Removal of toxic arsenite As(III) from the contaminated surface and groundwater is essential for human health. However, direct arsenite removal is difficult compared to arsenate As(V). Therefore, the ...peroxidation of arsenite to arsenate is vital for its effective removal from water. Herein, we investigated the removal efficiency of arsenic from groundwater by oxidizing it with UV activated potassium persulfate (KPS) and subsequently adsorbing it on iron oxide impregnated granular activated carbon (FeO/GAC). A batch experiment was carried out to determine the adsorption kinetics and thermodynamics. Further, the effects of the adsorbent mass (FeO/GAC), C/Fe molar ratio, pH, arsenic concentration, competing anions, and humic acid in arsenic adsorption was studied. The characterization of FeO/GAC adsorbent was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and zeta potential measurements. Using the UV activated KPS and FeO/GAC, a ∼100% removal amount was achieved for 10 ppm of the arsenic solution in 1 h. Also, the effect of pH showed the highest removal efficiency in the pH range of 6.0–7.0 and it decreased dramatically at higher and lower pH values. The groundwater collected from Cheongyang in South Korea was spiked with 10 ppm of the arsenic (III) and more than 82% removal of arsenic was achieved in 90 min even in the presence of natural contaminants. Therefore, the results suggest that the UV activated KPS with FeO/GAC provides an effective method for treating highly-arsenic-contaminated water sources and this may be a viable alternative method over the existing methods.
•Efficient oxidation of Arsenic in water using UV activated KPS followed by adsorption on an impregnated FeO/GAC adsorbent.•The arsenic removal efficiency was 100% in artificial water and 82% in groundwater collected from Cheongyang, South Korea.•Adsorption mechanism is associated with electrostatic interaction, ion exchange, surface complexation and coprecipitation.•The thermodynamic studies revealed that the adsorption process was endothermic, spontaneous and feasible.
Herein, a magnetically separable reduced graphene oxide (rGO)-supported CoFe2O4–TiO2 photocatalyst was developed by a simple ultrasound-assisted wet impregnation method for efficient photocatalytic ...H2 production. Integration of CoFe2O4 with TiO2 induced the formation of Ti3+ sites that remarkably reduced the optical band gap of TiO2 to 2.80 eV from 3.20 eV. Moreover, the addition of rGO improved the charge carrier separation by forming Ti–C bonds. Importantly, the CoFe2O4–TiO2/rGO photocatalyst demonstrated significantly enhanced photocatalytic H2 production compared to that from its individual counterparts such as TiO2 and CoFe2O4–TiO2, respectably. A maximum H2 production rate of 76 559 μmol g–1 h–1 was achieved with a 20 wt % CoFe2O4- and 1 wt % rGO-loaded TiO2 photocatalyst, which was approximately 14-fold enhancement when compared with the bare TiO2. An apparent quantum yield of 12.97% at 400 nm was observed for the CoFe2O4–TiO2/rGO photocatalyst under optimized reaction conditions. This remarkable enhancement can be attributed to synergistically improved charge carrier separation through Ti3+ sites and rGO support, viz., Ti–C bonds. The recyclability of the photocatalyst was ascertained over four consecutive cycles, indicating the stability of the photocatalyst. In addition, it is worth mentioning that the photocatalyst could be easily separated after the reaction using a simple magnet. Thus, we believe that this study may open a new way to prepare low-cost, noble-metal-free magnetic materials with TiO2 for sustainable photocatalytic H2 production.
Developing efficient photocatalysts for overall water‐splitting (OWS) has garnered considerable attention due to their potential in renewable energy conversion and storage. Enhancing the efficiency ...of interfacial spatial charge separation poses a key challenge in this field, as it plays a momentous role in the photocatalytic process. In this review article, a range of strategies aimed at improving interfacial spatial charge separation in photocatalysts for realizing high‐efficiency OWS are explored. To provide a comprehensive understanding, first the fundamentals of photocatalytic water‐splitting are introduced and the main bottlenecks in the reaction process, along with various charge separation and transfer mechanisms are identified. Subsequently, recent advancements and efforts in designing spatial charge separation at the interfaces of 0D, 1D, 2D, and 3D nanostructured photocatalysts are discussed. Finally, a summary is presented and a long‐term outlook for spatial charge separation in the field of OWS is offered. By consolidating the current state‐of‐the‐art research, this review highlights the key challenges and favorable circumstances for future advancements in the pursuit of efficient OWS.
Developing efficient photocatalysts for overall water‐splitting (OWS) has attracted considerable attention due to their potential in renewable energy conversion. Enhancing the efficiency of interfacial spatial charge separation poses a key challenge in this field. In this review article, a range of strategies aimed at improving interfacial spatial charge separation in photocatalysts for realizing high‐efficiency OWS are explored.
•Hierarchical MoS2/B-dopedrGO photocatalysts was prepared via hydrothermal route.•The MoS2/B-dopedrGO photocatalysts was used for Tetracycline hydrochloride (TC) degradation and Cr (VI) ...reduction.•The strong interaction between B-Mo-S led to extended light absorption up to 730 nm.•The TC degradation and Cr (VI) reduction efficiency of ~85.3% and ~80.1% was achieved, respectively.
