Fouling modeling in the ultrafiltration separation of oil emulsion from salty water

Abstract

Fouling may cause problems in the installations where ceramic membranes are used for the treatment of oily and saline waters. Therefore, research into oil separation and the fouling mechanism is expedient. The experimental research was carried out using oily and saline emulsions and a laboratory ultrafiltration apparatus equipped with a tubular ceramic membrane with a 300 kDa cut-off. The emulsions contained 500 or 1,500 ppm oil and 0.0%, 1.0%, or 3.5% NaCl, respectively. The transmembrane pressure applied was 0.05, 0.1, or 0.2 MPa while the linear flow velocity was set to 4, 5 or 6 m/s. The initial permeation flux J0 was in a range from 12.0 to 14.8 [10–5 m3 /(m2 s)]. The oil removal process proved successful. An average 97.13% rejection coefficient was achieved for the ultrafiltration trials. The study aimed to investigate and model the membrane fouling phenomenon in a modified approach. The main objective of the study was to identify the membrane fouling mechanism using the Hermia model. The classical approach approximates the experimental data with the linearized Hermia equation, determines the kinetic coefficients, and finds the most adequate out of four predetermined fouling mechanisms identified with previously assumed values of the n coefficient equal to 0, 1.0, 1.5, or 2.0. In the paper, it is postulated that n can be selected from the interval <0,2>. It means not only the main mechanisms mentioned above may take place but any transient states between these mechanisms exist or they may overlap each other. Additionally, remaining coefficients kn, Jss in Hermia’s model was identified in the proposed numerical integration and optimization procedure.