Photocatalytic Reduction Of 4-nitrophenol Research Articles

Photocatalytic reduction of 4-nitrophenol over eco-friendly NixCuxFe2O4 without an additional reducing agent in water

Organic pollutants such as 4-nitrophenol (4-NP) pose serious environmental extortions due to their chemical stability for which efficient catalytic materials are indispensable in treating them. In this regard, the present work involves the synthesis of two different types of ferrites (NiFe2O4, and CuFe2O4), and a combination of NixCuxFe2O4 with various ratios that systemically work as efficient photocatalysts without any additional reducing agents is reported. The structural, and morphological properties of NiFe2O4, CuFe2O4, and NiCuFe2O4 were characterized by XRD, FT-IR, SEM, and HRTEM techniques. Then, the catalytic role of individual ferrite catalysts was evaluated towards catalytic reduction of 4-NP under visible light. The progress dye reduction was examined via UV–vis spectrophotometry. The effect of various concentrations, and reduction time were investigated. The kinetic rate constants determined for NiFe2O4, CuFe2O4, and NixCuxFe2O4 revealed that Ni and Cu in bimetallic ferrites promoted the reduction reaction under visible light. The results demonstrated that the photo-reduction efficiency of the Ni0.7Cu0.3Fe2O4 catalyst over 4-NP (conc. 10 ppm) to 4-AP was determined as 82 % under 120 miniutes with good recyclability up to six cycles. The mechanism of photocatalytic reduction of ferrites without the use of a reducing agent was studied. Such facile and productive ferrite materials could be employed as efficient photocatalysts for the reduction of toxic organic contaminants in environmental treatment.

Facile preparation of a multicomponent catalytic system Bi2O3/Bi2S3/CDs with an exceptional catalytic activity in the photocatalytic reduction of 4-nitrophenol

Industrial and agricultural wastewater containing 4-nitrophenol (4-NP) has serious toxic effects on human beings and environments. We reported a novel visible-light-driven nanocomposite with carbon dots (CDs) doped on the surface of Bi2O3/Bi2S3 (abbreviated as BB), that is BB/CDs, acted as an efficient photocatalyst for 4-NP reduction. The structure, morphology and optical properties of the BB/CDs composite were characterized and investigated in detail. The reduction from 4-NP to 4-aminophenol (4-AP) could be completed within only 2 min over the optimized composite in the presence of NaBH4, while for saturated 4-NP solution, the completed reduction is within 1 h. This simple catalytic system might provide a new method for both industrial application and environmental remediation.

Photocatalytic Reduction of 4-Nitrophenol over Bismuth Sulfur/Titanium Dioxide Heterojunction: Influence of Bismuth Sulfur Content on the Reaction Efficiency

Photocatalytic reduction of 4-nitrophenol is one of the most promising methods to remove this hazardous pollutant from wastewaters and generated a raw compound widely use in industrial processes. In the present work, three Bi2S3/TiO2 catalysts with different Bi2S3 content, were synthesized by a hydrothermal method. The materials were characterized by XRD, X-ray fluorescence, physisorption of N2, HRTEM, UV-Vis reflectance spectroscopy and zeta potential measurements. The catalytic activity of the synthesized materials was tested in the photoreduction of 4-nitrophenol in aqueous medium. Although the results indicate the formation of heterojunction for all the samples, the physicochemical properties of each material depend on the Bi2S3 content. The material with 6%wt of Bi2S3 exhibit the major catalytic activity, reducing 80% of the target molecule within 60 minutes of reaction.

