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Extensive consumption, toxicity, and bioaccumulation of malathion (MLT) and lindane (γ-HCH) pesticides collectively attract the world’s attention. Herein, the nanocomposite of chitosan wrapped NiO@ZnO was synthesized by a green methodology using Azadirachta indica leaves extract. Structural and morphological analysis of chitosan-NiO@ZnO showed hollow sphere-flake shaped image adsorbed on a solid chitosan surface with a large surface area of 73 m2g-1. A decrease in values of lattice strain, dislocation density and crystallite size described the imperfection in crystal geometry and new peaks in FT-IR spectra at 698 cm-1 and 448 cm-1 of Ni-N and Zn-N, respectively confirms the coupling. The chitosan- NiO@ZnO nanocomposite with a reduced band gap due to the generation of new energy levels in the vicinity of of conduction and valence band. Chitosan-NiO@ZnO and individuals nanoparticles (NiO and ZnO) were well-characterized and utilized for degradation MLT and γ- HCH under direct sunlight and dark conditions. The highest degradation of pesticides (above 94%) resulted with 2 mg L-1 and 10 mg L-1 of MLT (π_π) and γ- HCH, respectively with a 20 mg catalyst dose, and pH of ~7 under daylight exposure (5 h). Chitosan-NiO@ZnO substantially suppressed the half-life of the targeted pesticides (MLT: 0.48 h; HCH 0.51 h) and demonstrated the first- order kinetics with a high adsorption capacity, Xm (MLT: 14.5 mg g-1 and γ- HCH 20.7 mg g-1), which also confirmed the strong binding with the pesticides, followed by their conversion into safer and smaller metabolites. The charge separation mechanism was elucidated by UV reflectance and photoluminescence data. Hydroxyl radicals were most frequently responsible for the degradation of pesticides as confirmed by scavenger analysis. The synthesized green-nano photocatalyst showed high reusability (up to 10th cycles), sensitivity, and stability within the degradation process, presumably making it suitable for industrial applications.

Synthetic dyes are known to be toxic and endocrine disruptors. Therefore, advance and fast processes based on low-cost and highly proficient nanomaterials are required for their elimination. Herein, zinc oxide coupled copper hexacyanoferrate (ZnO-CuHCF) nanocomposite was prepared using plant extract of Azadirachta indica. Nanocomposite was characterized throughspectroscopic and electron microscopic techniques. Distorted cubic nanocomposite with particle size range of 50–100 nm was obtained and appearance of stretching vibration around 483 cm−1 confirmed the bonding of O of ZnO and Cu of CuHCF to form ZnO-CuHCF. Subsequently, nanocomposite was utilized as photocatalyst for removal of selected dyes under sunlight. At moderate dosage and neutral pH, nanocomposites was found highly active for quantitative degradation (97–99%) of Eriochrome Black T (EBT) and of Rhodamine B (RB) within 3 h of sunlight exposure. Photodegradation of dyes by nanocomposite was consisting of initial Langmuir adsorption followed by first order kinetics. Comparative to natives, nanocomposite was more capable and lowered the t1/2 value of EBT (0.6 h) and RB (0.9 h) to a greater extent. The findings were attributed to higher surface area (95 m2 g−1) and particle stability (zeta potential: −40.4 mV) of nanocomposite as well as synergistic effects of parent materials. Mechanism of the photo-catalysis was investigated by using radical scavenger and understanding the steps involved in removal process. Applicability of the nanocomposite for almost ten cycles of dye removal ensures its stability and excellent catalytic efficiency. Overall, present work provides an effective and sustainable photocatalyst having worth of industrial applications.

In the era of nanotechnology, distinct engineered nanoparticles have been fabricated via a greener approach. Conventional methods, both physical and chemical, used for the fabrication of nanoparticles have various disadvantages for the environment and for human life. Traditional methods for the synthesis of nanoparticles involve utilization of toxic chemicals and consumption of high temperature. In order to address this issue, the integration of green chemistry principles into the rapidly evolving field is a necessity. Green nanotechnology is a multidisciplinary field that has become a swiftly developing research area. It serves as a significant technique that emphasizes creating procedures that are clean, safe, and environmentally friendly, in place of currently employed chemical and physical methods for the synthesis of nanomaterials. Green nanomaterials are considered safe, eco-friendly materials and are currently used in various industries. Natural products and their derived forms, such as the extracts or parts of different plants, wines, different amino acids, glucose, etc., act as reducing, capping, and stabilizing agents, due to the presence of polyphenols in these materials. Microorganisms like algae, bacteria, and yeasts are used for the green synthesis of nanoparticles. In this chapter, we have summarized comprehensive studies of different types of nanoparticles, including metal and metal-oxide green nanoparticles, polymer-based green nanoparticles, porous green nanoparticles, and magnetic nanoparticles.

