Study On Influence Of Algae Organic Matters During Adsorption Of Three Typical Odorants By Powdered Activated Carbon And The Mechanism

Odorants released by algae have caused frequent taste and odor（T&O）issues in the past decades,resulting in foul-smelling water bodies and reduced drinking water quality.Powdered activated carbon（PAC）process as the most commonly used means to control T&O issues is influenced by algae organic matter（AOM）,however,the related research is insufficient yet.In this study,typical odorant such as 2-methylisopropanol（2-MIB）,β-cyclocitral（β-cyclo）and butyl sulfide（BS）were selected which are widely distributed in China.The adsorption treatability,isotherms,kinetics and mechanisms of 2-MIB,β-cyclo and BS adsorption by PAC were evaluated.The results show that PAC adsorption was efficient and feasible for the removal of 2-MIB,β-cyclo and BS in a background without AOM competition,and its adsorption process can be described by the Freundlich isotherm equation.The homogeneous surface diffusion model（HSDM）can be used to predict the adsorption kinetics of the three odorants.The results of DFT calculations showed that the positive surface electrostatic potential contributed by the C-H structure was the key factor driving the adsorption of 2-MIB,β-cyclo and BS on the PAC surface,and the high degree of carbon chains’s flexibility promoted adsorption of the three odorants.Secondly,the influences of AOM on the adsorption of 2-MIB,β-cyclo and BS by PAC were evaluated in pure water and Shanghai Jinze reservoir raw water（JZ water）,the main competing components of AOM were identified,a predictive model of the AOM’s competition effects was developed,and the mechanism and driving force of AOM adsorption competition were explored.The results showed that the influences of AOM on the adsorption removals of 2-MIB,β-cyclo and BS was significant,and their adsorption competition was stronger than that of background natural organic matter（NOM）in JZ water.2-MIB,β-cyclo and BS adsorption rates determined the influence of AOM competition on their removals,and the faster the adsorption rate,the lower the influence.The faster the adsorption rate,the less the influence,and the influence of AOM can be predicted by the 1/n value of the Freundlich equation.The degree of AOM influence can be ranked from strong to weak 2-MIB<β-cyclo<BS.Coble A and Coble C are the main competing components of AOM,and DFT calculations show that the strong positive electrostatic potential provided by the H side of C-H,carbocyclic and-OH is the key driving force for the adsorption competition of Coble A and Coble C.Finally,the effects of the common preoxidation processes such as KMnO₄ and NaClO on the adsorption competition of AOM were evaluated,and the characteristic changes of the main competition components of AOM before and after the preoxidation were identified,as well as the ways in which the preoxidation processes of KMnO₄ and NaClO weakened the adsorption competition of AOM.The results showed that the preoxidation of AOM by KMnO₄ and NaClO in pure water improved both adsorption removals of 2-MIB andβ-cyclo,and improved the removals ofβ-cyclo in JZ water.The low dosage of KMnO₄ and NaClO had a weakening effect on the adsorption competition of AOM,and the high concentration of AOM is helpless for decreasing the adsorption competition of AOM.KMnO₄ and NaClO improved the adsorption of 2-MIB,β-cyclo and BS mainly by decomposing large molecule AOM into small molecule organic matter and changed physical properties of AOM.In this study,the adsorption of2-MIB,β-cyclo and BS by PAC in the background of AOM was investigated comprehensively,and the key influencing factors and driving forces were identified to provide relevant parameters and make theoretical pavement and guidelines for water treatment plants to cope with the odor problem caused by odorous substances.