Demonstrating scale-up of a novel water treatment process using super-bridging agents.

Fiber-based materials have emerged as a promising option to increase the efficiency of water treatment plants while reducing their environmental impacts, notably by reducing the use of unsustainable chemicals and the size of the settling tank. Cellulose fiber-based super-bridging agents are sustainable, reusable, and versatile materials that considerably improve floc separation in conventional settling tanks or via alternative screening separation methods. In this study, the effectiveness of fiber-based materials for wastewater treatment was evaluated at lab-scale (0.25 L) and at pilot-scale (20 L) for two separation methods, namely settling and screening. For the fiber-based method, the performance of floc separation during settling was slightly affected by an 80x upscaling factor. A small decrease in turbidity removal from 93 and 86 % was observed for the jar and pilot tests, respectively. By contrast, the turbidity removal of the conventional treatment, i.e., no fibers with a settling separation, was largely affected by the upscaling with turbidity removals of 84 and 49 % for jar and pilot tests, respectively. Therefore, results are suggesting that fiber-based super-bridging agents could be implemented in full-scale water treatment plants. Moreover, the tested fibers increase the robustness of treatment by providing better floc removal than conventional treatment under several challenging conditions such as low settling time and screening with coarse screen mesh size. Furthermore, at both lab-scale and pilot-scale, the use of fiber-based materials reduced the demand for coagulant and flocculant, potentially lowering the operational costs of water treatment plants and reducing the accumulation of metal-based coagulants and synthetic polymers in sludge. Acute toxicity tests using the model organism Daphnia magna show that the cellulose fibers introduce insignificant toxicity at the optimized fiber concentration. Although dedicated mechanistic studies are required at various scales to understand in detail the influence of fibers on water treatment (coagulation/flocculation time, floc formation, floc size distribution velocity gradient, etc.), the efficacy and scalability of the fiber-based approach, along with its minimal environmental impact, position it as a viable and sustainable option for existing and future wastewater treatment plants.

Effects of Surface Topography and Cellular Biomechanics on Nanopillar-Induced Bactericidal Activity.

Bacteria are mechanically resistant biological structures that can sustain physical stress. Experimental data, however, have shown that high-aspect-ratio nanopillars deform bacterial cells upon contact. If the deformation is sufficiently large, it lyses the bacterial cell wall, ultimately leading to cell death. This has prompted a novel strategy, known as mechano-bactericide technology, to fabricate antibacterial surfaces. Although adhesion forces were originally proposed as the driving force for mechano-bactericidal action, it has been recently shown that external forces, such as capillary forces arising from an air-water interface at bacterial surfaces, produce sufficient loads to rapidly kill bacteria on nanopillars. This discovery highlights the need to theoretically examine how bacteria respond to external loads and to ascertain the key factors. In this study, we developed a finite element model approximating bacteria as elastic shells filled with cytoplasmic fluid brought into contact with an individual nanopillar or nanopillar array. This model elucidates that bacterial killing caused by external forces on nanopillars is influenced by surface topography and cell biomechanical variables, including the density and arrangement of nanopillars, in addition to the cell wall thickness and elastic modulus. Considering that surface topography is an important design parameter, we performed experiments using nanopillar arrays with precisely controlled nanopillar diameters and spacing. Consistent with model predictions, these demonstrate that nanopillars with a larger spacing increase bacterial susceptibility to mechanical puncture. The results provide salient insights into mechano-bactericidal activity and identify key design parameters for implementing this technology.

Exposure protocol for ecotoxicity testing of microplastics and nanoplastics.

Despite the increasing concern about the harmful effects of micro- and nanoplastics (MNPs), there are no harmonized guidelines or protocols yet available for MNP ecotoxicity testing. Current ecotoxicity studies often use commercial spherical particles as models for MNPs, but in nature, MNPs occur in variable shapes, sizes and chemical compositions. Moreover, protocols developed for chemicals that dissolve or form stable dispersions are currently used for assessing the ecotoxicity of MNPs. Plastic particles, however, do not dissolve and also show dynamic behavior in the exposure medium, depending on, for example, MNP physicochemical properties and the medium's conditions such as pH and ionic strength. Here we describe an exposure protocol that considers the particle-specific properties of MNPs and their dynamic behavior in exposure systems. Procedure 1 describes the top-down production of more realistic MNPs as representative of MNPs in nature and particle characterization (e.g., using thermal extraction desorption-gas chromatography/mass spectrometry). Then, we describe exposure system development for short- and long-term toxicity tests for soil (Procedure 2) and aquatic (Procedure 3) organisms. Procedures 2 and 3 explain how to modify existing ecotoxicity guidelines for chemicals to target testing MNPs in selected exposure systems. We show some examples that were used to develop the protocol to test, for example, MNP toxicity in marine rotifers, freshwater mussels, daphnids and earthworms. The present protocol takes between 24 h and 2 months, depending on the test of interest and can be applied by students, academics, environmental risk assessors and industries.

