Catalytic Reduction Of Organic Dyes Research Articles

Highly efficient catalytic reduction of organic dyes, Cr (VI) and 4‐nitrophenol, and photocatalytic degradation of MB by an inorganic–organic hybrid polyoxometalate

It is urgent to remove various pollutants from the water environment. Therefore, an inorganic–organic hybrid polyoxometalate (POM) [PMoVI6MoV2VIV8O44{Co(2,2′‐bipy)2(H2O)}4]‐[PMoVI4MoV4VIV8O44{Co(2,2′‐bipy)2(H2O)}2]·4H2O (PMoVCo) was fully characterized by XRD, XPS, FTIR, SEM, BET and zeta potential techniques, and applied for the catalytic reduction of hazardous methylene blue (MB), methyl orange (MO), rhodamine B (RhB), Cr (VI) and 4‐nitrophenol (4‐NP) in aqueous media over NaBH4 under mild condition. The removal ratios were 99.6% (MB, 2.5 min), 97.0% (MO, 3.0 min), 92.5% (RhB, 2.0 min), 89.2% (Cr (VI), 2.0 min) and 89.6% (4‐NP, 2.5 min), respectively. The pseudo‐first‐order rate constants of the reactions were 1.992 min−1 (MB), 0.810 min−1 (MO), 1.768 min−1 (RhB), 1.186 min−1 (Cr (VI)) and 0.934 min−1 (4‐NP), respectively. Additionally, PMoVCo exhibited satisfactory catalytic activity for the photo‐Fenton‐like degradation of MB at neutral pH under visible light irradiation with a degradation rate up to 99.9% in 480 min. The results of the recycling experiment prove that PMoVCo has high catalytic reusability. Moreover, the possible mechanisms of the catalytic reduction and degradation processes were proposed. The catalytic activities of PMoVCo are better than other inorganic–organic hybrid POMs. All the results of this study indicate that PMoVCo has the potential to be a satisfactory catalyst for wastewater remediation via reduction or photocatalytic degradation.

Ti-doped Bi2(O,S)3 bimetal oxysulfide for highly efficient catalytic reduction of organic dyes and heavy metal pollutants in the dark

A bismuth-titanium bimetal oxysulfide BiTiOS catalyst was prepared via hydrolysis and characterized by different testing techniques. This BiTiOS catalyst, forming the Ti-doped Bi2(O,S)3 phase, can format the oxygen vacancy, increase its electrochemically active surface sites, enhance the electron lifetime, and facilitate fast electron transfer. The BiTiOS catalyst exhibits good electrochemical performance and long-term stability due to its excellent catalytic reduction activity for toxic organic of p-nitrophenol, organic dyes of methyl orange, methylene blue, and rhodamine, and the heavy metal ion of Cr(VI) in the presence of NaBH4 in the dark. The BiTiOS catalyst with the best reduction activity was prepared at a molar ratio of n(Bi): n(Ti): n(TAA) at 1: 2: 4. The 100 mL for each 20 ppm MO, MB, RhB, and 4-NP was reduced entirely in 4, 4, 2, and 8 min, respectively. In comparison, the reduction of 100 mL of 50 ppm Cr(VI) took 22 min. The BiTiOS-2 catalyst, showing fast reduction efficiency and excellent stability and durability, is expected to have great potential in wastewater treatment.

Ultralong hydroxyapatite nanowires-based flow-through reactor with high loading of silver nanoparticles for fast continuous catalytic reduction of organic dyes and disinfection of wastewater

