Removal Of Bisphenol A By Nanofiltration Membrane From Water Sources

Environmental endocrine disrupter influencing the function of normal hormone can cause the undamaged organism of the individual or the crowd endocrine disrupted. Bisphenol A which belongs to endocrine disrupter will bring about endocrine disorders and affect the fetus and the health of child. Although the conventional water treatment technology can reduce hardness and turbidity, the harmful material of the environment such as endocrine disruptor can not be rejected with high efficiency. Therefore, it is important to remove endocrine disruptors effectively from drinking water sources.Nanofiltration is one of the advanced technologies which has the advantages of good separation characteristic, low operating pressure, and high removal efficiency for the organic molecules and has the broad application prospect in water treatment. The BPA removal efficiency by nanofiltration has been investigated in this paper. The operating parameters as filtration time, operating pressure and water matrix as concentration, pH value, and ionic strength of the solution were also studied to further understand the removal mechanism of nanofiltration membrane.The results were as followed:(1)The observed retention of bisphenol A by nanofiltration has become increased and the water flux has been decreased along with the operating time because the membrane was compacted and the pore diameter of membrane is smaller.(2)As the operating pressure rising, the retention ratio of bisphenol A increased little due to the difference of pressure on both sides of the nanofiltration membrane, and resulted in increased driving force.(3)The concentration of bisphenol A is proportional to the rejection by nanofiltration membrane, and inversely proportional to the flux. On the one hand the increasing solute makes the pore diameter of nanofiltration membrane smaller, and cause membrane flux increased. On the other hand the increased concentration of solution led to the retention increased and membrane aperture material shrunk which reduces the membrane flux. (4)The retention is rising as the pH value of the solution increasing, with the same trend of membrane flux increased. The thickness of electric double layer of nanofiltration membrane increased at higher pH and the membrane surfaceζpotential can convert into negative value. Bisphenol A dissociated into the negatively charged BPA ions at pH above 9.8 which strengthened electrostatic with potential of negative of nanofiltration membrane surface, so the rejection efficiency increased. Membrane flux increased slightly with pH value, because the increasing of pH value will make bisphenol A hydration ionization increased, but the hydrogen bond strength with water reduced. Thus there will be more water molecules passed through the membrane freely, so the membrane flux increased.(5) The effect of ion presence to the bisphenol A removal by nanofiltration membrane was mainly due to the type of ions and the retention of the ions.This paper has investigated the removal mechanism of bisphenol A by nanofiltration membrane and influencing factors, and the interfacial process of molecules and membrane was also explored. The experimental results will be the guidance in further understanding of the rejection mechanism and extention of the application of nanofiltration in the field of micropollutants removal from water sources.