Expression of concern: Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

Expression of concern for 'Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 13245-13255, https://doi.org/10.1039/D1RA01056E.

Expression of concern: Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies.

Expression of concern for 'Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 2643-2655, DOI: https://doi.org/10.1039/D0RA09298C.

Synthesis and characterization of g-C3N4-CoFe2O4-ZnO magnetic nanocomposites for enhancing photocatalytic activity with visible light for degradation of penicillin G antibiotic.

Nowadays, antibiotic water pollution is an increasingly dangerous environmental threat. Thus, water treatment is essential for their reduction and removal. In recent decades, photocatalysts have attracted much attention due to their influential role in solving this issue. The photocatalytic process, which is one of the green processes and part of advanced oxidation processes, can be a good choice for treating contaminated water containing non-degradable organic matter. However, the design of high-performance photocatalysts under free sunlight can be challenging. In this study, g-C3N4-Ca, Mg codoped CoFe2O4-ZnO (gCN-CFO-ZnO) nanocomposite photocatalyst was applied in removing penicillin G (PENG) from drug effluents. Also, the effects of contaminant concentration, initial pH, irradiation time, and zinc oxide ratio in the nanocomposites were investigated. The hydrothermal method was carried out to prepare the appropriate composites. Then, the obtained products were characterized by powder X-Ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), Raman, field-emission scanning and transmission electron microscope (FE-SEM&TEM), energy dispersive X-Ray (EDX), diffuse reflectance spectroscopy (DRS), vibrating sample magnetometer (VSM) and Photoluminescence (PL) techniques. According to the findings, the degradation of PENG in an acidic environment occurred remarkably; under the same conditions, with decreasing pH from 9 to 5 in the gCN-CFO-ZnO (33.33%) nanocomposite, the degradation efficiency grew from 47% to 74%. Also, the degradation rate of PENG in gCN-CFO-ZnO (16.66%) and gCN-CFO-ZnO (50%) nanocomposites under optimal conditions (pH = 5, PENG the concentration of 10 ppm, and irradiation time of 120 min) was achieved 52% and 60%, respectively. Further, gCN-CFO-ZnO (33.33%) nanocomposite showed higher efficiency in PENG degradation compared to the other two nanocomposites.

Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

Fabricating suitable adsorbents with low-cost and high efficiency extraction for measurement of very small amounts of agricultural pesticides in food and water is playing a vital key role in personal and environmental health. Here, a new composite of zeolitic imidazolate framework-67@magnesium aluminate spinel (ZIF-67@MgAl2O4) has been fabricated by a simple method at room temperature with different weight ratios. Several techniques such as FE-SEM, BET, XRD, and TGA have been used to confirm the structural characterization of the obtained materials. The obtained ZIF-67@MgAl2O4 was utilized as an adsorbent in the solid phase microextraction technique to extract and preconcentrate the herbicide molinate (as an analyte) in aqueous solution. Corona discharge ionization-ion mobility spectrometry (CD-IMS) was applied for quantification of the analyte molecules. Extraction temperature, extraction time, stirring rate, and sample pH as the main parameters that affected the extraction proficiency were chosen and considered. Under optimal conditions, the linear dynamic range (LDR) of the various concentrations of the molinate and correlation coefficient were 10.0-100.0 µg L-1 and 0.9961, respectively. The limit of quantification (LOQ) and method detection limit (MDL) were 10.0 µg L-1 and 3.0 µg L-1, respectively. The relative standard deviation (RSD) of the ZIF-67@MgAl2O4 for extracting the molinate molecules (molinate concentration; 50 µg L-1) was calculated to be 4% and the enrichment factor (EF) was ∼5.

Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies.

Co-MOF-based zeolitic imidazolate frameworks (ZIF-67) with various morphologies were prepared via an innovative way under distinct reaction conditions. By changing the reaction conditions, including the cobalt source, solvent, time, temperature, and linking agent to the cobalt ions, the morphological evolution of Co-MOF-based ZIF-67 was investigated. The Co-MOF-based ZIF-67 was applied as an adsorbent fiber in the solid-phase microextraction (SPME) technique for extracting a herbicide, namely molinate (as a test compound), in aqueous samples. For recognizing the molinate molecules, drift tube ion mobility spectrometry (IMS) was employed as a sensitive, rapid, and simple detection technique. Two essential parameters, namely extraction temperature and extraction time, influenced the extraction efficiency, and these parameters were also analyzed and optimized. The linear dynamic range (LDR) and the determination coefficient were found to be 0.5-20.0 µg L-1 and 0.9990, respectively. In this regard, the limit of quantification (LOQ) and the detection limit (LOD) were calculated and found to be 0.5 µg L-1 and 0.15 µg L-1, respectively. Finally, the effect of the adsorbent with different morphologies on the extraction efficiency was compared.

