MEMCARE publication

2022
Srishti Gupta, Ngan Anh Nguyen, and Christopher L. Muhich. 7/2022. “Surface water H-bonding network is key controller of selenate adsorption on [012] α-alumina: An Ab-initio study.” Journal of Colloid and Interface Science, 617, Pp. 136-146. Publisher's VersionAbstract
Selenate adsorption onto metal oxide surfaces is a cost-effective method to remove the toxin from drinking water systems. However, the low selectivity of metal oxides requires frequent sorbent replacement. The design of selective adsorbents is stymied because the surface factors controlling selenate adsorption remain unknown. We calculate adsorption energies of selenate on the (0 1 2) α-Al2O3 surface using density functional theory to unravel the physics that controls adsorption. Our model is validated against experiment by correctly predicting selenate removal efficiency as a function pH. We find that the selenate adsorption energy on the anhydrous α-Al2O3 surface is surprisingly anti-correlated with the fully solvated adsorption energy; therefore, the direct interaction between adsorbate and sorbent is eliminated as the controlling mechanism. Rather, the change in number of surface hydrogen bonds after adsorption is the factor most correlated with the adsorption energy (R2 > 0.8); and is thus determined to be the factor controlling selenate adsorption. We find that pH affects adsorption by controlling the number of surface protons available for H-bonding to selenate. This work demonstrates that adsorption prediction should not be made based on gas phase sorption energies and suggests that surface engineering which increases surface protonation may be an effective strategy for increasing selenate sorption.
2021
Nilanjana Laha, Nathan Huey, Brent Coull, and Rajarshi Mukherjee. 9/24/2021. “On Statistical Inference with High Dimensional Sparse CCA.” arXiv.org. Publisher's VersionAbstract
We consider asymptotically exact inference on the leading canonical correlation directions and strengths between two high dimensional vectors under sparsity restrictions. In this regard, our main contribution is the development of a loss function, based on which, one can operationalize a one-step bias-correction on reasonable initial estimators. Our analytic results in this regard are adaptive over suitable structural restrictions of the high dimensional nuisance parameters, which, in this set-up, correspond to the covariance matrices of the variables of interest. We further supplement the theoretical guarantees behind our procedures with extensive numerical studies.
Chu C, Huang D, Gupta S, Weon S, Niu J, Stavitski E, Muhich C, and Kim JH. 8/30/2021. “Neighboring Pd single atoms surpass isolated single atoms for selective hydrodehalogenation catalysis.” Nat Commun, 30, 12(1), Pp. 5179.Abstract

Single atom catalysts have been found to exhibit superior selectivity over nanoparticulate catalysts for catalytic reactions such as hydrogenation due to their single-site nature. However, improved selectively is often accompanied by loss of activity and slow kinetics. Here we demonstrate that neighboring Pd single atom catalysts retain the high selectivity merit of sparsely isolated single atom catalysts, while the cooperative interactions between neighboring atoms greatly enhance the activity for hydrogenation of carbon-halogen bonds. Experimental results and computational calculations suggest that neighboring Pd atoms work in synergy to lower the energy of key meta-stable reactions steps, i.e., initial water desorption and final hydrogenated product desorption. The placement of neighboring Pd atoms also contribute to nearly exclusive hydrogenation of carbon-chlorine bond without altering any other bonds in organohalogens. The promising hydrogenation performance achieved by neighboring single atoms sheds light on a new approach for manipulating the activity and selectivity of single atom catalysts that are increasingly studied in multiple applications.

J Kidd, P Westerhoff, and A Maynard. 4/22/2021. “Survey of Industrial Perceptions for the Use of Nanomaterials for In-Home Drinking Water Purification Devices.” NanoImpact, 22, 100320, Pp. 1-6. Publisher's VersionAbstract

As businesses, specifically technology developers and industrial suppliers, strive to meet growing demand for higher quality drinking water, the use of engineered nanomaterials in commercial point-of-use (POU) in-home water purification devices are becoming an increasingly important option. Anecdotally, some businesses appear wary of developing and marketing nanomaterial-enabled devices because of concerns that they will face onerous regulation and consumer pushback. However, little of substance is known about business perceptions of and attitudes toward the use of engineered nanomaterials in POU water purification devices, or how these compare with consumer perceptions. To address this knowledge-gap, we administered a 14-question survey among 65 participants from US-based industrial companies focused on drinking water purification. Our results indicate that the dominant concerns for businesses are costs and public perceptions associated with nanomaterial-enabled POU devices for drinking water purification. Cost-specific barriers include competition from more conventional technologies, and tensions between operational versus capital costs. 57% of respondents were concerned or very concerned that public perceptions will influence the long-term viability of nanomaterial-enabled POU devices for drinking water purification. 49% of respondents stated that government regulation of nanomaterials would be the preferred approach to ensure public safety, followed by the certification of POU devices (28%). When asked about specific nanomaterials and their potential use in POU devices for drinking water purification, respondents ranked carbon nanotubes as the nanomaterial with highest concern for environmental health and safety, followed by silver, titanium dioxide, zinc oxide, and copper. Respondents ranked nanoclays as the nanomaterial with highest likelihood for public acceptance, followed by silica, cerium oxide, titanium dioxide, and aluminum oxide

