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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.

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

Extensive use of non-biodegradable plastic by anthropogenic activities is posing a severe threat to the global environment in the form of massive waste disposal and problems of closed-landfill sites and rising water and land pollution. Organisms are facing challenge to their lives once they consume plastic in the form of food. In addition, the plastic debris may have additive chemicals having possibility to leach out. Therefore, proper degradation of plastic to lessen negative environmental implications is necessary. Earlier the people were ignorant about this problem however, now-a-days, people are serious about its negative impact. Hence, biodegradable plastics are coming into the trend in the market. Interaction of plastic (adsorbing characteristics) with the environment results in new functional groups on its surface in a dynamic situation. In these circumstances, oxygenated, thermal, bio-based, and photocatalytic degradation of plastics is in high demand. Usually, different-rates along with diverse-pathways have been found in variable polymers like polyethylene, polypropylene, and polyethylene terephthalate. Polyethylene photo-degradation resulted in sharp infrared-peaks of ketones, esters, and acids due to oxidation reaction. Hydrogen peroxide is generated by oxidative action on methylene groups in the backbone of polyethylene terephthalate. The present chapter will provide compiled information about various polymers used in plastic as well as environmental concerns of plastic, finally the chapter concludes with comprehensive details about the degradation of various types of plastics. State-of-the-art on degradable plastics market with an emphasis on principle design for recyclable plastics and biodegradable plastics from renewable raw materials are also included. Factors affecting plastic degradation and metabolic pathways including past and present scenarios have also been discussed in this chapter.

Aromatic amines (AAs), the major group of industrial and environmental chemicals have raised concern due to their thermodynamic stability coupled with carcinogenicity. Thus, their effective elimination was carried out by nanomaterials especially metal hexacyanoferrates (MHCFs). Iron hexacyanoferrate (FeHCF), Nickel hexacyanoferrate (NiHCF) and Cobalt hexacyanoferrate (CoHCF) were synthesized using green methodology. TEM analysis showed the formation of hexagonal nanorods (

Discharge of dyes (major industrial coloring agents ∼700,000 tonnes) in environment is of concern due to their high perseverance, toxicity and carcinogenicity. Thus, effective elimination of organic dye (methylene blue) was carried out by poly(methyl methacrylate) (PMMA) incorporated metal oxide nanocomposites. Spherical and semi crystalline Fe3O4-PMMA, ZnO-PMMA, CuO-PMMA and Ni2O3-PMMA were self-assembled via green route employing Sapindus mukkorossi (Plant extract). At optimised conditions (dye conc: 2 mg L−1; catalyst: 80 mg: neutral pH) MO-PMMA showed maximum degradation efficiency (90–99%; t1/2 = 5.1–5.6 h) than that of individual MO (74–80%; t1/2 = 5.8–6.8 h) credited to improved thermal stability and surface area via incorporation of MO into PMMA matrix. Like MO, highest degradation with ZnO-PMMA (99%; Xm = 0.135 mg/g) followed by Ni2O3-PMMA (98%), CuO-PMMA (93%) and Fe3O4-PMMA (90%) could be attributed to its high surface area (85.32 m2 g−1) and least zeta potential (-22.5 eV). Adsorption of MB over catalyst was statistically significant with Langmuir isotherms (R2: 0.99 and p value: 0.0005) and first order kinetics with greatly reduced half-life. Comparatively higher degradation in sunlight than dark, and involving hydroxylation, oxidation and ring opening clearly reinforced boosted oxidation of MB by OH. Moreover, reduction in degradation (50-40%) in presence of OH scavengers supported the photocatalytic activity of nanocomposites. MB was degraded into minor non-toxic by-products such as (Z)-hexa-3,5-dien-1-ol and (Z)-buta-1,3-dien-1-ol and benzoquinone. Overall, by virtue of greater active sites, high surface activity and semiconducting nature, the as-synthesized MO-PMMA photocatalyst is a promising, recyclable (n = 10) and eco-friendly panorama in the treatment of organic- pollutants in water and wastewater-treatment.