The noble metal nanoparticles (NPs) immobilized flow-through reactors have attracted significant attention for the continuous and efficient purification of wastewater contaminated with organic dyes and microorganisms without the need of subsequent recycling processes. However, achieving both high loading of noble metal NPs and high permeation flux concurrently has been a challenge for most reported flow-through reactors. In this study, inspired by the mussel bio-adhesion strategy, we have employed the tannic acid coating method and successfully synthesized Ag NPs-loaded ultralong hydroxyapatite (HAP) nanowires that exhibited an ultra-high loading amount (21.8 wt%). These nanowires were utilized as building blocks alongside chitosan (CS) to fabricate robust and highly porous flow-through reactors (Ag@HAP/CS) for continuous catalytic reduction of organic dyes and water disinfection. The Ag@HAP/CS reactor demonstrates excellent catalytic reduction efficiency (99.3 %) towards MEB at a high flux (2000 L m−2 h−1) with an extremely low concentration of NaBH4 (MEB:NaBH4 = 1:1). This result is attributed to the high loading of Ag NPs, great structural stability in flowing water, and sufficient length along the flowing direction. The reactor also shows remarkable recyclability through water flushing. Ag@HAP/CS exhibits remarkable water disinfection performance against Escherichia coli and diverse bacteria in natural river water, achieving nearly 100 % disinfecting efficiency. This study provides new insights into the strategy of using nanomaterials as intermediate carriers of noble metal nanoparticles to fabricate 3D flow-through reactors, which enable fast and continuous purification of wastewater with ultra-high catalytic efficiency and antimicrobial performance.

Efficient reduction of organic pollutants by novel magnetic Bi2S3/NiCo2O4 MOF- derived composite: Exprimental and DFT investigation

Novel Bi2S3/NiCo2O4 nanocomposites (BS/NCO) with various mass ratios were prepared using NiCo-MOF as precursor. The morphology, composition and structure of the as-prepared catalysts were studied by different techniques such as FE-SEM, EDX, XRD, FT-IR, VSM and BET. The as-synthesized composite with 20 % Bi2S3 (%20 BS/NCO) demonstrated the best performance in reduction reaction of 4-nitrophenol (4-NP). The enhanced catalytic activity of %20 BS/NCO composite compared to the Bi2S3 and NiCo2O4 can be assigned to the optimized synergistic effects between the two pristine materials. Thermodynamic parameters and the activation energy of the reaction in the presence of %20 BS/NCO composite were calculated by conducting the reaction in various temperatures. Moreover, DFT calculations was used to explore the mechanism of 4-NP reduction in the presence of BS/NCO composite. BS/NCO composite was also used in catalytic reduction of organic dyes.

Facile phytosynthesis of gold nanoparticles-doped graphene oxide using Mangifera indica leaf extract: Characterization, antibacterial activity, and catalytic reduction of organic dyes

In this study, the gold nanoparticles-doped graphene oxide (AuNPs/GO) was prepared via a biosynthesis path using the Mangifera indica leaf extract. The characterization of produced AuNPs/GO was thoroughly conducted by modern methods such as X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, zeta potential, and so on. The analyses showed that spherical AuNPs were uniformly distributed on the GO sheets with an average diameter of 11–21 nm, proving the successful formation of AuNPs/GO nanocomposite. The initial effects of HAuCl4 volume, reaction time, pH level, the presence of 24-hour-prolonged GO, the amount of GO, and the experiment order were carried out to find the most suitable synthesis conditions and enhance the overall performance of AuNPs/GO. The results indicated that the most appropriate conditions for the fabrication process include 5 mL of extract, 1500 μL of HAuCl4, a reaction time of 120 s, at pH 7, 1500 μL of 24-hour-prolonged GO, and the experiment sequence of adding HAuCl4 to the remaining precursors. The nanocomposite was also discovered to effectively inhibit the growth of both Pseudomonas aeruginosa and Staphylococcus aureus bacteria strains, indicating nearly 100% of bactericidal rates at 50 μg/mL. Meanwhile, the catalytic reduction activity of organic dyes by NaBH4 using the AuNPs/GO support, tested with methylene blue, methyl orange, malachite green, and crystal violet dyes, was also excellent in terms of relatively high efficiency of 99.83, 93.81, 99.85, and 97.93%, respectively. Along with remarkable recovery and reusability confirmed, those results show the highly promising applications of AuNPs/GO in the antiseptics field and treatment of dye-contaminated water sources.

