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

Catalytic wet air oxidation removal of tetracycline by La2O3 immobilized on recycled polyethylene terephthalate using the response surface methodology

This study investigated the removal of tetracycline from the aqueous solutions by lanthanum oxide nanoparticles covered with polyethylene terephthalate (PET) using a low-cost and facile co-precipitation method, via catalytic wet air oxidation process (CWAO) by response surface methodology (RSM). XRD, FTIR, SEM, and EDX-map techniques have been employed to investigate the crystal structure, functional groups on the surface, morphologic characteristics, and elemental composition, respectively. Under optimum conditions (pH= 9, initial TC concentration= 20 mg L-1, nanocomposite dosage= 1.5 g L-1, pressure= 4 bar, temperature= 70 °C, and time= 90 min), TC removal efficiency by La2O3-PET was achieved at about 99.9%. The environmental parameters were assessed to determine tetracycline catalytic wet air oxidation degradation rate, which included cleaning gases, hydrogen peroxide, type of organic compounds, anions, radical scavenger and reusability. The ANOVA results indicated that the polynomial model proves that the model is entirely meaningful (F-value> 0.001 and P-value< 0.0001) and has high coefficient values of adjusted R2 (0.7404) and predicted R2 (0.5940). The findings indicated that the variables of time, pH, temperature, dosage, and TC concentration have the greatest role in removing tetracycline, respectively. However, pressure as a factor does not have a considerable influence on the performance of the system. In general, due to the presence of the role of additional anionics, the effectiveness of this method for removing tetracycline from drinking water was 82.76%. The catalyst indicated pleasing stability and recycling power during eight testing cycles. Further, the estimated electrical energy per order consumption (EEO) for the CWAO/La2O3-PET system was calculated as 5.31 kWh m-3 with an operational cost (OC) utilization of 1.78 USD kg-1 and it has been shown that this process is feasible and economically comparable to other CWAO processes. The breakdown intermediate products of tetracycline in the CWAO were examined using gas chromatography/mass spectrometry (GC-MS) analysis. The toxicity analyses for the removal of TC were carried out using Daphnia magna and the CWAO process achieved a remarkable decrease in the presence of La2O3-PET nanocomposite (LC50 and toxicity unit (TU) 48 h equal to 0.634 and 157.72 vol percent).

Advancements in Composite Materials and Their Expanding Role in Biomedical Applications

The synthesis of a Ni-doped ZnO nanocomposite incorporating chitosan (CS/Ni-doped ZnO) was achieved via a precipitation method, followed by annealing at 250 °C. This study comprehensively examined the nanocomposite's structural, functional, morphological, and porosity properties using various analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis. The presence of chitosan (CS) and nickel (Ni) within the nanocomposite, along with their influence on reducing the band gap of ZnO particles and enhancing the generation of electron-hole pairs, was confirmed using UV-visible near-infrared spectroscopy (UV-vis-NIR). The electrochemical properties of the CS/Ni-doped ZnO nanocomposite were investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) by utilizing a phosphate buffer solution with a pH of 6, which closely resembled the typical pH of bacterial cell walls. Finally, the prepared CS/Ni-doped ZnO nanocomposite was evaluated for its antibacterial and anticancer activities. The results demonstrated the highest inhibition of bacterial growth in P. vulgaris, whereas the lowest inhibition was found in S. aureus across various concentrations, thus highlighting its potential in antimicrobial applications. The cytotoxicity of CS/Ni-doped ZnO nanocomposites demonstrated remarkable effects with a half-maximum inhibitory concentration of approximately 80 ± 0.23 µg mL-1 against MCF-7 breast cancer cell lines, following a dose-dependent manner.