Structural design of semiconductor nanomaterials via facile and green methodology is noteworthy to advance their photocatalytic activity for resolving the problem of energy and environment. Herein, sunlight active zinc oxide coupled with cadmium sulfide (ZnO@CdS) was synthesized by employing the leaf extract of Azadirachta indica. Subsequently, it was used for removal of chlorpyrifos (CP) and atrazine (Atz) pesticides that have shown high persistence, bioaccumulation, and toxicity in the environment. Synthesized ZnO@CdS nanocomposite was characterized by spectroscopic and microscopic techniques. The unique morphology of nanocomposite (particle size ≤ 50 nm) and appearance of stretching vibrations at 600 cm−1 for Zn-S and 679 cm−1 for Cd-O has confirmed the coupling of ZnO with CdS. The degradation conditions were optimized by varying the pesticide amounts, catalyst dose, and pH under the sunlight irradiation. At moderate dosage and neutral pH, the nanocomposite was found highly efficient for the quantitative removal of pesticides (89–91%) due to improved surface area (111 m2g−1), low band energy (1.67 eV), and semiconducting nature resulted from synergism. The degradation followed Langmuir adsorption and first order kinetics. The Effect of ionic strength was helpful to understand the interaction mechanism involved in the removal of contaminants. Being more effective than natives, ZnO@CdS has substantially suppressed the half-life of pesticides as revealed from generation of smaller and less toxic metabolites in GC–MS analysis. The charge separation was supported by photoluminescence and UV-reflectance studies. A scavenger analysis has indicated the presence of active radicals in photocatalysis. The Applicability of green or alternative photocatalyst for multiple times (n = 10) confirmed its sustainability and high efficiency for environmental and industrial purposes.

Bimetallic metal oxide (BMO) are extremely useful heterogeneous and recoverable catalyst owing to improved semiconducting efficiency, cationic impurities and supports. Hence, their synthesis via ecofriendly green route based on biogenic sources (natural surfactant–water) is highly encouraging. Herein, three BMO nanoparticles, namely Ni-Cu oxide (NiCuO), Cu-Cr oxide (CuCr2O4) and Ni-Cr oxide (NiCrO3) were synthesized after employing Aegle marmelos leaf extract. Transmission electron microscopy analysis confirmed that highly crystalline BMO formed were below 50 nm with variable shapes, like nanorods of Ni-Cu oxide; nanospheres of Ni-Cr oxide and nanoflowers of Cu-Cr oxide. Successively, photocatalytic potential of BMO nanoparticles were evaluated for removal of various harmful phenols (phenol, 2, 4-dinitrophenol and 3-aminophenol) from simulated water. Under optimized conditions (phenol concentration: 1 × 10−4 M; catalyst dose: 15 mg; pH: ∼7.0), 3-aminophenol was supremely removed (97% Ni-Cu oxide > 95% Ni-Cr oxide > 92% Cu-Cr oxide) followed by phenol (95% Ni-Cu oxide > 92% Ni-Cr oxide > 89% Cu-Cr oxide) and 2,4-DNP (91% Ni-Cu oxide > 89% Ni-Cr oxide > 87% Cu-Cr oxide). Results seemed to appear in accordance of highest value of zeta potential, BET surface area and uniform distribution of Ni-Cu oxide. The maximum catalytic degradation of 3-aminophenol among other phenols was credited to its highest basicity. Minor and lesser-toxic metabolites like oxalic acid, benzoquinone, (Z)-hex-3-enedioic acid, (Z)-but-2-enal, (Z)-4-oxobut-2-enoic acid were identified, later undergo mineralization. Overall, green synthesized BMO nanocomposites are cheap, reusable (n = 10) with properties of greater active sites, high surface activity, low band gap with charge separation and semiconducting nature and recommended for bright future of environment.