Preparation of manganese-doped tin oxide nanoparticles for catalytic reduction of organic dyes

Sol-gel method is used to fabricate morphologically controlled manganese-tin (Mn-Sn) bimetallic nanoparticles using manganese nitrate and tin chloride as precursors. Energy dispersive X-ray spectroscopy (EDX) is used to study the elemental composition and chemical formula of the synthesized products. Scanning transmission electron microscopy (STEM) is used to characterize the morphology of products. The catalytic property of Mn-Sn bimetallic nanoparticles is enhanced due to synergistic effect of both metals. The morphology of catalyst and the structure of organic dyes and nitro-compounds are used to compare the values of apparent rate constant, reduction time and percentage reduction.

In‐Situ Stabilizing Nano‐Ag onto Nonwoven Fabrics via a Mussel‐Inspired Approach for Continuous‐Flow Catalysis Reduction of Organic Dyes

AbstractA novel nonwoven‐fabric‐supported‐nano‐Ag (NWF/Ag) reactor was obtained via a mussel‐inspired in‐situ fabrication method. The resulting NWF/Ag features a high catalytic activity for the reduction reaction of organic dyes in the presence of sodium borohydride. More importantly, it is also feasible for the scale‐up catalysis in NWF/Ag‐assembled continuous‐flow reactors. Such a NWF/Ag catalyst preserves the fiber‐based three‐dimensional architecture to effectively drive the continuous‐flow catalysis reactions at unprecedented efficiency, benefiting from it the easy diffusion of dye molecules to access the active catalytic sites of nano‐Ag. Moreover, the resulting NWF/Ag composites can serve as versatile platforms to assemble continuous‐flow reactors in different shapes, sizes, and configurations to extend the catalysis applications. In this study, the catalytic reduction conversion of methylene blue can reach more than 98 % in 270 seconds using the NWF/Ag‐based channel‐type continuous‐flow reactor. It also preserves good catalytic reduction performance to other organic dyes, including methyl orange and acid orange 7. The NWF‐based platforms, combined with a rational designed approach of surface functionalization and hybridization, probably provide new insights into the catalytic reduction of organic dyes in a continuous‐flow way.

A novel AgMoOS bimetallic oxysulfide catalyst for highly efficiency catalytic reduction of organic dyes and Chromium (VI)

To detoxify chemical pollutants discharge from industries, the researchers pursue always to get new, cost-effective, environmentally friendly and efficient technologies. Herein, novel silver molybdenum oxysulfide (AgMoOS) catalyst which is monoclinic structure with spherical shape nanoparticle and uniform distribution of its elemental composition was successfully synthesized by a facile method. The catalytic performance of AgMoOS was employed for the reduction of methylene blue (MB), methyl orange (MO), 4-Nitrophenol (4-NP), Rhodamine B (RhB) and Chromium (VI) in presence of NaBH4 under dark condition and a fastest reduction activity was obtained with 2-AgMoOS. A 10 mg of 2-AgMoOS completely reduced 100 mL of 20 ppm of MB, MO, 4-NP, RhB and Cr6+ within 6, 6, 15, 24 and 24 min, respectively and the reduction kinetic data indicated that the catalytic activity of all AgMoOS catalysts toward these chemical pollutants followed the order: MB > MO > 4-NP > RhB > Cr6+ ions. The re-usability data toward the reduction of MB, cyclic voltammogram, XPS and XRD spectrum of 2-AgMoOS after the reaction were confirmed a good stability and durability of AgMoOS catalyst. Hence, AgMoOS is an efficient catalyst and provides a practical application for toxic organic dyes degradation and toxic inorganic pollutants containing waste water treatment and other environmental issues.

Self-assembled lignosulfonate-inorganic hybrid nanoflowers and their application in catalytic reduction of methylene blue and 4-nitrophenol

