Efficient photocatalytic reduction of aqueous Cr (VI) by Zr4+ doped and polyaniline coupled SnS2 nanoflakes

DFT and experimental studies of the facet-dependent oxygen vacancies modulated WS2/BiOCl-OV S-scheme structure for enhanced photocatalytic removal of ciprofloxacin from wastewater

The present study explores visible light-assisted photodegradation of ciprofloxacin hydrochloride (CIP) antibiotic as a promising solution to water pollution. The focus is on transforming the optical and electronic properties of BiOCl through the generation of oxygen vacancies (OVs) and the exposure of (110) facets, forming a robust S-scheme heterojunction with WS2. The resultant OVs mediated composite with an optimal ratio of WS2 and BiOCl-OV (4-WS2/BiOCl-OV) demonstrated remarkable efficiency (94.3%) in the visible light-assisted photodegradation of CIP antibiotic within 1.5 h. The CIP degradation using 4-WS2/BiOCl-OV followed pseudo-first-order kinetics with the rate constant of 0.023 min-1, outperforming bare WS2, BiOCl, and BiOCl-OV by 8, 6, and 4 times, respectively. Density functional theory (DFT) analysis aligned well with experimental results, providing insights into the structural arrangement and bandgap analysis of the photocatalysts. Liquid chromatography-mass spectrometry (LC-MS) analysis utilized for identifying potentially degraded products while scavenging experiments and electron paramagnetic resonance (EPR) spin trapping analysis elucidated the S-scheme charge transfer mechanism. This research contributes to advancing the design of oxygen vacancy-mediated S-scheme systems in the realm of photocatalysis, with potential implications for addressing water pollution concerns.

Hexavalent Chromium Reduction Mediated by Interfacial Electron Transfer over the Co@NC Nanosheet-Assembled Microflowers

The reductive transformation of Cr(VI) into Cr(III) mediated by formic acid with efficient, stable, and cost-effective catalysts is a promising strategy for remediating Cr(VI) contamination. Herein, we report the facile construction of uniform Co@NC nanosheet-assembled microflowers for the reduction of Cr(VI). Both experimental results and density functional theory (DFT) calculations reveal the vital role of the intensive interfacial electronic interaction between Co nanoparticles and the N-doped carbon layer in facilitating the anchoring and dispersion of Co nanoparticles within the carbon framework. The interfacial electron transfer from Co to NC contributes to the interaction with Cr2O72- ions, promoting the subsequent H-transfer reaction. A Langmuir-Hinshelwood kinetic model has been established for the Cr(VI) reduction catalyzed by the CNCF2 (pyrolyzed at 700 °C), which shows a superior reaction performance. This study provides a facile strategy to delicately design well-assembled heterostructures with rich interfaces and strong interfacial interactions for a series of applications in environmental/thermal catalysis.

Unravelling the enhanced rifampicin photocatalytic degradation over green-synthesized SrO2@SnIn4S8 p-n heterojunction: Pathway, toxicity evaluation and mechanistic insights

In recent years, the discharge of pharmaceutical drugs into aquatic ecosystems has become a growing concern, posing a significant threat to aquatic life. In response to this environmental challenge, advanced oxidation processes have gained prominence in wastewater treatment due to their efficacy in eliminating pharmaceutical pollutants and their potential for reusability. In this study, we have fabricated SnIn4S8 coupled SrO2 nano-heterojunction (NH) using a greener co-precipitation approach using leaf extract derived from Acaphyla wilkesiana. The resulting NH exhibited exceptional photocatalytic activity against rifampicin (RIF), achieving a remarkable 97.4% degradation under visible light, surpassing the performance of its individual components. The morphological characteristics of the NH were thoroughly analyzed through SEM, TEM, XRD, and XPS techniques, while EIS, DRS, and BET techniques provided valuable insights into its photocatalytic and optical properties. Furthermore, radical scavenging assays and ESR analysis identified hydroxyl radicals (•OH) and superoxide radicals (O2•-) were the species contributing to the visible light-driven photocatalytic degradation. The study also elucidated the potential degradation pathways and intermediates of RIF through GC-MS analysis. Additionally, the toxicity of the produced intermediates was assessed using the ECOSAR model. The findings have significant implications for the treatment of pharmaceutical pollutants and underscore the importance of eco-friendly synthesis methods in addressing environmental challenges.

Insights into the performance of binary heterojunction photocatalysts for degradation of refractory pollutants

The uncontrolled discharge of industry- and consumer-derived micropollutants and synthetic contaminants into freshwater bodies represents a severe threat to human health and aquatic ecosystem. Inexpensive and highly efficient wastewater treatment methods are, therefore, urgently required to eliminate such non-biodegradable, recalcitrant, and toxic organic pollutants. In this context, advanced oxidation processes, particularly heterogenous photocatalysis, have received enormous attention over the past few decades. Among the different classes of photocatalysts explored by the scientific community, heterojunction photocatalysts, in general, and binary heterojunction photocatalysts, in particular, have shown tremendous promise, attributed to their many distinct advantages. As such, the present review highlights the application of diverse array of binary heterojunction photocatalysts for eliminating water-borne contaminants. Specifically, a bibliometric analysis has been conducted to identify the ongoing research trend and future prospects of heterojunction photocatalysts. It appears that metal oxide/metal oxide-based heterojunctions have superior thermal and mechanical stability compared to other heterojunction photocatalysts. In contrast, metal oxide/non-metal semiconductor-based heterojunctions are extremely effective in pollutant degradation without significant leaching of metal ions. The review concludes by proposing novel strategic research guidelines in order to make further advances in this rapidly evolving cross-disciplinary field of topical interest.

