The mechanism for degrading Orange II based on adsorption and reduction by ion-based nanoparticles synthesized by grape leaf extract

Photo-Oxidation of Organic Dye by Fe2O3 Nanoparticles: Catalyst, Electron Acceptor, and Polyurethane Membrane (PU-Fe2O3) Effects

The textile industry’s discharges have long been regarded as severe water pollution. The photocatalytic degradation of dyes using semiconductors is one of the crucial methods. The present study efficiently used the mechanical method to synthesize Iron oxide Nanoparticles. XRD, FT-IR, UV-Vis DRS, and Raman analyses were performed to analyze the structural and optical. From the data provided by XRD and Raman data, we believed that the as-synthesized Iron oxide was pure hematite (α-Fe2O3) with a hexagonal structure. Additionally, the EDS results show that the synthesized material is pure. By adjusting specific parameters, including the dye concentration, the catalyst dosage, the pH, and the oxidizing agent such as H2O2 and K2S2O8, the degradation of eosin yellowish using Fe2O3 as a photocatalyst has been discussed. Additionally, the kinetics of eosin yellowish degradation has been studied. A study was also conducted using Fe2O3 nanoparticles attached to polyurethane polymer (PU) to investigate its photocatalytic activity on methylene blue, methyl orange, and indigo carmine. In 30 minutes, nearly 90% of the dyes had degraded. The total organic carbon (TOC) analysis confirmed this result.

Nanomaterials as a Sustainable Choice for Treating Wastewater: A Review

The removal of dyes from textile effluents utilizing advanced wastewater treatment methods with high efficiency and low cost has received substantial attention due to the rise in pollutants in water. The purpose of this work is to give a comprehensive analysis of the different treatments for removing chemical dyes from textile effluents. The capability and potential of conventional treatments for the degradation of dyeing compounds in aqueous media, as well as the influence of multiple parameters, such as the pH solution, initial dye concentration, and adsorbent dose, are presented in this study. This study is an overview of the scientific research literature on this topic, including nanoreductive and nanophotocatalyst processes, as well as nanoadsorbents and nanomembranes. For the purpose of treating sewage, the special properties of nanoparticles are currently being carefully researched. The ability of nanomaterials to remove organic matter, fungus, and viruses from wastewater is another benefit. Nanomaterials are employed in advanced oxidation techniques to clean wastewater. Additionally, because of their small dimensions, nanoparticles have a wide effective area of contact. Due to this, nanoparticles' adsorption and reactivity are powerful. The improvement of nanomaterial technology will be beneficial for the treatment of wastewater. This report also offers a thorough review of the distinctive properties of nanomaterials used in wastewater treatment, as well as their appropriate application and future possibilities. Since only a few types of nanomaterials have been produced, it is also important to focus on their technological feasibility in addition to their economic feasibility. According to this study, nanoparticles (NPs) have a significant adsorption area, efficient chemical reactions, and electrical conductivity that help treat wastewater effectively.

Fe3N nanoparticles embedded in N-doped porous magnetic graphene for peroxymonosulfate activation: Radical and nonradical mechanism

The persistence of pharmaceutical and personal care products (PPCPs) such as norfloxacin (NFX) poses a serious threat to the water environment, and the development of efficient and cost-effective advanced oxidation catalysts is an important step toward resolving this issue. Herein, Fe and N co-doped graphene (FeNGO) was synthesized from graphene oxide (GO), urea, and iron salt via simple impregnation pyrolysis, and applied for activating peroxymonosulfate (PMS) to degrade NFX. FeNGO possessed a two-dimensional porous sheet structure and was rich in defects, nitrogen species, and active sites. Compared with the control catalyst doped with N or Fe alone, FeNGO/PMS system showed the best degradation performance with 97.7% removal of NFX after 30 min, the rate constant was 7.1 and 1.7 times than that for NGO and FeGO, respectively. Fe₃N was the main active site of FeNGO, and it is confirmed that singlet oxygen (¹O₂) and superoxide radical (O₂^•-) were the primary oxidation active species (ROS) during NFX degradation. The formation of ¹O₂ came from the transformation of O₂^•- and PMS decomposition. FeNGO showed strong pH adaptability, and also exhibited stale degradation performance in saliferous water matrices. It is believed that this work will offer theoretical and practical guidance for PMS activation by non-radical pathways.

Recent advances on botanical biosynthesis of nanoparticles for catalytic, water treatment and agricultural applications: A review

Green synthesis of nanoparticles using plant extracts minimizes the usage of toxic chemicals or energy. Here, we concentrate on the green synthesis of nanoparticles using natural compounds from plant extracts and their applications in catalysis, water treatment and agriculture. Polyphenols, flavonoid, rutin, quercetin, myricetin, kaempferol, coumarin, and gallic acid in the plant extracts engage in the reduction and stabilization of green nanoparticles. Ten types of nanoparticles involving Ag, Au, Cu, Pt, CuO, ZnO, MgO, TiO₂, Fe₃O₄, and ZrO₂ with emphasis on their formation mechanism are illuminated. We find that green nanoparticles serve as excellent, and recyclable catalysts for reduction of nitrophenols and synthesis of organic compounds with high yields of 83-100% and at least 5 recycles. Many emerging pollutants such as synthetic dyes, antibiotics, heavy metal and oils are effectively mitigated (90-100%) using green nanoparticles. In agriculture, green nanoparticles efficiently immobilize toxic compounds in soil. They are also sufficient nanopesticides to kill harmful larvae, and nanoinsecticides against dangerous vectors of pathogens. As potential nanofertilizers and nanoagrochemicals, green nanoparticles will open a revolution in green agriculture for sustainable development.

