Abstract
This study linked the chemical potential change to high specific filtration resistance (SFR) of gel layer, and then proposed a novel membrane fouling mechanism regarding gel layer filtration, namely, Flory-Huggins based filtration mechanism. A mathematical model for this mechanism was theoretically deduced. Agar was used as a model polymer for gel formation. Simulation of the mathematical model for agar gel showed that volume fraction of polymer and Flory-Huggins interaction parameter were the two key factors governing the gel SFR, whereas, pH and ionic strength were not related with the gel SFR. Filtration tests of gel layer showed that the total SFR value, effects of pH and ionic strength on the gel SFR well agreed with the perditions of model’s simulation, indicating the real occurrence of this mechanism and the feasibility of the proposed model. This mechanism can satisfactorily explain the extremely high SFR of gel layer, and improve fundamental insights into membrane fouling regarding gel layer filtration.
Highlights
This study linked the chemical potential change to high specific filtration resistance (SFR) of gel layer, and proposed a novel membrane fouling mechanism regarding gel layer filtration, namely, FloryHuggins based filtration mechanism
Long-term operation of a membrane bioreactor (MBR) system could generally lead to formation of a foulant layer on membrane surface, which could be subdivided into cake layer and gel layer
The foulant layer formed on membrane surface, as well as membrane used in MBRs, is a kind of porous media
Summary
Selecting agar as model gel material can minimize the effects of surface charge on SFR. The specific filtration resistance (SFR) of the agar gel was calculated by SFR = Rg mg (2). The prepared water solution was filtrated through the prepared gel layer. By recording the permeate production, the SFR of the gel layer can be calculated according to Eqs 1 and 2. Four prepared agar gel samples with certain weight were placed in an oven at 35 °C, and the weight of samples were recorded at intervals of one hour. The agar gels were made at room temperature in a stirred filtration cell under 50 kPa. the prepared gels were put in an oven with 60 °C for 12 hours before thermogravimetric analysis (TGA). The difference between two means was considered to be significant when P < 0.05
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