Application of ZnO-Fe3O4 nanocomposite on the removal of azo dye from aqueous solutions: Kinetics and equilibrium studies

In this study, zinc oxide was immobilized on magnetite nanoparticles by chemical method and it was used as an adsorbent to remove reactive black 5 (RB5) dye from aqueous solution. The removal efficiency of RB5 was studied as the function of adsorbent dosage, pH, initial RB5 concentration, H2O 2, and ionic strength (sodium carbonate, sodium bicarbonate, sodium sulfate, and sodium chloride). Removal efficiency of RB5 by ZnO-Fe 3O4 was greater than that by ZnO and Fe3O 4 in similar conditions. Maximum adsorption of ZnO-Fe 3O4 was obtained at neutral pH, and adsorption capacity was estimated to be 22.1 mg/g. Adsorption kinetic study revealed that the pseudo-second-order model better described the removal rate than the pseudo-first-order model. Adsorption isotherm was analyzed by both Langmuir and Freundlich equations, and results showed that it was better described by the Langmuir equation. The removal efficiency of RB5 was increased with increasing initial H2O2 concentrations from 2 to 5 mM but was decreased above 5 mM. The adsorption capacities of RB5 was increased in the presence of NaCl but was greatly decreased in the presence of bicarbonate, carbonate, and sulfate ion. Adsorption activity of RB5 by ZnO-Fe 3O4 composite was maintained even after five successive cycles, suggesting a promising adsorbent for wastewater-contaminated organic dyes. © Springer International Publishing Switzerland 2014

Removal of reactive black 5 dye from aqueous solutions by Fe3O4@SiO2-APTES nanoparticles

In this study, Fe3O4@SiO2-APTES nanoparticles were successfully synthesized via a one-pot route in order to remove reactive black 5 dye from aqueous solutions. To obtain optimal conditions on the dye removal efficiency, the effects of various parameters were investigated including solution pH, initial dye concentration, and absorbent dosage. According to the experimental results, the removal efficiency of the dye decreased with increasing in pH and initial dye concentration, as well as with decreased adsorbent dosage. In fact, about 100.00 % of reactive black 5 was removed from aqueous solution using Fe3O4@SiO2-APTES NPs at the adsorbent amount of 0.4 g L^-1 and pH = 3 in 90 min. The kinetics were found well match with pseudo-second-order equation. The isotherm analysis indicated that the equilibrium data were well fitted to the Langmuir isotherm model, showing a monolayer adsorption manner of the dyes on homogeneous surface of nanoparticles. Also, the results of absorbent recycling showed that this nanoparticle could be reused up to 6 times with high efficiency

Photocatalytic degradation of Metronidazole with illuminated TiO<inf>2</inf> nanoparticles

Metronidazole (MNZ) is a brand of nitroimidazole antibiotic, which is generally used in clinical applications and extensively used for the treatment of infectious diseases caused by anaerobic bacteria and protozoans. The aim of this investigation was to degrade MNZ with illuminated TiO2 nanoparticles at different catalyst dosage, contact time, pH, initial MNZ concentration and lamp intensity. Maximum removal of MNZ was observed at near neutral pH. Removal efficiency was decreased by increasing dosage and initial MNZ concentration. The reaction rate constant (kobs) was decreased from 0.0513 to 0.0072 min−1 and the value of electrical energy per order (EEo) was increased from 93.57 to 666.67 (kWh/m3 ) with increasing initial MNZ concentration from 40 to 120 mg/L, respectively. The biodegradability estimated from the BOD5/COD ratio was increased from 0 to 0.098. The photocatalyst demonstrated proper photocatalytic activity even after five successive cycles. Finally, UV/TiO2 is identified as a promising technique for the removal of antibiotic with high efficiency in a relatively short reaction time

Optimization of dimethyl phthalate degradation parameters using zero-valent iron nanoparticles by response surface methodology: Determination of degradation intermediate products and process pathway

