Coalescence/Filtration of an Oil-In-Water Emulsion in a Granular Organo-Clay/Anthracite Mixture Bed

Abstract

Bentonite organo-clay has been used as a sorbent in removing awide variety of organic pollutants including oil in the past. Thepercentage oil removal by this sorbent has been reported to be inthe range of 65 to 100. However, breakdown (filtration, coalescence) mechanisms involved in a granular organo-clay/anthracite mixture bed treating an oil-in-water emulsion have not been understood so far. The purpose of thisresearch was to evaluate the applicabilities of the well-knownCarman-Kozeny filtration equation and Sherony and Kintner coalescence model to a 1000 mm organo-clay/anthracite bed treating a standard mineral oil-in-water emulsion using six different flow rates (12, 16, 20, 24, 28 and 32 mL min-1). The analysis of the experimental data showed that the Carman-Kozeny constant values were 4.29 and 5.54 for single-phaseand two-phase flows, respectively. In addition, the values of the specific permeability coefficients for single-phase and two-phase flows were found to be 2.7 × 10-8 m2and 1.4 × 10-8 m2, respectively, which showed 48.1% reduction in the case of two-phase flow. The shape factorvalue was found to be 1.0 for the mixture. The results also showed that the head-loss across the organo-clay/anthracite filter can be well predicted using the Carman-Kozeny filtrationequation for single-phase flow. In two-phase flow, the Carman-Kozeny model may not yield accurate predictions at highflow rates. The coalescence efficiency within the bed increasedas flow rate increased and decreased as the bed depth increased. The coalescence efficiency ranged from 4.4 to 17.5% in theorgano-clay/anthracite bed. Overall, the study indicated possiblesimultaneous occurrence of filtration and coalescence of the oil-in-water emulsion used in the organo-clay/anthracite filter.