In this paper, the feasibility and performance of degradation, modeling of degradation, mineralization and toxicity reduction of agricultural organic pollutants (Alachlor and Fenitrothion) have been studied using immobilized titania nanophotocatalysis. Total organic carbon (TOC) and ion chromatography (IC) analyses were employed to obtain the details of the photocatalytic degradation and mineralization of both pesticides. Daphnia magna bioassay has been used to test the diminution of toxicity during the treatment process. Computational fluid dynamics (CFD) model was used to solve the mathematical equation describing degradation process. The model predictions were compared to those results obtained from experimental tests for the degradation of both pesticides and close agreement was achieved. Kinetic studies revealed that the degradation rate followed first-order model for both pesticides. Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO2. Inorganic anions such as nitrate and sulphate were detected as the photocatalytic mineralization of Alachlor and Fenitrothion. The results showed that immobilized titania nanophotocatalysis was an environmentally friendly method of degradation and toxicity reduction of agricultural organic pollutants (Alachlor and Fenitrothion).
ZnO/CuO nanofibers, with different CuO concentrations, were fabricated by one-step electrospinning of the polymer precursor and annealing in air. Scanning electron microscopy (SEM) showed smooth and beadless morphology for the synthesized nanofibers, while X-ray diffraction (XRD) analysis revealed formation of hexagonal and monoclinic crystalline structure phases for ZnO and CuO nanofibers, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of CuO on the surface of ZnO nanofibers. For further confirming the formation of chemical bonds, Fourier transform infrared (FT-IR) spectroscopy was employed. The effect of Cu contents in the overall electronic band structure of ZnO was explained by density functional theory (DFT) calculations. Diffuse reflectance spectroscopy (DRS) showed that the ZnO band gap energy reduced with increasing amount of CuO contents due to the presence of the Cu(3d) energy states above the valence band. Comparing the photocatalytic activity of ZnO/CuO nanofiber samples with different CuO concentrations under similar sunlight irradiation conditions revealed that the ZnO/(0.5 wt %) CuO sample exhibited the highest performance among all samples. This was explained by an effective suppression of electron–hole recombination as verified by both photoluminescence (PL) and photocurrent density measurements. By means of charge carrier scavengers, it was found that holes and hydroxyl radicals are the main surface species for photocatalytic degradation of methylene blue (MB) over the ZnO/(0.5 wt %) CuO nanofiber. Furthermore, the optimized sample demonstrated great activity for the degradation of bisphenol A (BPA) with a rate constant of 3.4 × 10–2 min–1. Finally, a photocatalytic degradation mechanism based on the main reactive oxygen species (ROS) and calculated band positions was proposed.
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In this paper, reduced graphene oxide (rGO)–ZnO nanorod composite was fabricated by one-pot hydrothermal method and used for photocatalytic decolorization of anionic (Direct Red 80, DR80) and cationic (Basic Red 18, BR18) dyes. The composite was characterized using FESEM, XRD, FTIR, TGA, and UV–vis. Response surface methodology (RSM) was used to model the decolorization efficiency. The optimization of the process was carried out using a genetic algorithm (GA) in order to find the maximum yield of photodecolorization. Maximum value of photodecolorization yield based on optimization of the input space by RSM integrated GA approach is obtained with a yield as high as 90.87% for DR80 and 88.33% for BR18 at initial dye concentration 17.68 and 20.39 mg/L, initial pH 5.68 and 5.37, rGO–ZnO dosage 0.0221 and 0.0308 g/L, and irradiation time 186.30 and 189.60 min for DR80 and BR18, respectively. The photostability of rGO–ZnO nanorod composite and ZnO was evaluated and compared after the three consecutive cycles for decolorization. The results revealed that presence of graphene in the composite, can greatly improve the dye photodecolorization ability due to retardation of electron–hole recombination and also concentrating of dyes around the surface by enhancing adsorption ability.