Novel sodalite stabilized zero-valent iron for super stable and outstanding efficiency in activating persulfate for organic pollutants fast removal

In this study, novel porous sodalite (SOD) was synthesized through Reactive Oxidation Species (ROS) route from industrial waste lithium silicon fume (LSF) to stabilize nZVI (SOD@nZVI), and used as an outstanding persulfate (PS) activator for efficient organic degradation. Characterization results revealed nZVI evenly distributed on SOD via ion-exchange, and the fabricated SOD@nZVI exhibited high stability and superior reactivity over a wide pH range of 2-12 during oxidation reaction. The mechanism responsible for fast organic degradation in the SOD@nZVI+PS system was carefully investigated, and weak magnetic field (WMF) and friction were found to contribute to improved SOD@nZVI performance. The fast redox cycle of Fe²⁺/Fe³⁺ on SOD@nZVI can be stimulated by changing the mixing condition and altering the friction layer to harvest mechanical energy during the reaction, which can maximum persulfate activation to generate more reactive radicals for organic fast degradation. This study is of great significance, as it offers a practical route turning waste into excellent PS activator for in-situ organic pollution remediation, as well as proposing a new idea to maximum PS activation performance by manipulating the inner lining of reactor.

Nanomaterials: An alternative source for biodegradation of toxic dyes

Environment contamination is a colossal worriment across the world, owing to its detrimental and negative impact on health and ecological systems. Dyes are one of the synthetic organic chemicals that are utilised in a variety of fields, including textiles. As a result, throughout one's production and subsequently in fibre colouring, these are becoming frequent industry-contributed contaminants. Increasing globalisation of international market has presented a problem to textile sector in terms of consistency and production. Textile processors' primary concern, as the highly competitive environment and environmental standards grow more severe is about being mindful of the grade of goods and even non-toxicity of their production processes. There seems to be an immediate necessity to look for methods and technologies which are useful in removing dye colours. Even though each has benefits and weaknesses, many physical, chemical, and biological approaches were explored and used with the application being dependent on the effluent properties, technical feasibility, and cost. Several remediation technologies are already developed, but they seem to be ineffective at removing dyes completely. There is a fast growth of nanoparticles applications in the past few years which has opened up newer, innovating, highly efficient, and low-cost dyes remediation systems. Nanomaterials with large surface areas change surface characteristics and distinctive electron conducting capabilities which make them ideal candidate for the treatment of wastewater that contains dyes. In this review, we have highlighted not only the role of nanotechnology in dye remediation processes but also different types of nanomaterials that can be used for the remediation of dyes.

Green Synthesis of Gold, Silver, and Iron Nanoparticles for the Degradation of Organic Pollutants in Wastewater

The green synthesis of nanoscale materials is of special interest to researchers all over the world. We describe a simple, robust, inexpensive, and environmentally friendly approach to the synthesis of gold, silver, and iron nanoparticles using a variety of biomolecules/phytochemicals as potential reducers and stabilizers. The green approach to the controlled synthesis of nanoparticles with different morphologies is based on the use of plant extracts. Green synthesized nanoparticles can be used as catalysts, photocatalysts, adsorbents, or alternative agents for the elimination of various organic dyes. The kinetic enhancement of nanoparticles for the degradation/removal of dyes could provide significant and valuable insights for the application of biochemically functionalized nanoparticles in engineering. In this review, current plant-mediated strategies for preparing nanoparticles of gold, silver, and iron are briefly described, and morphologically dependent nanoparticles for the degradation of organic pollutants in wastewater are highlighted. Overall, the approach presented in the article supports environmental protection and is a promising alternative to other synthesis techniques.

Antioxidant Capacity Assessment of Plant Extracts for Green Synthesis of Nanoparticles

In this work, water extracts from different bio-based products of plant origin were studied to evaluate their antioxidant capacity and their potential to form metal nanoparticles from aqueous solutions. Two traditional tests, the Folin–Ciocalteu assay and the DPPH radical scavenging capacity method were compared with a more recent one, SNPAC, based on the formation of silver nanoparticles. The silver nanoparticle antioxidant capacity method (SNPAC) was optimized for its application in the characterization of the extracts selected in this work; kinetic studies and extract concentration were also evaluated. The extracts were obtained from leaves of oak, eucalyptus, green tea, white and common thyme, white cedar, mint, rosemary, bay, lemon, and the seaweed Sargassum muticum. The results demonstrate that any of these three methods can be used as a quick test to identify an extract to be employed for nanoparticle formation. Additionally, we studied the synthesis of Cu, Fe, Pb, Ni, and Ag nanoparticles using eucalyptus extracts demonstrating the efficiency of this plant extract to form metallic nanoparticles from aqueous metal salt solutions. Metal nanoparticles were characterized by transmission electron microscopy and dynamic light scattering techniques.

Facile one step green synthesis of iron nanoparticles using grape leaves extract: textile dye decolorization and wastewater treatment

The existing knowledge on the reactivity of green iron particles on textile dye and wastewater decolorization is very limited. In this study, the potential of green iron particles synthesized using grape leaves extract on reactive dye (reactive red 195, reactive yellow 145, reactive blue 4 and reactive black 5) decolorization were investigated. 95-98% of decolorization was achieved for all reactive dyes at 1.4-2.0 g/L of green iron. Maximum decolorization was attained at lower dye concentration and showed very little impact on decolorization when pH was increased from 3 to 11. The pseudo-first-order fit confirms the reaction between iron particles and dye molecules with rate constant 0.317-0.422 and it is followed by adsorption, data fit with pseudo-second-order model. Hence, not only adsorption but also the reduction process is involved in the reactive dye decolorization. Benzene, phenyl sodium, 2-chloro-1,3,5-triazine, naphthalene, sodium benzene sulfonate, benzene 1,2 di amine, anthracene-9,10 dione, aniline, phenol, benzene sulfonic acid were the major intermediates detected in dye decolorization and the respective reaction pathway is proposed. Green iron from grape leaves extract demonstrated better performance and it is recognized as the promising cost-effective material for textile wastewater treatment.