Construction of Z-scheme Bi2O3/CeO2 heterojunction for enhanced photocatalytic capacity of TiO2 NTs

Photocatalytic technology was recognized to be the effective strategy to overcome the obstacles of environment pollution and energy shortage, and the novel photocatalyst design/construction was the key point for photocatalytic performance improvement. In this paper, the Z-scheme Bi2O3 and CeO2 heterojunction was constructed on TiO2 nanotube arrays (TiO2 NTs) by the hydrothermal deposition method. The Bi2O3-CeO2 cosensitization not only extended the solar absorption region but also accelerated the photoelectron separation and transfer, finally enhanced the photocatalytic property. The photocatalysts exhibited the high RhB/MB photodegradation and Cr(VI) reduction, and the photoelectric conversion and photocatalytic H2 evolution were also preeminent. The Z-scheme heterojunction construction was recognized to be the reason for the high photoactivity, and O2- and OH radicals were formed and investigated as the main active species for the dye photodegradation. The work gives the simple method and idea to construct novel ternary Z-scheme heterojunctions with high photocatalytic capacity for environment remediation and new energy development.

S-scheme MOF-on-MOF heterojunctions for enhanced photo-Fenton Cr(VI) reduction and antibacterial effects

The photocatalytic efficiency is commonly restrained by inferior charge separation rate. Herein, the S-scheme MIL-100(Fe)/NH2-MIL-125(Ti) (MN) photo-Fenton catalyst with the built-in electric field (BEF) was successfully constructed by a simple ball-milling technique. As a result, the MN-3 (the mass ratio of MIL-100(Fe) to NH2-MIL-125(Ti) was 3) composite presented the best visible-light-induced photocatalytic ability, in contrast to pure MIL-100(Fe) and NH2-MIL-125(Ti). The reduction efficiency of Cr(VI) almost reached 100% within 35 min of illumination. Moreover, the MN-3 heterojunction also exhibited the highest antibacterial activity, and about 100% E. coli and more than 90% S. aureus were killed within 60 min of illumination. In photo-Fenton system, In the photo-Fenton system, e-, O2•- and Fe2+ played vital roles for Cr(VI) reduction, and •OH, h+ and O2•- and 1O2 were responsible for sterilization. Additionally, 5 cyclic tests and relevant characterizations confirmed the excellent repeatability and stability of the composite. Also, the S-scheme charge transfer process was put forward. This work offers a novel idea for establishing the MOF-on-MOF photo-Fenton catalyst for high-efficiency environmental mitigation.

Efficient Photocatalytic Reduction of Hexavalent Chromium by BiVO4-Decorated MXene Photocatalysts and Their Charge Carrier Dynamics

The synergistically MXene (Ti3C2Tx) co-catalyst-decorated BiVO4-based heterostructured photocatalysts have been synthesized by a hydrothermal approach with varied loading concentrations of MXene (Ti3C2Tx) to drive the hexavalent chromium reduction efficiently. The formation of the heterostructured photocatalyst was confirmed by the appearance of X-ray diffraction (XRD) peaks corresponding to the monoclinic BiVO4 phase and MXene (Ti3C2Tx) and also the antisymmetric (834 cm-1) and symmetric stretching (715 cm-1) of tetrahedral VO4 and D (1330 cm-1) and G (1570 cm-1) bands corresponding to MXene (Ti3C2Tx) in the Raman spectrum. The worm-like structures of BiVO4 nanocrystals grew onto the lamellar sheets of MXene (Ti3C2Tx), as shown by field emission scanning electron microscopy (FESEM), and has an increased surface area of 15.62 m2g-1 in the case of BVO-20-TC. X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of V5+ and Ti3+states, and the uniform distribution of BiVO4 nanocrystals over lamellar sheets of MXene (Ti3C2Tx) is evident from energy-dispersive X-ray (EDX) analysis. The ultraviolet-diffuse reflectance spectroscopy (UV-DRS) spectra suggest a decrease in the band gap energy of BVO-20-TC to 2.335 eV, promoting a higher degree of visible light harvesting. Upon optimization, by varying the pH, the amount of the photocatalyst, and the concentration of Cr(IV), BVO-20-TC exhibits the highest photocatalytic efficiency (96.39%) while using a Cr(VI) concentration of 10 ppm at pH 2 and 15 mg of the photocatalyst, and the photoreduction of Cr(VI) to Cr(III) follows the pseudo-first-order reaction. The decrease in the PL intensity in BVO-20-TC reveals a faster transfer of electrons from MXene (Ti3C2Tx) to BiVO4. Further, the higher degree of band bending at the BiVO4/MXene (Ti3C2Tx) heterojunction, revealed from the Mott-Schottky analysis, facilitates efficient charge transfer and eventually faster and efficient photoreduction of Cr(VI) to Cr(III). The reusability and stability test undertaken for BVO-20-TC reveals that even after five cycles, the Cr (VI) photoreduction efficacy is retained. This work provides insights into photoreduction of Cr (VI) by using such heterostructures.

