Study On The Phase Distribution Laws Of Polycylic Aromatic Hydrocarbons And Its Reduction In Coking Sludge With The Presence Of Surfactants And Phenol

Polycyclic aromatic hydrocarbons(PAHs)are a kind of persistent organic pollutants which widely exist in environment,and they have serious damage to human healthy and ecological environment.Coking wastewater is one of the important sources of PAHs in our country,and the PAHs in the coking wastewater treatment systems are easily transferred to the sludge phase due to their lipophilicity,which results the high contents of PAHs in coking sludge,while this process becomes the limited procedure for the biodegradation of PAHs in coking sludge,as well as the urgent problem in the treatment and disposal of coking sludge.Based on the idea of enhancing biodegradation of PAHs in coking sludge by the solubilization of PAHs using surfactants and phenol,Triton X-100,SDS and phenol were selected to be the solubilization reagents,phenanthrene,pyrene and benzo [a] pyrene were taken as three representative PAHs,on the basis of suitable analysis methods for individual PAH by High Performance Liquid Chromatography(HPLC)and mixed PAHs by Gas Chromatography-Mass Spectrometry(GC-MS).Firstly,investigate the enhanced solubilization effect of phenanthrene,pyrene and benzo [a] pyrene by these solubilization reagents.Then,take the soil,municipal sludge and coking sludge with much difference in physicochemical properties as the solid matrix in the phase distribution systems,and the adsorption characteristics of the three PAHs with different initial concentrations were compared.Meanwhile,the phase distribution laws of the selected PAHs in different soil/sludge systems with the presence of phenol and surfactants were analyzed,and the effects of phenol on the phase of PAHs in the anaerobic and aerobic units of real coking wastewater treatment systems were explored.Finally,the desorption characteristics of enriched PAHs in coking sludge by phenol and surfactants were studied.Results showed that solubilization of phenanthrene,pyrene and benzo [a] pyrene by surfactants all fitted the linear model,the solubilization ability for PAHs were negatively related with their lipophilicity,and synergistic solubilization of the selected PAHs occurred when the surfactants coexisted.Solubilization of PAHs by phenol all fitted the non-linear model,and synergistic solubilization of the PAHs occurred in the tenary solute systems,while the solubilization ability depended on the hydrophobicity,melting point and molecular volume of PAHs.Freundlich adsorption isotherm model was used to describe the adsorption characteristics of PAHs on soil,municipal sludge and coking sludge,and the adsorption ability for PAHs were dominated by the lipophilicity of PAHs and the physicochemical properties of soil and sludge.In the phase distribution systems with the presence of surfactants and phenol,due to the changed surface properties of soil and sludge resulted from the adsorption solubilization reagents,the solubilization degree of phenanthrene,pyrene and benzo [a] pyrene were lower than that in the pure solution solubilization systems,and the adsorption characteristics of the three PAHs on soil and sludge changed too,which could be described by Langmuir adsorption isotherm model.In the anaerobic and aerobic units of real coking wastewater treatment systems,the phase distribution of PAHs with different rings were positively or negatively related with the concentration of phenol in aqueous,while the phase distribution characteristics may be influenced by the molecular properties of PAHs,the physicochemical characteristics of coking sludge and the difference in the coking wastewater treatment processes.At this time,the biodegradation of phenol and PAHs can be realized simultaneously in the anaerobic and aerobic units,while the initial concentration of phenol and PAHs and the matching of their biodegradation rates should be taken into consideration during this process.Surfactants and phenol can be used as desorption reagents for enriched PAHs in coking sludge,the desorption amounts of total PAHs was 1.12 mg with 1 g solubilization reagents(expressed by the mixed quality of Triton X-100 and SDS)under the condition of this research,1.15 mg with 1 g solubilization reagents(mixed quality of Triton X-100 and phenol),and 1.01 mg with 1 g solubilization reagents(mixed quality of SDS and phenol),while the desorption amounts of total PAHs was 0.61 mg with 1 g Triton X-100,0.83 mg with 1 g SDS and 0.47 mg with 1 g phenol,In the desorption process,the mixed adsorption layer and mixed micelles were formed by the multiple utilization of surfactants,competition for the adsorption sites and weak electron repulsion between suffactants and phenol gave rise to more surfactants and phenol for the desorption of PAHs.Therefore,surfactants and phenol can solve the mass transfer problem and facilitate the microbial degradation of PAHs in coking sludge.This study can be used for calculating the phenol and surfactants demands in the enhanced solubilization and co-substrates degradation processes employed for the bioremediation of PAHs in coking sludge.