Catalytic Reduction Of Organic Pollutants Research Articles

Ultrafast catalytic reduction of organic pollutants using ternary zinc–copper–nickel layered double hydroxide

Water is the utmost essential commodity for the support of life process in animals. In recent decades, rapid industrialization and uncontrolled agricultural practices have led to increased level of toxic pollutants in groundwater, including organic pollutants (dyes, nitroarene compounds, antibiotics, etc.), inorganic pollutants (heavy metals, nanoparticles, etc.), and pesticides, posing a serious threat to human health and the environment. Although various technologies such as adsorption, photocatalysis, reverse osmosis, filtration, sedimentation, flocculation, and precipitation are available for the elimination of toxic pollutants from wastewater, issues such as their cost and efficacy limit their usage. Recently, catalysis has been found to be the most effective approach since it exhibits significant capability to eliminate almost all the pollutants and offers the benefit of simple design and low initial cost. In the present study, ternary zinc–copper–nickel layered double hydroxide (ZnCuNi‐LDH) synthesized using facile acid hydrolysis method was employed as an efficacious heterogeneous catalyst for the reduction of NACs (para‐nitrophenol and para‐nitroaniline) and degradation of organic azo dyes (methyl orange, amaranth, and brilliant black). ZnCuNi‐LDH exhibited superior catalytic activity for the reduction of all five model pollutants with reduction efficiency of more than 95% within a short time span of 5 min. Therefore, keeping in view the layered structure, high specific surface area, and remarkable catalytic performance, ZnCuNi‐LDH holds immense potential for the large‐scale catalytic degradation of refractory pollutants.

Preparation of activated carbon-metal nanoparticle composite materials for the catalytic reduction of organic pollutants

This work focuses on the preparation of inexpensive composite materials based on activated carbon-containing metallic nanoparticles MNPs (M = Cu, Ag, Fe). The metal nanoparticles supported on the activated carbon were prepared by ultrasound followed by chemical treatment using a reducing agent NaBH4. The obtained materials were characterized by XRD, XRF, FTIR, XPS, TGA, SEM, and TEM analysis. The different samples were tested as catalysts for the catalytic reduction of organic pollutants (MB, MO, 4-NP) in a simple and binary system in the presence of NaBH4. The results confirmed that the content of metal nanoparticles was in the following sequence 2.12%, 11.15%, and 12.13% for the materials AC-Ag, AC-Cu, and AC-Fe, respectively. According to TEM analysis, the size and dispersion of nanoparticles differ from one catalyst to another, hence the AC-Cu material exhibited good dispersion of CuNPs having ultrafine particles in the range of 4–14 nm. In order to optimize the best conditions for the reduction reaction, the effect of the nature of the catalyst, the initial concentration of NaBH4, the concentration of the pollutant, the mass of the catalyst and the nature of the pollutant were studied, and discussed. In terms of efficiency, the AC-Cu sample was the most efficient catalyst compared to AC-Fe, and AC-Ag, mainly due to the good dispersion of CuNPs on the surface of activated carbon. The recorded rate constant for the MB, MO, and 4-NP in the single system using the same operating conditions was 0.0259 s−1, 0.0218 s−1, and 0.0074 s−1, respectively. In the binary system containing MB + MO or MB + 4-NP, the AC-Cu catalyst was more selective towards the MB dye in both systems. The reuse of the AC-Cu catalyst towards the reduction of the MB dye showed good performance during five consecutive cycles without losing its efficiency.

