Study On Degradation Of BTEXs And PAHs By Activated Persulfate

Crude oil exploitation,refining and transportation will inevitably cause some pollution,which will cause great damage to the environment and human health if not effectively treated.In this study,benzene,toluene,ethylbenzene,xylene?BTEXs?and four polycyclic aromatic hydrocarbons?PAHs?:fluorene,phenanthrene,fluoranthene,pyrene were selected as representative pollutants to study the influencing factors and activation methods in the degradation by sodium persulfate.The degradation experiment of BTEXs was carried out in aqueous phase.At 50?,sodium persulfate is an excellent oxidant,it has good effects on degradation of BTEXs,and the total removal efficiency can reach over 90%.The influence of anions on sulfate radical oxidation process was study in water,it was found that CO₃^2-/HCO₃^-could inhibit the degradation of BTEXs;the presence of Cl^-/Br^-could inhibit the degradation of benzene,promote the oxidation of xylene,and lead to the generation of halogen-containing by-product simultaneously;NO₃^-,SO₄^2-,PO₄^3-,HPO₄^2-,H₂PO₄^-do not affect the sodium persulfate oxidation of BTEXs.At 15?,the effect of sodium hydroxide activated sodium persulfate on the degradation of BTEXs was gradually enhanced with the increase of alkalinity;but at the same pH,the efficiency of different kinds of alkali to activate sodium persulfate was not the same,the activation effect was NaOH>Ca?OH?₂>CaO₂,prolonging oxidation time to 60 days found that CaO₂ inhibited the degradation of BTEXs.Fe²⁺,Fe²⁺+elhylene diamine tetraacetic acid?EDTA?and Fe²⁺+citric acid?CA?have excellent activation effect on sodium persulfate degradation of BTEXs.Fe³⁺activates sodium persulfate very weakly,but chelate citric acid has remarkable activation effect on sodium persulfate.The degradation of BTEXs by activated sodium persulfate is as follows:Fe²⁺+CA+PS?Fe³⁺+CA+PS>Fe²⁺+PS?Fe²⁺+EDTA+PS?Fe³⁺+PS?Fe³⁺+PS+EDTA.The degradation experiment of PAHs was carried out in aqueous phase.Removal efficiencies of fluorene,phenanthrene,fluoranthene and pyrene could reach 100%by potassium permanganate,and sodium persulfate could only oxidize pyrene,H₂O₂?H₂O₂+Fe²⁺could not degrade PAHs.Alkali activated PS did not promote the degradation of PAHs,but Fe²⁺?Fe²⁺+CA?Fe³⁺?Fe³⁺+CA could activit sodium persulfate and promote the PAHs degradation,and the promotion was mainly in the removal of phenanthrene and fluoranthene.