Synthesis and characterization of novel guar gum based waste material derived nanocomposite for effective removal of hexabromocyclododecane and lindane.

Herein, efficient degradation of hexabromocyclododecane (HBCD) and Lindane, a persistent organic pollutant using guar gum based calcium oxide doped silicon dioxide (GG-CaO@SiO2) has been reported. The nanocomposite was prepared by waste egg shell (CaO) and rice husk (SiO2) was well characterized. The maximum degradation of HBCD and Lindane were observed at 8 mg catalyst loading, neutral pH, and 2 mg L-1 of pollutant amount. The photocatalytic performance of GG-CaO@SiO2 for HBCD and Lindane photodegradation was evaluated, and it was found that the rate constant increased in the order of GG-CaO@SiO2 > CaO@SiO2 > GG. The polymeric GG-CaO@SiO2 nanocomposite showed maximum removal of both pollutants due to higher surface area (70 m2 g-1) and synergistic interactions among GG moieties. It achieved HBCD and Lindane elimination rates of 94 % and 90 % by photo-adsorptive degradation within 150 min. Meanwhile, the leaching of HBCD from expanded polystyrene (EPS) materials (0.14 ± 0.05 ppm) underwater with different time intervals and degradation of leachate HBCD were also assessed. The eradication of the pollutant manifested first-order kinetics, with the Langmuir adsorption. LC-MS analysis confirmed that GG-CaO@SiO2 effectively breaks down complex structure toxic pollutants into safer metabolites under natural sunlight exposure. The polymeric GG-CaO@SiO2 nanocomposite showed notable reusability up to ten cycle promotes sustainability.

Recent updates on remediation approaches of environmentally occurring pollutants using visible light-active nano-photocatalysts.

Photocatalysis emerges as a potential remedy for the issue of an unreliable light source. Recognized as the most dependable and potent energy source sustaining life on Earth, sunlight offers a promising solution. Sunlight is abundant and free, operational costs associated with running photocatalytic system using nanoparticles are often lower compared to system relying on artificial light source. The escalating problem of water pollution, particularly in highly industrialized nations, necessitates effective wastewater treatment methods. These methods aim to combat elevated pollution levels, encompassing pharmaceuticals, dyes, flame retardants, and pesticide components. Advanced oxidation processes within photocatalytic wastewater treatment exhibit substantial promise for removing complex organic pollutants. Doped nanomaterials, with their enhanced properties, enable efficient utilization of light. Coupled nanomaterials present significant potential in addressing both water and energy challenges by proficiently eliminating persistent pollutants from environment. Photocatalysis when exposed to sunlight can absorb photons and generate e- h + pairs. This discussion briefly outlines the wastewater treatment facilitated by interconnected nanomaterials, emphasizing their role in water-energy nexus. In exploring the capabilities of components within a functional photocatalyst, a comprehensive analysis of both simple photocatalysts and integrated photocatalytic systems is undertaken. Review aims to provide detailed explanation of the impact of light source on photon generation and significance of solar light on reaction kinetics, considering various parameters such as catalyst dosage, pH, temperature, and types of oxidants. By shedding light on these aspects, this review seeks to enhance our understanding of intricate processes involved in photocatalysis and its potential applications in addressing contemporary environmental challenges.

Green construction of biochar@NiFe2O4 nanocomposite for highly efficient photocatalytic remediation of pesticides from agriculture wastewater.

The world's attention is drawn to the widespread ingestion, toxicity, and bioaccumulation of the Atrazine (AT) and Endosulfan (ES). Pesticides have been proven to have endocrine-disrupting, genotoxic, and persistent characteristics. In this work, the structural design of green synthesized NiFe2O4 is incorporated in rice husk biochar to form BC@NiFe2O4 nanocomposite. Powder X-ray diffraction and microscopic analysis confirmed the semi-crystalline nature of BC@NiFe2O4 reduced due to the incorporation of amorphous BC. The green BC@NiFe2O4 nanocomposite degraded AT and ES up to 98 % and 92 %, respectively. The maximum degradation achieved by BC@NiFe2O4 nanocomposite with minimum pollutants concentration (50 mg L-1) with 10 mg catalyst dose at acidic pH in natural sunlight because of the higher negative value of zeta potential (-26.4 mV) and lower band gap (2.5 eV). The degradation process involves first-order kinetics followed by initial Langmuir adsorption. The presence of various radical quenchers (t-BuOH, p-BZQ, Na2EDTA) has led to the conclusion that hydroxyl radicals play a significant role in the degradation of the toxic substances AT and ES. Additionally, a green-fabricated BC@NiFe2O4 nanocomposite has exhibited exceptional efficiency in degrading AT and ES pollutants in actual wastewater samples. Furthermore, this nanocomposite has demonstrated outstanding sustainability and cost-effectiveness, maintaining its effectiveness for up to eight cycles without a noticeable reduction in activity. In summary, due to its favorable surface characteristics, the environmentally friendly BC@NiFe2O4 nanocomposite holds excellent promise as a unique and potential photocatalyst for various industrial applications.