Effective elimination of hexavalent chromium and lead from solution by the modified biochar with MgMn2O4 nanoparticles: adsorption performance and mechanism

Heavy metal pollution is one of the environmental problems that need to be solved urgently. The adsorption method is thought as the most effective and economical treatment technology. Nature biochar usually showed unsatisfactory adsorption capacity due to its relatively small adsorption capacity and slow adsorption rate. The metal of Mn has been widely applied in the modification of biochar, which could effectively improve the adsorption capacity of biochar. However, leaching of Mn2+ on the adsorbent materials would appear during the adsorption process. And it would increase the risk of secondary pollution. The multifunctional binary modified biochar could improve the adsorption capacity of environmental pollutant removal. In addition, it could also act as a metal support carrier, reducing the risk of secondary pollution. A novel effective biochar loaded by Mg-Mn binary oxide nanoparticles (MgMn2O4@Biochar) was prepared and applied for the Cr(VI) and Pb(II) removal in aqueous solution. The characteristic of MgMn2O4@Biochar was analyzed by SEM, TEM, FTIR, and XRD. The irregular and somewhat flaky shaped particles of different shape and sizes clustered on the surface of MgMn2O4@Biochar appeared. Abundant functional groups of O-H, -C-OH, C-O, and C-OOH could be observed on the surface of MgMn2O4@Biochar. The elements of Mg and Mn elements besides of C, O, and Si elements were presented on the surface of MgMn2O4@Biochar. The wt% of C, O, Mg, Mn, and Si were 42.82%, 48.99%, 2.83%, 4.44%, and 0.93%, respectively. The operational parameters had an important influence on adsorption capacity of Cr(VI) and Pb(II) removal. The results showed that the adsorption capacity of MgMn2O4@Biochar for Cr(VI) and Pb(II) would reach 33.5 mg/g and 536 mg/g, respectively, within 360 min. Additionally, the adsorption processes of Cr(VI) and Pb(II) in solution could be described with pseudo-second-order. For Cr(VI), the Langmuir model was suitable to the adsorption process. However, the adsorption process of Pb(II) in solution could be described with Freundlich model. Furthermore, it could be concluded that the possible mechanism of Cr(VI) and Pb(II) removal by MgMn2O4@Biochar was physical adsorption, surface complexation reaction, and electrostatic adsorption.

Co3O4 with upshifted d-band center and enlarged specific surface area by single-atom Zr doping for enhanced PMS activation

In this work, single-atom Zr doping is demonstrated to be an effective strategy to enhance the catalytic performance of Co₃O₄ toward peroxymonosulfate (PMS) by modulating electronic structure and enlarging specific surface simultaneously. The d-band center of Co sites upshifts owing to different electronegativity of Co and Zr in the bonds of Co-O-Zr confirmed by density functional theory calculations, leading to enhanced adsorption energy of PMS and strengthened electron transfer from Co^(II) to PMS. The specific surface area of Zr-doped Co₃O₄ increases by 6 times due to the decrease of crystalline size. Consequently, the kinetic constant of phenol degradation with Zr-Co₃O₄ is 10 times higher than that with Co₃O₄ (0.31 vs. 0.029 min^-1). The relative surface specific kinetic constant of Zr-Co₃O₄ for phenol degradation is still 2.29 times higher than that of Co₃O₄ (0.00660 vs. 0.00286 g m^-2 min^-1). In addition, the potential practical applicability of 8Zr-Co₃O₄ was also confirmed by practical wastewater treatment. This study provides deep insights into modifying electronic structure and enlarging specific surface area to enhance the catalytic performance.

Preparation and evaluation of celite decorated iron nanoparticles for the sequestration performance of hexavalent chromium from aqueous solution

The increasing usage of an important heavy metal chromium for industrial purposes, such as metallurgy, electroplating, leather tanning, and other fields, has contributed to an augmented level of hexavalent chromium (Cr(VI)) in watercourses negatively impacting the ecosystems and significantly making Cr(VI) pollution a serious environmental issue. In this regard, iron nanoparticles exhibited great reactivity in remediation of Cr(VI)-polluted waters and soils, but, the persistence and dispersion of the raw iron should be improved. Herein, this article utilized an environment-friendly celite as a modifying reagent and described the preparation of a novel composites namaly celite decorated iron nanoparticles (C-Fe⁰) and evaluation of C-Fe⁰ for the sequestration performance of Cr(VI) from aqueous solution. The results indicated that initial Cr(VI) concentration, adsorbent dosage, and especially solution pH are all critical factors to control C-Fe⁰ performance in Cr(VI) sequestration. We demonstrated that C-Fe⁰ could achieve a high Cr(VI) sequestration efficiency with an optimized adsorbent dosage. Fitness of the pseudo-second-order kinetics model with data indicated that adsorption was the rate-controlling step and chemical interaction controlled Cr(VI) sequestration on C-Fe⁰. The adsorption isotherm of Cr(VI) could be the best depicted by Langmuir model with a monolayer adsorption. The underlying sequestration path of Cr(VI) by C-Fe⁰ was then put forward, and the combined effect of adsorption and reduction implied the potentials of C-Fe⁰ in Cr(VI) removal.

