novel approach that integrates ozone-driven chemical oxidation to convert NO into soluble NO2, followed by the simultaneous absorption of NO2 and SO2 into a CaCO3-based slurry using the redox catalyst potassium iodide (KI). Using cyclic voltammetry, we demonstrate the redox properties of the I2/2I- couple, which facilitates NO2 reduction into soluble NO2- and catalyst regeneration through sulfite (SO32-)-driven reduction, thus establishing a closed catalytic cycle within the components of flue gas. In lab-scale wet-scrubbing tests, we explore the effect of various operational parameters (i.e., KI concentration, pH, and SO2 concentration), with a 15 h stability test demonstrating >60% NOx and >99% SO2 removal efficiency when the pH is controlled between 7.5 and 8.5. A successful pilot-scale implementation conducted at an inlet flow rate of 1000 m3 h-1 further confirmed the reproducibility of the proposed redox-catalytic cycle. Our study offers a cost-effective, sustainable, and scalable solution for effectively mitigating NOx and SO2 emissions at low temperatures.

Improvement of an In-Duct Two-Stage Electrostatic Precipitator via Diffusion Charging.

An in-duct two-stage electrostatic precipitator (ESP) improved by ion diffusion effect was studied. We increased the collection efficiency of a two-stage electrostatic precipitator without additional energy input by adjusting the space arrangement of the charger and the collector, which increased the particle diffusion charging time. The collection efficiency and the particle charge were systematically investigated according to the occurrence of diffusion charging and electric field charging in the charger as generated by the negative ions. The collection efficiency of the separated two-stage ESP was 39% higher, on average, than the theoretical efficiency at the same power consumption. Through simulation, it was verified that the ions generated in the carbon fiber ionizer penetrated the charger. We proposed a modified charging mechanism assuming that the penetrated ions cause additional particle charge. The optimal separation distance between the charger and the collector, which showed the maximum collection efficiency, was derived through the modified charging model. Therefore, the in-duct two-stage ESP developed in this study is a promising energy-efficient and cost-saving design for indoor air management.

Development of On-Demand Antiviral Electrostatic Precipitators with Electrothermal-Based Antiviral Surfaces against Airborne Virus Particles.

Particulate matter, including airborne pathogens, is of particular concern because it can cause the spread of diseases through aerosol transmission. In this study, a new concept is proposed: on-demand antiviral electrostatic precipitators (ESPs) with electrothermal-based antiviral surfaces. We applied electrothermal-based antiviral surfaces to air-purifying applications and demonstrated that the proposed method is effective with regard to collecting airborne virus particles on collection plates in a two-stage ESP. With alternating current power, MS2 bacteriophage and H1N1 viruses were completely deactivated after exposure to 50 °C for 30 min. This remarkable antiviral performance via electrothermal effects indicates that on-demand platforms for self-antiviral surfaces can perform sterilization immediately without generating secondary pollutants, thus effectively preventing the spread of infectious microorganisms in public places. We believe that the results of this study can provide useful guidelines for the design and realization of practical and wearable devices for antiviral air-purifying applications.