Indian Journal of Chemistry Vol. 31A, June 1992, pp. 361-365 Removal of phenol from refinery waste waters using liquid surfactant membranes in a continuous column contactor A N Goswami*, S K Sharma. Anshu Sharma & T C S M Gupta Indian Institute of Petroleum, Dehra Dun 248zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO nos The novel separation technique ofliquid surfactant! membrane permeation has been used for the removal of phenol from refinery waste waters. Experimental data are presented on continuous scale extraction of phenol, which is a typical toxic pollutant present in refinery waste waters, using liquid surfactant membranes in counter current Oldshue Rushton type stirred column. Experimental data have been generated under a range of operating parameters like flow rates, phase ratios and measurements include mass transfer, drop sizes and dispersed phase holdup. The effe-c-tsof these parameters on extraction of phenol kave been analyzed. Phenols are among the more refractory and hard-to-treat pollutants in petroleum refinery waste waters'. Typical concentrations of phenolics in oily and process waters range from 12 to 30 ppm and in caustic wash effluents from 50 to 200 ppm I. At present, biological treatment (trickling filters, activated sludge process, oxidation ponds, aerated lagoons) is being used in several Indian refineries to bring down the level of pollutants like phenols to meet MINAS specifications 1 (for phenol, MINAS specification limit concentrations to < 1 ppm). Biological treatment procedures require large land area, have attendant problems of sludge disposal and are often prone to failure from shock loadings. The novel separation process based on liquid surfactant membrane permeation has recently emerged as a versatile technique with proven potential in several fields. These membranes which may be of two types, "oil" or "aqueous", are formed when water-in-oilponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (WjO) emulsion or oil-in-water (OjW) emulsion is dispersed as drops in an external aqueous or oil phase respectively. Aqueous liquid membranes are used for the separation of hydrocarbons+' while oil liquid membranes are used for waste water cleanup", metal winning oper- ations' and biochemicallbiomedical separations" in general. At present two industrial scale plants on the liquid surfactant membrane process are in operation?", The process is more economical than solvent extraction or biological treatment for phenol removal from aqueous wastes", Several groups have reported experimental data on batch extraction of phenolics from waste waters using liquid surfactants membranes4.IO.ll.IS.16. The present authors have recently shown how a shape factor correction can be applied for effective diffusivity estimation in a simulation model developed for predicting batch extraction rates in these systems 1 2. However, an industrial scale separation based on this process will use continuous contacting equipment. Though the available information on industrial scale liquid surfactant membrane plants indicates that the continuous contactor used is basically a stirred counter current column typically used in liquid-liquid extraction operations, to date there have been very limited experimental data reported on continuous scale liquid surfactant membrane separations' in such type of eq uipment 13.14.Thepresen t paper reports resul ts of an experimental study on the removal of phenol from waste water using liquid surfactant membrane in a continuous scale Oldshue Rushton type contactor. Materials and Methods The continuous scale experiments have been carried out using an Oldshue Rushton column contactor (52 mm i.d.). This contactor is basically a compartmented stirred column (Fig. I). In a typical experiment, a water-in-oil emulsion of aqueous NaOH emulsified in kerosene containing 5% DIATROLITE SMO 80 (Dai khi Karkaria, Bom- bay) was introduced into the column at the bottom through a nozzle distributor while the phenolic feed water entered the column at the top. Metering pumps (Mjs V K Pump Industries, Bombay) were used to deliver the emulsion and phenolic feed water phases to the contactor from the respective reservoirs. The stirring action of the turbine impellers in each of the 25 compartments of the column breakup the emulsion into globules (100 to 300 urn diam.) as they rise through the contactor in counter current flow to the phenolic aqueous phase. It is the interstitial kerosene phase between the tiny microdropletes (I to 10 urn) of