Oxygen Vacancies-Rich S-Cheme BiOBr/CdS Heterojunction with Synergetic Effect for Highly Efficient Light Emitting Diode-Driven Pollutants Degradation

Recently, the use of semiconductor-based photocatalytic technology as an effective way to mitigate the environmental crisis attracted considerable interest. Here, the S-scheme BiOBr/CdS heterojunction with abundant oxygen vacancies (Vo-BiOBr/CdS) was prepared by the solvothermal method using ethylene glycol as a solvent. The photocatalytic activity of the heterojunction was investigated by degrading rhodamine B (RhB) and methylene blue (MB) under 5 W light-emitting diode (LED) light. Notably, the degradation rate of RhB and MB reached 97% and 93% in 60 min, respectively, which were better than that of BiOBr, CdS, and BiOBr/CdS. It was due to the construction of the heterojunction and the introduction of Vo, which facilitated the spatial separation of carriers and enhanced the visible-light harvest. The radical trapping experiment suggested that superoxide radicals (·O₂^-) acted as the main active species. Based on valence balance spectra, Mott-Schottky(M-S) spectra, and DFT theoretical calculations, the photocatalytic mechanism of the S-scheme heterojunction was proposed. This research provides a novel strategy for designing efficient photocatalysts by constructing S-scheme heterojunctions and introducing oxygen vacancies for solving environmental pollution.

Easy-handling semi-floating TiO2-based aerogel for solar photocatalytic water depollution

One of the capital issues of photocatalytic technology is how to use photocatalytic materials in real world conditions. Suspension photocatalysts are the most effective, while the handling and recovery of nanoparticles are very challenging and costly. Herein, we report the design of semi-floating aerogel TiO_2-based photocatalyst for the oxidation of dyes and photoreduction of Cr(VI). TiO₂ aerogel-based photocatalyst was fabricated through in situ polymerization using borax, poly(vinyl alcohol) and polyvinylidene in the presence of H₂O₂ as a catalyst. Cubic TiO₂ aerogel of few centimetres was designed for the photocatalytic tests under solar light irradiation. TiO₂ aerogel showed a good photoactivity against the oxidation of three types of dyes and Cr(VI) photoreduction. In terms of dyes, the kinetics of methylene blue oxidation was the fastest as compared to rhodamine B and methyl red, while, a total reduction of Cr(VI) at 10 ppm was obtained within 30 min after the addition of tartaric acid as hole scavenger. TiO₂ aerogel can be easily recovered, washed and recycled. TiO₂ aerogel can move freely from the top to the deep solution. The semi-floating property could be an advantage to enhance the mass transfer along with bulk solution, as compared to totally floating-based photocatalysts.

Novel insight on chemo-specific detection of toxic environmental chromium residues existing as recalcitrant Cr(III)-carboxyl complexes using plasmonic silver nanoplatform bi-functionalized with citrate and PVP

Chromium (Cr) is a toxic environmental pollutant that majorly exists in trivalent and hexavalent forms. Though Cr(VI) is more dangerous than Cr(III), the trivalent Cr forms complexes with environmentally-available organic molecules. This makes them potentially harmful and difficult to detect. In this study, we have designed an ultrasensitive plasmonic nanosensor using citrate and PVP functionalized Ag nanoparticles (Ag-citrate-PVPNPs) for the detection of trivalent chromium organic complexes such as Cr(III)-EDTA (Cr-E), Cr(III)-acetate (Cr-A), Cr(III)-citrate (Cr-C) and Cr(III)-tartrate (Cr-T). The nanoparticles (NPs) were structurally characterized by XRD, SEM, HRTEM, SAED, EDX and elemental mapping. The citrate and PVP molecules played a vital role in the detection mechanism and stability of the sensor. Upon detection, the yellow-colored Ag-citrate-PVP NPs turned into different shades of brown depending on the type of the Cr complex and concentration. It was accompanied by diminishing and/or shifting UV-Visible absorbance peaks due to the aggregation of Ag-citrate-PVP NPs. Further, a linear relationship was observed between absorbance reduction and analyte concentration. The selectivity tests showed that the sensor was non-functional to other metal ions and inorganic anions. The sensor was optimized using pH and temperature studies. The mechanism of detection was elucidated with the help of characterization techniques such as Raman spectroscopy, FTIR, XPS and UV-visible spectrophotometer. The limit of detection (LOD) was found to be 3.29, 4.87, 1.76 and 1.79 nM for Cr-E, Cr-A, Cr-C and Cr-T complexes respectively. This study provides a rapid and sensitive approach for the detection of multiple Cr(III)-organic complexes present in an aqueous solution.