Mechanisms of persulfate activation on biochar derived from two different sludges: Dominance of their intrinsic compositions

Sludge-derived biochar (SDBC) has been regarded as persulfate (PS) activator during the remediation of organic contamination. However, the complexity of sludge composition makes it difficult to predict the activity of SDBC and the efficacy of PS. To improve the understanding of how the composition of sludge regulated activity of its parent SDBC towards PS activation, we used two SDBCs derived from different sludges with significantly different organic compositions and metals. Results indicated the higher content of organic and nitrogen content in sludge led to higher polymerization and condensation of carbon layer and more moieties in SDBC1, whereas more Fe species (e.g. Fe-O, Fe²⁺ and Fe³⁺) formed in SDBC2. According to the results of phenol (PN) degradation in SDBC/PS, the apparent rate constants (k_obs) of SDBC2-700 (0.0037 min^-1) was 2 folds higher than that of SDBC1-700 (0.0016 min^-1), whereas the SDBC1-500 (6.0 ×10^-4 min^-1) exhibited higher k_obs than that of SDBC2-500 (4.9 ×10^-4 min^-1). The difference of PS activation by different SDBCs mainly relied on generated reactive oxygen species (ROS). The persistent free radicals (PFRs) and Fe species acted as redox sites for generated ROS, which were depended on the organic compositions and involved metals in used sludges.

Antimonate sequestration from aqueous solution using zirconium, iron and zirconium-iron modified biochars

Antimony (Sb) is increasingly being recognized as an important contaminant due to its various industrial applications and mining operations. Environmental remediation approaches for Sb are still lacking, as is the understanding of Sb environmental chemistry. In this study, biosolid biochar (BSBC) was produced and utilized to remove antimonate (Sb(V)) from aqueous solution. Zirconium (Zr), Zirconium-iron (Zr-Fe) and Fe-O coated BSBC were synthesized for enhancing Sb(V) sorption capacities of BSBC. The combined results of specific surface area, FTIR, SEM-EDS, TEM-EDS, and XPS confirmed that Zr and/or Zr-Fe were successfully coated onto BSBC. The effects of reaction time, pH, initial Sb(V) concentration, adsorbate doses, ionic strength, temperature, and the influence of major competitive co-existing anions and cations on the adsorption of Sb(V) were investigated. The maximum sorption capacity of Zr-O, Zr-Fe, Zr-FeCl3, Fe-O, and FeCl3 coated BSBC were 66.67, 98.04, 85.47, 39.68, and 31.54 mg/g respectively under acidic conditions. The XPS results revealed redox transformation of Sb(V) species to Sb(III) occurred under oxic conditions, demonstrating the biochar's ability to behave as an electron shuttle during sorption. The sorption study suggests that Zr-O and Zr-O-Fe coated BSBC could perform as favourable adsorbents for mitigating Sb(V) contaminated waters.

Sustainable Synthesis of Nanoscale Zerovalent Iron Particles for Environmental Remediation

Nanoscale zerovalent iron (nZVI) particles represent an important material for diverse environmental applications because of their exceptional electron-donating properties, which can be exploited for applications such as reduction, catalysis, adsorption, and degradation of a broad range of pollutants. The synthesis and assembly of nZVI by using biological and natural sustainable resources is an attractive option for alleviating environmental contamination worldwide. In this Review, various green synthesis pathways for generating nZVI particles are summarized and compared with conventional chemical and physical methods. In addition to describing the latest environmentally benign methods for the synthesis of nZVI, their properties and interactions with diverse biomolecules are discussed, especially in the context of environmental remediation and catalysis. Future prospects in the field are also considered.

Efficient removal of acid orange 7 using a porous adsorbent-supported zero-valent iron as a synergistic catalyst in advanced oxidation process

This study focuses on the synthesis of granular red mud reinforced by zero-valent iron (Fe@GRM) and its application for the removal acid orange 7 (AO7) from aqueous solution. Then ZVI is employed as a catalyst for the activation of persulfate (PS) to produce sulfate radicals (SO₄^•-) that are produced at 900 °C in an anoxic atmosphere using the direct reduction of iron oxide in the red mud with maize straw as the reductant. Furthermore, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used to illustrate the morphology and porous structure of the Fe@GRM. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that Fe@GRM was loaded with zero-valent iron. This characterization confirmed that the Fe@GRM was a porous structure material that contained zero-valent iron. The influence of conditions for AO7 elimination, including initial pH, Fe@GRM dosage, initial AO7 concentrations, and temperature, is also investigated. The removal efficiency of AO7 was 90.78% using Fe@GRM/PS, while only 18.15% was removed when Fe@GRM was used alone. The degradation kinetics were well fitted to a pseudo-first-order kinetic model, and the rate of removal increased with temperature, demonstrating an endothermic elimination process. The Arrhenius activation energy of the process was 20.77 kJ/mol, which indicated that the reduction of AO7 was a diffusion-mediated reaction. Fe@GRM is a low-cost material that demonstrated outstanding performance with great potential for wastewater treatment.