One pot green synthesis of Al doped zinc ferrite nanoparticle decorated with reduced graphene oxide for photocatalytic remediation of organic pollutants: Green synthesis, kinetics, and photoactivity.

The world is drawn to the widespread use, toxicity, and bioaccumulation of the Atrazine (AT) and Auramine O (AO). Pesticides and dyes also have endocrine disruptors, genotoxic and persistent properties. Therefore, the photodegradation of AT and AO in water was investigated. Herein, the structural design of Al-ZnFe2O4 incorporated in rGO nanocomposite has been synthesized via facile precipitation and green synthesis methodology. PXRD and microscopic analysis confirmed the reduced crystallinity nature of Al-ZnFe2O4 due to the incorporation of amorphous rGO. The green Al-ZnFe2O4@rGO nanocomposite (AT: 90%; AO: 95%) showed maximum degradation as compared to native nanoparticles with minimum pollutants concentration of 10 mg catalytic dose at neutral pH in sunlight irradiation due to negative zeta potential (-36.0 mV), higher surface area (163 m2g-1) and tailored band gap (2.1 eV). First-order kinetics followed by initial Langmuir adsorption constituted the degradation process. The presence of different radical quenchers (t-BuOH, p-BZQ, Na2EDTA) concluded that hydroxyl radical plays a significant role in the degradation of toxic AT and AO. Green fabricated Al-ZnFe2O4@rGO also showed excellent efficiency for the degradation of AT and AO pollutant in real wastewater sample. Nanocomposite demonstrated remarkable sustainability and cost-effectiveness by remaining effective for up to nine cycles without experiencing any appreciable activity reduction. Due to its favorable surface features, Al-ZnFe2O4@rGO nanocomposite made via green process is a unique and potential photocatalyst for industrial applications.

Efficient photo-adsorptive eradication of endocrine disrupting pesticides by chitosan co- decorated metal oxide bio-nanocomposite.

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, which respectively confirm the coupling. Chitosan-NiO@ZnO and individual 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.

An updated review on environmental occurrence, scientific assessment and removal of brominated flame retardants by engineered nanomaterials.

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.

Efficient removal of plastic additives by sunlight active titanium dioxide decorated Cd-Mg ferrite nanocomposite: Green synthesis, kinetics and photoactivity.

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 (CdMgFe2O4@TiO2) was synthesized by using plant extract of M. koenigii via co-precipitation. Sharp peaks obtained in PXRD ensured high crystallinity and purity of distorted spherical nanocomposite (5-25 nm). Subsequently, CdMgFe2O4@TiO2 nanocatalyst was evaluated for the effective elimination of plastic additives at variable reaction parameters (pollutant: 2-10 mgL-1; catalyst: 5-25 mg; pH: 3-7, dark-sunlight). With 20 mg of catalytic dose, CdMgFe2O4@TiO2 showed maximum degradation of 2 mgL-1 of TBBPA (91%) and BPA (94%) at neutral pH under sunlight. Considerable reduction in persistence of TBBPA (t1/2:2.4 h) and BPA (t1/2:2.1 h) indicated admirable photoactivity of CdMgFe2O4@TiO2. Results were supported by BET, zeta potential, band reflectance and photoluminescence analysis that indicated for higher surface area (90 m2g-1), larger particle stability (-20 mV), lower band gap (1.9 eV) and inhibited charge-pairs recombination in nanocomposite. Degradation consisted of initial Langmuir-adsorption followed by first order kinetics. Scavenger analysis revealed the role of hydroxyl radical in photodegradation studies. Nanocomposite was effective up to eight cycles without any significant loss of activity that advocated its high-sustainability and cost-effectiveness. Overall, with excellent surface characteristics, green synthesized CdMgFe2O4@TiO2 nanocomposite is a promising and alternative photocatalyst for industrial applications.