• Synthesis of hierarchical copper phosphate-lignosulfonate (Cu-LS) nanoflowers. • Structural confirmation of Cu-LS nanoflowers by FTIR, BET, XRD, SEM, elemental mapping and EDS analyses. • Catalytic performance of Cu-LS nanoflowers in the reduction of 4-NP and MB in aqueous media. • Cu-LS nanoflowers can be reused five times without any remarkable loss of catalytic activity. Hierarchical inorganic-organic nanostructures prepared using biosourced compounds have attracted a large amount of interest owing to their unique structure, good stability and potential applications. This study was undertaken to design efficient and green hierarchical copper phosphate-lignosulfonate (Cu-LS) nanoflowers with high catalytic sites by an eco-friendly self-assembly method for application in the catalytic reduction of organic dyes in aqueous media. The lignosulfonate played a critical role in controlling the size and morphology of Cu-LS nanoflowers. Moreover, catalytic tests showed the excellent catalytic degradation activity of Cu-LS nanoflowers toward methylene blue (MB) and 4-nitrophenol (4-NP) in the presence of NaBH 4 . In addition, the recycling tests showed the high stability and reusability of Cu-LS nanoflowers for at least five cycles with almost constant catalytic performance. This work presents new insights into the fabrication of lignin based catalysts with sustainable biomass derived components to degrade organic pollutants from aqueous solutions efficiently.

Catalytic Reduction of Organic Dyes by Multilayered Graphene Platelets and Silver Nanoparticles in Polyacrylic Acid Hydrogel

Graphene oxide has been widely used in the oxidative degradation of environmental pollutants. However, its catalytic role can be questioned as graphene oxide with oxygen-containing functional groups may also act as reactant in oxidative reactions. Herein, hydrogel composites loaded with multilayered graphene platelets showed excellent catalytic performance for the reduction of a wastewater organic pollutant (methylene blue) under NaBH4, which proved the catalytic role of multilayered graphene platelets. The liquid-based direct exfoliation method was used to prepare two-dimensional materials, which is compatible with other liquid phase methods to prepare nanomaterials. Hydrogel composites composed of multilayered graphene platelets, silver nanoparticles, and polyacrylic acid hydrogels were synthesized in water solution under irradiation with ultraviolet light, demonstrating the advantages of synthesizing nanocomposites using the liquid-based direct exfoliation method.

Green Synthesis of Silver and Gold Nanoparticles via Sargassum serratifolium Extract for Catalytic Reduction of Organic Dyes

The green synthesis of inorganic nanoparticles (NPs) using bio-materials has attained enormous attention in recent years due to its simple, eco-friendly, low-cost and non-toxic nature. In this work, silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) were synthesized by the marine algae extract, Sargassum serratifolium (SS). The characteristic studies of bio-synthesized SS-AgNPs and SS-AuNPs were carried out by using ultraviolet–visible (UV–Vis) absorption spectroscopy, dynamic light scattering (DLS), high-resolution transmission electron microscope (HR-TEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Phytochemicals in the algae extract, such as meroterpenoids, acted as a capping agent for the NPs’ growth. The synthesized Ag and Au NPs were found to have important catalytic activity for the degradation of organic dyes, including methylene blue, rhodamine B and methyl orange. The reduction of dyes by SS-AgNPs and -AuNPs followed the pseudo-first order kinetics.

Cyan color-emitting nitrogen-functionalized carbon nanodots (NFCNDs) from Indigofera tinctoria and their catalytic reduction of organic dyes and fluorescent ink applications.

The present study reports the synthesis of nitrogen-functionalized carbon nanodots (NFCNDs) by a low-cost hydrothermal method using the leaf extract of Indigofera tinctoria as a novel carbon precursor. The synthesized NFCNDs were characterized by diverse spectroscopic techniques. The optical properties of N-CNDs were analyzed by UV-visible and fluorescence spectroscopic studies. The quantum yield (QY) for the prepared NFCNDs was found to be 12.6%. The surface morphology, functional groups, and crystallinity of NFCNDs were evaluated by HR-TEM, FT-IR, XRD and Raman spectroscopic methods, respectively. The Raman results revealed the moderate graphite structure of NFCNDs, and the calculated ID/IG value was 0.49. The spherical appearance of the synthesized NFCNDs was confirmed by HR-TEM, and the calculated size of the NFCNDs was 4 nm. The XRD and SAED pattern results gives an evidence for the amorphous nature of the prepared NFCNDs. The thermal stability of NFCNDs was studied by TGA analysis. The resulting NFCNDs acted as a green nanocatalyst and thus efficiently improved the reducing capability of sodium borohydride (NaBH4) in the catalytic reduction of methylene blue (MB) and methyl orange (MO) dyes. Furthermore, the bright cyan emission characteristics of synthesized NFCNDs were utilized as a labeling agent in anti-counterfeiting applications.