Palladium nanoparticles on polydimethylsiloxane film for C−C coupling reactions, and catalytic reduction of organic pollutants in water

AbstractIn this study, we present a novel method for immobilizing Palladium nanoparticles (Pd NPs) onto a polydimethylsiloxane (PDMS) support (Pd NPs@PDMS). To enhance the stability of Pd NPs on the PDMS surface, we functionalized a PDMS thin film with amine groups. The structure and morphology of the resulting Pd NPs@PDMS material were characterized using various techniques, including field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS) measurements. Furthermore, we investigated the catalytic performance of the Pd NPs@PDMS nanocatalyst for the reduction of well‐known environmental pollutants, such as 4‐nitrophenol (4‐NP), 2‐nitrophenol (2‐NP), 4‐nitroaniline (4‐NA), Methyl Orange (MO), Methylene Blue (MB), and Congo Red (CR), in the presence of sodium borohydride (NaBH4) at room temperature (RT). Additionally, we explored the application of the prepared nanocatalyst in carbon‐carbon (C−C) coupling reactions, specifically Suzuki Miyaura and Sonogashira reactions. The results obtained in this study demonstrated the high efficiency and environmentally friendly nature of Pd NPs@PDMS as a catalyst for both C−C coupling reactions and the degradation of organic pollutants.

Pd@MgAl LDH/2-ThCA: A sustainable, active and recyclable nanocatalyst system for the rapid and efficient catalytic reduction of organic pollutants

Catalytic reduction of toxic pollutants such as nitroaromatics and organic dyes found in water/wastewater by heterogeneous nano-structured metallic catalysts is a promising method for wastewater treatment. The need for effective and reusable catalyst systems is recently increasing due to the soaring water pollution. For this purpose, in this study, a newly Pd@MgAl LDH/2-ThCA catalyst system was successfully developed by depositing palladium nanoparticles onto a modified MgAl LDH support, characterized and then used to eliminate these contaminants in the presence of NaBH4. Catalytic applications indicated that Pd@MgAl LDH/2-ThCA catalyst efficiently reduced 2-nitroaniline (2-NA), 4-nitrophenole (4-NP), 4-nitroaniline (4-NA), and 4-nitro-o-phenylenediamine (4-NPDA) with rate constants of 0.011 s−1, 0.0075 s−1, 0.017 s−1, and 0.02 s−1, respectively. Additionally, Pd@MgAl LDH/2-ThCA successfully degraded methyl orange (MO) and rhodamine B (RhB) with rate constants of 0.019 s−1 and 0.015 s−1, respectively. Furthermore, it was found that methylene blue (MB) was immediately degraded by Pd@MgAl LDH/2-ThCA. Reusability tests revealed that Pd@MgAl LDH/2-ThCA maintained its activity/stability after the 5 successive cycles, verifying its practical application potential. This paper reveals that Pd@MgAl LDH/2-ThCA is an effective, sustainable, and alternative catalyst system for the treatment of toxic environmental pollutants.

Amine-functionalized reduced graphene oxide-supported silver nanoparticles for superior catalytic reduction of organic pollutants.

In this work, a simple and environmentally friendly approach has been followed to synthesize amine-functionalized reduced graphene oxide (RGO)-supported silver nanoparticle (AgNPs) having superior catalytic efficiency towards the reduction of organic pollutants. RGO/AgNPs nanohybrid was synthesized by a one-pot hydrothermal reduction of silver nitrate in the presence of amino-propyl trimethoxy silane (APTMS)-functionalized graphene oxide (GO) nanosheets. The structural and morphological characterization of as-synthesized RGO/AgNPs nanohybrid was done by using XRD, SEM, TEM, FT-IR, and Raman spectroscopy techniques. APTMS plays an important role in controlling the size of anchored AgNPs on the nanohybrid in the present study. The -NH2 groups on the surface of APTMS-modified GO function as effective and well-organized nucleation centers facilitating uniform growth of discrete and smaller-sized spherical AgNPs on the surface of RGO nanosheets. In the absence of APTMS, the nanohybrid comprised of bigger-sized AgNPs with few hundred of nanometers in dimension. The catalytic efficiency of RGO/AgNPs nanohybrid was evaluated for the reduction of two model organic pollutants: 4-nitrophenol (4-NP) and methylene blue (MB). Due to the synergistic effects of RGO, APTMS, and Ag components, RGO/AgNPs nanohybrid developed in the present study exhibited superior catalytic activity towards the reduction of 4-NP and MB in comparison with previously reported graphene/graphene oxide/reduced graphene oxide-supported AgNPs catalysts. The catalytic reduction of 4-NP and MB followed pseudo-unimolecular kinetics and the rate constants were found to be 18.83 × 10-3 s-1 and 131.5 ×10-3 s-1 respectively for 4-NP and MB. Furthermore, RGO/AgNPs nanohybrid showed admirable recyclability with negligible loss in its activity until five recycle runs. The superior catalytic activity, favorable kinetic parameters, and sustained catalytic efficiency after recycling make RGO/AgNPs nanohybrid a promising catalyst for the reduction of organic pollutants in environmental remediation.