Chrysene is a high molecular weight polycyclic aromatic hydrocarbon and priority pollutant due to its persistent nature and toxicity. Ecological concern of this emerging contaminant calls for low-cost and efficient removal practices. Recently, doped or coupled nanomaterials with advanced characteristics are fascinating. Therefore, we have synthesized crystalline nanocubes (∼100 nm) of Fe2O3@ZnHCF nanocomposite using plant extract of Azadirachta indica and subsequently used it for degradation of chrysene. Under sunlight, a rapid initial exponential decrease in concentration of chrysene over time revealed high photo-activity of doped Fe2O3@ZnHCF because of remarkably improved surface area (343.436 m2 g−1) and band gap energy (2.18 eV). At optimum catalyst dose (25 mg) and neutral pH photodegradation of chrysene (2 mg L−1) up to 92% followed first order kinetics and Langmuir isotherms. Comparing with constituents, doped nanocubes (Xm = 45.45 mg g−1) were more effective for degradation as revealed by three to six times greater adsorption of chrysene than ZnHCF (Xm = 16.22 mg g−1) and Fe2O3 (Xm = 7.348 mg g−1). Moreover, it reduced the t1/2 value of chrysene (0.54 h) manifolds than that of Fe2O3 (t1/2 = 23.41 h) and ZnHCF (t1/2 = 8.66 h) nanoparticles. GC–MS results revealed the presence of smaller and safer by-products like malealdehyde, propionic acid and but-2-ene-1,2,4-triol that are formed by oxidation of chrysene by OH radical. Catalysts were also found reusable for ten cycles without significant loss in activity. Overall, Fe2O3@ZnHCF nanocubes might be believed to be a promising photocatalyst for environmental protection by virtue of greater active sites, high surface activity, low band gap with charge separation and semiconducting nature.

Herein, a green and facile methodology was used for the structural design of semiconductor nanomaterials and employed as efficient photocatalyst to resolve the environmental issues of water pollutants. Titanium oxide coupled with bismuth oxide (TiO2@Bi2O3) nanocomposite was synthesized by employing the seed extract of Sapindus mukorossi (commonly found plant in India) and subsequently used for the elimination of toxic, and persistence industrial pollutants namely bisphenol A (BPA) and methylene blue (MB). Microscopic and spectroscopic techniques revealed particle size of synthesized nanocomposite found less than 50 nm along with high crystallinity. Appearance of stretching vibrations at 459 cm−1 for Bi–O–Ti in the IR spectra of nanocomposite has established the coupling of TiO2 with Bi2O3. The parameters of degradation were optimized by varying the pollutant concentration, catalytic amount and pH in the presence of natural sunlight. The nanocomposite TiO2@Bi2O3 showed maximum degradation (MB: 94% and BPA: 91%) at a minimum concentration of pollutant (50 mgL−1) with catalyst amount (35 mg), neutral pH and reduces half-life of pollutants (BPA: 1h, MB: 0.5h). Owing of higher surface area (80 m2g-1), lower band gap (2.5 eV), and more negative zeta potential value (−40.3 mV) results into excellent photocatalytic properties. The breakage of S–N conjugated system in MB results into rapid degradation as compare to BPA. The degradation followed first-order kinetics and Langmuir adsorption in both the cases. Presence of active radicals during the photocatalysis process was responsible for quick degradation and strongly supported by scavenger analysis. GC-MS analysis revealed the degradation of toxic pollutants into safer metabolites and finally mineralized. Multiple times (n = 8) reusability of green photocatalyst advocated sustainability and appropriate for industrial applications.

Expanded polystyrene (EPS) is a major component of marine debris globally. Recently, hazardous hexabromocyclododecanes (HBCDDs) were detected in EPS buoys used for aquaculture farming. Subsequently, enrichment of HBCDDs was found in nearby marine sediments and mussels growing on EPS buoys. It was suspected that EPS buoys and their debris might be sources of HBCDDs. To confirm this, the release of HBCDDs from EPS spherules detached from a buoy to seawater was investigated under field (open sea surface and closed outdoor chambers with sun exposure and in the dark) and laboratory (particle-size) conditions. In all exposure groups, initial rapid leaching of HBCDDs was followed by slow desorption over time. Abundant release of HBCDDs was observed from EPS spherules exposed to the open sea surface (natural) and on exposure to sunlight irradiation or in the dark in controlled saline water. Water leaching and UV-light/temperature along with possibly biodegradation were responsible for about 37% and 12% of HBCDDs flux, respectively. Crumbled EPS particles (≤1 mm) in samples deployed on the sea surface for 6 months showed a high degree of weathering. This implies that surface erosion and further fragmentation of EPS via environmental weathering could enhance the leaching of HBCDDs from the surface of EPS. Overall, in the marine environment, HBCDDs could be released to a great extent from EPS products and their debris due to the cumulative effects of the movement of large volumes of water (dilution), biodegradation, UV-light/temperature, wave action (shaking), salinity and further fragmentation of EPS spherules.