Recent developments in nanotechnology have led to the production of a number of nanomaterials based on metal, polymer, carbon, and their analog nanocomposites. Nanotechnology has gained great public attention because of the application of nanomaterials in activities including industry, agriculture, business, medicine, and public health. Environmental exposure to nanomaterials is inevitable as nanomaterials have become part of our daily life, and as a result, nanotoxicity research is gaining attention. Many of the materials and processes currently used are not only dependent on nonrenewable resources but also create hazardous wastes. The combination of green chemistry principles with nanotechnology applications has thus become a key component for the future of nanotechnology. The use of natural ingredients to synthesize nanomaterials and design environmentally benign synthetic processes has been extensively explored. Green nanomaterials are those that are either synthesized via a green route following green chemistry principles or are biocompatible with lower toxicity. Green nanomaterials are being employed in environmental remediation for organic and inorganic pollutants. Legislation addressing the environmental, health, and safety aspects of nanomaterials in consumer products and ensuring their safe use is being continuously updated in the European Union (EU) and globally. Despite the extensive application of nanomaterials, their health and safety effects and what levels of exposure to them may be acceptable are not yet fully understood. This chapter presents a summary of recent research on environmental, legal, health, and safety issues of green nanomaterials. A critical evaluation of challenges and future needs for ensuring environmentally safe nanotechnology have also been discussed.

Polycyclic aromatic hydrocarbons (PAHs) are causing environmental concerns due to their persistent nature and carcinogenicity. Hence, their removal through advanced nanomaterials with characteristics of low-cost and high efficiency is essential. In view of this, bimetallic oxides (BMOs) nanocomposites of NiO-ZnO, ZnCo2O4, MnCo2O4 and CoFe2O4 were synthesized via green route using leaf extract of Aegle marmelos. Subsequently, these BMOs were investigated for photocatalytic removal of selected PAHs like anthracene (ANTH) and phenanthrene (PHEN) from water. Nanospheres of NiO-ZnO, ZnCo2O4, and CoFe2O4 and nanosheets of MnCo2O4 with particle size range of 10–30 nm were confirmed by transmission electron microscopy. At neutral pH, nanocomposites showed excellent ability in degrading 2 mg L−1 of PAHs (ANTH: 98%; PHEN: 93%) within 12 h under the exposure of sunlight. Among the synthesized BMOs, NiO-ZnO was found best followed by ZnCo2O4, MnCo2O4 and CoFe2O4. This fact is attributed to the highest surface area (129 m2 g−1) and particles stability (zeta potential: −30 eV) of NiO-ZnO. Photodegradation of PAHs by nanocomposites followed first order kinetics and fitted in Langmuir model for adsorption. Higher degradation under sunlight and lower removal efficiency with scavenger confirmed the photodegradation activity of nanocomposites. Overall, reusable (n = 10) nanocomposites with no loss of activity have high photocatalytic potential in the removal of carcinogenic PAHs.

Due to the extensive manufacturing and use of brominated flame retardants (BFRs), they are known to be hazardous, bioaccumulative, and recalcitrant pollutants in various environmental matrices. BFRs make flame-resistant items for industrial purposes (textiles, electronics, and plastics equipment) that are disposed of in massive amounts and leak off in various environmental matrices. The consumption of plastic items has expanded tremendously during the COVID-19 pandemic which has resulted into the increasing load of solid waste on land and water. Some BFRs, such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDs), are no longer utilized or manufactured owing to their negative impacts, which promotes the utilization of new BFRs as alternatives. BFRs have been discovered worldwide in soil, sludge, water, and other contamination sources. Various approaches such as photocatalysis-based oxidation/reduction, adsorption, and heat treatment have been found to eradicate BFRs from the environment. Nanomaterials with unique properties are one of the most successful methodologies for removing BFRs via photocatalysis. These methods have been praised for being low-cost, quick, and highly efficient. Engineered nanoparticles degraded BFRs when exposed to light and either convert them into safer metabolites or completely mineralize. Scientific assessment of research taking place in this area during the past five years has been discussed. This review offers comprehensive details on environmental occurrence, toxicity, and removal of BFRs from various sources. Degradation pathways and different removal strategies related to data have also been presented. An attempt has also been made to highlight the research gaps prevailing in the current research area.

Large use of flame retardants or additives in plastic industries have caused scientific attention as their leaching from consumer products is indicative of environmental concern. Moreover, plastic additives have proven features of endocrine disruptors, genotoxicity and persistence. Therefore, photodegradation of tetrabromobisphenol A (TBBPA) and bisphenol A (BPA) were explored in water. Seeing environmental safety, titanium dioxide decorated magnesium substituted cadmium ferrite (CdMgFe