Sustainable magnetically recoverable Iridium-coated Fe3O4 nanoparticles for enhanced catalytic reduction of organic pollutants in water.

The reduction of nitroarenes to aromatic amines is one of the potential pathways to remediate the hazardous impact of toxic nitroarenes on the aquatic environment. Aromatic amines obtained from the reduction of nitroaromatics are not only less toxic than nitroaromatics but also act as important intermediates in the synthesis of dyes, drugs, pigments, herbicides, and polymers. There is a huge demand for the development of cost-effective, and eco-friendly catalysts for the efficient reduction of nitroarenes. In the present study, Fe3O4@trp@Ir nanoparticles were explored as efficient catalysts for the reduction of nitroarenes. Fe3O4@trp@Ir magnetic nanoparticles were fabricated by surface coating of Fe3O4 with tryptophan and iridium by co-precipitation method. As-prepared Fe3O4@trp@Ir nanoparticles are environmentally benign efficient catalysts for reducing organic pollutants such as 4-nitrophenol (4-NP), 4-nitroaniline (4-NA), and 1-bromo-4-nitrobenzene (1-B-4-NB). The key parameters that affect the catalytic activity like temperature, catalyst loading, and the concentration of reducing agent NaBH4 were optimized. The obtained results proved that Fe3O4@trp@Ir is an efficient catalyst for reducing nitroaromatics at ambient temperature with a minimal catalyst loading of 0.0025%. The complete conversion of 4-nitrophenol to 4-aminophenol took only 20s with a minimal catalyst loading of 0.0025% and a rate constant of 0.0522s-1. The high catalytic activity factor (1.040s-1mg-1) and high turnover frequency (9min-1) obtained for Fe3O4@trp@Ir nanocatalyst highlight the possible synergistic effect of the two metals (Fe and Ir). The visible-light photocatalytic degradation of 4-NP was also investigated in the presence of Fe3O4@trp@Ir. The photocatalytic degradation of 4-NP by Fe3O4@trp@Ir is completed in 20min with 95.15% efficiency, and the rate of photodegradation of 4-NP (0.1507min-1) is about twice the degradation rate of 4-NP in the dark (0.0755min-1). The catalyst was recycled and reused for five cycles without significant reduction in the conversion efficiency of the catalyst.

Catalytic reduction of organic pollutants, antibacterial and antifungal activities of AgNPs@CuO nanoparticles-loaded mesoporous silica.

In this work, the mesoporous silica MCM-41 was prepared by a hydrothermal method and then modified using silver and copper. The obtained samples were used as antibacterial/antifungal agents and as catalysts for the reduction of the following dyes: Methylene Blue (MB), Congo Red (CR), Methyl Orange (MO), and Orange G (OG). Several parameters affecting the reduction of dyes were investigated and discussed such as the catalyst nature, the initial concentration of the dye, the dye nature, the selectivity of the catalyst in a binary system as well as the catalyst reuse. The catalysts were characterized using XRD, nitrogen sorption measurements, XRF, FTIR, XPS, SEM/EDS, and TEM. XRD, XPS, and TEM analysis clearly showed that the calcination of copper- and silver-modified silica leads to the formation of well-dispersed CuO and AgNPs having sizes between 5 and 10nm. As determined by XRF analysis, the content of silver nanoparticles was higher compared to CuO in all samples. It has been shown that the dye reduction is influenced by the size and the content of nanoparticles as well as by their dispersions. The catalytic activity was shown to be the highest for the Ag-Cu-MCM(0.05) catalyst with a rate constant of 0.114, 0.102, 0.093, and 0.056s-1 for MO, MB, CR, and OG dyes in the single-dye system, respectively. In the binary system containing MB/OG or MB/MO, the catalyst Ag-Cu-MCM(0.05) was more selective toward the MB dye. The reuse of the catalyst for three consecutive cycles showed higher MB conversion in a single system with an increase in reaction time. For antifungal and antibacterial properties, the application of calcined and uncalcined materials toward six different strains showed good results, but uncalcined materials showed the best results due to the synergistic effect between CuO and unreduced species Ag+ which are considered responsible for the antibacterial and antifungal action.