Polycyclic aromatic hydrocarbons (PAHs), pervasive and precedence pollutants have potential to decimate the bionetwork and human health. Therefore, photocatalytic degradation of toxic three membered PAHs, namely acenaphthene (ACN), phenanthrene (PHN) and fluorene (FLU) was explored in water and soil. Titanium dioxide based zinc hexacyanoferrate framework (TiO

Nonylphenol (NP) and 2,4-dinitrophenol (2,4-DNP) are causing serious environmental concerns owing to their toxic, carcinogenic, persistentancy and bio-accumulating properties. It has been found that their concentrations are abundant near to industries and in many water bodies due to untreated release. Therefore, their complete removals using low-cost, efficient and environmental friendly techniques from water are required. Sunlight active metal hexacyanocobaltates nanoparticles have been reported beneficial heterogeneous and recoverable catalysts. Therefore, a green route based on utilization of natural material (Azadirachta indica leaf extract) and water was developed for the synthesis of cadmium hexacynocobaltate (CdHCC) and manganese hexacyanocobaltate (MnHCC) nanoparticles. Electron microscopic analysis revealed nanometer range (∼100 nm) for CdHCC and MnHCC particles. Synthesized nanomaterials were employed for the degradation of substituted phenols under direct Sunlight to follow the natural scenario. Maximum degradation of selected phenols (CdHCC- NP: 70 %; 2,4-DNP: 77 %, MnHCC- NP: 90 %; 2,4-DNP: 97 %) required 25 mg of catalyst per 50 mg L−1 of phenols at neutral pH under Sunlight irradiation. This excellent photocatalytic activity of the MnHCC might be due to high surface activity (surface areas of CdHCC and MnHCC were 95 m2 g-1 and 448 m2 g-1, respectively) and particles stability (as observed from zeta potential, CdHCF: -13.5 mV; MnHCF: -19.2 mV). The degradations followed first-order kinetics. Adsorption plots were best fitted with Langmuir isotherm. GC–MS analysis of the final reaction mixtures showed the formation of low molecular weight and safer compounds, which were finally mineralized. Degradation mechanism of NP and 2,4-DNP involved OH radicals based oxidation, hydroxylation, and ring-opening. These materials were found reusable up to ten times revealing sustainability. Overall, these Sunlight responsive novel metal hexacyanocobaltate nanomaterials might be promising and sustainable materials for remediation of environmental contaminants.

Transition metal oxides (TMO) constitute a most amazing class of materials with a wide range of properties and applications; therefore, their synthesis using a green approach is a necessity. As such, sunlight irradiation was employed to synthesize various TMO nanostructures (ZnO, CuO, Co3O4, NiO and Cr2O3) using water as a solvent. Nanoparticles obtained with distinct morphologies, such as nanotubes (ZnO; 86.86% (CuO) > 85.89% (NiO) > 80.35% (Co3O4), depending on the sizes of the respective TMO nanoparticles. This is also supported by the finding of small and non-toxic by-products such as but-2-enal, sulfur trioxide and benzoquinone. With high potential observed in the removal of dyes, TMO nanoparticles have a bright future with respect to their use as important adsorbents in waste water treatment. The advantage of the present work lies in the green synthesis of nanoparticles and their application in helping to make our environment green.