Correction: Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

[This corrects the article DOI: 10.1039/D1RA01056E.].

Application of zinc oxide and sodium alginate for biofouling mitigation in a membrane bioreactor treating urban wastewater.

This research aimed to mitigate fouling in membrane bioreactors (MBR) through concurrent usage of zinc oxide as an antibacterial agent (A) and sodium alginate as a hydrophilic agent (H) within a polyacrylonitrile membrane (PM) structure. The antibacterial polymeric membranes (APM) and antibacterial hydrophilic polymeric membranes (AHPM) synthesized showed a higher porosity, mechanical strength and bacterial inhibition zone, and a lower contact angle in comparison with PM membranes. EDS, SEM and AFM analyses were used to characterize the chemical, structural, and morphological properties of PM, APM, and AHPM. The flux of PM, APM, and AHPM in MBR was 37, 48, and 51 l m-2 h-1 and COD removal was 81, 93.5, and 96.7%, respectively. After MBR operation for 35 days in an urban wastewater treatment, only 50% of the flux of PM was recovered, while the antibacterial and hydrophilic agents yielded a flux recovery of 72.7 and 100% for APM and AHPM, respectively.

Photocatalytic degradation of acetaminophen and codeine medicines using a novel zeolite-supported TiO2 and ZnO under UV and sunlight irradiation.

Pharmaceutical compounds are considered as emerging contaminants in the aquatic environments that are not easily eliminated by conventional treatment processes. In the present study, the photocatalytic oxidation of acetaminophen and codeine medicines under UV and solar irradiation was investigated in the aqueous solutions using a novel synthesized zeolite from stone cutting sludge as a support for TiO2 and ZnO. The effect of photocatalyst synthesis conditions including catalyst dose, mixing time, calcination time, and temperature on the efficiency of the pharmaceutical removal were optimized using Taguchi process optimization method. The prepared photocatalysts were characterized using X-ray diffractometer, field emission scanning electron microscopy, energy-dispersive X-ray, the BET surface area, and the Fourier transformation infrared. The results indicated that the performance of ZnO-zeolite for the removal of acetaminophen-codeine under UV and solar radiation with 58.7% and 45.7% was better than that of TiO2-zeolite with 44.3% and 39.2% efficiency, respectively. Removal efficiency under UV and solar radiation was comparable, suggesting that sunlight could be a promising source for treatment of contaminated water by acetaminophen and codeine using photocatalytic degradation. Regeneration of the prepared photocatalysts after 4 cycles revealed a slight decrease in their efficiency. Overall, photocatalytic degradation of the medicines in the water and wastewater using the ZnO-zeolite and TiO2-zeolite could be developed as an efficient treatment process.

Employing magnetism of Fe3O4 and hydrophilicity of ZrO2 to mitigate biofouling in magnetic MBR by Fe3O4-coated ZrO2/PAN nanocomposite membrane.

The aim of this research is benefiting from the synergistic effect of the simultaneous presence of Fe3O4 and ZrO2 in the form of Fe3O4-coated ZrO2 (Fe3O4@ZrO2) nanoparticles within the structure of PAN membrane to reduce membrane fouling. The role of Fe3O4 nanoparticles in increasing the pore size and magnetic saturation as well as the role of ZrO2 in decreasing surface roughness and hydrophobicity can mitigate membrane fouling in magnetic-assisted membrane bioreactors. For this purpose, Fe3O4, ZrO2, and Fe3O4@ZrO2 nanoparticles were embedded into PAN membrane structure and magnetic (M nM), hydrophilic (H nM), and magnetic-hydrophilic (HM nM) membranes were synthesized. H 1M (1ZrO2/PAN) membrane with a contact angle of 31 degrees, M 1N (1Fe3O4/PAN) with a pore size of 90 nm, and H 3M (3ZrO2/PAN) membrane with an RMS roughness of 13.5 nm were the most hydrophilic, porous, and smoothest membranes, respectively. High sensitivity to magnetic field along with high porosity, high hydrophilicity and low surface roughness simultaneously exist within the structure of MHMs membranes, such that MH 1M (1Fe3O4@ZrO2/PAN) indicated 116% greater flux, 121% greater flux recovery, and 85% less total filtration resistance in comparison with the blank membrane in magnetic membrane bioreactor, at a magnetic field intensity of 120 mT and MLSS = 10,000 mg/l. As an overall conclusion, the output of this research was compared with other research in term of normalized flux. Results reveal that at MLSS = 10,000 mg/l, HRT = 8 h and TMP = 0.3 bar, MH 1M membrane has normalized flux equal to 1.56 g/m2 h bar which is an acceptable value compared to normalized flux reported by other researchers.