    Katherine von Stackelberg and Pamela RD Williams. 4/2021. “Evolving Science and Practice of Risk Assessment.” Risk Anal, 41, 4, Pp. 571-583. Publisher's VersionAbstract
    Managing public health risks from environmental contaminants has historically relied on a risk assessment process defined by the regulatory context in which these risks are assessed. Risk assessment guidance follows a straightforward, chemical-by-chemical approach to inform regulatory decisions around the question "what is the risk-based concentration protective of human and ecological health outcomes?" Here we briefly summarize regulatory risk assessment in the context of innovative risk assessment approaches based on an evolving understanding of the underlying scientific disciplines that support risk analysis more broadly. We discuss scientific versus regulatory tensions in the application of these approaches for future risk assessments, and challenges in translating our improved understanding of the underlying scientific complexity to the regulatory landscape to better inform decision making that extends beyond conventional regulatory mandates.
    PMID: 33295028; PMCID: PMC8257268 (available on 2022-04-01); DOI: 10.1111/risa.13647
    Mayuri Bhatia, Aaron J Specht, Vallabhuni Ramya, Dahy Sulaiman, Manasa Konda, Prentiss Balcom, Elsie M Sunderland, and Asif Qureshi. 2021. “Portable X-ray Fluorescence as a Rapid Determination Tool to Detect Parts per Million Levels of Ni, Zn, As, Se, and Pb in Human Toenails: A South India Case Study.” Environ Sci Technol, 55, 19, Pp. 13113-13121. Publisher's VersionAbstract
    Chronic exposure to inorganic pollutants adversely affects human health. Inductively coupled plasma mass spectrometry (ICP-MS) is the most common method used for trace metal(loid) analysis of human biomarkers. However, it leads to sample destruction, generation of secondary waste, and significant recurring costs. Portable X-ray fluorescence (XRF) instruments can rapidly and nondestructively determine low concentrations of metal(loid)s. In this work, we evaluated the applicability of portable XRF as a rapid method for analyzing trace metal(loid)s in toenail samples from three populations (n = 97) near the city of Chennai, India. A Passing-Bablok regression analysis of results from both methods revealed that there was no proportional bias among the two methods for nickel (measurement range ∼25 to 420 mg/kg), zinc (10 to 890 mg/kg), and lead (0.29 to 4.47 mg/kg). There was a small absolute bias between the two methods. There was a strong proportional bias (slope = 0.253, 95% CI: 0.027, 0.614) between the two methods for arsenic (below detection to 3.8 mg/kg) and for selenium when the concentrations were lower than 2 mg/kg. Limits of agreement between the two methods using Bland-Altman analysis were derived for nickel, zinc, and lead. Overall, a suitably calibrated and evaluated portable XRF shows promise in making high-throughput assessments at population scales.
    Paul Westerhoff, Pedro JJ Alvarez, Jaehong Kim, Qilin Li, Alessandro Alabastri, Naomi J Halas, Dino Villagran, Julie Zimmerman, and Michael S Wong. 2021. “Utilizing the broad electromagnetic spectrum and unique nanoscale properties for chemical-free water treatment.” Current Opinion in Chemical Engineering, 33. Publisher's VersionAbstract
    Clean water is critical for drinking, industrial processes, and aquatic organisms. Existing water treatment and infrastructure are chemically intensive and based on nearly century-old technologies that fail to meet modern large and decentralized communities. The next-generation of water processes can transition from outdated technologies by utilizing nanomaterials to harness energy from across the electromagnetic spectrum, enabling electrified and solar-based technologies. The last decade was marked by tremendous improvements in nanomaterial design, synthesis, characterization, and assessment of material properties. Realizing the benefits of these advances requires placing greater attention on embedding nanomaterials onto and into surfaces within reactors and applying external energy sources. This will allow nanomaterial-based processes to replace Victorian-aged, chemical intensive water treatment technologies.
    2020
    Holly E Rudel, Mary Kate M Lane, Christopher L Muhich, and Julie B Zimmerman. 2020. “Toward Informed Design of Nanomaterials: A Mechanistic Analysis of Structure-Property-Function Relationships for Faceted Nanoscale Metal Oxides.” ACS Nano.Abstract
    Nanoscale metal oxides (NMOs) have found wide-scale applicability in a variety of environmental fields, particularly catalysis, gas sensing, and sorption. Facet engineering, or controlled exposure of a particular crystal plane, has been established as an advantageous approach to enabling enhanced functionality of NMOs. However, the underlying mechanisms that give rise to this improved performance are often not systematically examined, leading to an insufficient understanding of NMO facet reactivity. This critical review details the unique electronic and structural characteristics of commonly studied NMO facets and further correlates these characteristics to the principal mechanisms that govern performance in various catalytic, gas sensing, and contaminant removal applications. General trends of facet-dependent behavior are established for each of the NMO compositions, and selected case studies for extensions of facet-dependent behavior, such as mixed metals, mixed-metal oxides, and mixed facets, are discussed. Key conclusions about facet reactivity, confounding variables that tend to obfuscate them, and opportunities to deepen structure-property-function understanding are detailed to encourage rational, informed design of NMOs for the intended application.