Green synthesis of Ag nanoparticles on the modified graphene oxide using Capparis spinosa fruit extract for catalytic reduction of organic dyes

The utilization of various plants extracts for the green synthesis of nanoparticles is growing rapidly due to its widespread application in green chemistry. In the present study, a new green nanocomposite (Ag NPs-F-rGO) has been prepared by using Capparis spinosa fruit extract as a reducing factor. The organic groups were located on the surface of graphene oxide to increase the active sites of the nanocatalyst. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4‐nitrophenol (4‐NP), methylene blue (MB), methyl orange (MO), and rhodamin (Rh6g) in the presence of NaBH4 at room temperature. The apparent rate constants for 4-NP, MB, MO, and Rh6g reduction were calculated to be 0.020 s−1 (2 mg catalyst), 0.024 s−1 (2 mg catalyst), 0.023 s−1 (2 mg catalyst), and 0.008 s−1 (2 mg catalyst), respectively. The results show that Ag NPs-F-rGO nanocatalyst has good activity and recyclability, and can be reused several times without major loss of activity in the reduction process. The structure, morphology, and crystallinity phases of prepared nanocomposite (Ag NPs-F-rGO) were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD), respectively. The magnetic Ag NPs-F-rGO nanocomposite was prepared by adding Fe3O4 NPs and characterized by a vibrating-sample magnetometer (VSM).

Pd on poly(1-vinylimidazole) decorated magnetic S-doped grafitic carbon nitride: an efficient catalyst for catalytic reduction of organic dyes

A novel magnetic catalyst, (SGCN/Fe3O4/PVIs/Pd) was synthesized by growing of poly(1-vinylimidazole) on the surface of ionic liquid decorated magnetic S-doped graphitic carbon nitride, followed by stabilization of palladium nanoparticles. Catalytic activity of the prepared heterogeneous catalyst was explored for the catalytic reduction of hazardous dyes, methyl orange and Rhodamine B, in the presence of NaBH4. Besides, the effects of the reaction variables on the catalytic activity were investigated in detail. The kinetics study established that dye reduction was the first order reaction and the apparent activation energy was calculated to be 72.63 kJ/mol and 68.35 kJ/mol1 for methyl orange and Rhodamine B dyes, respectively. Moreover, ΔS# and ΔH# values for methyl orange were found to be − 33.67 J/mol K and 68.39 kJ/mol respectively. These values for Rhodamine B were − 45.62 J/mol K and 65.92 kJ/mol. The recycling test verified that the catalyst possessed good stability and reusability, thereby making it a good candidate for the catalytic purposes. Furthermore, a possible catalytic mechanism for dye catalytic reduction over SGCN/Fe3O4/PVIs/Pd was proposed.

Mussel-Inspired Magnetic Nanoflowers as an Effective Nanozyme and Antimicrobial Agent for Biosensing and Catalytic Reduction of Organic Dyes.

Mussel-inspired chemistry has been embodied as a method for acquiring multifunctional nanostructures. In this research, a novel mussel-inspired magnetic nanoflower was prepared through a mussel-inspired approach. Herein, magnetic PDA–Cu nanoflowers (NFs) were assembled via incorporating magnetic Fe3O4@SiO2–NH2 core/shell nanoparticles (NPs) into mussel-inspired polydopamine (PDA) and copper phosphate as the organic and inorganic portions, respectively. Accordingly, the flower-like morphology of MNPs PDA–Cu NFs was characterized by scanning electron microscopy (SEM) images. X-ray diffraction (XRD) analysis confirmed the crystalline structure of magnetic nanoparticles (MNPs) and copper phosphate. Vibrating sample magnetometer (VSM) data revealed the superparamagnetic behavior of MNPs (40.5 emu/g) and MNPs PDA–Cu NFs (35.4 emu/g). Catalytic reduction of MNPs PDA–Cu NFs was evaluated through degradation of methylene blue (MB). The reduction of MB pursued the Langmuir–Hinshelwood mechanism and first-order kinetics, in which the apparent reduction rate Kapp of MB was higher than 1.44 min–1 and the dye degradation ability was 100%. MNPs PDA–Cu NFs also showed outstanding recyclability and reduction efficiency, for at least six cycles. Furthermore, the prepared MNPs PDA–Cu NFs demonstrated a peroxidase-like catalytic activity for catalyzing 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue oxidized TMB (oxTMB) solution in the presence of H2O2. Antimicrobial assays for MNPs PDA–Cu and PDA–Cu NFs were conducted on both Gram-negative and Gram-positive bacteria. Moreover, we demonstrated how the existence of magnetic nanoparticles in PDA–Cu NFs influences the inhibition of an increasing zone. Based on the results, mussel-inspired magnetic nanoflowers appear to have great potential applications, including those relevant to biological, catalysis, and environmental research.