In this research, cobalt ferrite (CoFe2O4) magnetic nanoparticles as well as MIL-53(Fe) structure were synthesized by the hydrothermal and solvothermal methods, respectively. Moreover, magnetic composites of MIL-53(Fe)/CoFe2O4 nanoparticles with different cobalt ferrite loadings (i.e.; 0.05, 0.1 and 0.2 g) were prepared via the solvothermal method. The main novelty of the present research was to synthesize a magnetic composite of MIL-53(Fe)/CoFe2O4 nanoparticles in order to perform rapid photodegradation of Direct Red 23 (DR23) dye under the LED visible light irradiation. Good magnetic properties of the fabricated composite led to easy separation and rapid retrieval of the catalyst from the reaction mixture. Effects of operational variables such as the initial dye concentration, photocatalyst loading and solution pH upon the performance of synthesized materials were understudied. Characterizations of the prepared photocatalysts were performed through the XRD, SEM, TEM, EDX, FTIR, as well as VSM, DRS, BET-BJH and EIS analyses. Results of the XRD, SEM and FTIR analyses confirmed successful synthesis of CoFe2O4, MIL-53(Fe) and their magnetic composites. Moreover, the desired magnetic value of 28.5 emu/g at 8128 Oe was determined for the MIL-53(Fe)/0.1gCoFe2O4 material. Furthermore, the highest light absorption intensity by this composite was obtained through the UV–Visible DRS analysis. In addition, the value of optical bandgap energy (Eg) for the aforementioned composite was determined to be 2.1 eV. Furthermore, the BET surface areas of the MIL-53(Fe), MIL-53(Fe)/0.1gCoFe2O4 and CoFe2O4 species were evaluated to be 13, 34 and 52 m2/g, respectively. Finally, the photocatalytic degradation of the DR23 over the MIL-53(Fe)/0.1gCoFe2O4 was revealed to be 99.35% after 80 min of duration under the LED irradiations. This was higher than the rest of other understudied materials. In addition, results displayed that, the hydroxyl radicals (OH) as well as photo-generated holes (h+) were the main active species in photocatalytic degradation process undertaken. Ultimately, sufficient yet simple rate law models of the aforementioned dye degradation implementing first- and second-order chemical kinetics upon the prepared catalysts were developed.
In this work, zeolitic imidazolate framework-8 (ZIF-8)-titania nanocomposites (ZT) with different amounts of titania nanoparticle (0.2, 0.4 and 0.6 g denoted as ZT-0.2, ZT-0.4 and ZT-0.6, respectively) as nanoporous photocatalysts were synthesized and characterized. A halogen lamp (500 W) was used as an irradiation source. The pollutant (Acid Blue 92 (AB92)) degradation mechanism was studied in details. The XRD, FTIR, SEM, TEM, BET, TGA and zeta potential were used to characterize the synthesized nanomaterials. The data showed that the ZT-0.4 nanocomposite had higher dye degradation ability due to the synergistic effect of ZIF-8 and titania. Dye degradation followed zero-order kinetics. The degradation rate of AB92 for 0.005, 0.010, 0.020 and 0.030 g of catalyst (ZT-0.4) was 0.00009, 0.00070, 0.00150 and 0.00190 mg/L min, respectively. The removal efficiency suggested that OH• possesses a major role for photocatalytic degradation of AB92. The synthesized nanocomposite showed stability and reusability over three cycles.
Nanophotocatalysis using nanostructured semiconductors constitute one of the emerging technologies for destructive oxidation of organics such as dyes. This paper deals with the decolorization and mineralization of reactive dyes by heterogeneous nanophotocatalysis using an immobilized TiO2 nanoparticle photocatalytic reactor. A simple and effective method was used to immobilization of titanium dioxide nanoparticles. Reactive Orange 107 (RO 107, sulphatoethylsulphonyl reactive dye) and Reactive Red 152 (RR 152, monochlorotriazine reactive dye) were used as model compounds. UV–vis and ion chromatography (IC) analyses were employed to obtain the details of the photocatalytic degradation of the selected dyes. The effects of operational parameters such as H2O2, dye concentration, anions (NO3 −, Cl−, SO4 2−, HCO3 − and CO3 2−) and pH were investigated. Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO2. Nitrate, sulfate and chloride anions were detected as the photocatalytic mineralization of RO 107 and RR 152. Kinetics analysis indicates that the photocatalytic decolorization rates can usually be approximated zero-order model for RO 107 and first-order model for RR 152 dyes. Results show that the photocatalytic process occurred at solution bulk and the employment of optimal operational parameters may lead to complete decolorization and mineralization of dye solutions.
The cleaner production of metal-organic framework nanocomposite includes room/low temperature synthesis and the use of harmless solvents. In this paper, metal-organic framework (NENU: Northeast Normal University) - graphene oxide (GO) nanocomposites (NENU/GO) with different amounts of GO (0.005, 0.01, 0.015, 0.02 and 0.03 g denoted as NENU/0.005GO, NENU/0.01GO, NENU/0.015GO, NENU/0.02GO and NENU/0.03GO, respectively) were synthesized at room temperature using ethanol as a harmless solvent. The pollutant (dye) removal ability of the materials from water was studied in details. The GO nanosheet was prepared from graphite. The synthesized nanomaterials were characterized using Brunauer–Emmett–Teller, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and zeta potential. Dye removal at 5, 10 and 20 mg/L of dye concentration was 87, 84 and 59%, respectively. The pollutant adsorption capacity of the NENU, NENU/0.005GO, NENU/0.01GO, NENU/0.015GO, NENU/0.02GO and NENU/0.03GO was 125, 130, 151, 170, 183 and 243 mg/g, respectively. The pollutant uptake data confirmed the Freundlich isotherm and pseudo-second order kinetics.