Polymer–assisted preparation of porous wood–based metallic composites for efficient catalytic reduction of organic pollutants

The unreasonable emission of nitroaromatic organic pollutants (NOPs) has threatened the ecological environment. However, the existing catalytic materials for NOPs reduction can not meet the actual practical application due to various functional deficiencies. In this work, novel cellulose–based metallic composites with high catalytic activity for NOPs reduction were developed through polymer–assisted electroless deposition (ELD) technique coating metallic nanoparticles onto cellulose–based porous wood surfaces. The fabricated metallic composites display outstanding catalytic ability, catalytic universality and excellent durability for most NOPs, due to the uniform catalytic metal coating enabled by polymer–assisted ELD approach and sufficient catalytic sites provided by the porous wood host surfaces. The continuous flow catalytic systems using the fabricated bulk composites were further demonstrated showing the broad prospects of such designed metallic composites in actual practical applications. This work provides a new avenue to realize rational design and large–scale fabrication of novel high–performance catalysts for NOPs reduction applications.

Biogenic synthesis of reduced graphene oxide decorated with silver nanoparticles (rGO/Ag NPs) using table olive (olea europaea) for efficient and rapid catalytic reduction of organic pollutants

In this work, graphene oxide (GO) sheets were prepared via a facile electrochemical exfoliation of graphite in acidic medium and subsequent oxidation with potassium permanganate. The GO sheets were employed for preparation of reduced GO adorned with nanosized silver (rGO/Ag NPs) using green reduction of GO and Ag(I) via olive fruit extract as a reducing and immobilizing agent. The crystal phase, morphology, and nanostructure of the prepared catalyst were characterized by XRD, SEM, EDX, UV–Vis and Raman spectroscopy techniques. The as-prepared rGO/Ag NPs showed superior catalytic performance towards the complete reduction (up to 99%) of 4-nitrophenol (4-NPH) to 4-aminophenol (4-APH) and rhodamine B (RhB) to Leuco RhB within 180 s using NaBH4 at ambient condition. The rate constant (k) values were found to be 0.021 and 0.022 s−1 for 4-NPH and RhB reduction, respectively. In addition, the regenerated catalyst could be reused after seven cycles without losing any apparent catalytic efficiency. Accounting for the excellent catalytic capability, chemical stability and environment-friendly synthesis protocol, the rGO/Ag NPs has great potential working as a heterogeneous catalyst in the transforming harmful organic contaminants into less harmful or harmless compounds.

Black phosphorus@Au NPs decorated on a porous spherical montmorillonite as a self-sedimentary catalyst for cost-effective and efficient catalysis

Black phosphorus (BP) has exhibited its potential application as the cocatalyst substrate for catalytic reduction of organic pollutants due to its excellent electron transfer ability. However, the application was limited by the reuse process due to its light mass with abundant recovery devices involved. In this work, a micro-sized spherical montmorillonite (SMt) with the self-sedimentary property was used to support BP@Au NPs. The strong adsorption ability of porous SMt could increase the concentration of 4-nitrophenol near the catalytic active sites, thus, accelerating the catalytic process. The optimized apparent reduction rate constant of 6.1 min−1 and the turnover frequency of 648 h−1 were obtained, which was one of the most efficient catalytic system. More importantly, the fabricated SMt supported heterogeneous catalyst could be facile recycled without any devices involved. The morphology and catalytic performance were almost unaltered after recycling 20 times. Our straightforward strategy to solve the issue of the reuse process through a self-sedimentary substrate facilitates the practical application of these catalysts in the reduction of organic pollutants.