Bisphenol-A (BPA) is an alleged endocrine-disrupter and carcinogen compound. Due to this, complete removal of BPA from environment is highly imperative to protect living organisms. Metallic ferrites have been proven with excellent properties and efficiency in various commercial applications. Therefore, crystalline nanoparticles of size less than 50 nm, of cobalt (CoFe2O4) and zinc (ZnFe2O4) ferrites were fabricated employing leaf-extract of Azarachita indica and water. Both ferrites (20 mg) were found effective in Sunlight assisted photocatalytic removal of 50 mg L−1 of toxic BPA from water at neutral pH. Nanoparticles of ZnFe2O4 showed highest efficiency (92%) followed by CoFe2O4 (89%) than bared ones like Fe2O3 (70%), ZnO (68%) and Co3O4 (54%). Results obtained were in good agreement with uppermost BET surface-area and Zeta-potential value, of uniformly distributed nanoparticles of two ferrites. Calculated band gap energies of ZnFe2O 4 and CoFe2O 4 were, 2.14 eV and 2.42 eV, respectively. GC–MS analysis of reaction mixture revealed the formation of minor and non-toxic metabolites (mass below 100) that finally undergo mineralization. Proposed degradation pathways revealed the role of hydroxyl radical that led to subsequent oxidation and hydrolysis of the BPA. Total organic carbons and scavenger analysis indicated the 58% mineralization after 5 h and involvement of free radical mechanism under direct sunlight. Overall, green synthesized ferrites were found remarkable photocatalysts and reusable (n = 10) with significant retain of activity. Furthermore, such ferrites nanoparticles may be recommended for further treatment of noxious contaminants in view of their large surface area, high charge separation capacity.

Polycyclic aromatic hydrocarbons (PAHs), pervasive and precedence pollutants have potential to decimate the bionetwork and human health. Therefore, photocatalytic degradation of toxic three membered PAHs, namely acenaphthene (ACN), phenanthrene (PHN) and fluorene (FLU) was explored in water and soil. Titanium dioxide based zinc hexacyanoferrate framework (TiO2@ZnHCF) nanocomposite was synthesized via a two step A. indica mediated co-precipitation method. Under sunlight, fall in concentration of PAHs (Water- 93%–96%, soil- 82%–86% and river sediment- 81.63%–85.43%) with time revealed superior activity of nanocomposite (TiO2@ZnHCF) as compared to the bared one. Slower degradation in soil and sediment could be attributed to the reduced diffusion caused by the interaction between the organic content of soil/sediment with PAHs. Doping caused an increase in surface area (118.15 m2g-1) with decrease in band gap energy (1.65 eV) and photoluminescence intensity. PAHs removal (Xm = 9.48 mg g−1 of ACN, 9.35 mg g−1 of PHN and 8.96 mg g−1 of FLU) involved role of “cation- π” interaction with nanocomposite. Besides, it reduced t1/2 values of ACN (1.88 h), PHN (2.09 h) and FLU (2.86 h) and resulted into smaller by-products. Smaller by-products like (Z)-prop-1-ene-1,2,3-triol (m/z = 91) and (E)-3-hydroxyacrylaldehyde (m/z = 71) identified in GC–MS, evidently braced e− excitement from encapsulated nanocatalyst followed by OH (active species) based oxidation of PAHs. Lower photoluminescence intensity indicates the least charge carrier recombination with highest photocatalytic activity of nanocomposites. Inclusive of the present study provides promising photocatalyst with greater surface activity, low quantum yield with charge separation, reusable up to ten cycles deprived of substantial loss of its action and suppressing the cost of process.

Bisphenol-A (BPA) is suspected of been endocrine-disrupter and carcinogen. Hence, removal of extensively used BPA by low-cost and efficient coupled-nanomaterials is viewed as vital to environmental protection. Herein, nanocomposite of ZnO doped with zinc-hexacyanoferrate (ZnO@ZnHCF) was employed for photodegradation of BPA. Green synthesized nanocomposite consisted of ZnO wrapped ZnHCF distorted nanocubes piled together. Under daylight, prompt early exponential decline in concentration over time revealed elevated photo-activity of nanocomposite. Improvement in surface-area (113.491 m2g−1) and band-gap (2.2 eV) of catalyst was resulted from synergism of semiconducting and intercalative feature of ZnO and ZnHCF. At optimum catalyst-dose (25 mg) and neutral pH, photodegradation of BPA (97% of 2 mgL−1) followed first-order-kinetics involving initial Langmuir adsorption isotherms (R2 ≥ 0.996; p ≤ 0.05). Nanocomposites were more effective for greater adsorption of BPA (Xm = 18.0 mg g−1) than the ZnHCF (10.8 mg g−1) and ZnO (3.9 mg g−1). Moreover, doped ZnO@ZnHCF reduced the half-life of BPA upto 2.8 h than that with bared ZnHCF (8 h) and ZnO (17.4 h). GC–MS revealed presence of smaller and safer byproducts clearly supported electron excitement from wrapped-nanocomposite followed by oxidation of BPA with countless OH. Degradation pathways were constructed to track-ways leading to mineralization. Overall, due to greater surface-activity, reusability upto ten-cycles and charge separation (e−+h+ pairs) led to promotion of huge free radicals, ZnO@ZnHCF might be supposed a promising photocatalyst.