Green synthesis of stable Fe,Cu oxide nanocomposites from loquat leaf extracts for removal of Norfloxacin and Ciprofloxacin

Mass production of nanomaterials to remove pollutants from water still faces many challenges, mainly due to the complexity of the synthesis methods involved and the use of dangerous reagents. The green method of preparation of nanomaterials from plants can effectively solve these problems. Fe,Cu oxide nanocomposites (Fe-Cu-NCs) were synthesized by a green and single-step method using loquat leaf extracts, and were used as an adsorbent for removal of Norfloxacin (NOR) and Ciprofloxacin (CIP) from aqueous solution. The synthesized adsorbent showed excellent adsorption properties for NOR and CIP. The experimental equilibrium data fitted the Redlich-Peterson and Koble-Corrigan models well and the maximum adsorption capacities of Fe-Cu-NCs calculated by the Langmuir model for NOR and CIP were 1.182 mmol/g and 1.103 mmol/g, respectively, at 293 K. Additionally, the morphologies and properties of Fe-Cu-NCs were characterized by transmission electron microscopy (TEM), scanning electron microscopy X-ray energy-dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis and the adsorption mechanism of NOR and CIP onto Fe-Cu-NCs was discussed. Thermodynamic parameters revealed that the adsorption process was spontaneous and endothermic. This study indicated that Fe-Cu-NCs are a potential adsorbent and provide a simple and convenient strategy for the purification of antibiotics-laden wastewater.

Feasibility of nanoscale zero-valent iron (nZVI) for enhanced biological treatment of organic dyes

Biodegradation of recalcitrant organic contaminants such as organic dyes is a fundamental challenge in wastewater treatment. We report herein the integration of nanoscale zero-valent iron (nZVI) with membrane bioreactors (nZVI-bio system) to achieve enhanced degradation of Congo red (CR) in wastewater. nZVI pretreatment converts the large and bio-recalcitrant CR molecules into smaller and more biodegradable organic compounds in continuous flow stirred tank reactors (CFSTR). A nZVI-bio system was experimented continuously for 52 d with a color removal efficiency of 99% and a reduction of chemical oxygen demand (COD) from 167 mg L^-1 to less than 70 mg L^-1. However, a conventional biotreatment system treating identical wastewater achieved color removal efficiency of just 30-70% and the COD reduction to 116 mg L^-1. This suggests that integrated nZVI-bio system has potential for the treatment of recalcitrant organic dyes. On-line measurements of pH and redox potential in the CSFTR can be conveniently used to monitor and regulate treatment performance.

Enhanced removal of Cr(VI) in the Fe(III)/natural polyphenols system: role of the in situ generated Fe(II)

This study developed a cost-effective and eco-friendly method by coupling plant extracts (take green tea for example) and Fe(III) to reduce Cr(VI) and precipitate Cr(III). At acidic pH, 1.43 mM Fe(III) combined with 1.33 g/L green tea extracts could reduce 93% of Cr(VI) in 180 min, which was much larger than ˜50% by green tea extracts alone. Moreover, 52% of Cr(III) could automatically precipitate out as mixed Fe(III)-Cr(III) (oxy)-hydroxide solids. In the viewpoint of mechanism, polyphenols in green tea extracts were the reactive constituents and transformed Fe(III) to Fe(II), by which step the aqueous Fe(II) level was maintained to continuously reduce Cr(VI) to Cr(III), and thus accelerating Cr(VI) reduction. The generated Fe(III) partially participated in the reaction with polyphenols again and some Fe(III) formed precipitates with Cr(III). Overall, the electron transfers in the polyphenol-Fe-Cr cyclic reactions made Fe(III) used for multiple times, thus accelerated Cr(VI) reduction. The applicability of the combined process was further verified by removing 100% and 70% of Cr(VI) from electroplating wastewater and contaminated soil, respectively. As polyphenols can be derived from plant wastes and Fe(III) is naturally abundant, this study provides a promising method for in situ remediation of Cr(VI)-contaminated sites.

A novel graphene oxide-carbon nanotubes anchored α-FeOOH hybrid activated persulfate system for enhanced degradation of Orange II

Persulfate activation has been applied as one of the efficient advanced oxidation processes (AOPs) to remediate polluted environments. In this study, a novel α-FeOOH anchored by graphene oxide (GO)-carbon nanotubes (CNTs) aerogel (α-FeOOH@GCA) nanocomposite activated persulfate system (α-FeOOH@GCA + K₂S₂O₈) was applied for decolorization of Orange II (OII). The decolorization of OII was remarkably enhanced to a level of ~99% in this system compared with that of pristine α-FeOOH (~44%) or GO-CNTs (~18%). The enhanced catalytic activity of α-FeOOH@GCA was due to the formation of a heterojunction by α-FeOOH and GO-CNTs as confirmed by the presence of Fe-O-C chemical bonds. The degradation intermediates of OII were comprehensively identified. The proposed degradation pathway of OII begins with the destruction of the conjugated structures of OII by the dominant reactive oxygen species, surface-bound SO₄^•-. The decolorization efficiency of OII by the α-FeOOH@GCA activated persulfate system decreased from the first to third cycle of recycling. Ultraviolet (UV) irradiation or introduction of a small amount of Fe²⁺ could restore the activation of this system. The results show that the α-FeOOH@GCA persulfate activation system promises to be a highly efficient environmental remediation method for organic pollutants.

