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The Study On Phenols Wastewater Treatment With PDMS/PS Composite Hollow Fiber Membranes

Posted on:2007-10-21Degree:MasterType:Thesis
Country:ChinaCandidate:Z Q WangFull Text:PDF
GTID:2121360182983949Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
Phenols, i.e. highly toxic hydroxy compounds of aromatic hydrocarbons, pose great harm to environment and become one of key controlling objects in wastewater treatment field. Phenols are common pollutants of wastewater streams from petroleum refineries, petrochemical industries, the production of phenolic resins, pesticides, etc. Recovery phenols methods include solvent extraction, activated carbon and polymer adsorption and biochemical technology. However, it is difficult to get a satisfying result by these processes.Polydimethylsiloxane (PDMS), a kind of non-porous polymeric material, exhibits high permeability to hydrophobic organic molecules and can be used as membrane material for the extraction of these compounds from one phase into another, provided that an organic activity gradient is maintained across the membrane. During last several years, PDMS membrane technologies such as membrane solvent extraction and pervaporation processes have attracted great attention for removal of volatile organic compounds (VOCs) from waste waters.The present thesis describes a novel process to treat phenol wastewater with composite hollow fiber membranes, which consist of a thin dense selective PDMS layer coated on a microporous polysulfone (PS) layer. The rate of organic transfer through the approximately 1~2μm PDMS layer membranes is much higher than that of a 0.5mm PDMS dense membrane reported in the reference. In our experiments, the removal of phenol can be 99.9% and 96.9% from 0.939g/l and 8.977g/l wastewater, respectively. The overall mass transfer coefficient (OMTC) through thin PDMS layer is up to 5.31×10~-7m/s and 3.92×10~-7m/s calculated by mathematic model established in this thesis, larger than 1.31 ×10~-7m/s and 1.29×10~-7m/s through PDMS dense membrane (tube) when treating 8.977g/l and 0.939g/l phenol wastewater, respectively, and than that of the organic solvent extraction system.The effect on OMTC of phenol through thin PDMS/PS composite hollow fiber membranes is studied. The transmembrane pressure has no effect on OMTC of phenol. The concentration of NaOH aqueous solution has no effect on OMTC of phenol, close to the result from our mathematics model. The removal of phenol from electrolyte solutions containing NaCl, H2SO4, HC1 has also been studied, respectively. OMTC of phenol containing NaCl increases dramatically, up to 1.11×10~-6m/s when the concentration of NaCl is 200g/l;and the same effect can be illustrated by H2SO4. On the contrary, OMTC of phenol decreases when phenol aqueous solution contains HC1.The resistances-in-series model is used to describe the transport of phenol through PDMS/PS composite hollow fiber membranes with liquid films on both sides. The resistance in the NaOH solution phase is negligible based on gas-liquid absorption theory and the result from the experiments is consistent with the theory. A Wilson plot is used to obtain individual mass transfer resistances in both phenol solution phase and membrane phase, and the experiment result shows that the mass transfer resistance is dominant in the former. A correlation for shell side mass transfer in hollow fiber membrane is established. Finally, it is testified that the removal of phenol through shell side of membrane module is better than that through tube side in expetiments.
Keywords/Search Tags:Phenol, PDMS, Composite Hollow Fiber Membrane, OMTC
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