The Study Of Zeta Potential And Oil-Removal Efficiency Of Water Treatment Filter Media

In waste water depth processing and the feedwater treatment, the filtration is one kind of technology which used generally. The adherency process between filter media and pollutant is decided by the intermolecular force and electric double layer mutual function which relate to the zeta potential of filter media. For a long time, many researchers have all approved that zeta potential of filter media have great influence on filtration mechanism and have determined that zeta potential of filter media is important to enhance filtration efficiency and is a good reference to develop new filter media.Firstly, because of the diversity of streaming potential and zeta potential values reported in the literature, an apparatus for measuring streaming potential of filter media was designed and made according to the relationship between streaming potential and zeta potential of filter media. This paper intended to provide the necessary information to construct and properly operate a simple streaming potential apparatus capable of measuring streaming potential of filter media. Through an understanding of the principles of the technology, such a device can readily be used in the study of a variety of granular materials. The streaming potential measurements were carried out in the electrolyte solution of KCl, and the temperature of the electrolyte solution was controlled at 25℃. The production of the streaming potential and its effect factors were herein discussed. The streaming potentials of quartz sand, walnut shell, zeolite ,anthracite, magnetite, manganese, haydite were measured by this apparatus. The stability time of filter media and the influence of pressure descents to stability time were examined, and the influence of the pH values of the electrolyte solution to the streaming potential was also discussed. The results show that 1) when the pressure descents are equal to 2cm water column, the stability time of quartz sand, walnut shell, zeolite, anthracite, magnetite, manganese, haydite are 45min around, 60min around, 120min around,35min around,60 min around,45min around,35min around respectively;2) We should determine the streaming potential in as large pressure descent as possible under the condition of laminar flow, because the larger pressure descent corresponds shorter stability time;3) The streaming potential turns from positive value to negative value as the pH values change from lower values to higher values and the results show that the isoelectric point of quartz sand, walnut shell ,zeolite, anthracite, magnetite, manganese, haydite are pH=5.0 around, pH=3.0 around, pH=3.0around, pH=3.0around, pH=5.0around, pH=3.0around, pH=3.0around respectively.Secondly, based on measurement, when particle size distribution was between 0.60mm and 0.90mm, zeta potential on 7 common filter media were figured out. zeta potential value of quartz sand, walnut shell, zeolite ,anthracite, magnetite, manganese, haydite were-6.20 mV, -4.18mV, -8.78mV, -4.29mV, -8.81mV, -5.08 mV, -4.08 mV respectively , zeta potential value of different filter media are as follows: magnetite > zeolite > quartz sand > manganese > anthracite > walnut shell > haydite .FTIR and XPS results showed that the diversity of zeta potential of quartz sand, walnut shell ,zeolite, anthracite, magnetite, manganese and haydite could be ascribed to the differences of their surface chemical structure.Thirdly, in determinate velocity of filtration and height of filter bad, the filtering results of different filter media were studied. The oil-removal result of different kinds of filter media are as follows: anthracite > magnetite >haydite > quartz sand > zeolite. Through the analysis to the oil removal result and surface property of filter media, we found that both electrochemical property and wettability of filter media take important function in filtration, but the wettability plays a more obvious part in the process of filtration.