Effect of Co-catalyst (CuO, CoO or NiO) on Bi2O3–TiO2 Structures and Its Impact on the Photocatalytic Reduction of 4-nitrophenol

CoO, NiO or CuO oxides were employed as co-catalysts on Bi2O3–TiO2 (BT) structure in the photocatalytic reduction of 4-nitrophenol under UV light irradiation. The intimate contact between the co-catalysts and base material contributed to an enhancement in the photocatalytic activity due to the formation of the p-n heterojunction that effectively separates charge carriers. CuO–BT, NiO–BT and Co–BT showed a reduction of 4-nitrophenol of 83%, 59% and 52% after 60 min under illumination, respectively, which are higher than that obtained with the BT semiconductor. The co-catalysts increase the donor density favoring the reduction of 4-nitrophenol. The donor density calculated for CuO–BT, NiO–BT and Co–BT was of Nd = 15.5 × 1018 cm−3, Nd = 12.4 × 1018 cm−3 and Nd = 9.41 × 1018 cm−3, respectively. The results were associated to that CuO and NiO oxides are considered as reduction co-catalysts while CoO oxide is used as oxidation co-catalyst.

Palladium Nanoparticles Embedded in Yolk–Shell N-Doped Carbon Nanosphere@Void@SnO2 Composite Nanoparticles for the Photocatalytic Reduction of 4-Nitrophenol

Herein, a novel visible-light-driven yolk–shell nanoreactor has been fabricated, called as Pd/N–Cs@SnO2, which is consisted of movable nitrogen-doped carbon sphere (N–Cs) yolk, interlayer void, mesoporous tin oxide (SnO2) shell, and encapsulated palladium nanoparticles (Pd NPs). The obtained yolk–shell Pd/N–Cs@SnO2 nanoreactor can serve as an excellent catalyst in the visible-light-driven photocatalytic reduction of 4-nitrophenol (4-NP). More importantly, Pd/N–Cs@SnO2 exhibits a remarkable superior activity and higher reusability than core–shell Pd@SnO2 and yolk–shell Pd/N–Cs@mSiO2 nanoreactors. The fabulous character of Pd/N–Cs@SnO2 nanoreactor is attributed to (I) the mesostructured SnO2 shell provides a large surface area for the collection of light as well as the anchoring of Pd to avoid aggregating or leaching; (II) the interlayer void space improves the light absorption by multiple scattering, as well as favors the contact of active sites with reactants in the photocatalytic reactions; (III) the N–Cs allow more permeable visible-light absorption, and accelerate the photoexcited electrons transportation from SnO2 semiconductor to Pd NPs to suppress the electron–hole recombination. This enriches the electron density of Pd NPs surface and then facilitates the photocatalytic reduction of 4-NP. Both the structural advantages and enhanced synergy of Pd/N–Cs@SnO2 nanoreactor make it to be an efficient and stable photocatalyst, which can open an avenue for designing photocatalysts in a board range of organic reactions.

Photocatalytic reduction of 4-nitrophenol using effective hole scavenger over novel Mg-doped Zn(O,S) nanoparticles

Novel Mg-doped Zn(O,S) nanoparticles were synthesized by a chemical precipitation process at 90℃ and the prepared nanoparticles were characterized by XRD, SEM, HRTEM, XPS, UV–vis, DRS, PL, EIS, and photocurrent response. The photocatalytic reduction for the 4-nitrophenol using Na2SO3 under UV light irradiation showed that Mg–Zn(O,S)-2.5 exhibited higher activity compared with other samples. 96.7% of 4-nitrophenolate ion reduced into 4-aminophenol within 45min. Mg–Zn(O,S)-2.5 was also tested for hydrogen evolution, where the rates of 1035μmol/g for the 4-NP-free sample and 705μmol/g for the 4-NP-added one were achieved. Finally, the stability and reaction mechanism was mentioned.

Photocatalysis as an advanced reduction process (ARP): The reduction of 4-nitrophenol using titania nanotubes-ferrite nanocomposites.