Characterization of iron nanoparticles/reduced graphene oxide composites synthesized by one step eucalyptus leaf extract

Biosynthesis of nanoparticles using plant extract is one kind of the effective approach in developing rapid, clean, nontoxic, and eco-friendly technology. In this work, iron nanoparticles/reduced graphene oxide composites (Fe NPs/rGO) were facilely fabricated through one-step method with eucalyptus leaf extract. The synthesized Fe NPs/rGO was investigated by various characterization methods. SEM results disclosed that Fe NPs with regular spherical shape of 70 ± 10 nm was uniformly dispersed on rGO. A basal plane of rGO with high surface area, providing more load sites for Fe NPs, which was confirmed by TEM. XRD and FTIR results indicated that biomolecules from eucalyptus extract were capped on Fe NPs/rGO. The EDS mapping showed that Fe NPs dispersed evenly on rGO, and XPS further confirmed that Fe NPs/rGO composite was mainly comprised with Fe NPs and rGO. Furthermore, the biomolecules of eucalyptus leaf extract were identified by GC-MS to confirm that alcohol phenols acted as reducing agent, while alcohol acids and ketones acted as capping agents. In addition, the removal efficiency of Methylene blue (MB) up to 93% with Fe NPs/rGO. This work provides a simple, green cost-effective and environmentally friendly method to fabricate metal/rGO composite.

AgI loading BiOI composites with enhanced photodegradation efficiency for bisphenol A under simulated solar light

Bismuth oxyiodide (BiOI) is a narrow band gap semiconductor which can be driven by visible irradiation. In order to efficiently separate photo-generated carriers and utilization of visible light, a facile solvothermal approach was used to synthesize a novel AgI loading BiOI 3D hierarchical composite (AgI-BiOI). The AgI-BiOI with Ag and Bi molar ratio of 1:8 (AgI-BiOI (1-8)) showed great enhancement for photocatalytic degradation of bisphenol A (BPA) with pseudo-first degradation rate constant about 3.7 or 14.5 times than that of pristine BiOI or AgI under simulated solar light. This synergistic enhancement for BPA degradation on AgI-BiOI(1-8) is mainly ascribed to enhancing the light absorption intensity and accelerating photo-generated carriers separation due to the formation of AgI-BiOI heterojunction. Free radical quenching experiments proved that positive holes (h⁺) and superoxide (O₂^•-) radicals were dominantly responsible for the degradation of BPA rather than singlet oxygen (¹O₂) or hydroxyl radicals (•OH). The AgI-BiOI(1-8) hardly showed any ecotoxicity to C. elegans through lethal experiments. The luminance bacteria acute toxicity of degradation intermediates of BPA increased before 30 min then reduced significantly with reaction. The good durability and environmental-friendly characteristics make AgI-BiOI(1-8) catalyst to be a good solar light-driven candidate.

Iron-based nanoparticles prepared from yerba mate extract. Synthesis, characterization and use on chromium removal

Iron-based nanoparticles were synthesized by a rapid method at room temperature using yerba mate (YM) extracts with FeCl₃ in different proportions. Materials prepared from green tea (GT) extracts were also synthesized for comparison. These materials were thoroughly characterized by chemical analyses, XRD, magnetization, SEM-EDS, TEM-SAED, FTIR, UV-Vis, Raman, Mössbauer and XANES spectroscopies, and BET area analysis. It was concluded that the products are nonmagnetic iron complexes of the components of the extracts. The applicability of the materials for Cr(VI) (300 μM) removal from aqueous solutions at pH 3 using two Cr(VI):Fe molar ratios (MR), 1:3 and 1:0.5, has been tested. At Cr(VI):Fe MR = 1:3, the best YM materials gave complete Cr(VI) removal after two minutes of contact, similar to that obtained with commercial nanoscale zerovalent iron (N25), with dissolved Fe(II), and with a likewise prepared GT material. At a lower Cr(VI):Fe MR (1:0.5), although Cr(VI) removal was not complete after 20 min of reaction, the YM nanoparticles were more efficient than N25, GT nanoparticles and Fe(II) in solution. The results suggest that an optimal Cr(VI):Fe MR ratio could be reached when using the new YM nanoparticles, able to achieve a complete Cr(VI) reduction, and leaving very low Cr and Fe concentrations in the treated solutions. The rapid preparation of the nanoparticles would allow their use in removal of pollutants in soils and groundwater by direct injection of the mixture of precursors.

Biogenic magnetite nanoparticles: A potent and environmentally benign agent for efficient removal of azo dyes and phenolic contaminants from water

A comprehensive study was conducted toward the green and facile synthesis of biocompatible magnetite nanoparticles for the efficient removal of organic contaminants from water. The nanoparticles were synthesized using a modified co-precipitation method and functionalized by the taxane diterpenoids extracted from Taxus baccata L., and fully characterized using UV-vis spectroscopy, SEM, FTIR, VSM, and XRD. The synthesized monodisperse magnetite nanoparticles, with a narrow size distribution of less than 50 nm, displayed significant and stable magnetic activity without surface oxidation after several months. The batch experiments clearly indicated the efficient iron-catalyzed removal of Nile blue, methylene blue, methylene orange, and 4-nitrophenol for several cycles without significant loss of catalytic activity. The relevant kinetic data of the dyes removal reactions were fitted to a pseudo-first order model. Moreover, in vitro MTT assay revealed high biocompatibility of the nanoparticles with no significant toxicity on different human cell lines. The overall results indicated high potential of green synthesized, biocompatible magnetite nanoparticles for the environmental applications especially wastewater remediation.