Mechanism of Cr(VI) reduction by an indigenous Rhizobium pusense CR02 isolated from chromite mining quarry water (CMQW) at Sukinda Valley, India

Toxicological assessment of CMQW generated due to chromite mining activities at Sukinda Valley has revealed high chromium contamination along with Zn and Fe. The present study focused on the mechanism of chromate reduction by an indigenous multi-metal tolerant bacterium, Rhizobium pusense CR02, isolated from CMQW. The isolated strain has shown resistance up to 520 mg/L of Cr(VI) with an IC50 value of 385.4 mg/L. The highest reduction rate 8.6 × 10^-2/h was recorded with 20 mg/L of initial concentration of Cr(VI). Extracellular (3.06 ± 0.012 U/mL), intracellular (3.60 ± 0.13 U/mL), and membrane (1.89 ± 0.01 U/mL) associated chromate reductases were found to be involved for reduction. The extracellular polymeric substances (EPS) produced by the isolate also enhanced reduction activity of 46.32 ± 1.69 mg/L after 72 h with an initial concentration of 50 mg/L. FTIR analysis revealed the involvement of functional groups -OH, -CO, and -NH for Cr(VI) biosorption whereas P=O, -CO-NH- and -COOH interacted with Cr(III). Zeta potential with less negative surface charge favored reduction of Cr(VI). Treatment of CMQW by bacterial isolate detoxified Cr(VI) minimizing chromosomal aberrations in root cells of Allium cepa L., suggesting the role of Rhizobium pusense CR02 as a promising bio-agent for Cr(VI) detoxification.

Photoreduction behavior of Cr(VI) on oxidized carbon nanoparticles: From photocatalytic efficiency to oxygenated groups

Clarifying the reaction process and specific mechanism between variable-valence elements and oxidized carbon nanoparticles is essential to evaluate the environmental impact of carbon nanomaterials. In this study, the photocatalytic reduction of Cr(VI) on oxidized carbon nanotubes (OCNTs), oxidized graphene ribbons (OGRs), and graphene oxide sheets (GOs) was explored by batch experiments and spectroscopic analyses. The reaction efficiencies strongly depended on the number of oxygenated groups in the oxidized carbon nanoparticles. The abundant oxygenated groups enabled the GOs to exhibit the highest photocatalytic activity, followed by the OGRs and OCNTs. As a result, the photoreduction efficiency of Cr(VI) reached 96% for GOs, whereas those of OGRs and OCNTs were only 40% and 13%, respectively. In addition, different types of oxygenated groups exhibited various activities based on molecular model tests, following the sequence carboxylic > hydroxyl > carbonyl > ether > aldehyde > edge. Based on the underlying relationship between the oxygenated groups, topological structures, and mechanical strain in the carbon nanoparticles, we speculate that mechanical strain plays a critical role in the formation of oxygenated groups, thereby regulating their photocatalytic activities. The findings in this work provide novel insights into the roles of oxygenated groups and the mechanical strain of carbon nanoparticles in their environmental behavior.

Hierarchical Ultrathin Layered GO-ZnO@CeO2 Nanohybrids for Highly Efficient Methylene Blue Dye Degradation

Highly efficient interfacial contact between components in nanohybrids is a key to achieving great photocatalytic activity in photocatalysts and degradation of organic model pollutants under visible light irradiation. Herein, we report the synthesis of nano-assembly of graphene oxide, zinc oxide and cerium oxide (GO-ZnO@CeO₂) nanohybrids constructed by the hydrothermal method and subsequently annealed at 300 °C for 4 h. The unique graphene oxide sheets, which are anchored with semiconducting materials (ZnO and CeO₂ nanoparticles), act with a significant role in realizing sufficient interfacial contact in the new GO-ZnO@CeO₂ nanohybrids. Consequently, the nano-assembled structure of GO-ZnO@CeO₂ exhibits a greater level (96.66%) of MB dye degradation activity than GO-ZnO nanostructures and CeO₂ nanoparticles on their own. This is due to the thin layers of GO-ZnO@CeO₂ nanohybrids with interfacial contact, suitable band-gap matching and high surface area, preferred for the improvement of photocatalytic performance. Furthermore, this work offers a facile building and cost-effective construction strategy to synthesize the GO-ZnO@CeO₂ nanocatalyst for photocatalytic degradation of organic pollutants with long-term stability and higher efficiency.

Efficient adsorption of hexavalent chromium ions onto novel ferrochrome slag/polyaniline nanocomposite: ANN modeling, isotherms, kinetics, and thermodynamic studies