Background and purpose: Phthalic acid esters (PAEs) are a group of organic compounds that are used as additives in plastic industry. Among PAEs, dimethyl phthalate (DMP), the simplest compound in phthalates, is an aromatic pollutant that disturbs endocrine function. The aim of this study was to assess the effect of zero-valent iron nanoparticles (NZVI) on the DMP degradation. Materials and methods: NZVI were prepared by reduction of ferric chloride using sodium borohydride. Physical properties of nanoparticles were determined using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Vibrating Sample Magnetometer (VSM). Then, the effect of pH, DMP concentrations, the amount of NZVI, and contact time were investigated on DMP removal efficiency. Response surface methodology based on Box- Behnken was used to study the interaction between variables. Results: Maximum efficiency (99) of DMP removal by NZVI was achieved in optimum conditions (pH=3, NZVI dosage =0.6 g/l, DMP concentration = 2 mg/l, and contact time= 65 min). The Box-Behnken analysis confirmed that pH and NZVI dosage have had the highest and lowest effect in the process of DMP removal by NZVI, respectively. Conclusion: According to findings, NZVI in small amounts have a proper efficiency in DMP removal. Also, DMP degradation efficiency did not change much, after being used in five consecutive cycles of degradation reactions. This shows a potential application prospect of the synthesized NZVI in real water treatment. © 2015 Journal of Mazandaran University of Medical Sciences. All Rights Reserved

Optimization of dimethyl phthalate degradation parameters using zero-valent iron nanoparticles by response surface methodology: Determination of degradation intermediate products and process pathway

Background and purpose: Phthalic acid esters (PAEs) are a group of organic compounds that are used as additives in plastic industry. Among PAEs, dimethyl phthalate (DMP), the simplest compound in phthalates, is an aromatic pollutant that disturbs endocrine function. The aim of this study was to assess the effect of zero-valent iron nanoparticles (NZVI) on the DMP degradation. Materials and methods: NZVI were prepared by reduction of ferric chloride using sodium borohydride. Physical properties of nanoparticles were determined using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Vibrating Sample Magnetometer (VSM). Then, the effect of pH, DMP concentrations, the amount of NZVI, and contact time were investigated on DMP removal efficiency. Response surface methodology based on Box- Behnken was used to study the interaction between variables. Results: Maximum efficiency (99) of DMP removal by NZVI was achieved in optimum conditions (pH=3, NZVI dosage =0.6 g/l, DMP concentration = 2 mg/l, and contact time= 65 min). The Box-Behnken analysis confirmed that pH and NZVI dosage have had the highest and lowest effect in the process of DMP removal by NZVI, respectively. Conclusion: According to findings, NZVI in small amounts have a proper efficiency in DMP removal. Also, DMP degradation efficiency did not change much, after being used in five consecutive cycles of degradation reactions. This shows a potential application prospect of the synthesized NZVI in real water treatment. © 2015 Journal of Mazandaran University of Medical Sciences. All Rights Reserved

Application of Ni-doped ZnO rods for the degradation of an azo dye from aqueous solutions

Ni-doped ZnO rods were applied as a photocatalyst for the degradation of an azo dye (Reactive Black 5). Effects of solution pH, catalyst dosage, initial RB5 concentration, H2O2 concentration, different purging gases, and type of organic compounds on the removal efficiency of RB5 were studied. Ni-doped ZnO rods were synthesized by co-precipitation method. Neutral pH was selected as an optimal pH condition due to a photo-corrosion of ZnO in acidic and basic conditions. Photocatalytic degradation efficiency of RB5 was increased as the catalyst dosage increased up to 1 g/L, while it was decreased by increasing initial RB5 concentration. Pseudo-first-order rate constant (kobs) decreased from 0.122 to 0.0051 min-1 and electrical energy per order (EEo) increased from 39.34 to 941.18 (kWh/m3) by increasing RB5 concentration from 5 to 100mg/L, respectively. Photocatalytic degradation efficiency of RB5 increased by increasing H2O2 concentration, but this trend was not observed above 10 mM. Photocatalytic degradation efficiency of RB5 increased in the presence of folic acid and citric acid while interference was observed in the presence of humic acid, EDTA, oxalic acid, and phenol. Photocatalytic activity was maintained even after five successive cycles. © 2016, Korean Institute of Chemical Engineers, Seoul, Korea

Application of thiol-functionalized mesoporous silica-coated magnetite nanoparticles for the adsorption of heavy metals

