Biodemulsification combined with fixed-bed biosorption for the recovery of crude oil from produced water

Abstract

Produced water can be used as a source of potable water and valuable chemical components (pure elements, minerals). The recovery and beneficial use of emulsified and dissolved hydrocarbons from these brines are not a priority. Oil removal methods focus on water decontamination without further management of recovered oil. In this work, biosorption combined with “green” demulsification is applied to recover paraffinic crude oil from artificial brine. Soapwort extract at a concentration of 0.5 g/L destabilized oil/water emulsion allowed 85–95 % oil recovery. Adsorption beds made of sunflower pith were applied to remove dissolved hydrocarbons. To enhance sorption capacity, the plant material was impregnated with polydimethylsiloxane (PDMS) and hydrophobic nanosilica. The oil removal kinetics on the modified pith followed a pseudo-second order model. The adsorption isotherm at 20 °C was well described by the Temkin model, while the Toth model provided the best fit to experimental data at 40 °C. The maximum sorption capacities in a two-phase oil-water system were 3.544 g/g and 4.187 g/g for the hydrophobized and raw pith, respectively. The pith filter performed well. A maximum oil reduction of 73 % in effluent was achieved at 10 cm bed height and 15 mL/min flow rate. Sorbent regeneration studies show that residual oil from spent material can be easily drained, and the recovery ratio is up to 68 %. Both bioprocesses, biodemulsification and biosorption, are effective technologies that can be used to separate oil from oily water.