Effects of weathering on the properties and fate of secondary microplastics from a polystyrene single-use cup.

In this work, we probed the changes to some physicochemical properties of polystyrene microplastics generated from a disposable cup as a result of UV-weathering, using a range of spectroscopy, microscopy, and profilometry techniques. Thereafter, we aimed to understand how these physicochemical changes affect the microplastic transport potential and contaminant sorption ability in model freshwaters. Exposure to UV led to measured changes in microplastic hydrophobicity (20-23 % decrease), density (3% increase), carbonyl index (up to 746 % increase), and microscale roughness (24-86 % increase). The settling velocity of the microplastics increased by 53 % after weathering which suggests that UV aging can increase microplastic deposition to sediments. This impact of aging was greater than the effect of the water temperature. Weathered microplastics exhibited reduced sorption capacity (up to 52 % decrease) to a model hydrophobic contaminant (triclosan) compared to unaged ones. The adsorption of triclosan to both microplastics was slightly reversible with notable desorption hysteresis. These combined effects of weathering could potentially increase the transport potential while decreasing the contaminant transport abilities of microplastics. This work provides new insights on the sorption capacity and mobility of a secondary microplastic, advances our knowledge about their risks in aquatic environments, and the need to use environmentally relevant microplastics.

Tissue Clearing To Localize Microplastics via Three-Dimensional Imaging of Whole Organisms.

Understanding the biological impacts of plastic pollution requires an effective methodology to detect unlabeled microplastics in environmental samples. Detecting unlabeled microplastics in an organism generally requires a digestion protocol, which results in the loss of spatial information on the distribution of microplastic within the organism and could lead to the disappearance of the smaller plastics. Fluorescence microscopy allows visualization of ingested microplastics but many labeling strategies are nonspecific and label biomass, thus limiting our ability to distinguish internalized plastics. While prelabeled plastics can be used to avoid nonspecific labeling, this approach precludes the detection of environmental microplastics in organisms. Also, using prelabeled microplastics can affect the viability of the organism and impact plastic uptake. Thus, a method was developed that employs nonspecific labeling with a tissue-clearing technique. Briefly, unlabeled microplastics are stained with a fluorescent dye after ingestion by the organism. The tissue-clearing technique then removes tissue-bound dye while rendering the structurally intact organism transparent. The internalized plastics remain stained and can be visualized in the cleared tissue with fluorescence microscopy. The technique is demonstrated using polystyrene beads in living aquatic organismsTigriopus californicusandDaphnia magnaand by spiking a model vertebrate (Cephalochordata) with different microplastics.

Antibacterial Pickering emulsions stabilized by bifunctional hairy nanocellulose.

HYPOTHESIS: Pickering emulsions, defined as emulsions that are stabilized by colloidal particles, provide dispersion stability by preventing coalescence of the dispersed phase. In this study, we used a bifunctional hairy nanocellulose (BHNC) bearing both aldehyde and carboxylic acid groups as an stabilizer. We hypothesize that these particles as Pickering stabilizers can effectively reside at the oil-water interface, better than hairy nanocelluloses containing only carboxyl groups or aldehyde groups, and provide long-term stability without the need of any surfactants. EXPERIMENTS: Varying concentrations of BHNC were tested to explore the optimal concentration that provides emulsion stability. The effects of various preparation conditions such as salt and pH were also studied. Finally, carvacrol, an antibacterial essential oil, was loaded in the oil phase to develop antibacterial emulsions. FINDINGS: It was shown that a 1% BHNC suspension provides 90% and 80% stability for a duration of 30 and 60 days, respectively. A theoretical model using nuclear magnetic resonance relaxometry data is developed to prove that only a monolayer of BHNC covers oil droplets. Increasing the concentration of BHNC decreased the size of oil droplets, which as a result increases the surface area available for monolayer coverage. It was also shown that the antibacterial emulsions are highly effective against Gram-negative (i.e. E. coli) and Gram-positive (i.e. S. aureus) bacteria. Accordingly, BHNC as a highly functionalized bio-derived colloidal particle opens new opportunities for engineering highly stable Pickering emulsions.