The current research is concerned with the adsorption behavior of chromium (IV) ions in an aqueous solution using a novel ferrochrome slag/polyaniline nanocomposite (FeCr-PANI) adsorbent. The effect of process parameters such as temperature, pH solution, initial Cr (VI) ions concentration, adsorbent dosage, and contact time on the adsorption process is experimentally investigated in this study. Furthermore, we have trained a multilayer artificial neural network (ANN) using the experimental data of various process parameters to successfully predict the adsorption behavior of chromium (IV) ions onto the FeCr-PANI adsorbent. The ANN model was trained using the Lavenberg-Marquardt algorithm and ten neurons in the hidden layer and was able to estimate the % removal efficiency of chromium (IV) under the influence of different process parameters (R² = 0.991). Initial solution pH was observed to have a significant influence on the % removal efficiency. The % removal efficiency was found to be high at 97.10% for the solution with pH 3 but decreased to 64.40% for the solution with pH 11. Cr (VI) % removal efficiency was observed to increase with an increase in solution temperature, adsorbent dosage, and contact time. However, the % removal efficiency was found to decrease from 96.9 to 54.8% with increasing the initial dye concentration from 100 to 400 ppm. Furthermore, the adsorption capacity increased from 9.69 to 21.93 mg/g with an increase in the initial concentration from 100 to 400 ppm, as expected. The Langmuir isotherm model exhibited the best fit with the experimental data (R² = 0.9977). The maximum adsorption capacity was found to be 22.523 mg g^-1 at 298 K. The experimental data fitted well with the pseudo-second-order kinetic model.

CdS Nanoparticles Decorated 1D CeO2 Nanorods for Enhanced Photocatalytic Desulfurization Performance

CdS nanoparticles were constructed onto one-dimensional (1D) CeO2 nanorods by a two-step hydrothermal method. The X-ray diffraction (XRD), transmission election microscopy (TEM), Raman spectra, X-ray photoelectron spectra (XPS) and UV-Vis diffuse reflection spectroscopy (DRS) techniques were used to characterize these CdS/CeO2 nanocomposites. It was concluded that when the molar ratio of CdS and CeO2 was 1:1, the nanocomposites exhibited the best photocatalytic desulfurization activity, reaching 92% in 3 h. Meanwhile, transient photocurrent (PT) measurement, photoluminescence (PL) spectra and electrochemical impedance spectroscopy (EIS) measurement indicated that the modification of CeO2 nanorods by CdS nanoparticles could significantly inhibit the recombination of photogenerated electrons and holes. In addition, the possible mechanism of photocatalytic oxidation desulfurization of the nanocomposites was proposed. This study may provide an effective CeO2-based photocatalyst for photocatalytic desulfurization applications.

High efficiency of Ag0 decorated Cu2MoO4 nanoparticles for heterogeneous photocatalytic activation, bactericidal system, and detection of glucose from blood sample

The novel Ag0/Cu2MoO4 nanoparticles was simply synthesized via chemical method. Ag/Cu2MoO4 nanoparticles was characterized by FESEM image, XRD curve, UV-vis spectroscopy, BET analysis, and XPS spectrum. XRD pattern depicts that the cubic crystalline phase of particles. The band gap of Ag/Cu2MoO4 nanoparticles was achieved to 2.04 eV, which that depicted the best activity under visible light irradiation. Ag/Cu2MoO4 nanoparticles exhibits 99.74% degradation under light and persulfate ion which was higher response than Cu2MoO4 nanoparticles (83.56%) under this condition. The scavenging test indicates the important reactive species in removal process were •OH, and •SO4-. The Ag/Cu2MoO4 nanoparticles was indicated highly photo-stability for the MG degradation after 5th cycle. Ag/Cu2MoO4 exhibits substantial antibacterial properties against P. aeruginosa and S. pneumoniae. Moreover, Ag/Cu2MoO4 nanoparticles was experimented to peroxidase-like performance for the colorimetric detection of glucose with the Limit of Detection about 52.23 nM.

Sunlit expeditious visible light-mediated photo-fenton degradation of ciprofloxacin by exfoliation of NiCo2O4 and Zn0·3Fe2·7O4 over g-C3N4 matrix: A brief insight on degradation mechanism, degraded product toxicity, and genotoxic evaluation in Allium cepa

Pharmaceutical pollutant in the environmental water bodies has become a major concern, which causes adverse effect to aquatic entities. This study provides an incisive insight on the photocatalytic degradation of ciprofloxacin (CIP) and the development of rationally engineered g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite for boosted photocatalytic performance under visible light irradiation. The g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite was synthesized via ultrasonication-assisted hydrothermal method. The characterization of the as-prepared material was evaluated by XPS, SEM, HR-TEM, PL, FT-IR, EIS, ESR, XRD, BET, and UV-Vis DRS techniques. Furthermore, the effect of catalytic dosage, drug dosage, and pH changes was explored, where g-C3N4-NiCo2O4-Zn0.3Fe2·7O4-10% unveiled excellent visible light photo-Fenton degradation of 92% for CIP at 140 min. The hydroxyl radicals (OH.) served as the predominant radical species on the photodegradation of CIP, which was confirmed by performing a radical scavenging test. Furthermore, the degradation efficiency was determined by six consecutive cycle tests, where the nanomaterial exhibited excellent stability with 98.5% reusable efficiency. The degradation of CIP was further scrutinized by GC-MS analysis, where the degraded intermediate products and the possible pathway were elucidated. The degraded product toxicity was determined by ECOSAR program, where the degraded products haven't exhibited any considerable toxic effects. In addition, the genotoxicity of the nanomaterial was determined by treating them with root tips of A. cepa, where it was found to be non-toxic. Here, the prepared g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite (CNZ NCs) shows eco-friendly and excellent photo-Fenton activity for environmental applications.

