Research About The Influence Of Negative Air Ions On Indoor Environmental Particles

Negative air ions(NAIs)is an important component of air and play very important role in many fields.In recent years,the use of NAIs for dust removal has evolved into a very mature and effective means for air purification.However,most of the research on NAIs used for dust removal is concentrated in application field,and there are few reports that specialize in theoretical basic research.Therefore,on the basis of summarizing the previous studies,this work focused on the influence of air negative ions on the indoor environmental particulate matter at micro level,and conducts in-depth research.The contents are as follows:1.The inhibition effect of negative air ions on the adsorption between volatile organic compounds(VOCs)and environmental particulate matter was investigated.This work focused on the chemisorption behavior of VOCs on particles smaller than 2.5?m(PM2.5).The test results showed that the content of different types of VOCs adsorbed on the surface of PM2.5 particles is mainly related to their functional groups,and they are sequentially reduced in the order of hydroxyl group,carbonyl group,ether group,and hydrocarbon group(CxHy)as 70.02,21.35,6.42 and 2.21%,respectively.The chemical adsorption mechanism shows that the stronger the electronegativity of oxygen atoms in the oxygen-containing functional groups of VOCs,the easier to adsorb on silicate PM2.5 particles.As the main components of PM2.5 is silicate,which was easily to form silicon hydroxyl groups in acidified environment,so that the stronger electronegative functional groups in VOCs can form intermolecular hydrogen bonds with silicon hydroxyl groups.As a result,VOCs are adsorbed on PM2.5.In addition,NAIs could weaken the ability of lone pairs of electrons in oxygen-containing functional groups in VOCs,thereby greatly reducing the possibility of forming hydrogen bonds with silanol groups.Therefore,NAIs can effectively inhibit the adsorption between VOCs and PM2.5,leading to a significant reduction in VOCs on the surface of PM2.5.2.The influencing factors towarded to the agglomeration of particulate matter in the indoor environment were studied.In recent years,indoor environmental pollutants,especially ultrafine particles(UFPs)have attracted much attention.In this paper,by simulating the black wall phenomenon,the agglomeration mechanism of UFPs and related influencing factors were studied.The results showed that mobile charge—negative air ions(NAIs)is the necessary condition for UFPs to agglomerate.Mobile charge could change the physical properties of UFPs particles and can make the particles show obvious magnetism.The magnetic strength determined the microscopic morphology of UFPs after agglomeration,including leaf shape and granular shape.The thickness of the agglomerated particulate matter was positively correlated with the roughness of the attachment surface.In other words,the roughness determines the amount of UFPs that can agglomerate.The rougher the attachment surface,the easier to adsorp on the attachment surface.The electrical conductivity of the attachment surface could affect where the UFPs reunite.In addition,we systematically elaborated the possible agglomeration mechanism of UFPs and described the agglomeration process in detail.These findings may contribute to the study of new air purification methods and the microscopic mechanism of atmospheric particles.3.A new method for quickly removing sub-fine particles in indoor environment using three-stage electrostatic precipitators was proposed.In this work,we proposed a feasible method for removing sub-fine particles in indoor air and described the possible mechanism of which negative air ions promote the sub-fine particles to settle.In order to effectively remove sub-fine particles with an aerodynamic diameter of less than 0.3 ?m,we simulated a domestic ventilation channel in the laboratory and applied a dual-reverse electrode matrix arrangement mode.The dual-reverse electrode matrix is composed of 16 pairs of carbon fiber electrodes connected to the positive and negative power sources,and these electrodes are symmetrically distributed on both sides of the electrostatically filtered copper mesh.It is divided into three parts by modifying the channel structure:negative ion reaction chamber,electrostatic filtering copper mesh,and positive ion reaction chamber.In the first stage of electrostatic dust removal,more than 95%of the sub-fine particles can quickly aggregate to make the particle size larger and can be filtered by the electrostatic copper mesh.Very few particles without agglomeration were completely removed by changing the direction of travel in the positive ion reaction chamber.With this method,the air relseased from the ventilation channel can always be kept within the superior air index range.4.A new method for preparing hydrated negative air ions(HNAIs)is proposed.At first,a large number of charged droplets were prepared by the air-water collision method based on the Lenard effect.Then,these small droplets collide again on the surface of the photo-excited catalytic material,rosin-titania,to capture a large number of free electrons generated by ultraviolet light excitation,thereby improving the actual effective yield of HNAIs.Photocatalytic materials are often used in the field of photolysis water because of their excellent performance and low cost.Compared with the traditional corona discharge method,this method can make the yield of HNAIs more stable.In addition,the factors affecting the stability of HNAIs were discussed.The stability of HNAIs is related to molecular weight and relative humidity.The higher the molecular weight of HNAIs,the lower the mobility and the lower the possibility to collide with other air particles,which can avoid the loss of charge and maintain stability.The higher the ambient humidity,the more stable the prepared HNAIs.This is because in an environment with high humidity,water molecules cannot easily escape from the surface of HNAIs,which can protect the charge and prolong the survival time of HNAIs.