Emerging Materials and Environment

This chapter provides a brief overview of emerging materials that either have the potential to be or have already been identified as problematic for the environment. The growing population, estimated to be \(\approx \)10 billion people by the year 2050, will create asymmetric pressure on available resources, leading to the need for novel materials to drive technological advancement and alleviate the burden on natural resources. Development and implementation of new materials and technologies driven by necessity may exacerbate environmental contamination as these new materials are rushed into use without forethought into their environmental impacts. In this chapter, various aspects of 3D printing, nanocomposites, electronic waste (E-waste), biomaterials, cellulosic materials, volatile organic compounds (VOC), microplastics, and antibiotics have been discussed in terms of their current or potential environmental relevance. For example, Ag- and TiO\(_2\)-nanoparticles (NPs) have potential for antibacterial, and UV protection applications, respectively, and are used in textiles, medical devices, dental fillings, etc. However, these NPs can pose a threat if released into the environment, which may occur through leaching mechanisms or through textile laundering. The annual global E-waste production is projected to increase to 74.7 Mt by the year 2030, thus increasing the potential for environmental contamination unless efficient recovery and remediation technologies are developed. Photovoltaic panels (PVs) are one such example that have emerged as significant E-waste contaminants. These devices have only recently been classified as E-waste by the European Commission, and their volumes are anticipated to increase rapidly. During pyrolysis processes (combustion, biomass conversion, etc.), a significant quantity of VOCs such as benzene, toluene, and phenol are expected to be released and pose both carcinogenic and noncarcinogenic health hazards to the workforce, neighboring general population, and environment. Furthermore, the tracking and detection of increased antibiotic resistance, and accumulation of microplastics leading to organic and metallic pollutants will be highlighted. One major environmental contaminant relevant in today’s society, per- and polyfluoroalkyl substances (PFAS), will not be discussed in this chapter as this topic is discussed in two separate chapters in the book. Material types, pros and cons, and modes of release into the environment will be discussed. The topics reviewed in this chapter will support parallel research on environmental impacts of next-generation materials as new technologies are developed and implemented in society.

We describe the modifications that a spatially varying external force produces on a Born-Oppenheimer potential energy surface (PES), and in this chapter, we present a formulation for describing a Generalized Force-Modified Potential Energy Surface (G-FMPES). Our formulation shows that the spatially varying force resembling hydrostatic pressure results in the G-FMPES having curvature different from that of the unmodified PES. Using electronic structure methods, the effect of pseudo-hydrostatic pressure on the PES is exemplified by calculating atomistic quantities (including transition states) for (i) conformational transitions in ethane (\(\text {C}_{2}\text {H}_{6}\)) and RDX (hexahydro-1,3,5-trinitro-s-triazine) molecules, (ii) the decomposition of RDX, and (iii) a Diels-Alder reaction between 1,3-butadiene and ethylene. The calculated transition states and Hessian matrices of stationary points of ethane and RDX molecules show that spatially varying external forces shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules are blue-shifted with increasing compressive “pressure.” Some stationary points on the RDX-PES disappear under the application of the external force, indicating the merging of an energy minimum with a saddle point. This change in the topology of the PES demonstrates that new reaction pathways may be introduced by the application of mechanical forces. Part of this chapter is reproduced with permission from Refs. (J Chem Phys 143(13):134109 [1]) Copyright 2015 AIP Publishing, (J Chem Phys 145(7):074307 [2]) Copyright 2016 AIP Publishing, and  (Int J Quantum Chem 117(20):e25426 [3]) Copyright 2017 John Wiley & Sons.