Design and modeling of diazinon degradation in hydrous matrix by Ni-doped ZnO nanorods under ultrasonic irradiation: process optimization using RSM (CCD), kinetic study, reaction pathway, mineralization, and toxicity assessment

In first, the Ni-doped ZnO nanorods used as an appeal sonocatalyst was synthesized through co-precipitation method. Afterwards, the crystalline structure, functional groups, surface morphology, and elemental composition were characterized by a set of analysis. Removal of diazinon ((DZ) as a renowned pesticide) was investigated using sonocatalytic performance of US/Ni-doped ZnO system. In this empirical study, response surface methodology (RSM) based central composite design (CCD) was applied for optimization of operational factors. Under the optimum conditions such as initial pH = 5, initial DZ concentration = 15 mg L^-1, sonocatalyst dosage = 1 g L^-1, and in the presence of organic compounds (oxalic acid, humic acid, and folic acid) = 3 mg L^-1, the sonocatalytic degradation of DZ after 15 min was 82.29%. The F-value (6.64) and P-value (< 0.0001) for DZ degradation in the quadratic model imply the proposed model was significant. A-factor (pH) considers as a prominent factor owing to having the highest F-value. In addition, the sonocatalytic data in this study exhibited valid fitting for the first order kinetic model (R² > 0.98). After six consecutive cycles, the Ni-doped ZnO nanorods could be recyclable for sonocatalytic degradation of DZ. The five main compounds produced during the US/Ni-doped ZnO embracing 2-isopropyl-6-methyl-4-pyrimidinol (IMP), diethyl phosphonate, diazoxon, hydroxyldiazinon, and diazinon methyl ketone are formed in the path of DZ degradation. OFAT style also revealed 99.99% of DZ degradation with 73.26% of mineralization rate in optimum status. The Ni-doped ZnO presented agreeable sonocatalytic facility in the refinement of real water and wastewater matrix. Finally, the results of toxicity evaluation (Daphnia magna) in the sonocatalytic degradation of DZ (by US/Ni-doped ZnO system) showed that the toxicity of the DZ solution lessened under US waves (LC₅₀ and TU 48 h equal to 36.472 and 2.741 volume percent, respectively).

Adsorptive removal of organic dyes via porous materials for wastewater treatment in recent decades: A review on species, mechanisms and perspectives

Organic dyes, a type of high toxic and carcinogenic chemicals that present severe threats to human and aquatic life, are the most commonly seen organic pollutants in wastewater of industries such as textile, rubber, cosmetic industry etc. Various techniques for the removal of dyes are compared in this review. Adsorption has proven to be a facile and promising approach for the removal of dyes in wastewater. This work focuses on the latest development of various porous materials for the adsorption of organic dyes. The characteristics, functionalization and modification of different porous materials are also presented. Furthermore, adsorption behaviors and mechanism of these adsorbents in the adsorption of organic dyes are critically reviewed. Finally, challenges and opportunities for future research in the development of novel materials for the highly efficient removal of dyes are proposed.

Conversion of biomass to N, S co-doped porous graphene as an adsorbent for mercury vapor removal: optimization and DFT study

This study is devoted to optimization synthesis conditions of the N, S co-doped porous graphene via a single step thermal chemical activation process from agricultural wastes such as cabbage waste. To this end, the response surface method (RSM) was considered, and the synthesis parameters were varied in specific ranges. By doing so, the optimum conditions in terms of the best performance in mercury removal was determined which was characterized by TEM, SEM, BET, XRD, XPS, and FTIR techniques. The chosen key process parameters were Activation agent to carbon precursor ratio (A: KOH/C), Reaction time (B: Time), Activation temperature (C: Temperature), and (Dopant to carbon precursor ratio (D: Dopant/C). Each parameter was investigated in 3 levels with lower and upper bounds being A: 2-6; B:30-90 min.; C: 600-800 ˚C; D:2-10. The optimum conditions of the process were determined to be as: A: 2; B: 30 min.; C: 600 ˚C and D: 2. The optimized sample was prepared in repeated runs with reproducible results with Hg vapor adsorption capacity of 2100 µg/g at 40 ˚C and 2266 µg/g at 90 ˚C. In addition to the experiments, DFT calculations were also carried out which elucidated the positive role of N and S co-doping in improving the mercury adsorption intensity.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00712-y.