Polycyclic aromatic hydrocarbons (PAHs) the ubiquitous, persistent and carcinogenic environmental contaminants have raised concern worldwide. Recently, their removal methodologies are advanced after exploring nanomaterials. Therefore, degradation of selected toxic PAHs (3–5 rings) using potassium zinc hexacyanoferrate (KZnHCF) nanocubes was studied. Highly crystalline and sharp KZnHCF nanocubes (∼100 nm) were obtained by green route using sapindus mukorossi. In both water and soil, anthracene and phenanthrene were degraded to maximum extent (80–93%), whereas, the degradation of fluorene, chrysene and benzo (a) pyrene were ∼70–80%.Because of small size (lower molecular weight), large number of anthracene and phenanthrene molecules were adsorbed on catalyst as compared to other PAHs. Higher degradation of PAHs in water than in the soil is attributed to the easy absorption of PAHs on catalyst in water and slow diffusion of PAHs on organic content of soil. PAHs were degraded at the concentration of 50 mg/L, 25 mg catalyst dose, neutral pH and solar irradiation. Higher proficiency of the catalyst was revealed by degradation of PAHs into small and non-toxic by-products such as malealdehyde, 4-oxobut-2-enoic acid and o-xylene. Overall, the potential KZnHCF nanostructures open future scope for eradication of other pollutants from the environment.

The role of marine plastic debris and microplastics as a carrier of hazardous chemicals in the marine environment is an emerging issue. This study investigated expanded polystyrene (EPS, commonly known as styrofoam) debris, which is a common marine debris item worldwide, and its additive chemical, hexabromocyclododecane (HBCD). To obtain a better understanding of chemical dispersion via EPS pollution in the marine environment, intensive monitoring of HBCD levels in EPS debris and microplastics was conducted in South Korea, where EPS is the predominant marine debris originate mainly from fishing and aquaculture buoys. At the same time, EPS debris were collected from 12 other countries in the Asia-Pacific region, and HBCD concentrations were measured. HBCD was detected extensively in EPS buoy debris and EPS microplastics stranded along the Korean coasts, which might be related to the detection of a quantity of HBCD in non-flame-retardant EPS bead (raw material). The wide detection of the flame retardant in sea-floating buoys, and the recycling of high-HBCD-containing EPS waste inside large buoys highlight the need for proper guidelines for the production and use of EPS raw materials, and the recycling of EPS waste. HBCD was also abundantly detected in EPS debris collected from the Asia-Pacific coastal region, indicating that HBCD contamination via EPS debris is a common environmental issue worldwide. Suspected tsunami debris from Alaskan beaches indicated that EPS debris has the potential for long-range transport in the ocean, accompanying the movement of hazardous chemicals. The results of this study indicate that EPS debris can be a source of HBCD in marine environments and marine food web.

In this study, the fractionation and ecotoxic potential of Cr, Ni, Cu and Pb in water and sediments of the river Yamuna (Delhi stretch) is presented. The river water is used for various purposes such as irrigation, industrial, domestic and drinking. The investigations suggest that the availability of metals in water follows the sequence Ni>Cr>Pb>Cu whereas a different pattern (Pb>Cu>Ni>Cr) is observed in sediments. Statistically significant spatial variations are indicated by two-way ANOVA in different geochemical forms of the metals and physicochemical parameters of water and sediments of the river Yamuna. Principal component analysis (PCA) suggests a similar source for all four metals probably from the sewage from municipal drains. PCA also indicates some independent sources of Cu and Pb. The hot spots were identified using hierarchical cluster analysis considering bioavailable forms of the metals in water and sediments as objects and the sampling sites as variables. Risk assessment code analysi...