In this paper, CuMnO2 nanomaterial was synthesized and its dye removal ability was studied. The characteristics of the synthesized nanomaterial were investigated using Fourier transform infrared, scanning electron microscopy and X-ray diffraction. Adaptive neuro-fuzzy inference system (ANFIS) was applied for modeling of dye removal from colored wastewater. The effect of adsorbent dosage and dye concentration on dye removal was studied. Dye removal process followed pseudo-second-order model and Langmuir isotherm. Furthermore, good agreement between values of predicted and experimental dye removal percentage was observed. The results showed that ANFIS could effectively predict the behavior of the process.
In this paper, poly(vinyl alcohol) (PVA) nanofiber was prepared and modified by diethylenetriamine (DETA) and ethylenediamine (EDA) in the presence of glutaraldehyde (GA). Dye removal ability of the modified nanofiber (PVA/DETA/EDA/GA) as a nanoadsorbent from water was studied. Fourier transform Infrared (FTIR) and scanning electron microscopy (SEM) were used to investigate the characteristics of the modified nanofiber. Direct Red 23 (DR23) and Direct Blue (DB78) were used. The effect of operational parameters such as pH, initial dye concentration, contact time, temperature and adsorbent dosage on dye removal was studied. The dye adsorption isotherms, kinetics and thermodynamics were investigated. The maximum dye adsorption capacity of the modified nanofiber was 370 and 400 mg/g for DR23 and DB78, respectively. Four isotherms, the Langmuir, the Freundlich, Tempkin and a modified Langmuir-Freundlich model were used. Dye adsorption on the modified nanofiber followed the Langmuir isotherm and pseudo-second kinetic order. Thermodynamic data showed that dye removal was a spontaneous, endothermic and physisorption process.
Herein, Kiwi peel activated carbon (AC), Materials Institute Lavoisier (MIL-88B (Fe), and AC/MIL-88B (Fe) composite were synthesized and used as catalysts to degrade Reactive Red 198. The material properties were analyzed by the FTIR, BET-BJH, XRD, FESEM, EDX, TGA, and UV–Vis/DRS. The BET surface area of AC, MIL-88B (Fe) and AC/MIL-88B (Fe) was 1113.3, 150.7, and 199.4 m2/g, respectively. The band gap values (Eg) estimated by Tauc plot method, were obtained 5.06, 4.19 and 3.79 eV for AC, MIL-88B (Fe) and AC/MIL-88B (Fe), respectively. The results indicated that the AC/MIL-88B (Fe) composite had higher photocatalytic activity (99%) than that of pure AC (79%) and MIL-88B (Fe) catalysts (87%). The decolorization kinetic was matched well with the second-order model. Moreover, the data were modeled using least squares support vector machine which optimized with Cuckoo optimization algorithm. The optimal parameters were found 0.837 and 3.49e+02 based on σ2 and γ values, respectively. The mean square error (MSE) and correlation coefficient (R2) values were obtained 3.97 and 0.948. Therefore, the attained data, materials characterization and prediction of modeling validate the composite form of MIL-88B(Fe) with new AC, had better photocatalytic activity in comparison with the individual form.
In this work, dithiocarbamate-functionalized graphene oxide (GO-DTC) has been synthesized and applied in removal of cationic dyes; Basic Blue 41 (BB41) and Basic Red 46 (BR46). Morphology and chemical structure of the prepared GO-DTC were studied by SEM and FTIR analyses. Dye removal from wastewater solutions with variable concentration of dyes, pH, and GO-DTC dosage was evaluated. The experiments suggested a pseudo-second order kinetic model for dye adsorption onto GO-DTC, while dye adsorption isotherm data were found to fit Langmuir model. The adsorption efficiency of synthesized GO-DTC towards BB41 and BR46 was calculated to be 128.5 and 111 mg/g, respectively.
The surface of polyacrylonitrile (PAN) nanofiber was modified by Tectomer and its dye removal ability from binary systems was studied. The characteristics of nanofibers were investigated by FTIR, AFM, SEM, BET and BJH methods. FTIR showed successful grafting of Tectomer to the surface through the formation of imine group. Decrease in the average roughness and total surface area of nanofiber were detected by AFM and BET analysis, respectively. The adsorption capacity of Tectomer grafted nanofiber for Direct Red 80 and Direct Red 23 was 1250 and 1111mg/g, respectively. Adsorption of dyes follows the Langmuir isotherm and pseudo-second order kinetics.
In this work, magnetic nanoparticles of ZIF-8/NiFe2O4 were synthesized using a simple method to employ the photocatalytic activity under visible-light irradiation for the degradation of methylene blue. The ZIF-8/NiFe2O4 photocatalyst with 30 wt.% of NiFe2O4 demonstrated the best photocatalytic performance with a degradation efficiency of 94% in 120 min and the stability was good after 4 cycles. The ZIF-8/NiFe2O4 composite could easily separate from the water environment by an external magnet. The present study would open a new horizon for highly efficient visible-light photocatalysts for the degradation of organic dyes in wastewater.