High effective catalyst based on Ni doped TiO2 coated natural cotton fibers for catalytic reduction of organic pollutants

ABSTRACT A new type of nickel doped titanium oxide (Ni-TiO2) coated natural cotton fibers (CF) and Ni-TiO2 wrapped sodium alginate (Alg) hydrogel was developed for the efficient reduction of different contaminants. Ni-TiO2 was prepared by low-temperature method and coated on CF using Alg as a binder and entrapped inside Alg hydrogel. Ni-TiO2 coated CF (Ni-TiO2/CF) and Ni-TiO2 wrapped Alg (Ni-TiO2/Alg) were utilized for catalytic elimination of wastewater pollutants. Ni-TiO2/CF and Ni-TiO2/Alg were initially tested as nanocatalysts for reduction of potassium ferricyanide, 4-nitrophenol, congo red, and methylene blue (MB), and exhibited superior catalytic performance toward MB reduction. Different parameters such as catalyst amount, MB concentration, reducing agent amount, and recyclability were optimized. Comparatively, Ni-TiO2/CF revealed the best catalytic performance for MB reduction having the highest reaction rate constant (2.1564 min−1). Ultimately, the catalyst preserved superior activity in recyclability evaluation, confirming that Ni-TiO2/CF is a good catalyst for the efficient removal of MB up to four cycles. Ni-TiO2/CF can more easily be recovered compared to Ni-TiO2/Alg by easily pulling out the fibers from reaction medium, which is the main advantage of Ni-TiO2/CF. Moreover, Ni-TiO2/CF and Ni-TiO2/Alg were examined in real samples, providing the effective reduction of MB. The developed nanocatalyst offers a cost- and time-effective material for environmental safety purpose.

Biosynthesis of bifunctional silver nanoparticles for catalytic reduction of organic pollutants and optical monitoring of mercury (II) ions using their oxidase-mimic activity.

In this study, an aqueous extract of Sclerocarya birrea leaves was used as a reducing agent to synthesize silver nanoparticles (AgNPs). The synthesis was carried out at room temperature and was both rapid and simple. Different characterization techniques such as UV/visible spectroscopy, surface-enhanced Raman spectroscopy, X-ray diffraction, and focused ion beam scanning electron microscopy were used to confirm the formation of AgNPs. The synthesized nanoparticles exhibited catalytic activity for the reduction of 4-nitrophenol, methyl orange, methylene blue, and rhodamine 6G. The catalytic activity was monitored by measuring the UV/visible absorbance spectra of the compounds using sodium borohydride as a reducing agent and found to be high. Additionally, the particles displayed oxidase-like activity. In the presence of AgNPs, 3, 3', 5, 5'-tetramethylbenzidine (TMB) which is colorless was transformed to oxidized TMB, which is blue, using dissolved oxygen as the oxidant. In the presence of Hg2+, the oxidase-like activity was enhanced. On the basis of this observation, an assay for the analysis of Hg2+ was developed. The linear range of the calibration curve is wide (0-600µM) and the limit of detection (LOD) is low, as small as 34.8nM. The method is strongly selective towards Hg2+. Tap water obtained from the laboratory where these experiments were carried out was used to study the feasibility of the method in real sample analyses.