Photocatalytic removal of bentazon by copper doped zinc oxide nanorods: Reaction pathways and toxicity studies

In this study, bentazon herbicide was degraded photocatalytically by copper doped zinc oxide nanorods fabricated by using a facile co-precipitation method. The crystal structure, morphology, surface composition, functional groups on the surface and valence state of the nanorods were investigated by XRD, SEM-EDX, FTIR, and XPS material characterization techniques. Environmental parameters including solution pH, catalyst dose, bentazon concentration, purging gases, H₂O₂ content, organic compound type and reusability affecting the rate of photocatalytic degradation of bentazon were evaluated. Under the optimal conditions, [Bentazon]₀ = 20 mg L^-1, Cu-ZnO loading = 0.5 g L^-1, H₂O₂ = 2 mM, pH = 7 and in the presence of oxygen gas, 100% of the herbicide was removed within 60 min. By raising bentazon concentration (10-50 mg L^-1), k_obs decreased to values between 0.14 and 0.006 min^-1 and the calculated electrical energy per order (E_Eo) increased from 38.16 to 727.27 (kWh m^-3), respectively. The degradation removal of the herbicide using the UV/Cu-ZnO method (98.28%) was higher than that of the UV/ZnO method (32.14%) process. Interestingly, the photocatalytic performances in the first and fifth reuse cycles during catalyst recyclability tests were found to be similar. Generally, the efficacy of the method in the decomposition of bentazon in drinking water (78.95%) and actual sewage (46.77%) declined because of the presence of other anions due to their role as a scavenger of photogenerated reactive species. Intermediate products in the photocatalytic degradation of bentazon identified by gas chromatography/mass spectrometry (GC/MS) analysis were 2-amino-N-isopropyl-benzamide, 2-amino-benzoic acid, N-isopropyl-2-nitro-benzamide, and acids such as pentenedioic acid, oxalic acid and propenoic acid. Furthermore, the main mechanism for the photocatalytic removal of bentazon was determined to be via attack by hydroxyl radicals (^•OH). The results of toxicity in the photocatalytic removal of bentazon by D. magna showed LC₅₀ and toxicity unit (TU) 48 h equal to 46.10 and 9.56 vol percent.

Evaluation the effect of ZnO nanoparticle derived Bacillus subtilis on the expression of efflux pump genes (AdeB AdeRS) in Acinetobacter baumannii

PURPOSE

Green approach to the nanoparticles, including metal oxides due to inevitable disadvantages of physical or chemical synthesis routes is attractive nowadays. Zink oxide (ZnO) nanoparticles play a key role in the medical and pharmaceutical fields. This research aimed to study the biologically synthesized ZnO nanoparticle using Bacillus subtilis, and evaluated its antibacterial properties.

METHODS

Bacillus subtilis culture in a broth nutrient environment was used, followed by adding the Zinc acetate dehydrate. Biosynthesis of the nanoparticles was confirmed by the XRD, FTIR, and SEM imaging. The antibacterial effects of NPs on the expression of AdeB efflux pump genes and the AdeRS regulator were studied; clinical species of the Acinetobacter baumannii were collected from clinical samples of Khorramabad, using the phenotypic (MIC) and the genotypic methods through real-time PCR.

RESULTS

X-ray diffraction pattern (XRD) result showed, that all of the peaks were related to the ZnO, and no other peaks were detected; it also demonstrated nanostructure nature with crystallite size of 25-50 nm. The results indicated, that the antibacterial properties of the nanoparticle increased the AdeRS expression and decreased the AdeB expression in 40% of the A. Baumannii. In addition, there was an increase in the AdeB expression in 60% of the species, indicating an increased probability for mutation.

CONCLUSION

Given the desirable inhibitory effects of biosynthesized ZnO NPs on the expression of AdeB and AdeRS, which play an important role in the pharmaceutical resistance of Acinetobacter species, it seems that ZnO NPs can be used as a medication candidate in pharmaceutical industry in the future.