Green reduction of graphene oxide using eucalyptus leaf extract and its application to remove dye

Reduction of graphene oxide (RGO) utilizing green methods such as plants has attracted much attention due to its efficiency, eco-friendly features and low cost. However, the key components in plant extracts and their bioreduction functions concerning GO are still not well understood. In this study, the GO was reduced by Eucalyptus leaf (EL) extract. The optimal conditions for bioreduction were at volume ratio of leaf extract (10 g L^-1) and GO (0.5 g L^-1) solution of 1:4 for 8 h at 80 °C. The RGO was characterized with Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), transmission electron microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). Results confirmed the oxygen-containing groups in GO were efficiently removed, formation of capping layer on the surface of RGO, and good dispersion of RGO in aqueous solution. Furthermore, biomolecules were identified by Gas Chromatography-Mass Spectrometer (GC-MS), where eucalyptols, aldehydes, terpineols, alcohols, amides and ethers of Eucalyptus leaf extract may act as reducing and capping agents for the formation of RGO. Finally, the methyl blue (MB) adsorption on EL-RGO, activated carbon, graphite powder and commercial graphene were investigated separately. The order of the maximum adsorption capacity of different adsorbents emerged as: EL-RGO > commercial graphene > activated carbon > graphite powder.

Phytofabrication of Iron Nanoparticles for Hexavalent Chromium Remediation

Hexavalent chromium is a genotoxic and carcinogenic byproduct of a number of industrial processes, which is discharged into the environment in excessive and toxic concentrations worldwide. In this paper, the synthesis of green iron oxide nanoparticles using extracts of four novel plant species [Pittosporum undulatum, Melia azedarach, Schinus molle, and Syzygium paniculatum (var. australe)] using a "bottom-up approach" has been implemented for hexavalent chromium remediation. Nanoparticle characterizations show that different plant extracts lead to the formation of nanoparticles with different sizes, agglomeration tendencies, and shapes but similar amorphous nature and elemental makeup. Hexavalent chromium removal is linked with the particle size and monodispersity. Nanoparticles with sizes between 5 and 15 nm from M. azedarach and P. undulatum showed enhanced chromium removal capacities (84.1-96.2%, respectively) when compared to the agglomerated particles of S. molle and S. paniculatum with sizes between 30 and 100 nm (43.7-58.7%, respectively) in over 9 h. This study has shown that the reduction of iron salts with plant extracts is unlikely to generate vast quantities of stable zero valent iron nanoparticles but rather favor the formation of iron oxide nanoparticles. In addition, plant extracts with higher antioxidant concentrations may not produce nanoparticles with morphologies optimal for pollutant remediation.

Fabrication of Zr-doped TiO2/chitosan composite catalysts with enhanced visible-light-mediated photoactivity for the degradation of Orange II dye

Zirconium/titanium/chitosan (Zr/Ti/CHT) composite catalysts were synthesized by sol-gel method using different chitosan amounts (5-20 wt.%) and their activity in the photocatalytic degradation of Orange II dye was evaluated for the first time. The results were compared with Zr/Ti, Zr/CHT and Ti/CHT catalysts. The composite catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy analysis. XRD analysis revealed that the Zr/Ti/CHT composite catalyst showed high crystallinity of anatase TiO₂ phase. Photocatalytic experiments showed that adding CHT into the catalyst structure increased the photocatalytic degradation under visible light irradiation. Also, the first-order reaction rate constant, k_app, was calculated using the Langmuir-Hinshelwood (L-H) equation. The k_app values were found to be 0.009, 0.0013, 0.012 and 0.014 min^-1 for Zr/Ti, Zr/CHT, Ti/CHT and Zr/Ti/CHT, respectively. According to stability tests, after the first cycle Orange II dye degradation was found to be 95%, while it was 37% after the fifth cycle. The results showed that the composite catalyst could be used several times for Orange II dye degradation.

Greener and size-specific synthesis of stable Fe-Cu oxides as earth-abundant adsorbents for malachite green

A greener and sustainable pathway to the assembly of Fe, Cu -based adsorbent is described using Virginia creeper (Parthenocissus quinquefolia) leaf extracts in presence of oxalic acid which avoids the use of toxic chemicals. Characterization of the synthesized mixed Fe, Cu oxides are carried out by SEM, TEM, XRD, FT-IR, XPS, and BET techniques; SEM and TEM results disclosed particle size ranging from 160 nm to 1 μm in presence of varying oxalic acid amounts of 0 and 0.1 mol/L. The X-ray photoelectron spectroscopy studies revealed that the sample comprised of Fe, Cu-based hybrid oxides and oxalates. The ensuing results from altered operational parameters namely initial pH, initial malachite green (MG) concentration, the sample dosage and the reaction temperature suggest that the MG adsorption capacity of synthesized materials could be well structured by simply varying the amount of oxalic acid. The optimal sample (S3 sample) has a remarkably high maximum adsorptive capacity (~1399 mg/g) for aqueous MG removal at 303 K and natural pH (~ 6.58), which is superior to recently documented sorbents. The results demonstrate that the adsorption is spontaneous (i.e., ∆G < 0) via an endothermic process wherein the synthesized adsorbent displayed excellent characteristics: 1) maintained a high adsorption capacity under a wide range of pH conditions; 2) remained chemically stable under ambient storage environments to allow for extended stowage; and 3) portrayed high reusability with no waning effect after 4 adsorption/desorption cycles.