Efficient degradation of organic pollutants by novel titanium dioxide coupled bismuth oxide nanocomposite: Green synthesis, kinetics and photoactivity.

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.

Sunlight-induced photocatalytic degradation of organic pollutants by biosynthesized hetrometallic oxides nanoparticles.

Dyes and phenols are extensively used chemicals in petrochemicals, pharmaceuticals, textile, and paints industries. Due to high persistence, bioaccumulation, and toxicity, their removal from the environment is highly imperative by advanced techniques. Single metal oxide nanomaterials are generally associated with limitations of large bandgap (> 3eV) and charge recombination. Therefore, heterometallic oxides (HMOs) as CuFe2O4, CuMn2O4, and MnZn2O4 have been synthesized via green route by employing leaf extract of Azadirachta indica. XRD revealed the crystalline nature of HMOs nanospheres with particle size less than 100 nm. Subsequently, HMOs nanocatalysts were used as photocatalyst for removal of 3-amino phenols (3-AP) and eriochrome black T (EBT) from water under sunlight. Reaction parameters namely pollutant concentration (50-130 mgL-1), catalyst dose (20-100 mg), and pH (3-11) were optimized in order to get best results. Substantial degradation (80-95%) of pollutants (50 mgL-1) by HMOs (80 mg) was achieved at neutral pH under sunlight exposure. Highest removal by CuFe2O4 might be due to its high surface area (35.7 m2g-1), low band gap (2.4 eV), larger particle stability (Zeta potential: -22.0 mV), and lower photoluminescence intensity. Sharp declines in curves were visually confirmed by color change and indicated for first-order kinetics of degradation with initial Langmuir adsorption. Spectrophotometric analysis revealed that half-life (t1/2) of 3-AP (0.9-1.7 h) and EBT (0.6-0.8 h) were significantly reduced. Faster degradation of EBT than 3-AP was because of less electronegative N-atom at the diazo group. Scavenger analysis indicated the presence of active radicals in photo-catalytic degradation of 3-AP and EBT. All HMOs have shown high reusability (n=8) which ensures their stability, sustainability, and efficiency. Overall, green synthesized HMOs nanoparticles with prominent surface characteristics offer a viable alternative photocatalyst for industrial applications.

Green synthesis of sunlight responsive zinc oxide coupled cadmium sulfide nanostructures for efficient photodegradation of pesticides.

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.

Insight in to sunlight-driven rapid photocatalytic degradation of organic dyes by hexacyanoferrate-based nanoparticles.

Release of colouring agents into the environment alarms the need to design a cheap, quick and safe process. Owing to environmental safety concern, synthesis of two metal hexacyanoferrates (MHCFs) based on cadmium (CdHCF) and manganese (MnHCF) was carried out using natural plant extract of Azadirachta indica and water as a solvent. Synthesized MHCFs were utilized for the removal of an acid dye (fuchsin acid, FA) and a xanthenes dye (rhodamine B, RB). The reactions were optimized at various conditions of dye concentration, catalyst dose, reaction pH, time and source of light. The MHCFs showed excellent results with both the dyes within very limited span of time (2 h). Consequently, 98% of FA and 97% of RB were degraded with 10 mg of CdHCF, at neutral pH and under sunlight. The degradation process followed the first-order reaction kinetics having t1/2 around 0.3 min. The MHCFs exhibited difference of only little percentage in degradation owing to a very slight difference between their surface areas (CdHCF: 54.1 m2 g-1; MnHCF: 49.7 m2 g-1). The synthesised nanocatalysts were stable as indicated by their higher negative zeta potential values. The adsorption of dyes was found to be maximum with CdHCF having Xm value 19.69 mg g-1 and 18.15 mg g-1 for FA and RB, respectively. Photocatalytic degradation involved the main role of hydroxyl radical as indicated by decline in activity of nanocatalyst in the presence of scavengers. All in all, this study presents highly active nanomaterials with higher surface area, stability and semiconducting properties under natural conditions.