Fabrication of graphene-based porous materials: traditional and emerging approaches.

The anisotropic nature of 'graphenic' nanosheets enables them to form stable three-dimensional porous materials. The use of these porous structures has been explored in several applications including electronics and batteries, environmental remediation, energy storage, sensors, catalysis, tissue engineering, and many more. As method of fabrication greatly influences the final pore architecture, and chemical and mechanical characteristics and performance of these porous materials, it is essential to identify and address the correlation between property and function. In this review, we report detailed analyses of the different methods of fabricating porous graphene-based structures - with a focus on graphene oxide as the base material - and relate these with the resultant morphologies, mechanical responses, and common applications of use. We discuss the feasibility of the synthesis approaches and relate the GO concentrations used in each methodology against their corresponding pore sizes to identify the areas not explored to date.

Fate of microfibres from single-use face masks: Release to the environment and removal during wastewater treatment.

Single-use face masks can release microfibres upon exposure to environmental conditions. This study investigates the number of microfibres released in the presence and absence of UV irradiation and mechanical friction and the removal of the released microfibres in a simulated conventional wastewater treatment process. UV exposure results in a four-fold increase in the number of microfibres released from new masks and used masks resulting in ~2400 microfibres/mask and ~1100 microfibres/mask, respectively. Application of mechanical friction to the UV-exposed new and used masks further increases the number of released microfibres per mask. In a simulated coagulation/flocculation process, the removals of microfibers originating from new masks and used masks are 79% and 91%, respectively. XPS analysis reveals that the silica content of the used masks is 240% higher than that of new masks, which could explain the higher removal efficiency of microfibers from used masks. FTIR analysis of the masks after UV exposure shows carbonyl indices of 0.73 ± 0.70 and 0.27 ± 0.10 for the microfibres from used and new masks, respectively. Based on available data, we estimate that 4-47 million polypropylene microfibres can be released into natural waters per day after wastewater treatment in an urban environment (for a population of 4300 persons/km2).

Microfluidic Study of Bacterial Attachment on and Detachment from Zinc Oxide Nanopillars.

Nanopillars can influence how bacterial cells attach to a surface. Herein, we investigated whether self-assembled zinc oxide (ZnO) nanopillars synthesized on glass substrates via the conventional hydrothermal route possess anti-biofouling properties either by reducing the amount of initially attached cells or promoting the detachment of cells from the surface or both. To avoid complications associated with manual intervention methods of assessing bacterial attachment on nanopillar surfaces, we implemented a microfluidic approach. In our study, we synthesized two nanopillar topographies: a low surface density of ZnO nanopillars and a high surface density of ZnO nanopillars. Next, we mounted microfluidic channels to each of these substrates. This microfluidic approach allowed us to gently flow Pseudomonas aeruginosa, Staphylococcus aureus, or Bacillus subtilis cells onto the nanopillars for initial attachment before systematically increasing the flowrate to attempt to detach remaining attached cells without introducing air-liquid interface artefacts during the assay. Generally, initial bacterial attachment was similar across all substrates. However, cells consistently detached more readily from high-surface-density nanopillars compared to low-surface-density nanopillars. Electron microscopy revealed that cells that attached to high-surface-density nanopillars rested atop the nanopillars, fully exposed to microfluidic shear, whereas many cells became trapped in the void space between neighboring low-surface-density nanopillars, shielding these cells from detachment. Our findings indicate that self-assembled ZnO nanopillars can provide anti-biofouling properties under submerged flow but only if synthesized at high surface density.

Surface Wettability Is a Key Feature in the Mechano-Bactericidal Activity of Nanopillars.

