Produced water treatment for beneficial use: emulsified oil removal

摘要

The development of novel carbon material, high accessible surface area, interconnected porosity, and stable nanofiber nonwoven media for emulsified oil droplets separation from oily wastewater, in particular for oilfields produced water treatment, is discussed in this thesis. Firstly, the quantity and quality of the generated produced water from five of the largest oilfields in the south of Iraq were studied based on the oil production profiles of these oilfields. This type of wastewater is heavily contaminated with different types of pollutants such as oil, suspended solids, heavy metals, and salts. This study shows that the properly treated produced water in the south of Iraq could be a substantial valuable water resource in a region with increasing water shortages. An adsorption process using activated carbon is a potential method for oil removal from oily wastewater. In this work, the activated carbon nanofiber nonwoven (ACNFN), which is a form of activated carbon, is fabricated from polymeric solution using the electrospinning method and followed by subsequent thermal steps. The results show that optimizing the fabrication conditions are essential to produce ACNFN with enhanced mechanical strength and specific surface area. According to the batch dynamic adsorption test, ACNFNs showed a very high removal efficiency of up to 95%, thereby outperforming (non-activated) carbon nonwoven (CNFN) and a commercial granular activated carbon (GAC), due to its high accessible surface area, porosity, and hydrophobicity. A dead-end normal flow system was used to investigate the operating conditions for the removal of emulsified oil from water using nonwoven media. The results showed that the oil droplets were removed by size exclusion and adsorption mechanisms. Characteristic breakthrough behavior was observed with subsequent clogging. The high porosity of ACNFN was shown to play a role in the small oil droplets removal. Removal efficiency increased with contact time and thickness. However, the pressure drop over the system was increased due to the excluded oil droplets on the top side of the first layer of the nonwoven. A novel testing method was used to allow the emulsion to pass through the cross sectional area of the thin sheet of ACNFN nonwoven. The results show an efficient ability of ACNFN nonwovens to remove emulsified oil from water by adsorption in a continuous process without an obvious increase in pressure drop over the system. Furthermore, the regenerability of ACNFN for oil adsorption was studied by washing the saturated ACNFN sheet with an organic solvent. The results showed no significant change in the oil adsorption characteristics for three adsorption/cleaning cycles.