Abstract
Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. Membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and detergent. The separation properties of O/W emulsions by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size; applied pressure; cross-flow velocity; and detergent concentration on rejection of O/W emulsion and flux were systematically studied. At the condition achieving complete separation of O/W emulsion the pressure-independent flux was observed and this flux behavior was explained by gel-polarization model. The O/W emulsion tended to permeate through the membrane at the conditions of larger pore size; higher emulsion concentration; and higher pressure. The O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties. The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model.
Highlights
Washing systems using water soluble detergent are used in electrical and mechanical industries instead of the systems using organic solvent and the wastewater containing O/W emulsion is discharged from these systems
O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties
The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model
Summary
Washing systems using water soluble detergent are used in electrical and mechanical industries instead of the systems using organic solvent and the wastewater containing O/W emulsion is discharged from these systems. In the MF and UF of O/W emulsion the pressure independent flux was commonly observed and the flux behaviors were explained by pore clogging [5,6], concentration polarization [4,7] and/or gel-polarization [6,8] models. The rejection of O/W emulsion depends on various experimental parameters including membrane pore size, membrane material, operating conditions, O/W emulsion concentration and stability, and coexistence materials in feed stream [11,12]. The phenomena at membrane surface during MF of O/W emulsions are quite complex because of the complexity of force applied to emulsions including surface tension between emulsion and pore surface, filtration pressure, and shear stress from feed fluid, etc. The effects of pore size, applied pressure, cross-flow velocity, and detergent concentration on rejection of O/W emulsion and flux were systematically studied. The conditions where O/W emulsion can permeate the membranes were discussed in terms of the stability of O/W emulsion in the gel-layer
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