Enhanced photocatalytic crystal-violet degradation performances of sonochemically-synthesized AC-CeO2 nanocomposites

Decolorization and degradation of crystal violet dye by electron beam radiation: Performance, degradation pathways, and synergetic effect with peroxymonosulfate

Ionizing radiation (mainly including gamma ray and electron beam) technology provides a more efficient and ecological option for dye-containing wastewater treatment, which is supported by its successful achievements in industrial-scale applications. However, the degradation pathway of triphenylmethane dyes by radiation technology is still unclear. In this study, crystal violet (CV) was selected as representative cationic triphenylmethane dye, the decolorization and degradation performance by electron beam radiation technology was systematically evaluated. The results showed that CV can be efficiently decolorized and mineralized by radiation, and its degradation kinetics followed the first-order kinetic model. The effect of inorganic anions and chelating agents commonly existed in dye-containing wastewater on CV decolorization and total organic carbon (TOC) removal was explored. Quenching experiments, density functional theory (DFT) calculation and high performance liquid chromatography mass spectrometry (HPLC-MS) analysis were employed to reveal CV decolorization and degradation mechanism and pathway, which mainly included N-demethylation, triphenylmethane chromophore cleavage, ring-opening of aromatic products and further oxidation to carboxylic acid, and mineralization to CO2 and H2O. Additionally, electron beam radiation/PMS process was explored to decrease the absorbed dose required for decolorization and degradation, and the synergetic effect of radiation with PMS was elucidated. More importantly, the findings of this study would provide the support for treating actual dyeing wastewater by electron beam radiation technology.

Accelerated sonochemical fabrication of MIn2S4 (M = Zn, Mg, Ni, Co) for ultra-high photocatalytic hydrogen peroxide production

Ternary metal sulfide (MIn2S4) by virtue of large extinction coefficient, suitable band gap and stability, has been proposed as a candidate for photocatalytic synthesis hydrogen peroxide (H2O2). However, MIn2S4 is conventionally synthesized by solvothermal method that is generally characterized by tedious operational steps and long reaction time. In this work, four sonoMIn2S4 (M = Zn, Mg, Ni, Co) were successfully prepared by sonochemical method within 2 h. These as-synthesized sonoMIn2S4 delivered much high-efficient photocatalytic H2O2 generation. Particularly, the sonoZnIn2S4 presented H2O2 production rate of 21295.5 μmol∙g-1∙h-1 in water/benzylalcohol system, which is 3.0 times that of ZnIn2S4 prepared by solvothermal method. The remarkably improved photocatalytic performance of sonoZnIn2S4 might be due to the multiple defects and fast electron-hole pair separation caused by ultrasound cavitation effect. Other metal sulfide photocatalysts with high performance were efficiently fabricated by facile sonochemical technology as well. The sonochemical method realized the rapid preparation of metal sulfide photocatalysts and efficient production of H2O2, which benefits to meet the United Nations Sustainable Development Goals (SDGs) including SDG-7 and SDG-12.

One-pot hydrothermal synthesis of fluorophore-modified cerium oxide nanoparticles

Cerium oxide nanoparticles (CeO2 NPs), which have powerful antioxidant properties, are promising nanomaterials for the treatment of diseases associated with oxidative stress. The well-developed surface of CeO2 NPs makes them promising for use as a multifunctional system for various biomedical applications. This work demonstrates a simple approach that allows the direct formation of a molecular fluorophore on the surface of CeO2 NPs using a simple one-pot hydrothermal synthesis. Thus, we were able to synthesize CeO2 NPs of ultra-small size ∼2 nm with a narrow distribution, highly stable fluorescence, and a quantum yield of ∼62%. UV-visible transmission studies revealed that the resulting CeO2 NPs exhibited fast autogenerative catalytic reduction. In vitro results showed high biocompatibility of CeO2 NPs; their internalization occurs mainly in the region of cell nuclei. Thus, the resulting NPs have the necessary parameters and can be successfully used in biovisualization and therapy.