Nanopillar-textured surfaces are of growing interest because of their ability to kill bacteria through physical damage without relying on antimicrobial chemicals. Although research on antibacterial nanopillars has progressed significantly in recent years, the effect of nanopillar hydrophobicity on bactericidal activity remains elusive. In this study, we investigated the mechano-bactericidal efficacy of etched silicon nanopillars against Pseudomonas aeruginosa at nanopillar hydrophobicities from superhydrophilic to superhydrophobic. Assessing cell viability and bacterial morphology in immersed wet conditions, we observed negligible bactericidal activity; however, air/liquid interface displacement during water evaporation established a bactericidal effect that strongly depends on substrate hydrophobicity. Specifically, bactericidal activity was highest on superhydrophilic surfaces but abated with increasing hydrophobicity, diminishing at substrate contact angles larger than 90°. Calculation of the surface tension and Laplace pressure forces during water evaporation for each substrate subsequently highlighted that the total capillary force, as an external driving force responsible for bacterial deformation, is significantly weaker on hydrophobic substrates. These findings suggest that superhydrophilic nanopillared surfaces are a superior choice for mechano-bactericidal activity, whereas superhydrophobic surfaces, although not bactericidal, may have antibiofouling properties through their self-cleaning effect. These findings provide new insights into the design and application of nanopillared surfaces as functional antibacterial materials.

Single-Particle Resolution Fluorescence Microscopy of Nanoplastics.

Understanding of nanoplastic prevalence and toxicology is limited by imaging challenges resulting from their small size. Fluorescence microscopy is widely applied to track and identify microplastics in laboratory studies and environmental samples. However, conventional fluorescence microscopy, due to diffraction, lacks the resolution to precisely localize nanoplastics in tissues, distinguish them from free dye, or quantify them in environmental samples. To address these limitations, we developed techniques to label nanoplastics for imaging with stimulated emission depletion (STED) microscopy to achieve resolution at an order of magnitude superior to conventional fluorescence microscopy. These techniques include (1) passive sorption; (2) swell incorporation; and (3) covalent coupling of STED-compatible fluorescence dyes to nanoplastics. We demonstrate that our labeling techniques, combined with STED microscopy, can be used to resolve nanoplastics of different shapes and compositions as small as 50 nm. The longevity of dye labeling is demonstrated in different media and conditions of biological and environmental relevance. We also test STED imaging of nanoplastics in exposure experiments with the model worm Caenorhabditis elegans. Our work shows the value of the method for detection and localization of nanoplastics as small as 50 nm in a whole animal without disruption of the tissue. These techniques will allow more precise localization and quantification of nanoplastics in complex matrices such as biological tissues in exposure studies.

Metabolic Consequences of Developmental Exposure to Polystyrene Nanoplastics, the Flame Retardant BDE-47 and Their Combination in Zebrafish.

Single-use plastic production is higher now than ever before. Much of this plastic is released into aquatic environments, where it is eventually weathered into smaller nanoscale plastics. In addition to potential direct biological effects, nanoplastics may also modulate the biological effects of hydrophobic persistent organic legacy contaminants (POPs) that absorb to their surfaces. In this study, we test the hypothesis that developmental exposure (0-7 dpf) of zebrafish to the emerging contaminant polystyrene (PS) nanoplastics (⌀100 nm; 2.5 or 25 ppb), or to environmental levels of the legacy contaminant and flame retardant 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47; 10 ppt), disrupt organismal energy metabolism. We also test the hypothesis that co-exposure leads to increased metabolic disruption. The uptake of nanoplastics in developing zebrafish was validated using fluorescence microscopy. To address metabolic consequences at the organismal and molecular level, metabolic phenotyping assays and metabolic gene expression analysis were used. Both PS and BDE-47 affected organismal metabolism alone and in combination. Individually, PS and BDE-47 exposure increased feeding and oxygen consumption rates. PS exposure also elicited complex effects on locomotor behaviour with increased long-distance and decreased short-distance movements. Co-exposure of PS and BDE-47 significantly increased feeding and oxygen consumption rates compared to control and individual compounds alone, suggesting additive or synergistic effects on energy balance, which was further supported by reduced neutral lipid reserves. Conversely, molecular gene expression data pointed to a negative interaction, as co-exposure of high PS generally abolished the induction of gene expression in response to BDE-47. Our results demonstrate that co-exposure to emerging nanoplastic contaminants and legacy contaminants results in cumulative metabolic disruption in early development in a fish model relevant to eco- and human toxicology.

Weathering pathways and protocols for environmentally relevant microplastics and nanoplastics: What are we missing?