Silver nanoparticles decorated on graphene oxide modified polyester fabric: Catalytic reduction of 4-nitrophenol, organic dyes and SERS application

We report on the immobilization of silver nanoparticles on functional graphene oxide modified polyester fabric (AgNPs@GO/PET) for catalytic reduction of organic pollutants. In this work, the polyester fabric was modified with hydrophobic graphene nanosheets using a simple dip-coating method. The as prepared hydrophobic inert graphene oxide modified polyester fabric (GO/PET) substrate was used to stabilize oleylamine coated monodispersed silver nanoparticles. The morphology, size, and structure of the catalyst was investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Raman spectroscopy. Outstanding catalytic performance was exhibited by the AgNPs@GO/PET catalyst for the reduction reaction of 4-nitrophenol, methyl orange and methyl red. Surface enhanced Raman scattering (SERS) was also employed for the time dependent monitoring of reduction of 4-Nitrothiophenol. The present work highlights the importance of the as developed catalyst for the catalytic reduction of organic pollutants and SERS sensing with excellent stability and reusability.

Insights into Catalytic Reduction of Organic Pollutants Catalyzed by Nanoparticles Supported on Zeolite Clinoptilolite

Insights into Catalytic Reduction of Organic Pollutants Catalyzed by Nanoparticles Supported on Zeolite Clinoptilolite

Role of nanomaterials in catalytic reduction of organic pollutants

Developing innovative technologies for the effective treatment of wastewater containing organic pollutants is of extreme importance across the globe. The organic pollutants such as dyes and nitrophenols are the common hazardous pollutants known for their adverse effects on humans and aquatic organisms. Various methods have been used for the removal of organic pollutants from wastewater but they suffer limitations such as high cost, time consuming removal process and production of sludge or toxic by-products. In recent years, chemical reduction method is becoming popular for removal of organic pollutants using various nanomaterials as catalysts. Nanomaterials show great potential for removal of organic pollutants due to large surface area which provides high catalytic activity. In the present review, current studies on catalytic reduction of organic pollutants (dyes and nitrophenols) using four different types of nanomaterials specifically carbon nanotubes, silica, metal oxide and chitosan polymer based have been explored. The factors affecting the catalytic process and mechanism of catalysis is explained in detail.In addition, a critical discussion about the pros and cons of each nano-catalyst have also been included for developing better understanding of the choice of catalyst.

Urchin-like hybrid nanostructures of CuOx/Fe2O3 from Cu-mediated pyrolysis of Fe-MOFs for catalytic reduction of organic pollutants.

MOFs have been widely used as templates to design and construct catalysis materials, such as LDH, metal oxides, and carbon. Herein, we developed a Cu-mediated pyrolysis protocol for the synthesis of urchin-like CuOx/Fe2O3 hybrid nanostructures using Fe-MOFs as the precursor. The hierarchical hybrids were composed of an inner CuOx-dispersed Fe2O3 octahedral matrix covered with radially grown Fe2O3 nanorods. This novel hierarchical hybrid nanostructure was generated likely due to the difference in the inward contraction rates between the Cu and Fe species during pyrolysis. Given the structural and compositional benefits, the urchin-like CuOx/Fe2O3 hybrids exhibited outstanding catalytic activity for the chemical reduction of 4-nitrophenol (4-NP) and dyes. Besides, CuOx/Fe2O3 was found to be highly catalytic in the reduction of 4-NP even after 30 consecutive runs, manifesting outstanding durability for continuous operation.

Zirconium nanoparticles-poly (N-isopropylacrylamide-methacrylic acid) hybrid microgels decorated graphene sheets for catalytic reduction of organic pollutants

First approach towards fabrication of zirconium-microgels@graphene is developed in this work. Hybrid microgels are loaded onto graphene sheets to boost the electron relay among pollutants and borohydride ions. For this purpose, poly(N-isopropylacrylamide-co-methacrylic acid) p(NIPAM-MAA) microgel is synthesized through precipitation polymerization method. Zirconium nanoparticle is fabricated inside microgels through in-situ reduction of zirconium ions then hybrid microgels are decorated onto graphene. Zr-p(NIPAM-MAA)@graphene composite is used as catalyst for reduction of following organic pollutants: Congo red, 4-nitrophenol, Safranine, methylene orange, methylene blue, 4-nitroanisole, 2,4 dinitrophenol and 4-nitrobenzoic acid. Values of apparent rate constant, percentage reduction and reduction time are calculated and compared.