Polycyclic aromatic hydrocarbons (PAHs), pervasive plus priority emerging pollutants have the potential to destruct the bionetwork. Therefore, photocatalytic decay of toxic 4- and 5-ring membered PAHs, namely benz[a]anthracene (BaA) and benzo[a]pyrene (BaP), was explored in water. The nanocomposite of zinc hexacyanoferrate encapsulated with zinc oxide (ZnHCF@ZnO) was synthesized by Azadirachta indica mediated co-precipitation under normal conditions. Sunlight exposure caused a quick downfall in the concentration of PAH with composite exposing its eminent photo-activity. Encapsulation resulted in enhanced surface area (113 m2 g−1) and lesser band gap energy (2.2 eV) of nanocomposite owing to the synergism of semiconducting stuff of zinc oxide and intercalative properties of ZnHCF. At neutral pH, photo-degradation of PAHs (2 mg L−1) by optimum dose of catalyst followed first order kinetics and Langmuir isotherms (R2≥0.98; p ≤ 0.05). Slightly lower elimination of BaP (90%) than BaA (93%) might be due to its higher molecular weight and conjugation. Mechanism exploration revealed the involvement of “cation- π” interaction effectively between nanocomposite and PAHs (Xm =25.6 mg/g of BaA and 21.7 mg/g of BaP) than bared (ZnO and ZnHCF). Besides, it compacts the t1/2 value of BaA(0.35 h) and BaP (0.49 h) up to manifolds than its constituents (13–26 h). Smaller by-products like prop-2-en-1-ol, propionic acid and acrylic acid identified in GC MS, clearly supported electron excitement from encapsulated nanocomposite followed by OH (active species)based oxidation of PAHs. Particularly, the mineralization evaluation of PAHs through TOC analysis confirmed its conversion into H2O and CO2. Inclusive of the present study provides promising photo-catalyst with greater surface activity, low quantum yield with charge separation and reusable for ten cycles deprived of substantial loss of its action. Similar studies can be promoted to build up methods that can accurately predict the acceleration in the environment clean up strategies.

Organochlorines (OCs) are the most hazardous class of pesticides, therefore, banned or restricted in several countries. The major sources of OCs include food industries, agriculture and sewage wastes. Their effluents discharged into the water bodies contain extremely high concentration of OCs which ultimately causes environmental concern. Because of their high persistence, toxicity and potential to bioaccumulation, their removal from wastewater is imperative. The degradation techniques are now advanced using nanomaterials of various kinds. During the last few years, nanoparticles such as TiO2 and Fe are found to be excellent adsorbents and efficient photocatalysts for degrading more or less whole OCs as well as their toxic metabolites, which opens the opportunities for exploring various other nanoparticles as well. It is noteworthy that such methodologies are economic, fast and very efficient. In this review, the detailed information on different types of OC pesticides, their metabolites, environmental concern and present status on degradation methods using nanoparticles have been reviewed. An attempt has also been made to highlight the research gaps prevailing in the current research area.

The widespread occurrence of pesticide residues in different agricultural and food commodities has raised concern among the environmentalists and food chemists. In order to keep a proper track of these materials, studies on their decay profiles in the various segments of ecosystem under varying environmental conditions are needed. In view of this, the metabolites of quinalphos in water and soil under controlled conditions and in plants, namely tomato and radish in field conditions have been analysed and possible pathways suggested. In order to follow the decay of the pesticide, an HPLC procedure has been developed. Studies conducted in water at different temperatures, pH and organic content reveal that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH is more or less apparent on a similar line. On an average a faster decay is observed in the case of plants than in water and soil. The decay profiles in all these cases follow first order kinetics. The metabolites were identified by GC-MS. The investigations reflect that degradation occurs through hydrolysis, S-oxidation, dealkylation and thiono-thiol rearrangement. The pathways seem to be complex and different metabolites were observed with the change in the matrix. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and quinoxaline-2-thiol were observed in all the matrices. Results further indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than parent compound, persist for a longer time.