Facile construction of multifunctional xNiCo2O4/BiVO4 heterojunction with accelerated charge transfer for efficient photocatalytic treatment of Cr (VI), MB and TC under visible light

The release of industrial effluents, comprising of organic dyes, antibiotics, and heavy metals poses substantial environmental and ecological threats. Among the different approaches, the utilization of heterogeneous photocatalysis based on semiconducting metal oxides is of paramount important to removal of organic ( MB dye and TC antibiotic) and inorganic pollutants ( Cr (VI) ) in wastewater. In this work, a new approach for creating type-II heterojunction photocatalysts named xNiCo2O4/BiVO4 or BNC is suggested. The as-prepared samples were thoroughly examined by means of several sophisticated analytical tools to investigate their physicochemical properties. These composites were utilized in the decomposition of MB dye, TC drug and the reduction of Cr (VI) under visible light irradiation. According to the findings, the creation of type-II heterojunction at BiVO4-NiCo2O4 interface greatly improved charge transportation while successfully preventing electron-hole recombination. Among the various composites studied, BNC-2 demonstrated an enhanced photocatalytic activity towards degradation of MB and TC, which were found to be 91 % over a period of 150 min and 95 % within only 60 min, respectively. Moreover, the photocatalytic reduction of Cr (VI) was accomplished 96 % within just 25 min. Additionally, it is discovered that BNC-2 displayed promising photostability and recyclability with a retention of >90 % after five consecutive cycles. The enhanced photocatalytic activity of BNC-2 is evidently attributed to the expedited separation and transfer of charges, as proven by photocurrent measurement, photoluminescence and electrochemical impedance spectroscopy analyses. Hence, the current amalgamation of NiCo2O4 and BiVO4 heterojunction composite has paved novel paths towards photocatalytic removal of organic as well as inorganic contaminants.

Synergistic photocatalysis of a hydrochar/CeO2 composite for dye degradation under visible light

The synthesis and characterization of a hydrochar/CeO2 composite along with its evaluation in methylene blue degradation under visible light are presented. The methodology consisted of a single-pass hydrothermal method, having as synthesis conditions 9 h of reaction time, 210 °C, autogenous pressure, and a biomass/CeO2 ratio of 100:1. The composite characterization revealed good dispersion of CeO2 in the carbonaceous matrix and significant synergy in the composite activation using visible irradiation. The photodegradation experiments showed an efficiency of 98% for white LED light, 91% for UV light, 96% for solar irradiation, and 85% for blue LED light using as conditions pH 7.0, 50 mg of composite, 50 mL of solution, 10 mg/L of dye initial concentration, and 120 min of contact time. Meanwhile, the reusability experiments evidenced a reuse capacity of up to five times with a constant photodegradation efficiency (99%); moreover, it was determined that the presence of electrolytes at pH below 7.0 during degradation negatively affected methylene blue degradation. Finally, the results of this work demonstrate that the hydrochar/CeO2 composite can be synthesized by a green method and used for the efficient treatment of water contaminated with methylene blue.

Fabrication of Ru loaded MgB2 with guar gum hybrid for photocatalytic degradation of crystal violet

Today, dyes/pigment-based materials are confronting a serious issue in harming marine ecology. Annihilate these serious water pollutants using photoactive 2D nanohybrid catalysts showed promising comparativeness over available photocatalysts. In the present work, a facile route to decorate Ruthenium (Ru) on 2D MgB2 flower-like nanostructures was developed via ecofriendly guar gum biopolymer substantial template (MgB2/GG@Ru NFS) and its photocatalytic performance was reported. Synthesis of MgB2@Ru, MgB2/GG@Ru NFS and commercial MgB2, was studied by FTIR, XRD, FE-SEM, EDX, AFM, TEM, UV-vis spectra, and XPS analysis. From the results, the MgB2/GG@Ru NFS exhibited a superior photocatalytic performance (99.7 %) than its precursors MgB2@Ru (79.7 %), and MgB2 (53.7 %), with the degradation efficiency of the crystal violet (CV) within 100 min under visible light irradiation. The proposed photo-catalyst MgB2/GG@Ru NFS showed negligible loss of photocatalytic activity even after five successive cycles, revealing its reusability and enhanced stability due to the network structure. The photocatalytic mechanism for MgB2/GG@Ru NFS was evaluated by trapping experiment of active species, verifying that superoxide (O2-) and electron (e-) contributed significant role in the dye degradation.