Catalytic activity, structure and stability of proteinase K in the presence of biosynthesized CuO nanoparticles.

Here, CuO nanoparticles were synthesized using Sambucus nigra (elderberry) fruit extract. Further, the binding of proteinase K, as a model enzyme with green synthesized nanoparticles was investigated. The results demonstrated that the structural changes in enzyme were induced by the binding of nanoparticles. These changes were accompanied by the decrease in the Michaelis-Menten constant at 298 K. This means that the enzyme affinity for the substrate was increased. Thermodynamic parameters of protein stability and protein-ligand binding were estimated from the spectroscopic measurements at 298-333 K. Depending on the temperature, CuO nanoparticles showed a dual effect on the thermodynamic stability and binding affinity of enzyme. Nanoparticles increase the stability of the native state of enzyme at room temperature. On the other hand, nanoparticles stabilize the unfolded state of enzyme at 310-333 K. An overall favorable Gibbs energy change was observed for the binding process at 298-333 K. The enzyme-nanoparticle binding is enthalpically driven at room temperature. It was concluded that hydrogen bonding plays a key role in the interaction of enzyme with nanoparticles at 298-310 K. At higher temperatures, the protein-ligand binding is entropically driven. This means that hydrophobic association plays a major role in the proteinase K-CuO binding at 310-333 K.

Synthesis and characterization of cadmium sulfide nanostructures by novel precursor via hydrothermal method.

A thioglycolic acid (TGA)-assisted hydrothermal process has been developed to synthesize cadmium sulfide nanostructures via reaction between a new precursor cadmium (II) phthalate and TGA. X-ray diffraction, transmission electron microscopy, photoluminescence spectroscopy and Fourier transform infrared were employed to characterize the obtained product. The effects of the reactant concentration, mole ratio of TGA to the Cd2+, temperature and reaction time on the morphology, size of particles, and phase of nanocrystalline CdS products were investigated.

Synthesis, characterization and catalytic oxidation of para-xylene by a manganese(III) Schiff base complex on functionalized multi-wall carbon nanotubes (MWNTs).

In the present study, hydroxyl functionalized manganese(III) Schiff-base; [Mn((OH)(2)-salophen)Cl] [(OH)(2)-salophen] = (N,N'-bis(4-hydroxysalicylidene)phenylene-1,2-diamine); has been covalently anchored on modified multi-wall carbon nanotubes (MWNTs); [Mn((OH)(2)-salophen)Cl]@MWNTs]. The new modified MWNTs have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron (XPS), thermal analysis, FT-IR spectroscopy and elemental analysis. The results suggest that the symmetrical Schiff-base is a bivalent anion with tetradentate N(2)O(2) donors derived from the phenolic oxygen and azomethine nitrogen. 4-Hydroxy salophen; [(OH)(2)-salophen], complex of manganese, grafted on the walls of MWNTs have been investigated as catalysts for the aerobic oxidation of para-xylene in the absence of added halogen promoters and using tert-butylhydroperoxide (TBHP) as the initiator at low temperatures. The major products include toluic acid, toluyl aldehyde and toluyl alcohol. The MWNTs-grafted complex did not undergo any colour change during the reaction and could be easily separated and reused many times. In contrast, the neat complex, while they were active in the first cycle, was completely destroyed during the run and changed colour. They, however, gave lower conversions compared to the grafted catalyst.

Sonochemical synthesis of Dy2(CO3)3 nanoparticles, Dy(OH)3 nanotubes and their conversion to Dy2O3 nanoparticles.

Dysprosium carbonates nanoparticles were synthesized by the reaction of dysprosium acetate and NaHCO(3) by a sonochemical method. Dysprosium oxide nanoparticles with average size about 17 nm were prepared from calcination of Dy(2)(CO(3))(3).1.7H(2)O nanoparticles. Dy(OH)(3) nanotubes were synthesized by sonication of Dy(OAC)(3).6H(2)O and N(2)H(4). The as-synthesized nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Photoluminescence measurement shows that the nanoparticles have two emission peaks around 17,540 cm(-1) and 20,700 cm(-1), which should come from the electron transition from (4)F(9)(/)(2)-->(6)H(15)(/)(2) levels and (4)F(9)(/)(2)-->(6)H(13)(/)(2) levels, respectively. The effect of calcination temperature and sonication time was investigated on the morphology and particle size of the products. The sizes could be controlled by the feeding rate of the precipitating agent (NaHCO(3) and N(2)H(4)) and slower feeding rate lead to smaller nanoparticles.