TiO2 photocatalysis is an advanced process, employed worldwide for the oxidation of organic compounds, that leads to significant technological applications in the fields of health and environment. The use of the photocatalytic approach in reduction reactions seems very promising and can open new horizons for green chemistry synthesis. For this purpose, titanium dioxide nanotubes (TNTs) were developed in autoclave conditions using TiO2 P25 as a precursor material. Based on these nanotubular substrates, TiO2/CoFe2O4 (TCF) nanocomposites were further obtained by wet impregnation method. The materials were thoroughly characterized and their structural, textural, vibrational, optoelectronic and magnetic properties were determined. The composite materials combine absorbance in the visible optical range and high BET surface area values (˜100 m2/g), showing extremely high yield in the photocatalytic reduction of 4-nitrophenol (4-NP), exceeding 94% within short illumination time (only 35 min). The developed nanocomposites were successfully reused in consecutive photocatalytic experiments and were easily removed from the reaction medium using magnets. Both remarkable recycling ability and high-performance stability in the photocatalytic reduction of nitrophenol were observed, thus justifying the significant economic potential and industrial perspectives for this advanced reduction process.

Photoreduction of 4-Nitrophenol in the presence of carboxylic acid using CdS nanofibers

The photocatalytic reduction of 4-Nitrophenol was assisted with blue light irradiation using CdS semiconductor nanofiber. The kinetic study of the blue-photoreduction of 4-Nitrophenol to 4-Aminophenol was performed by using Na2SO3 as “hole scavenger” in the presence of middle carboxylic acids (acetic, oxalic and citric acid). The effect of photocatalyst load, the carboxylic acid concentration and of the pH solution (acid, neutral and alkaline media) were investigated. The maximum 4-Nitrophenol photoreduction rate was reached in neutral media and it is related to the enhanced “hole scavenging” effect caused by the SO32− or HSO32− ions in the presence of carboxylic acid. Electrochemical characterization of CdS nanofiber was made in the presence of 4-NP and citric acid. The 4-NP photoreduction reaction follows a zero order reaction and a possible mechanism to explain the fast electron transfer process is discussed as a consequence of the carboxylic acid adsorbed on the CdS surface.

Photocatalytic reduction of 4-nitrophenol on in situ fluorinated sol–gel TiO2 under UV irradiation using Na2SO3 as reducing agent

The in situ fluorination of the TiO2 semiconductor was performed via sol–gel method. Photocatalysts with different fluoride percentage were synthesized using ammonium fluoride as hydrolysis catalyst and as anionic precursor. For comparison, sol–gel TiO2 was also studied as a reference material. The solids were characterized using several techniques in order to analyze their structural, textural and optical properties. The fluorination of the TiO2 favored the preferential formation of the anatase phase and an increase in the crystallinity; in contrast, a decrease in the specific surface area was observed. The photocatalytic activity of the materials was evaluated in the 4-nitrophenol photoreduction to 4-aminophenol using Na2SO3 as reducing agent under UV light irradiation. It was found that the generation of the ≡Ti–F surface species increased the photocatalytic properties of the semiconductor; thus, the 4-nitrophenol photoreduction rate using the fluorinated solids was higher compared with the sol–gel TiO2 and Degussa P-25. Favorable efficiency in the photoreduction of the 4-NP molecule after the recycling experiments of the photocatalyst was observed.

Synthesis, Characterization and Photocatalytic Application of Different Sizes of Gold Nanoparticles on 4-Nitrophenol

In this work, different sizes of gold nanoparticles were synthesized at room temperature by using trisodium citrate as a surfactant stabilizing agent and sodium borohydride as a reducing agent. Transmission Electron Microscopy (TEM) confirmed that the samples were synthesized in spherical shapes with three different particle sizes: 4 nm, 7 nm and 11 nm. Ultraviolet-visible spectra measurements were used to analyze the way that surface plasmon bands were affected by the different particles sizes. The effect of sphere size on photocatalytic reduction of 4-Nitrophenol was then studied and the rate constant of the reduction was calculated to be 0.014 s-1, 0.0091 s-1 and 0.003 s-1 for particles sizes of 4 nm, 7 nm and 11 nm, respectively. The results obtained indicated that small particles were more active in catalytic reduction due to their high surface energy.

Synthesis of new ZnS–Bipy based hybrid organic–inorganic materials for photocatalytic reduction of 4-nitrophenol

4,4-Bipyridine ligand was attainted to react with ZnS surface forming ZnS–Bipy materials that are efficient catalysts for photoreduction of 4-nitrophenol.