Facile fabrication of hybrid titanium(IV) isopropoxide/pozzolan nanosheets (TnS-Pz) of high photocatalytic activity: characterization and application for Cr(VI) reduction in an aqueous solution

This paper presents the synthesis of a hybrid material through the use of natural pozzolan and titanium(IV) isopropoxide using the sol-gel method and its application in the photocatalytic hexavalent chromium reduction. The characterization data indicated a mesoporous material possessing a surface area of 271.7 m² g^-1. The morphology studies (SEM and TEM) showed nanosheet hybrid structures. The analysis of DRUV, FTIR, XRD, and Mössbauer spectroscopy provides a different electronic structure of the synthetized material when compared with the originals, proving the hybridization process between pozzolan and titanium(IV) isopropoxide. The photocatalytic reduction of Cr(VI) to Cr(III) using the hybrid material showed a better performance than conventional photocatalysts (precursor and TiO₂-P25). Operational conditions such as chromium initial concentration (0.02-0.20 mM), solution pH (3-6), and type of scavenger (citric or tartaric acid) were evaluated in order to determine the best experimental conditions for the Cr(VI) photoreduction. At their optimum (catalyst load of 15 mg L^-1, tartaric acid as scavenger, [scavenger]₀/[Cr(VI)]₀ M ratio = 3:1, pH 3, and 25 °C), the total photoreduction of 0.20 mM Cr(VI) was achieved in 180 min. The novel hybrid materials synthesized from pozzolan and titanium(IV) isopropoxide showed to be a potential catalyst for the Cr(VI) reduction in aqueous solution. Graphical abstract.

Mineralization of Diazinon with nanosized-photocatalyst TiO2 in water under sunlight irradiation: optimization of degradation conditions and reaction pathway

The photocatalytic degradation of Diazinon under sunlight irradiation is investigated by using the nanosized photocatalyst TiO₂. Eight intermediates are detected during the degradation, and the reaction pathway is proposed on the base of their intermediates. The degradation parameters, concerning photocatalyst concentration, temperature, pH, sunlight intensity and irradiation time are optimized. Under the optimal conditions, the photocatalytic degradation of Diazinon can be completed within 60 min. The photodegradation is found to follow the pseudo-first-order kinetic law at a rate constant of 0.068 min^-1. The activation energy is 14.7 kJ/mol. The formations of sulphate, phosphate, nitrate and ammonium ions during the degradation are observed. About 83% of the initial N is detected as ammonium and nitrate ions during 50 h of irradiation time.

Application of ZnO nanorods doped with Cu for enhanced sonocatalytic removal of Cr(VI) from aqueous solutions

The aim of this research was to develop a simple and inexpensive process for reduction of Cr(VI) to Cr(III). Zinc oxide nanoparticles were synthesized with an easy co-precipitation procedure, and the addition of Cu²⁺ doping agent effectively enhanced the Cr(VI) reduction in the presence of ultrasound (US). XRD, FT-IR, FE-SEM, EDX, VSM, and XPS were used to determine the structural specifications of the zinc oxide nanoparticles. Under optimal conditions such as pH 3, initial Cr(VI) content of 20 mg/L, and catalyst dosage of 0.8 g/L, the ultrasonic/Cu-ZnO process showed a higher sonocatalytic activity (96.83%) than ultrasonic/ZnO (67.36%) after 60 min. By increasing pH and Cr(VI) concentration, the removal efficacy of Cr(VI) declined. The experimental data was well described with the first-order kinetic model. When initial Cr(VI) concentration increased from 10 to 50 mg/L, the first-order rate constant declined from 0.2326 to 0.0019 min^-1 and electrical energy per order (E_EO) enhanced from 19.81 to 2425.26 kWh/m³. Also, the ultrasonic/Cu-ZnO system exhibited considerable sonocatalytic performance in Cr(VI) reduction in the presence of hydrogen peroxide and citric acid, and complete removal was achieved within 60 min. The presence of anions negatively affected Cr(VI) reduction. Complete reduction was attained when ultrasound was applied at a power of 100 W. The catalyst activity was well maintained up to six consecutive cycles. In addition, the removal efficiency was approximately 62 and 65% for field water and real electroplating wastewater samples, respectively.