To date, most studies of microplastics have been carried out with pristine particles. However, most plastics in the environment will be aged to some extent; hence, understanding the effects of weathering and accurately mimicking weathering processes are crucial. By using microplastics that lack environmental relevance, we are unable to fully assess the risks associated with microplastic pollution in the environment. Emerging studies advocate for harmonization of experimental methods, however, the subject of reliable weathering protocols for realistic assessment has not been addressed. In this work, we critically analysed the current knowledge regarding protocols used for generating environmentally relevant microplastics and leachates for effects studies. We present the expected and overlooked weathering pathways that plastics will undergo throughout their lifecycle. International standard weathering protocols developed for polymers were critically analysed for their appropriateness for use in microplastics research. We show that most studies using weathered microplastics involve sorption experiments followed by toxicity assays. The most frequently reported weathered plastic types in the literature are polystyrene>polyethylene>polypropylene>polyvinyl chloride, which does not reflect the global plastic production and plastic types detected globally. Only ~10% of published effect studies have used aged microplastics and of these, only 12 use aged nanoplastics. This highlights the need to embrace the use of environmentally relevant microplastics and to pay critical attention to the appropriateness of the weathering methods adopted moving forward. We advocate for quality reporting of weathering protocols and characterisation for harmonization and reproducibility across different research efforts.

Nanoplastics are neither microplastics nor engineered nanoparticles.

Increasing concern and research on the subject of plastic pollution has engaged the community of scientists working on the environmental health and safety of nanomaterials. While many of the methods developed in nano environment, health and safety work have general applicability to the study of particulate plastics, the nanometric size range has important consequences for both the analytical challenges of studying nanoscale plastics and the environmental implications of these incidental nanomaterials. Related to their size, nanoplastics are distinguished from microplastics with respect to their transport properties, interactions with light and natural colloids, a high fraction of particle molecules on the surface, bioavailability and diffusion times for the release of plastic additives. Moreover, they are distinguished from engineered nanomaterials because of their high particle heterogeneity and their potential for rapid further fragmentation in the environment. These characteristics impact environmental fate, potential effects on biota and human health, sampling and analysis. Like microplastics, incidentally produced nanoplastics exhibit a diversity of compositions and morphologies and a heterogeneity that is typically absent from engineered nanomaterials. Therefore, nanoscale plastics must be considered as distinct from both microplastics and engineered nanomaterials.

Cranberry-Derived Proanthocyanidins Potentiate ß-Lactam Antibiotics against Resistant Bacteria.

The emergence and spread of extended-spectrum ß-lactamases (ESBLs), metallo-ß-lactamases (MBLs), or variant low-affinity penicillin-binding proteins (PBPs) pose a major threat to our ability to treat bacterial infection using ß-lactam antibiotics. Although combinations of ß-lactamase inhibitors with ß-lactam agents have been clinically successful, there are no MBL inhibitors in current therapeutic use. Furthermore, recent clinical use of new-generation cephalosporins targeting PBP2a, an altered PBP, has led to the emergence of resistance to these antimicrobial agents. Previous work shows that natural polyphenols such as cranberry-extracted proanthocyanidins (cPAC) can potentiate non-ß-lactam antibiotics against Gram-negative bacteria. This study extends beyond previous work by investigating the in vitro effect of cPAC in overcoming ESBL-, MBL-, and PBP2a-mediated ß-lactam resistance. The results show that cPAC exhibit variable potentiation of different ß-lactams against ß-lactam-resistant Enterobacteriaceae clinical isolates as well as ESBL- and MBL-producing E. coli We also discovered that cPAC have broad-spectrum inhibitory properties in vitro on the activity of different classes of ß-lactamases, including CTX-M3 ESBL and IMP-1 MBL. Furthermore, we observe that cPAC selectively potentiate oxacillin and carbenicillin against methicillin-resistant but not methicillin-sensitive staphylococci, suggesting that cPAC also interfere with PBP2a-mediated resistance. This study motivates the need for future work to identify the most bioactive compounds in cPAC and to evaluate their antibiotic-potentiating efficacy in vivoIMPORTANCE The emergence of ß-lactam-resistant Enterobacteriaceae and staphylococci compromises the effectiveness of ß-lactam-based therapy. By acquisition of ESBLs, MBLs, or PBPs, it is highly likely that bacteria may become completely resistant to the most effective ß-lactam agents in the near future. In this study, we described a natural extract rich in proanthocyanidins which exerts adjuvant properties by interfering with two different resistance mechanisms. By their broad-spectrum inhibitory ability, cranberry-extracted proanthocyanidins could have the potential to enhance the effectiveness of existing ß-lactam agents.

Green synthesis of carbon dots and their applications.