Synergistic effects of zinc oxide coupled copper hexacyanoferrate nanocomposite: Robust visible-light driven dye degradation.

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.

Synergic effect of Guggul gum based hydrogel nanocomposite: An approach towards adsorption-photocatalysis of Magenta-O.

The article is related to sunlight and UV-visible mineralization of harmful magenta-O (FB) dye. The nanocomposite used is a cross linked network of acrylic acid synthesized inside poly(acrylamide) grafted Guggul gum in the presence of UV-visible respondent bismuth ferrite nanoparticles. The synthesis of poly(acrylamide) grafted Guggul gum (Sample I) and synthesizing a crosslinked network inside it (Sample II) involved a two-step synthesis for optimizing various reaction parameters. The maximum % water uptake obtained for polymeric samples I and II was calculated as 1227.78% and 387.97%, respectively. Average particle size of bismuth ferrite nanoparticles was 47.34 nm. The nanocomposite could maximum uptake-mineralize FB dye as 97.3% and 98.8% under sunlight and photochemical reactor, respectively for 500 mg nanocomposite dose in 10 mg/L concentrated FB solution. Dye uptake occurs through ionic interactions. However, mineralization is a consequence of advanced oxidation process involving free radical species (OH and O2-.). The overall process of uptake-mineralization resembled second order kinetics and Langmuir theorem (monolayer adsorption). Intraparticle diffusion model gave an idea about the multistep (three steps) process of adsorption. Physico-chemical properties of FB dye got changed after mineralization except for the pH. The maximum uptake-mineralization was observed to be 76.2% after consecutive reuse of the nanocomposite hydrogel for five cycles.

Degradation of tricyclic polyaromatic hydrocarbons in water, soil and river sediment with a novel TiO2 based heterogeneous nanocomposite.

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.

Mineralization of carcinogenic anthracene and phenanthrene by sunlight active bimetallic oxides nanocomposites.

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.

One-pot green synthesis of polymeric nanocomposite: Biodegradation studies and application in sorption-degradation of organic pollutants.

The research work proposes the synthesis of a nanocomposite hydrogel which is a dual combination of binary interpenetrating network (BIPN) and bismuth ferrite nanoparticles. BIPN synthesized from binary graft copolymer (BGC) used as starting material. The cross-linked network of BGC is interpenetrating the newly synthesized cross-linked network of poly(acrylic acid) and the product is named as BIPN. Binary graft copolymer had been synthesized from grafting of guggul aqueous extract with copolymeric chains of acrylamide (primary monomer) and acrylic acid (secondary monomer) crosslinked by N,N'-methylene bisacrylamide (MBA). The maximum percentage swelling was evaluated for BGC through optimization of various reaction parameters: amount of water, binary ratio of acrylamide to acrylic acid, concentrations of MBA, ammonium persulphate, pH, temperature and time. Considering pre-optimized parameters for BGC synthesis, BIPN formation required optimization of only acrylic acid. Maximum percentage swelling obtained was 1497.79% and 308.15% for BGC and BIPN, respectively. Maximum percentage biodegradation of 90.64% and 82.38% were calculated for BGC and BIPN, respectively using composting method. Degradation efficiency of brilliant blue (BB) and fuchsin basic (FB) dyes was in the order: Nanocomposite ≫ BIPN > BGC. Maximum percentage degradation observed in case of nanocomposite was 94.1% and 99.3% in sunlight for BB and FB, respectively. The interaction of dyes with the nanocomposite involved mainly ionic interactions. The adsorption models Freundlich and Langmuir were applicable to overall adsorption and degradation process of BB and FB, respectively. Maximum adsorption capacities corresponding to minimum concentration i.e. 10 mg L-1 for BB and FB were calculated as 0.409 mg g-1 and 0.439 mg g-1, respectively. Second order and first order kinetics were found to be suitable for BB and FB adsorption-degradation pathways, respectively. Intraparticle diffusion mechanism was favorable to both dyes and adsorption followed three steps. Gas chromatography coupled with mass spectrometric analysis could give the degraded products which was helpful in drawing degradation pathway. The degradation process involved active radical species (O2-., OH.) and they carry out oxidation-reduction reactions on dyes to give decolorized solution containing mineral ions.