Catalytic degradation of Orange II in aqueous solution using diatomite-supported bimetallic Fe/Ni nanoparticles

A functional diatomite-supported Fe/Ni nanocomposite successfully remediated Orange II contaminant in aqueous solution. The hypothesis was that diatomite-supported Fe/Ni would not only be more effective than Fe/Ni but also require less metallic loading to effect the catalytic reaction. Batch experiments indicate that 99.00% of Orange II was removed using diatomite-supported Fe/Ni, while only 86.64 and 3.59% of Orange II were removed using bimetallic Fe/Ni nanoparticles and diatomite, after 6 h of reaction, respectively. Characterisation by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) indicates that the use of diatomite as a support material reduced the aggregation of bimetallic Fe/Ni nanoparticles, thereby resulting in an enhancement in the reactivity. A synergistic mechanism for the removal of Orange II by diatomite-supported Fe/Ni was proposed which involves adsorption, followed by catalytic reduction. This study has demonstrated that diatomite may be a suitable support material for stabilizing and dispersing bimetallic Fe/Ni nanoparticles and the resulting diatomite-supported Fe/Ni composite could be a promising catalyst for the remediation of dye-contaminated wastewater.

A functional diatomite-supported Fe/Ni nanocomposite successfully remediated Orange II contaminant in aqueous solution.

Harnessing the wine dregs: An approach towards a more sustainable synthesis of gold and silver nanoparticles

In recent years, the management of food waste processing has emerged as a major concern. One such type of food waste, grape pomace, has been shown to be a great source of bioactive compounds which might be used for more environmentally - friendly processes for the synthesis of nanomaterials. In this study, grape pomace of Vitis vinifera has been used for the obtainment of an aqueous extract. Firstly, the reducing activity, total phenolic content and DPPH scavenging activity of the aqueous extract were determined. Then, the aqueous extract was used for the synthesis of gold and silver nanoparticles. The formation of spherical and stable nanoparticles with mean diameters of 35.3±5.2nm for Au@GP and 42.9±6.4nm for Ag@GP was confirmed by UV-vis spectroscopy and transmission electron microscopy. Furthermore, the functional group of biomolecules present in grape pomace extract, Au@GP and Ag@GP, were characterized by Fourier transform infrared spectroscopy prior to and after the synthesis, in order to obtain information about the biomolecules involved in the reducing and stabilization process. This study is the first to deal with the use of Vitis vinifera grape pomace in obtaining gold and silver nanoparticles through an eco-friendly, quick, one-pot synthetic route.

Preparation of nanoscale iron (oxide, oxyhydroxides and zero-valent) particles derived from blueberries: Reactivity, characterization and removal mechanism of arsenate

The application of iron nanoparticles (FeNPs) to the removal of various pollutants has received wide attention over the last few decades. A synthesis alternative to obtain these nanoparticles without using harmful chemical reagents, such as NaBH₄, is the use of extracts from different natural sources that allow a lesser degree of agglomeration, in a process known as green synthesis. In this study, FeNPs were synthesized by 'green' (hereafter, BB-Fe NPs) and 'chemical' (hereafter, nZVI) methods. Extracts of leaves and blueberry shoots (Vaccinium corymbosum) were used as reducing agents for FeCl₃·6H₂O solution in the green synthesis method. FeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrophoretic migration, Brunauer-Emmett-Teller (BET) surface area analysis and X-ray diffraction (XRD) and evaluated for the removal of As(V) from aqueous systems. In both synthesis methods, XRD analysis confirmed the presence of the different kinds of iron nanoparticles. SEM analysis showed that the average size of BB-Fe NPs was 52.4nm and that a variety of nanoparticles of different forms and associated structures, such as lepidocrocite, magnetite, and nZVI, were present, while the dimensions of nZVI were 80.2nm. Comparatively significant differences regarding the electrophoretic mobility were found between both materials pre- and post-sorption of As(V). The velocity of As(V) removal by BB-Fe NPs was slower than that by nZVI, reaching equilibrium at 120min compared to 60min for nZVI. The removal kinetics of As(V) were adequately described by the pseudo-second-order kinetic model, and the maximum adsorbed amounts of this analyte are in close accordance with the experimental results. The Langmuir-Freundlich model is in good agreement with our experimental data, where the sorption capacity of nZVI and BB-Fe NPs was found to be 52.23 ± 6.06 and 50.40 ± 5.90 (mg·g^-1), respectively. The use of leaves of Vaccinium corymbosum affords an easy-to-synthesize, low-cost, and eco-friendly material with capabilities similar to nZVI. BB-Fe NPs are promising for arsenic remediation, which has emerged as a new alternative for water purification and sanitation.

Dye degradation by green heterogeneous Fenton catalysts prepared in presence of Camellia sinensis

This work describes the synthesis and characterization of supported green iron catalysts, prepared with Camellia sinensis tea extract, and their application in heterogeneous Fenton degradation of pollutant dyes. The influence of the catalyst synthesis conditions in the iron and organic content were investigated by X-ray fluorescence and thermogravimetric analyses. Irregular, chain-like nanoparticles, in the size range of 20-100 nm, capped by polyphenolic natural compounds, were visualized by TEM micrographs. TEM-EDS revealed a high iron content in the nanoparticles as well as a high carbon content all over the catalyst surface, indicating the coverage by the polyphenolic compounds of the tea. X-ray powder diffraction revealed the amorphous nature of the nanoparticles, tentatively ascribed to iron(II)/(III) oxides and oxohydroxides composites. The Fenton degradation of different dyes was successfully accomplished, leading to complete decolourization in less than 3 h of reaction. Influence of hydrogen peroxide concentration, catalyst dosage, pH, temperature and catalyst support, were investigated. The catalysts prepared with black tea over silica furnished the higher iron contents and were the most actives for dye degradation.