Graphene oxide‐based noble‐metal nanoparticles composites for environmental application

Noble metal nanoparticles (NPs)-based materials have been widely applied in various environmental applications, including the catalytic reduction of organic pollutants and elimination of the microbial pathogens in wastewater due to its unique physicochemical properties. However, the stability and catalytic activity of NPs-based materials are limited due to their severe aggregation in aqueous environments. Recently, graphene oxide (GO), a 2D material with large specific surface area, has been used as a platform to load NPs as a NPs@GO nanocomposite with enhanced catalytic performance and stability. In this review, we focus on the discussion about the recent progress in the synthesis methods and properties of NPs@GO nanocomposites, recyclability of NPs@GO nanocomposites, and applications of the NPs@GO nanocomposites in catalytic reduction of organic pollutants and elimination of microbial pathogens in wastewater as well as the corresponding catalytic and antibacterial mechanisms. Finally, we conclude with perspectives on the remaining challenges as well as the recommendations for future development in this field.

Ultrasonic preparation of a new composite poly(GMA)@Ru/TiO2@Fe3O4: Application in the catalytic reduction of organic pollutants

This work concerns the preparation of a new composite material based on poly(Glycidyl methacrylate), Ru/TiO2 and Fe3O4 using ultrasound treatment. Several composites were prepared by varying the percentage of Ru/TiO2 and Fe3O4. Then, they were applied as catalysts for the reduction of several organic pollutants. 4-Nitrophenol (4-NPh), Methylene blue (MB) and Orange G (OG) were used as a model to study the photocatalytic reduction process in the presence of NaBH4 at room temperature. The obtained photocatalysts were characterized by different methods such as XRD, FTIR, XPS, SEM, EDX, TEM, STEM, TGA, ultraviolet–visible (UV–vis) spectroscopy and Zeta potential measurements. The results showed that the use of ultrasound gave a good dispersion of all species into the polymeric matrix. These solids have shown good activity via the photocatalytic reduction of organic pollutants. The best performance was obtained for the photocatalyst having the higher content of metal NPs “CP(30)”. The rate constant Kapp of composite CP(30) towards catalytic reduction of MB, OG and 4-NPh reached a high level up to 0.55 min−1, 0.241 min−1 and 0.3 min−1, respectively. Finally, the recyclability of the photocatalyst CP(30) was also evaluated. The results showed that the performance of this photocatalyst was satisfactory during its reuse.

Fe and Ni nanoparticles-loaded zeolites as effective catalysts for catalytic reduction of organic pollutants

Three zeolites with different structures (mazzit, faujasite and MFI) were prepared by hydrothermal way, and then were used to stabilize the Fe and Ni nanoparticles using ion exchange followed by treatment with a solution of NaBH4 as reducing agent. The designed nanocatalysts were used in the catalytic reduction of methylene blue dye (MB) and 4-nitrophenol (4-NP) in a simple and binary system under NaBH4 solution to determine their effectiveness in wastewater treatment. The obtained samples were characterized by XRD, XPS, nitrogen sorption at 77 K, XRF, FTIR, UV–vis, SEM and TEM. The obtained results revealed that the structure of the zeolites was well retained after immobilization of metal nanoparticles (NPs), but their textural properties were slightly reduced. The XPS results clearly show that the zero charge nanoparticles were well obtained using NaBH4 solution. As confirmed by TEM the nanoparticles were well dispersed in the surface of the zeolites their sizes were around 3–13 nm for the zeolites modified by Fe NPs and 2–6 nm for those modified by Ni NPs. The catalyst Ni–Y exhibited excellent catalytic activity towards the reduction of MB dye and 4-NP in binary and simple system due to its large surface area containing well dispersed Ni nanoparticles. The rate constant in a simple system was 0.02 s−1 and 0.005 s−1 for 4-NP and MB dye respectively, while in the binary system was 0.002 s−1 and 0.014 s−1. The catalyst Ni–Y was used in five consecutive experiments without important loss of activity, confirming its stability.