Carbon dots (CDs) are nanoparticles with tunable physicochemical and optical properties. Their resistance to photobleaching and relatively low toxicity render them attractive alternatives to fluorescent dyes and heavy metal-based quantum dots in the fields of bioimaging, sensing, catalysis, solar cells, and light-emitting diodes, among others. Moreover, they have garnered considerable attention as they lend themselves to green synthesis methods. Increasingly, one-pot syntheses comprising exclusively of renewable raw materials or renewable refined compounds are gaining favor over traditional approaches that rely on harsh chemicals and energy intensive conditions. The field of green CD synthesis is developing rapidly; however, challenges persist in ensuring the consistency of their properties (e.g., fluorescence quantum yield) relative to conventional preparation methods. This has mostly limited their use to sensing and bioimaging, leaving opportunities for development in optoelectronic applications. Herein, we discuss the most common green CD synthesis and purification methods reported in the literature and the renewable precursors used. The physical, chemical, and optical properties of the resulting green-synthesized CDs are critically reviewed, followed by a detailed description of their applications in sensing, bioimaging, biomedicine, inks, and catalysis. We conclude with an outlook on the future of green CD synthesis. Future research efforts should address the broad knowledge gap between CDs synthesized from renewable versus non-renewable precursors, focusing on discrepancies in their physical, chemical, and optical properties. The development of cost effective, safe, and sustainable green CDs with tunable properties will broaden their implementation in largely untapped applications, which include drug delivery, photovoltaics, catalysis, and more.

Exposure of nanoplastics to freeze-thaw leads to aggregation and reduced transport in model groundwater environments.

Despite plastic pollution being a significant environmental concern, the impact of environmental conditions such as temperature cycling on the fate of nanoplastics in cold climates remains unknown. To better understand nanoplastic mobility in subsurface environments following freezing and thawing cycles, the transport of 28 nm polystyrene nanoplastics exposed to either constant (10°C) temperature or freeze-thaw (FT) cycles (-10°C to 10°C) was investigated in saturated quartz sand. The stability and transport of nanoplastic suspensions were examined both in the presence and absence of natural organic matter (NOM) over a range of ionic strengths (3-100 mM NaCl). Exposure to 10 FT cycles consistently led to significant aggregation and reduced mobility compared to nanoplastics held at 10°C, especially at low ionic strengths in the absence of NOM. While NOM increased nanoplastic mobility, it did not prevent the aggregation of nanoplastics exposed to FT. We compare our findings with existing literature and show that nanoplastics will largely aggregate and associate with soils rather than undergo long range transport in groundwater in colder climates following freezing temperatures. In fact, FT exposure leads to the formation of stable aggregates that are not prone to disaggregation. As one of the first studies to examine the coupled effect of cold temperature and NOM, this work highlights the need to account for climate and temperature changes when assessing the risks associated with nanoplastic release in aquatic systems.

Polymer-Free Emulsion-Templated Graphene-Based Sponges for Contaminant Removal.

An emulsion-templated porous material can be formed by polymerizing the continuous phase of high internal phase Pickering emulsions (HIPEs). Although polymerization is a key step to maintain the pore size and integrity of the final sponge, it lowers the effective specific surface area of the final sponge as the continuous phase makes up at least half of the HIPE's volume. Hence, eliminating the need of polymerization not only eases the material processing but also leads to a greater specific surface area. Here, we report a novel strategy in which none of the emulsion phases require polymerization and is therefore a versatile methodology. For this purpose, several oil-in-water Pickering emulsions were prepared using graphene oxide (GO) and cellulose nanocrystals (CNCs) as the stabilizing agents. GO nanosheets are then reduced by mixing the emulsions with an adequate amount of vitamin C as a green reducing agent. Removal of the oil phase via multiple washing and boiling steps results in the formation of the ultimate reduced graphene oxide (rGO)/CNC sponge. The integrity of the structure remains intact and results in the formation of pores that are comparable in size to the droplets because of (i) the strong adhesion of GO and CNC at the oil/water interface in the initial Pickering emulsions and (ii) the strong intermolecular interactions between GO and CNC particles within the water phase. The sponge was then evaluated for its contaminant removal applicability using methylene blue and found to be effective in different water chemistries and outperform previously reported poly(HIPEs) and granular activated carbon. This is the first report on the formation of a polymer-free emulsion-templated sponge, and we believe that this novel nanomaterial paves the road for the fabrication of other emulsion-templated sponges. Although the proposed application in this work is contaminant removal, it could also be utilized in forming electronic devices and sensors because of the incorporation of rGO as a conductive component.