Conversion of Fe-rich waste sludge into nano-flake Fe-SC hybrid Fenton-like catalyst for degradation of AOII

Permanently increasing in the amount of sludge resulted in the serious environment burden. This work reports a novel carbothermal process for converting the Fe-rich waste sludge into cleaner nano-flake Fenton-like catalyst to relieve the crisis. The transformation of Fe species at different carbothermal temperature was evaluated by XRD analysis. SEM and XPS analyses were involved to characterize the morphology and chemical bonds of the catalysts. Results shown that the resulted catalyst carbonized at 800 °C (Fe-SC-800) was composed of Fe(0) and Fe3O4, performing nano-flake-like structure. The Fe-SC-800 has the highest catalytic activity in degradation of AOII in C0 = 200 mg/L. The efficiency achieves at 98% within 30 min at neutral pH, which is ascribed to the hydroxyl radical oxidation. Moreover, no iron is leached and the Fe-SC-800 could be recycled for three times at least. Thus, the Fe rich sludge could be reutilized as a valuable source for eco-friendly catalyst production, constituting an ecological way to manage these sludge wastes and eliminate the sludge and organic pollution to environment.

Textile dye degradation using nano zero valent iron: A review

Water soluble unfixed dyes and inorganic salts are the major pollutants in textile dyeing industry wastewater. Existing treatment methods fail to degrade textile dyes and have limitations too. The inadequate treatment of textile dyeing wastewater is a major concern when effluent is directly discharged into the nearby environment. Long term disposal threatens the environment, which needs reclamation. This article reviews the current knowledge of nano zero valent iron (nZVI) technique in the degradation of textile dyes. The application of nZVI on textile dye degradation is receiving great attention in the recent years because nZVI particles are highly reactive towards the pollutant, less toxic, and economical. The nZVI particles aggregate quickly with respect to time and the addition of supports such as resin, nickel, zinc, bentonite, biopolymer, kaolin, rectorite, nickel-montmorillonite, bamboo, cellulose, biochar, graphene, and clinoptilolite enhanced the stability of iron nanoparticles. Inclusion of supports may in turn introduce additional toxic pollutants, hence green supports are recommended. The majority of investigations concluded dye color removal as textile dye compound removal, which is not factual. Very few studies monitored the removal of total organic carbon and observed the products formed. The results revealed that partial mineralization of the textile dye compound was achieved. Instead of stand alone technique, nZVI can be integrated with other suitable technique to achieve complete degradation of textile dye and also to treat multiple pollutants in the real textile dyeing wastewater. It is highly recommended to perform more bench-scale and pilot-scale studies to apply this technique to the textile effluent contaminated sites.

Cultivation of Chlorella on brewery wastewater and nano-particle biosynthesis by its biomass

This study investigated an integrated and sustainable approach for iron nanoparticles synthesis using Chlorella sp. MM3 biomass produced from the remediation of brewery wastewater. The algal growth characteristics, biomass production, nutrient removal, and nanoparticle synthesis including its characterisation were studied to prove the above approach. The growth curve of Chlorella depicted lag and exponential phase characteristics during the first 4days in a brewery wastewater collected from a single batch of brewing process (single water sample) indicating the growth of algae in brewery wastewater. The pollutants such as total nitrogen, total phosphorus and total organic carbon in single water sample were completely utilised by Chlorella for its growth. The X-ray photoelectron spectroscopy spectra showed peaks at 706.56eV, 727.02eV, 289.84eV and 535.73eV which corresponded to the zero-valent iron, iron oxides, carbon and oxygen respectively, confirming the formation of iron nanoparticle capped with algal biomolecules. Scanning electron microscopy and particle size analysis confirmed the presence of spherical shaped iron nanoparticles of size ranging from 5 to 50nm. To our knowledge, this is the first report on nanoparticle synthesis using the biomass generated from phycoremediation of brewery wastewater.

One-step green synthesis of bimetallic Fe/Pd nanoparticles used to degrade Orange II

To reduce cost and enhance reactivity, bimetallic Fe/Pd nanoparticles (NPs) were firstly synthesized using grape leaf aqueous extract to remove Orange II. Green synthesized bimetallic Fe/Pd NPs (98.0%) demonstrated a far higher ability to remove Orange II in 12h compared to Fe NPs (16.0%). Meanwhile, all precursors, e.g., grape leaf extract, Fe(2+) and Pd(2+), had no obvious effect on removing Orange II since less than 2.0% was removed. Kinetics study revealed that the removal rate fitted well to the pseudo-first-order reduction and pseudo-second-order adsorption model, meaning that removing Orange II via Fe/Pd NPs involved both adsorption and catalytic reduction. The remarkable stability of Fe/Pd NPs showed the potential application for removing azo dyes. Furthermore, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the changes in Fe/Pd NPs before and after reaction with Orange II. High Performance Liquid Chromatography-Mass Spectrum (HPLC-MS) identified the degraded products in the removal of Orange II, and finally a removal mechanism was proposed. This one-step strategy using grape leaf aqueous extract to synthesize Fe/Pd NPs is simple, cost-effective and environmentally benign, making possible the large-scale production of Fe/Pd NPs for field remediation.

Synthesis and adsorption application of amine shield-introduced-released porous chitosan hydrogel beads for removal of acid orange 7 from aqueous solutions

An effective and low-cost adsorbent named amine shield-introduced-released porous chitosan hydrogel beads (APCB) was synthesized and used for the removal of acid orange 7 from aqueous solutions.