Composites beads based on Fe3O4@MCM-41 and calcium alginate for enhanced catalytic reduction of organic dyes

This work concerns the preparation of composite beads based on calcium alginate and Fe3O4@MCM-41. In the first step, the material Fe3O4@MCM-41 was prepared mechanically using several Fe3O4 contents, then was encapsulated by calcium alginate as a cross-linking matrix to give the composites MC@CA(x). The composite beads were used as catalysts for the reduction of MB and OG dyes in a simple system. Several parameters affecting the reduction reaction were investigated such as effect of the shape of composite beads, concentration of NaBH4, Fe3O4 content, catalyst mass and initial concentration of dye. The obtained results showed a higher immobilization of Fe3O4@MCM-41 in the alginate matrix leading to a high porous structure. The results showed that these catalysts have interesting catalytic activities towards the reduction of MB dye in which the reaction was more efficient with the catalyst containing a higher content of Fe3O4. The MC@CA(1) aerogel catalyst was the best in terms of stability compared to its MC@CA(1) hydrogel counterpart. Finally, the MC@CA(1) aerogel composite was reused in five successive cycles, with a slight loss of its activity during the fifth cycle due to the slight leaching of iron in the reaction medium.

Eco-friendly floatable foam hydrogel for the adsorption of heavy metal ions and use of the generated waste for the catalytic reduction of organic dyes.

Benefiting from their three-dimensional network structure and various functional groups, hydrogels have emerged as efficient adsorbents for the removal of heavy metal ions from wastewater. However, the obvious drawbacks of hydrogels such as generation of toxic secondary waste after adsorption and difficulty in their separation and collection limit their practical application in wastewater treatment. Herein, we introduced a facile strategy of combining mechanical frothing and in situ radical polymerization to prepare a floatable porous foam hydrogel, which not only efficiently removed Cu2+ from water, but also could be easily collected. After adsorption, to avoid the generation of secondary toxic waste, a sustainable strategy of turning the waste into useful materials was introduced. The waste of the Cu2+_ adsorbed hydrogel was processed using NaBH4 solution to obtain a Cu nanoparticle (Cu NP)-loaded composite hydrogel, which was further employed as a catalyst for the catalytic reduction of organic dyes. Thus, this work established a convenient and sustainable strategy for the preparation of an eco-friendly floatable foam hydrogel for the efficient removal of heavy metal ions such as Cu2+ from water and turning the generated waste into useful materials, which is a concept envisaged to be applicable to other heavy metal ion-adsorbed hydrogel systems and will efficiently avoid unwanted secondary pollution.

