Promotion Of LiCl Liquid Desiccant With Minor 2-EH To Inactivate Mold Aerosols In Air-conditioning Systems

Liquid desiccant air-conditioning（AC）system can effectively capture and inhibit the mold aerosols in the airflow by the direct contact between LiCl solution and air,reducing the risk of mold exposure to indoor personnel.However,due to the strong hydrophobicity and resistance of the mold itself,inactivating mold aerosols by using LiCl solution alone still has some shortcomings,mainly including: 1)the inactivation efficiency is not ideal,2)the concentration of LiCl solution required for effective inactivation is too high and prone to crystallize in the system.These shortcomings restrict the air purification effect of liquid desiccant AC system.In order to improve the inactivation performance of system,how to overcome the hydrophobicity and resistance of mold is a critical problem to be solved.This work experimentally studied the effects of minor 2-EH（2-ethyl-1-hexanol）surfactant on improving the LiCl liquid desiccant inactivation ability against two commonly detected mold spores in air conditioning systems,A.niger and P.citrinum.Microbial activity analysis,inactivation kinetic analysis,SEM analysis were adopted to study: 1)the effects of minor surfactant on the mold inactivation efficacies and rate of LiCl liquid desiccant;2)the mechanism of surfactant to strengthen the mold inactivation of LiCl solution;3)applicable concentration range of surfactant.The results showed that minor addition of 2-EH（50～300 ppm）substantially improved the mold inactivation performance of LiCl liquid desiccant（by 1260%）.The improvement was particularly significant for the dilute LiCl solution（about 20%）,which considerably reduced the essential LiCl concentration for effective mold inactivation.The inactivation efficacies of the 20% LiCl aqueous solution on A.niger spores were markedly improved from 7.8% to 100% by adding only 300 ppm 2-EH.SEM analysis showed that the addition of minor 2-EH accelerated the surface shrinkage of mold spores,whose cell structures were seriously damaged and collapsed.This may be attributed to the attachment of hydrophobic groups of surfactant and hydrophobic proteins of mold,which enhanced the interaction of mold spores and LiCl.Minor addition of 2-EH substantially improved the mold inactivation rate of LiCl liquid desiccant.The time required to inactivate 90% of A niger spores was sharply reduced from 1171.4 min to16.4 min by adding 100 ppm 2-EH to 30% LiCl solution.This study may help prevent mold aerosol transmission in air-conditioning systems and reduce the exposure risks for indoor occupants.