This study investigated the removal of heavy metals such as Ni(II), Cu(II), and Cr(III) in aqueous solutions by the synthesis of thiol-functionalized mesoporous silica-coated magnetite nanoparticles (TF-SCMNPs) with different pH levels, contact times, and adsorbent dosages. The synthesis of TF-SCMNPs samples occurred with simple co-precipitation methods. FT-IR, X-ray diffraction, SEM, energy dispersive X-ray, and VSM techniques were used for characterization of the prepared adsorbent. The removal efficiency of heavy metals by TF-SCMNPs was more than that of magnetite in similar conditions. The results showed that the maximum adsorption of TF-SCMNPs for Ni(II), Cu(II), and Cr(III) was obtained at pH 7, 10, and 10 during the contact time of 20 min, respectively. By increasing adsorption dosage the removal efficiency was increased. The study of the adsorption kinetic model revealed that the pseudo-second-order model was the best applicable one to describe the adsorption of Ni(II) and Cu(II), pseudo-first-order model for Cr(III)onto TF-SCMNPs. Adsorption data were analyzed by both Langmuir and Freundlich adsorption isotherms and the results showed that it was better described by the Langmuir model for Ni(II), Cu(II), and Freundlich model for Cr(III). The maximum adsorption capacities were estimated to be 4.476, 4.038, and 1.119 mg/g at optimum pH and room temperature for Cu(II), Ni(II), and Cr(III), respectively. TF-SCMNPs nanoparticles were maintained even after five successive cycles, suggesting a promising adsorbent for aquatic-contaminated heavy metals. © 2015 Balaban Desalination Publications. All rights reserved

Synthesis, characterization, and application of ZnO/TiO2 nanocomposite for photocatalysis of a herbicide (Bentazon)

The purpose of this investigation was to study the applicability of ZnO�TiO2 composite as a photocatalyst for degradation of Bentazon. Effects of various parameters such as catalyst dosage, pH, initial Bentazon concentration, oxygen purging gas, hydrogen peroxide concentration and type of organic compounds on the removal efficiency of Bentazon were studied. The results of SEM and FT-IR analysis demonstrated favorable immobilization of zinc oxide nanoparticles onto TiO2. The greatest removal of Bentazon was observed at neutral pH due to photo-corrosion of ZnO on composite in acidic and basic conditions. The pseudo-first-order rate constant (kobs) and electrical energy per order (EEo) were greatly dependent on the Bentazon concentration. Removal efficiency of Bentazon was increased with O2 purging and addition of H2O2, while it was decreased in the presence of organic compounds. Removal efficiency of Bentazon by UV/ZnO/TiO2 process was greater than that by UV/TiO2 process, UV/ZnO, and UV alone. Photocatalytic activity was maintained even after five successive cycles. © 2015 Balaban Desalination Publications. All rights reserved

Enhanced photocatalytic activity of Fe3O4-WO3-APTES for azo dye removal from aqueous solutions in the presence of visible irradiation

Development of highly active photocatalysts for treatment of dye-laden wastewaters is vital. The photocatalytic removal of azo dye Reactive Black 5 was investigated by Fe3O4-WO3-3-aminopropyltriethoxysilane (APTES) nanoparticles in the presence of visible light. The Fe3O4-WO3-APTES nanoparticles were synthesized via a facile coprecipitation method. The photocatalyst was characterized by XRD, FT-IR, SEM, EDX, VSM, UV�Vis, and pHPZC techniques. The effects of some operational parameters such as solution pH, nanophotocatalyst dosage, initial RB5 concentration, H2O2 concentration, different purging gases, and type of organic compounds on the removal efficiency were studied by the Fe3O4-WO3-APTES nanoparticles as a photocatalyst. Maximum phtocatalytic activity was obtained at pH 3. The photocatalytic removal of RB5 increased with increasing H2O2 concentration up to 5�mM. The removal efficiency declined in the presence of different purging gases and all types of organic compounds. First-order rate constant (kobs) decreased from 0.027 to 0.0022�min�1 and electrical energy per order (EEo) increased from 21.33 to 261.82 (kWh/m3) with increasing RB5 concentration from 10 to 100�mg/L, respectively. The efficiency of LED/Fe3O4-WO3-APTES process for RB5 removal was approximately 89.9, which was more effective than the LED/Fe3O4-WO3 process (60.72). Also, photocatalytic activity decreased after five successive cycles. © 2018 Taylor & Franci