The paper in the Nature Nanotechnology is here: https://doi.org/10.1038/s41565-018-0307-8
Treating unconventional water sources to a usable quality is critical for addressing global water scarcity. However, water treatment processes are expensive, energy-intensive, and occupy a large land area. A reason for this inefficiency is that water treatment technologies independently cannot remove multiple contaminant types simultaneously and are therefore required to function in series (i.e., sequence of several different technologies) to meet water quality standards. There is a need for an efficient and easily-operated technology to simultaneously remove all contaminants from water. To address this need, we recently developed a water treatment material capable of removing a broad spectrum of water contaminants within a single treatment step.
Coagulation is a simple and conventional water treatment process. By adding coagulants into water, colloidal and suspended particles aggregate into large precipitates and settle. However, conventional coagulants cannot adequately remove dissolved small contaminants, such that coagulation is mainly used to remove large colloidal and suspended particles as a pretreatment step for advanced treatment processes. A multifunctional coagulant on the other hand must be designed to capture small dissolved contaminants while simultaneously hydrolyzing into large aggregates, or flocs. However, introducing multiple components into a single coagulant can induce precipitation during preparation and storage, thus negating its ability to stably disperse in water and remove contaminants. The novelty of this study is that we synthesized a highly-stable, multi-functional nanocoagulant that is different from conventional coagulants in structure, performance, and behavior.
We found our inspiration for our nanocoagulant from the unique structure and behavior of the marine predator Actinia. The organism has a spherical body with tentacles that are retracted while resting but extended while preying. Similar to Actinia, our nanocoagulant retains its stable structure during storage but readily everts its configuration during coagulation. The novel coagulant can thoroughly remove a broad spectrum of water contaminants (ranging from typical water quality indicators such as turbidity and nitrate to emerging trace micropollutants such as persistent organic pollutants), many of which cannot be removed by conventional coagulants and are of considerable public health concern. The unique core-shell structure produces this treatment capability. During coagulation, the shell of the coagulant hydrolyzes into large flocs to destabilize and enmesh large contaminants, while also inducing the eversion of the retracted nanocoagulant and exposing the aliphatic core to capture small contaminants.
This is the first demonstration of a core-shell micellar nanocoagulant that is distinct from conventional coagulants in performance and behavior. The eversion response of the nanocoagulant under specific conditions is a proof-of-concept that opens doors for fabricating “smart” materials that have ability to transform configuration and function. Such materials could be applied in a wide-range of applications. For water treatment practice specifically, we expect conventional coagulation, which has been around for several centuries, to evolve to a novel and premier water treatment process.