Synergistic activities of silver indium sulfide/nickel molybdenum sulfide nanostructures anchored on clay mineral for light-driven bactericidal performance, and detection of uric acid from gout patient serum

In this study, the hydrothermal method was used to synthesis of silver indium sulfide/nickel molybdenum sulfide (AgInS₂/NiMoS₄) nanostructure and decorated on Palygorskite (Plg) as an excellent carrier of antibacterial materials. The performance of the prepared AgInS₂/NiMoS₄/Plg composites was investigated for light-driven antibacterial process and detection of uric acid from biological samples. The result shows the highest antibacterial activity of the AgInS₂/NiMoS₄/Plg with the minimum inhibitory concentrations about 0.2-0.3 mg/mL. The prepared AgInS₂/NiMoS₄/Plg as sensor depicted enhanced peroxidase-like activity for detection of acid uric. The detection limit of acid uric by AgInS₂/NiMoS₄/Plg was about 26.1 nM. Therefore, the AgInS₂/NiMoS₄/Plg can be developed in the bactericidal process and sensing in complex biological systems.

The state of the art review on photocatalytic Cr(VI) reduction over MOFs-based photocatalysts: From batch experiment to continuous operation

This state of the art review presented the photocatalytic reduction from highly toxic Cr(VI) to lowly toxic Cr(III) with metal-organic frameworks (MOFs) and their composites. The construction of composites facilitated the transportation of the photo-induced charges to enhance the Cr(VI) reduction, in which the corresponding mechanisms were clarified by both experimental tests and DFT calculations. The immobilized MOFs onto some substrates accomplished continuous operations toward Cr(VI) reduction even under real solar light. As well, the environmental applications of the Cr(VI) reduction were analyzed, in which the influence factors toward the Cr(VI) reduction were clarified. This review reported that a big breakthrough was achieved from the batch experiment to the continuous operation for Cr(VI) reduction, in which MOFs demonstrated a bright prospective in the field of photocatalytic Cr(VI) reduction.

Solid-State Synthesis of ZnO/ZnS Photocatalyst with Efficient Organic Pollutant Degradation Performance

To improve the separation efficiency of photogenerated carriers in ZnS, constructing a ZnS-based heterostructure with ZnO is assessed to be an efficient strategy, and a ZnO/ZnS photocatalyst was prepared by a solid-phase approach, and the structure and morphology were systematically studied. The ZnO/ZnS photocatalyst showed excellent photocatalytic properties on methyl orange, rhodamine B and tetracycline under UV light irradiation, indicating that the photocatalyst exhibited efficient broad-spectrum photocatalytic performance. Compared with ZnS, the degradation rates of ZnO/ZnS photocatalysts for methyl orange, rhodamine B and tetracycline under UV light increased from 21%, 9% and 32% to 96%, 94% and 93%, respectively, higher than the reported ZnO/ZnS composites synthesized by a novel wet chemical route, attributing to the improvement of light absorption ability and the effective separation of carriers. In addition, the influence of the sacrificial agent on the reaction system was investigated, and the synergistic mechanism of ZnO and ZnS in the catalytic process was analyzed according to the fluorescence spectra, photocurrent and first-principles calculation results, and a possible catalytic mechanism was put forward.

Construction of Z-scheme CdS/Ag/TiO2 NTs photocatalysts for photocatalytic dye degradation and hydrogen evolution

The ternary CdS/Ag/TiO₂ NTs photocatalysts with indirect Z-scheme heterojunctions were synthesized by the photoreduction deposition of Ag and successive ionic layer adsorption and reaction (SILAR) of CdS on TiO₂ nanotube arrays (TiO₂ NTs). The elemental composition, microstructure, photoresponse and photoelectrochemical property of the photocatalyst were systematically characterized. The results proved that compared with binary heterojunction, the light absorption range of the ternary CdS/Ag/TiO₂ NTs photocatalyst was significantly extended, and the photoelectron transportation efficiency was improved. Under sunlight irradiation, the photocatalytic capacity was verified by investigating the photodegradation of MB and RhB dyes. The CdS/Ag/TiO₂ NTs exhibited the optimal photocatalytic performance with the degradation efficiency of 82.24% for RhB and 100% for MB. The synthesized CdS/Ag/TiO₂ NTs had high photocatalytic hydrogen evolution capacity and stability, and the hydrogen production reached 806.33 μmol·cm^-2. Based on the results of electron spin resonance spectroscopy (ESR) and free radical trapping, the photocatalytic reaction mechanism was explained. The synthesis of ternary CdS/Ag/TiO₂ NTs provides a practical reference and guidance for designing high-efficient photocatalysts with Z-scheme heterojunctions toward solar energy development for H₂ generation, pollutant remediation and photoelectric conversion.