Insight in to the degradation of bisphenol A by doped ZnO@ZnHCF nanocubes: High photocatalytic performance.

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.

Promoting sun light-induced photocatalytic degradation of toxic phenols by efficient and stable double metal cyanide nanocubes.

Aromatic substituted phenols and their by-products discharged from numerous industries are of environmental concern due to their toxic, carcinogenic, recalcitrant, and bioaccumulating properties. Therefore, their complete removal from waters by low-cost, efficient, environmentally friendly nanomaterial-based treatment techniques is desirable. Double metal cyanide complexes (DMCC) are the extremely useful heterogeneous and recoverable catalyst. Hence, green route has been developed for several DMCC and their photocatalytic efficiency was evaluated for degradation of toxic phenols. Herein, nanocubes for hexacyanocobaltate of iron (FeHCC ~ 200 nm), nickel (NiHCC < 10 nm), and zinc (ZnHCC ~ 500 nm) were synthesized after employing Aegle marmelos. Subsequently, at neutral pH and sunlight irradiation, 15 mg of catalysts were able to degrade the maximum extent of phenols (1 × 10-4 M) in the order: 3-aminophenol (96% ZnHCC > 94% FeHCC > 93% NiHCC) > phenol (94% ZnHCC > 92% FeHCC > 91% NiHCC) > 2,4-DNP (92% ZnHCC > 91% FeHCC > 90% NiHCC). This is attributed to highest basicity of 3-aminophenol containing excess of free electrons. Highest catalytic potential of ZnHCC (Xm = 0.54-0.43 mg/g) is because of its highest surface area and negative zeta potential along with sharp morphology and crystallinity. Adsorption of phenols over catalyst was statistically significant with Langmuir isotherms (R2 ≥ 0.96; p value ≤ 0.05). Small and non-toxic by-products like oxalic acid, benzoquinone, (Z)-hex-3-enedioic acid, (Z)-but-2-enal, and (Z)-4-oxobut-2-enoic acid were identified in GC-MS. Degradation modes involving hydroxylation, oxidative skeletal rearrangement, and ring opening clearly supported enhanced oxidation of phenols by •OH. Overall, due to greater active sites, high surface activity, low band gap, and semiconducting nature, DMCC revealed promising potential for solar photocatalytic remediation of wastewater.

Removal of chlorpyrifos, thiamethoxam, and tebuconazole from water using green synthesized metal hexacyanoferrate nanoparticles.

The low-cost and highly efficient pesticides are largely used in residential, agricultural, and commercial applications. Their prevalent occurrence, bioaccumulation, and chronic toxicity to living beings have raised environmental concern and call for their whole eradication, especially from water. By virtue of semiconducting nature and high surface area, nanomaterials have become efficient adsorbent and photocatalyst in removal of toxins. To confirm this, the potential of highly crystalline metal hexacyanoferrates (MHCFs) of Zn, Cu, Co, and Ni was evaluated in deprivation of selected hazardous pesticides, viz., chlorpyrifos (CP), thiamethoxam (TH), and tebuconazole (TEB). Sharp nanocubes of ZnHCF (~ 100 nm), distorted nanocubes of CuHCF (~ 100 nm), and nanospheres of CoHCF and NiHCF (< 10 nm) were synthesized via green route using Sapindus mukorossi (raw ritha). At 50 mg L-1 of pesticide, 15 mg of MHCF photocatalyst, neutral pH and sunlight irradiation, selected agrochemicals were degraded to maximum extent (91-98%) by ZnHCF followed by CuHCF (85-91%), NiHCF (73-85%), and CoHCF (70-83%). This might be because of highest zeta potential and BET surface area of ZnHCF. The highest adsorption of CP (83-98%) followed by TH (76-95%) and TEB (70-91%) on acidic surface of catalysts might be related to access of free electrons in their structures. On treatment with MHCF photocatalyst, targets underwent mineralization along with formation of some minor and non-toxic by-products such as (Z) but-2-enal, 3-aminopropanoic acid, and pyridin-3-ol, identified after mass spectrometric analysis of reaction mixture. Based on them, degradation pathways have been proposed to reveal the potential of MHCF for solar photocatalytic removal of organic pollutants in environment.

Degradation of toxic PAHs in water and soil using potassium zinc hexacyanoferrate nanocubes.

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.