Oilfield-produced water treatment using bare maghemite nanoparticles

Abstract

Oilfield-produced water (PW) can be cleaned using a variety of techniques. However, traditional methods are often expensive and can generate secondary waste that pollutes the environment. In addition, PWs contain highly stable micronized dispersed oil, which makes conventional treatment ineffective in meeting regulatory requirements. As a result of their unique properties, magnetized nanoparticles can effectively remove emulsified and dissolved oil from PW. This study aims to evaluate the residual oil removal efficiency of bare maghemite (γ-Fe2O3) nanoparticles in treating oilfield-produced water (produced water).Several techniques for manufacturing maghemite nanoparticles were evaluated to select one that is both cost-effective and produces high-quality nanoparticles. After manufacturing nanoparticles with the selected method, the mineral composition and properties of the nanoparticles were determined. Subsequent experiments used synthetic and commercial nanoparticles to treat samples of PWs derived from oil and gas wells. By measuring the oil content of PW before and after treatment, the removal efficiencies of the nanoparticles were determined. Nanoparticles were recovered from treated PW samples, washed, and reused. Over ten times, they were recycled. The recycling potential of nanoparticles is evaluated by assessing the reduction in oil removal efficiency after recycling. Using fresh nanoparticles, over 98% of residual oil can be removed. Even after recycling more than 11 times, the oil content of treated PW samples was below the disposal limit. However, a slight reduction in the efficiency of the nanoparticles was observed. The reduction could be attributed to their dissolution in water and carryover during the treatment/demulsification operation.