Comparison of Cr(VI) adsorption and photocatalytic reduction efficiency using leonardite powder

It is very important to treat Cr(VI) from the aquatic environment due to its toxic and harmful effects. Conventional treatment methodology involving biological pathways is generally ineffective for wastewater containing Cr(VI). Therefore, it is necessary to develop environmentally friendly and economical methods to remove Cr(VI) from the aquatic environment. In this study, leonardite, which is a natural mineral that has no harmful effects on the environment, was used for Cr(VI) removal. Leonardite was used in both adsorption and photocatalytic treatment systems by only pulverizing without any chemical treatment. Characterizations of leonardite were obtained using X-ray fluorescence (XRF), fouirer transform infrared spektrofotometre (FTIR), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) analyses methods. The effects of solution pH (2-10), particle size (45-300 μm), adsorbent dose (0.25-3 g/L), and initial concentration (10-30 mg/L) on Cr(VI) removal efficiency were investigated in both adsorption and photocatalytic experiments. In the adsorption process, a complete removal efficiency (100%) was obtained for 3 g/L of adsorbent dose with an initial Cr(VI) concentration of 10 mg/L at pH 2 for 2 h. In the photocatalytic process, 100% removal efficiency of Cr(VI) was obtained when four times less adsorbent dosage was used under the same conditions. In addition, the reuse of leonardite powder was also investigated under optimum experimental conditions. Leonardite powder preserved approximately 70% of its activity in the photocatalytic process while it lost 50% of its activity after 5 reuses in adsorption process.

Synergistic Cr(VI) Reduction and Chloramphenicol Degradation by the Visible-Light-Induced Photocatalysis of CuInS2: Performance and Reaction Mechanism

Despite significant scientific efforts in the field of water treatment, pollution of drinking water by toxic metal ions and synthetic organic compounds is becoming an increasing problem. The photocatalytic capabilities of CuInS₂ nanoparticles were examined in this study for both the degradation of chloramphenicol (CAP) and the reduction of Cr(VI). CuInS₂ nanoparticles were produced using a straightforward solvothermal approach and subsequently characterized by many analysis techniques. Simultaneous photocatalytic Cr(VI) reduction and CAP oxidation by the CuInS₂ nanoparticles under visible-light demonstrated that lower pH and sufficient dissolved oxygen favored both Cr(VI) reduction and CAP oxidation. On the basis of active species quenching experiments, the possible photocatalytic mechanisms for Cr(VI) conversion with synchronous CAP degradation were proposed. Additionally, the CuInS₂ retains a high rate of mixed pollutant removal after five runs. This work shows that organic contaminants and heavy metal ions can be treated concurrently by the visible-light-induced photocatalysis of CuInS₂.

Ag doped Sn3O4 nanostructure and immobilized on hyperbranched polypyrrole for visible light sensitized photocatalytic, antibacterial agent and microbial detection process

Ag doped Sn₃O₄ Nanostructure and immobilized on hyperbranched polypyrrole is investigated in this project. The product was synthesized by the hydrothermal synthesis method. The surface and structural characteristics of the product was studied by different instrumental analysis. The fabricated nanocomposites was utilized as a nano photocatalyst in the removal of methylene blue dye. The crystallography results depicts the triclinic phase of Sn₃O₄ with the crystallite size 36.3 nm. The band gap of the Ag-Sn₃O₄/hyperbranched polypyrrole was found 1.50 eV from kubelka-munk measurements. The specific surface area was increased in the presence of the hyperbranched polypyrrole as compared to Ag-Sn₃O₄ samples. The photo-catalytic activity of composites was found 100.0% degradation of CR in 30 min under visible light irradiation. The catalytic kinetic was followed from the first kinetic model. Moreover, the Ag/Sn₃O₄/hyperbranched polypyrrole was applied as a bactericidal agent against Streptococcus pneumoniae, and Pseudomonas aeruginosa bacteria. Determination of Streptococcus pyogenes as a pathogenic bacteria was investigated by using aptamer/Ag/Sn₃O₄/hyperbranched polypyrrole in peroxidase activity. The detection limit of S. pyogenes was 71.0 CFU/mL by using the nano-aptamer.

Subsurface and solid solution-type defect engineering in CoCr2O4-Bi2WO4-NiS2 nanocomposite for visible light degradation of doxycycline and chromium removal and its genotoxic evaluation in Allium cepa

In the present work, ternary CoCr2O4-Bi2WO4-NiS2nanocomposite (CCO-BWO-NS NCs), a semiconductor photocatalyst prepared for the effective minerization of doxycycline and photocatalytic removal of Cr(VI). Here, the modification of BiO-WO4-BiO (BWO) as...

NaFeSi2O6 nanocrystals as a catalyst for heterogeneous photo-Fenton degradation of organic wastewater

In this work, a novel, earth-abundant, and environmentally benign NaFeSi2O6 catalyst is synthesized by a one-step solvothermal method without the introduction of any surfactants.

In situ construction of a C3N5 nanosheet/Bi2WO6 nanodot S-scheme heterojunction with enhanced structural defects for the efficient photocatalytic removal of tetracycline and Cr(vi)

A novel 2D/0D C3N5/Bi2WO6 S-scheme heterojunction with enhanced structural defects has been designed for the efficient elimination of pharmaceutical antibiotics and Cr(vi).

A p–n heterostructural g-C3N4/PANI composite for the remediation of heavy metals and organic pollutants in water

A novel g-C3N4/PANI composite was fabricated via surface charge-induced electrostatic self-assembly method, which showed excellent a photocatalytic performance for Cr(vi) reduction and MO degradation under visible-light.