Synthesis of silver/reduced graphene oxide for antibacterial activity and catalytic reduction of organic dyes

The present study involved the preparation of silver-reduced graphene oxide (Ag/rGO) using co-precipitation method. The characteristics of Ag/rGO were confirmed by X-ray Diffraction patterns, Fourier transformation infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area, scanning electron microscopy, and energy-dispersive spectroscopy. The results demonstrated that silver nanoparticles (AgNPs) having diameter of 16 ± 3.7 nm were uniformly integrated on reduced graphene oxide (rGO) The as-synthesized Ag/rGO had a specific area of 54m2/g and 67.36 wt% silver. Antibacterial and catalytic properties of Ag/rGO were then further investigated. Ag/rGO was found to effectively inhibit the developing of gram-negative and gram-positive bacteria such as Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa with the bactericidal rates of 89.35, 95.67, and 99.99 %, respectively. In addition, the catalytic property of Ag/rGO in the reduction of organic dyes was tested with different dosage of reducing agent, amount of catalyst, type of dye, and reaction time. More than 99 % of dyes in aqueous solution at 20 mg/L concentration were reduced after 30 min with amounts of Ag/rGO and sodium borohydride of 10 and 30 mg successively. All results confirmed the potential application of Ag/rGO in the treatment of infected water and dye contamination.

Catalytic Reduction of Organic Dyes with Green Synthesized Silver Nanoparticles using Aloe vera Leaf Extract

In this present study, we report a facile, cost-effective and non-toxic method of synthesis of silver nanoparticles using 4mM silver nitrate and aqueous leaf extract of Aloe vera as reducing and capping agent in presence of 25% ammonia solution. Then these green synthesized nanoparticles are used as catalysts for the degradation of organic dyes. The synthesized silver nanoparticles (AVSNPs) were characterized using different techniques like UV-Visible spectroscopy, Fourier infrared spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray diffraction (XRD), Field emission-scanning electron microscopy (FESEM) and Energy Dispersive X-Ray Spectroscopy (EDAX). Further, the nanoparticles were seen to degrade organic dyes which were visibly seen and also recorded in UV-Visible Spectrometer. The initial synthesis of silver nanoparticles is confirmed by a peak at 417nm. The nanoparticles were found to be spherical in shape with an average size ranging between 11-23 nm. XRD analysis confirmed the formation of silver nanoparticles of crystalline nature and a face-centered cubic (fcc) lattice and FTIR analysis showed the involvement of the biomolecules in the reduction of silver to form silver nanoparticles and the EDAX confirmed the presence of silver nanoparticles. The green synthesized nanoparticles catalyze the degradation of different organic dyes in a very short period of time. The green synthesized silver nanoparticles were seen to show excellent activity in catalyzing the degradation of organic dyes in an aqueous medium in the presence of the electron donor sodium borohydride (NaBH 4 ). Keywords: Aloe vera, catalysis, dye reduction, green synthesis, NaBH4, organic dyes, silver nanoparticles

Quaternized polyhedral oligomeric silsesquioxanes stabilized Pd nanoparticles as efficient nanocatalysts for reduction reaction

Hydrophilic quaternized polyhedral oligomeric silsesquioxane (QPOSS) stabilized palladium nanoparticles hybrids (PdNPs@QPOSS) were successfully constructed for catalytic reduction of organic dyes and nitrophenols. The size of PdNPs can be effectively regulated through the molar ratio between QPOSS and Pd precursors. Uniformly dispersed nano-sized QPOSS encapsulated ultra-fine PdNPs with average diameter of 2.38 nm were obtained as the molar ratio of precursors was 1:8. It was found that low-dose PdNPs@QPOSS nanohybrids as catalysts exhibited outstanding catalytic reduction activity for methylene blue (MB) and nitrophenol (4-NP) with high conversion frequencies (TOF) of 213.7 and 17.8 min−1 respectively, which is superior to commercial Pd/C catalyst. The nanocatalysts we prepared could be stably dispersed in water for one month and there was no significant loss of catalytic activity in four catalytic cycle. The enhanced catalytic activity and good stability can be attributed to QPOSS as a stabilizer having strong coordination with as-generated PdNPs. In addition, we evaluated the decolorizing properties of common organic pollutants including methyl orange (MO), congo red (CR), methyl orange (MO), rhodamine 6G (R6G), rhodamine B (RhB), rhodamine 6G (R6G), and nitrophenol derivatives. The organic-inorganic hybrid nanocatalyst PdNPs@QPOSS is very effective in catalytic reduction of a series of colored dyes and nitrophenols, which also means that the nanohybrid as catalyst has a wide range of applications in industrial degradation of organic pollutants in wastewater.