Evaluation of Magnetic Nano-adsorbents for Selectively Removing Metals of Value from Reverse Osmosis Reject Streams

Currently, membrane processes are the most widely used technology for removing dissolved constituents from water (i.e., desalination); however, membrane processes are hindered by a variety of challenges, such as membrane fouling and the generation of a concentrated reject stream. Engineered nano-adsorbents, such as functionalized magnetic nanoparticles, are a possible new technology for selectively removing/recovering dissolved metals of value (e.g., Au3+, Li+, Ag3+) from liquid streams like reverse osmosis (RO) concentrate streams, whose recovery could offset some of the costs associated with treatment. Maghemite (γ-Fe2O3) is a superparamagnetic material that has been used for removing heavy metals from industrial wastewaters. By using this type of concentrate management strategy, it might be possible to increase the recovery rate of RO systems while monetizing what was before another waste source. This presentation will cover our work to date on the use of magnetic nano-adsorbents (γ-Fe2O3) for selectively removing scale forming elements (Ca2+, Mg2+, SO42-) and dissolved metals (e.g., Au3+, Li+, Ag3+) from brackish water sources. We will present on a variety of possible surface coatings that may be used for increased removal/recovery of constituents and provide a cost-benefit analysis for recovering specific metals of value from oil and gas produced waters.