Effects Of Concentration And Valence Of Different Ions And Humic Acid On Nanofiltration Separation Characteristics Of Perfluoro Compounds

As a typical short-chain perfluorinated compound,perfluorobutyl sulfonic acid（PFBS）has been widely detected in natural waters around the world presently,its toxicological and harmful effects have gradually emerged.Nanofiltration（NF）membrane has a good effect on the removal of perfluorinated compounds in water.In order to deeply analyze the behavior of PFBS in the separation of PFBS in water and promote the application of NF membrane in actual production,this study investigated the common inorganic salt cations(Na⁺/K⁺/Ca²⁺/Mg²⁺/Fe³⁺)and anions(Cl^-/SO₄^2-/PO₄^3-)concentration and valence state on the PFBS nanofiltration separation characteristics,and studied the coupling effect and mechanism of humic acid（HA）and cations on PFBS separation.Concluded as follow:（1）The effect of ion concentration:（1）The removal rate of PFBS is negatively correlated with the concentration of Na⁺/K⁺/Ca²⁺/Mg²⁺/Cl^-,and positively correlated with the concentration of SO₄^2-/PO₄^3-;the characteristics of Fe³⁺effect on NFBS removal and the change The pattern is different.（2）In the presence of Na⁺/K⁺/Ca²⁺/Mg²⁺/Cl^-,electrostatic repulsion is the dominant separation mechanism for PFBS removal by NF membrane;different concentrations of Fe³⁺have different effects on PFBS removal:Fe³⁺（0.1）and Fe³⁺（1）have an effect on NF membrane Removal of PFBS has a certain inhibitory effect.After filtering to 8h,the effect of Fe³⁺（0.5）on the removal of PFBS from NF membrane changed from inhibition to promotion;SO₄^2-and PO₄^3-can simultaneously enhance the screening and electrostatic repulsion to improve PFBS Removal rate.（3）The Zeta potential of the NF membrane surface and the PFBS stock solution is negatively correlated with Na⁺/K⁺/Ca²⁺/Mg²⁺/Cl^-concentration,and positively correlated with Fe³⁺/SO₄^2-/PO₄^3-concentration;the addition of inorganic salt ions can increase the particle size of the solution The particle size increases with the increase of ion concentration,the amount of pollutants accumulated on the membrane surface gradually increases,and the amplitude of membrane flux attenuation also gradually increases.（2）The effect of ionic valence:（1）The removal rate of PFBS decreases with the increase of the cation valence,and increases with the increase of the anion valence,this is because the electrostatic repulsive force of NF membrane on PFBS and the cation valence The state is negatively correlated and positively correlated with the anion valence state.（2）In the Na⁺/K⁺/Ca²⁺/Mg²⁺solution,the potential of the NF membrane surface and the solution decreases with the increase of the cation valence state in the solution;Fe³⁺changes the Zeta potential of the membrane surface due to bridging,hydrolysis and other effects.Other cations;in SO₄^2-/PO₄^3-solution,the potential of the membrane surface and the original solution rises with the increase of the anion valence state in the solution,and the change trend of Cl-corresponding is just the opposite,because in Na Cl solution,the dominant ion is a Price Na⁺.（3）The effect of HA synergistic cation:In the presence of Na⁺,the addition of HA can increase the rejection rate of PFBS;in the presence of Ca²⁺/Fe³⁺,the concentration polarization caused by the pollution layer reduces the rejection rate of PFBS;the hydrolysis results in Fe³⁺in the system The concentration is greatly reduced,the electrical neutralization of Fe³⁺and HA,and the bridging ability are reduced.The relationship between the electrostatic repulsion of the contaminated film and PFBS is:HA+Na⁺>HA+Ca²⁺>HA+Fe³⁺.