Widespread usage of pharmaceuticals, personal care products (PPCPs), and agrochemicals followed by the release of household waste, industrial and hospital wastes has affected the environment and ecosystems immensely. These toxic chemicals are primarily classified under contaminants of emerging concerns (CEC) and/or environmental pollutants (EPs). Due to their harmful effects, timely removal of these EPs is an utmost requirement under risk management of the environment. A series of traditional techniques are accepted by the environmental organization to remove these products from the environment. Adsorption is one of the low-budget, easy to perform, and efficient approaches. With the advancement of nanotechnology, materials like carbon nanotubes (CNTs), magnetic nanoparticles, modified activated carbons/biochar, clay polycations, polyamide nanofilters (PNF), etc. have emerged as the materials of interest at present time. Along with the existing hazardous chemicals in the ecosystems, every day thousands of new chemicals are introduced to the environment. As a result, there is a continuous requirement for efficient materials which are capable of adsorbing these contaminants from the environment. In this perspective, chemometric-based modeling and machine learning (ML) models are shown to be capable of predicting important structural and physicochemical features that are responsible for the efficient adsorption property of these emerging materials. Once these features are identified, further modification in the structure of these materials can be performed to make them much more efficient adsorbers than the existing materials. The present chapter discusses the CECs and EPs, emerging materials in the present time, along with details about the chemometric and ML models which can be employed for modeling of the adsorption of EPs. Finally, successful case studies for the prediction of adsorption of EPs onto different emerging materials are meticulously discussed with mechanistic interpretations.

Chemicals of concern may emerge in our environment in many ways. Two distinct ways are through the design of the compound or by molecules/functionalities added to the original compound. In this chapter, we will use ionic liquids (ILs) and halloysite nanotubes (HNTs) to illustrate these two ways. ILs are salts that are typically composed of organic cations and inorganic anions. While they were initially promoted as “green” solvents, this characterization is not necessarily true. The potential number and uses for ILs seem almost limitless. HNTs are a form of naturally occurring clay, possessing mostly a nanotubular structure and a similar chemical composition to kaolin. The tubular morphology and the aluminum silicate structure of HNTs have allowed them extensive use in science, engineering, and medicine. The growth of the biorefinery and green chemistry, circular chemistry, and sustainability will provide increasing access of these compounds into the environment. This extended use of both ILs and HNTs increases their presence in the environment. While the ILs which may be toxic depending upon their composition, HNTs may become toxic due to what is loaded in/on them. While the utility of these chemicals is unquestionable, understanding their environmental behavior, fate, and effects is critical.

Emerging materials and manufacturing technology form the quintessential cornerstones to cater to the rapidly-growing demands in water-food-energy (WEF) nexus due to increasing human population and human-technology interfaces that has severely strained our resources and environment globally. To respond to such demands, twenty-first century science and research in nanomaterials have revolutionized new frontiers for materials engineering and development due to the unique properties and functionalities that emerge at nanoscale. Thus, global market size for metal-based composite nanomaterials is projected to reach US$ 620.4 M by 2027—growing at a CAGR of 4.4% over 2020–2027. However, scalable, facile, and chemically clean synthesis of functional heterostructured nanocomposites (HNCs) with low product variability (<10–15%) and desired functionality is still elusive yet, imperative for technological translation of such materials into US’s engineering sector. Specifically, enabling science and technology that can tailor these HNCs to tune their structure–property relations for desirable interfacial properties are imperative for their use in catalytic, optoelectronic, and electrochemical applications—all of which, bear impacts for the fast-paced sustainable energy and environmental research. To this end, this book chapter reports the development and deployment of a facile, non-equilibrium and yet, “green” synthesis route—called Laser Ablation Synthesis in Solution—Galvanic Replacement Reaction (LASiS-GRR)—that allows a disruptive merger of high-energy LASiS with chemically reactive GRR in solution-phase for one-pot manufacturing of diverse and complex HNCs comprising metal, metal oxide (M/MO_x), and intermetallic nanocomposites (NCs)/nanoalloys (NAs). The chapter will showcase a few of the authors’ formative works in employing LASiS-GRR for the synthesis of advanced HNCs comprising: (1) graphitic shell coated Al NPs as energetic nanomaterials (ENMs), and (2) PtCo NAs in CoO_x matrices as superior bi-functional ORR/OER electrocatalysts. The detailed research and discussions presented here is anticipated to provide a broad overview on the future of hierarchically-designed HNCs synthesized via LASiS-GRR route for sustainable electrochemical energy conversion/storage and defense/national security applications. It should be noted here that various sections of this chapter are adopted/reused in part or whole from the principal author, D. Mukherjee’s publications, Appl.Surf. Sci. 473, 156–163 (2019), Appl. Catal. B: Environ. 182, 286–296 (2016), and book chapter in Multifunctional Nanocomposites for Energy & Environmental Applications with copyrights and contents permission via License Nos.: 5283130233336 (Apr 06, 2022), 5287761493623 (Apr. 14, 2022) from Elsevier Publishing Company, and License Nos.: 5340460703005 (July 01, 2022) from John Wiley and Sons respectively.