Ultrasensitive functionalized CeO2/ZnO nanocomposite sensor for determination of a prohibited narcotic in sports pethidine hydrochloride

The extraordinary features of cerium oxide (CeO₂) and zinc oxide (ZnO) nanostructures have encouraged substantial attention to those nanocomposites as probable electroactive complexes for sensing and biosensing purposes. In this study, an advanced novel factionalized CeO₂/ZnO nanocomposite-aluminum wire membrane sensor was designed to assess pethidine hydrochloride (PTD) in commercial injection samples. Pethidine-reineckate (PTD-RK) was formed by mixing pethidine hydrochloride and ammonium reineckate (ARK) in the presence of polymeric matrix (polyvinyl chloride) and o-nitrophenyl octyl ether as a fluidizing agent. The functionalized nanocomposite sensor displayed a fast dynamic response and wide linearity for the detection of PTD. It also revealed excellent selectivity and sensitivity, high accuracy, and precision for the determination and quantification of PTD when compared with the unmodified sensor PTD-RK. The guidelines of analytical methodology requirements were obeyed to improve the suitability and validity of the suggested potentiometric system according to several criteria. The developed potentiometric system was suitable for the determination of PTD in bulk powder and commercial products.

Mechanochemically interlocked cubane copper complex interface for WOLED

In the rapid development of organic light-emitting diodes (OLEDs), phosphorescent transition metal complexes have played a crucial role as the most promising candidates for next generation display and lighting applications. However, most devices are fabricated using iridium and platinum-based complexes which are expensive and available in very limited quantities, whereas using relatively abundant organometallic complexes for fabrication results mostly in inefficient performance results. To overcome these issues, we have synthesized tetra copper iodide with tetra triphenyl cage like structure (denoted as CIPh) as an emerging class of luminescent material by mechanochemical grinding followed by thermal treatment for application in white OLED. The CIPh complex exhibits considerable quantum yield and a millisecond decay lifetime. Phosphorescent OLEDs were fabricated using CIPh complex as emitter shows a remarkable performance with external quantum efficiency and current efficiency of 5.28 % and 22.76 cd/A, with a high brightness of 4200 cd m^-2, respectively. White OLEDs were also fabricated with a fluorescent blue and phosphorescent red emitted with (CIPh) as green emitter and achieved an impressive CRI of 82 with an EQE of over 3 %. This is the first ever attempt at fabricating WOLEDs using organocopper complex.

Cyanide within gold mine waste of the free state goldfields: A geochemical modelling approach

Cyanide, which remains the preferred chemical used in the gold extraction process, has the potential to be disposed of on goldmine tailings. South Africa has nine goldfields, producing approximately a third of the world's gold to date. The cyanide interacts with metals in the tailings environment, where Prussian blue [Formula: see text] and Turnbull's blue [Formula: see text] are among these. In previous studies, Prussian blue or Turnbull's blue have been found as a blue substance in tailings material. PHREEQC modelling software was used adding the mineralogical data from 16 tailings samples from the Free State goldfield. The results revealed that Prussian blue prefers to precipitate in an oxic environment and Turnbull's blue prefers an anoxic environment. It was also determined that their precipitation is affected by the availability of iron in solution. As soon as all of the iron is consumed in solution, all excess cyanide produces HCN, which is a free cyanide which volatilizes. Contrarily, Prussian and Turnbull's blue are CN_SAD compounds, only dissociating in extremely low pH condition in the absence of photolysis. Ultimately, these iron-cyanide compounds are able to immobilize cyanide, preventing seepage into environments such as the ground water. This along with an anoxic environment such as mine void, keeping the pH high, may be a possible solution for cyanide remediation.