Novel biomaterial design based on Pseudomonas stutzeri–carbon xerogel microspheres for hydrocarbon removal from oil-in-saltwater emulsions: A new proposed treatment of produced water in oilfields

Abstract Large amounts of produced water from oilfields is one of the consequential environmental problems caused by the oil and gas industry. This work is the first to attempt the production of biomaterials based on the immobilization of a hydrocarbon-degrading bacterial strain (P. stutzeri) on xerogel microspheres. It aims to evaluate their ability to adsorb and decompose hydrocarbons (benzene, toluene, and phenol (BTP) system) and crude oil from oil-in-saltwater emulsions (O/W). Four xerogel microspheres are prepared by the sol–gel method: carbonized and functionalized microspheres labeled as organic microspheres (OMe), carbonized microspheres (CMe), and carbonized-functionalized microspheres with nitrogen (CMeN) and phosphorous atoms (CMeP). Their textural properties are characterized by scanning electron microscopy, N2 adsorption, and mercury porosimetry. X-ray photoelectron spectroscopy and isoelectric point are employed for the chemical characterization. Biomaterials are developed by the excess impregnation of P. stutzeri strain in the stationary phase onto the microspheres. Finally, the removal of crude oil and BTP system from O/W emulsions using biomaterials is assessed, and the residual oil and BTP contents are analyzed by gas chromatography–mass spectrometry and high-performance liquid chromatography, respectively. Results show that the BTP removal is better in the following order of materials: Microspheres without P. stutzeri (support) > biomaterials > free P. stutzeri with removal percentages of up to 100 %, 84.8 %, and 60.8 %, respectively. For crude oil, biomaterials and supports lead to the complete removal of hydrocarbons from O/W emulsions, i.e., 100 % in 72 h, whereas that of free microorganisms only reach 61 % over the same duration