Ceria, a prototypical reducible oxide, has been shown to possess enzyme-like catalytic activities in recent years, which makes it an attractive enzyme mimic with possible applications in medicine, biochemistry, and environment remediation. This chapter reviews the current literature for mechanistic understanding of the phosphatase, superoxide dismutase, and catalase mimetic actions of ceria from experimental and theoretical approaches. Some inconsistencies stemming from common views of the role of the Ce³⁺/Ce⁴⁺ redox couple are identified and discussed. Alternative interpretations of experimental observations are suggested in hopes of unlocking the technological potentials of ceria.

Even today, getting safe drinking water is one of the big challenges for society. As per World Health Organization (WHO), several millions of people are lacking drinking water that is free from viruses, toxic chemicals, and bacteria. Here, we discuss the new development of a water filtration systems using a two-dimensional (2D) nanomaterials. Due to atomically thin surface and good mechanical strength, 2D graphene, graphene oxide, as well as transition metal dichalcogenides are considered to be advanced membrane materials. This chapter highlights the recent reports on how emerging material-based membranes have been used to tackle water desalination. Notably, we discuss the synthetic method development for the design of novel membranes which have the capability for the separation of toxic chemicals and pathogens. Finally, we have discussed the future challenges and prospects of current development.

The past several decades have seen persistent and cumulative contamination of the environment by per- and polyfluoroalkyl substances due to the increase in utilization of such compounds in a myriad of applications owing to their inherent stability. While this stability resulting from their exceptional thermodynamically-stable C–F bonds has been a boon in applications, in contrast, with regard to their post-application lives, it has become a bane due to the remarkable recalcitrance of the C–F bonds upon permeation of the environment. Deleterious effects of such compounds on human and bio-organisms include a host of diseases and other environmental problems. Extensive studies on containment strategies for PFASs during the past few decades have included steps such as capture and thermal incineration, various catalytic degradation strategies, and biodegradation efforts using microorganisms leading to partial destruction of these compounds. This review specifically focuses on the most recent emergent techniques in this area.

Per- and polyfluoroalkyl substances (PFASs) are an expansive class of highly-fluorinated anthropogenic organic compounds that were developed for demanding speciality uses. Exceptional chemical properties led them to be incorporated in consumer products, industrial products, and industrial processes. Their extensive production and widespread application ultimately led to environmental release. Certain members of these compounds were found to be ubiquitous throughout the environment and in biota, having been transported to even the most remote locations. Findings of negative health outcomes associated with the biological occurrence of two particular PFASs (perfluorooctanesulfonic acid, or PFOS, and perfluorooctanoic acid) spurred a legislative movement to cope with the potential hazards of PFAS usage. Meanwhile, the scientific community embarked on a diverse research effort to understand PFAS life cycle considerations including production levels and utilization, environmental release and occurrence, environmental transformation, biological exposure and occurrence, and epidemiology. Furthermore, significant efforts are underway to understand how PFAS release can be prevented, and how to remediate contaminated matrices. Many of the properties making PFASs useful cause unique challenges for their ongoing management. An equilibrium has yet to be fully established between the clear utility provided by using PFASs and the associated risk.