Hierarchical layered structures of dichalcogenides have assumed significant part in the feasible removal of harmful metals and antibiotic degradation. In this paper, the hierarchical MoS2 was fabricated with B-rGO sheets using facile and low-cost hydrothermal approach and characterized through XRD, HRSEM, HRTEM, Raman, and UV-DRS. The MoS2/B-rGO nanocomposites exhibit higher photo-responsive region than the visible window. From the UV-DRS studies, the optimized band gap level calculated as 1.7 eV for MoS2/B-rGO this is due to a direct connection between the B-rGO layers would strongly suppress the electron-hole pair recombination. The maximum photocatalytic degradation efficiency of ~85.3% towards Tetracycline hydrochloride (TC) and Cr (VI) to Cr (III) of ~80.1% was achieved. This investigation was likely to be new open window for the development of environmental and energy applications for future generations.
Molecular oxygen performs a vital role in the photocatalytic activity of anatase TiO2, but there is a little experimental insight into the role of molecular oxygen on the synthesis of TiO2 based ...photocatalysts. Herein, we have shown that Ni(OH)2/TiO2 prepared in the presence and absence of molecular oxygen results in significantly varied hydrogen production activity. The sample synthesized in the presence of O2 and N2 produced 6624 μmol/h/g and 4468 μmol/h/g of hydrogen under direct solar light exposure. Additionally, the samples prepared in the presence of light irradiation produced 8289 μmol/h/g of hydrogen, a 72 fold jump in hydrogen production compared to TiO2. XPS, FTIR, Raman, and ESR measurements were carried out to investigate the underlined mechanism for such variation in the photocatalytic activity. Our results suggest that the presence of molecular oxygen during Ni(OH)2/TiO2 synthesis causes the formation of terminal OH and reduced the oxygen vacancies on the surface of TiO2, which can significantly alter the H2 production. Also, the reusability of the photocatalysts is greatly affected by the synthesis conditions, namely the presence of light and molecular oxygen.
•Ni(OH)2/TiO2 (ONT) was prepared with and without molecular oxygen and light.•O2-ONT produced 8289 μmol/h/g of H2 under direct solar light irradiation.•O2 purging during synthesis of ONT resulted in 1.5 times higher H2 production.•Improved H2 activity due to the presence of terminal OH groups on the surface of TiO2.
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•P doped and Ni complex modified rod-shaped g-C3N4 is prepared by the hydrothermal method.•g-C3N4 is oxygen functionalized via N-O and C-O bonds and P is bonded to CN heterocycle via ...PN bond.•Ni complex incorporation and P doping effectively reduced the conduction band edge and bandgap of g-C3N4.•Ni complex/P-g-C3N4 photocatalysts degraded 86 % tetracycline in 20 min. and produced 3272 μmol/g of H2 in 4 h.•Ni complex/P-g-C3N4 photocatalysts showed high stability and reusability up to 16 h.
Solar hydrogen energy generation via photocatalysis can play a vital role in reducing global warming, environmental pollution, and the ever-increasing energy demand. Herein, phosphorus and Ni complex modified g-C3N4 were prepared by a hydrothermal method. The bonding of electron-rich phosphorous heteroatom to the g-C3N4 changed the morphology of the g-C3N4 from nanosheets into nano-rods and significantly altered the electronic structure, as evident by the shift in the conduction band edge and bandgap of g-C3N4. FTIR and XPS measurements revealed
that the triazine ring is oxygen functionalized and the P atom bonded to g-C3N4 via PN bond. Furthermore, EPR, UPS, and UV-DRS measurements revealed that the P and Ni complex reduced the localized π-conjugated structure defects of g-C3N4 and extended the light absorption into the near IR region. The Ni complex in the photocatalysts provided the additional charge transfer band of IMCT and OMCT. EDS color mapping revealed that the Ni complex is distributed uniformly on the P-g-C3N4 surface. These surface embedded Ni complex acts as an electron trap state, thereby suppressing the charge pair recombination rate which was confirmed by the PL and TRPL measurements. The synergetic effect of Ni complex and P resulted in 86 % tetracycline degradation in 20 min. and 3272 μmol/g of H2 production in 4 h. Compared to bulk g-C3N4, 818 times higher H2 production activity was achieved for the P and Ni complex modified g-C3N4.
Iron oxide-loaded Cu
2
O photocatalysts were prepared by a facile hydrothermal method. The binary mixed metal oxide photocatalyst was characterized by XRD, FE-SEM, FTIR, UV–Vis-DRS, particle size and ...zeta potential measurements. XRD analysis showed that Fe
2
O
3
/Cu
2
O catalysts were phase pure and highly crystalline in nature. FE-SEM images revealed the formation of nanospherical Fe
2
O
3
over the Cu
2
O surface during hydrothermal reaction. From UV–Vis diffuse reflectance spectroscopy studies, the optical band gap of the Fe
2
O
3
/Cu
2
O photocatalyst was found to be slightly red-shifted to 1.85 eV, after loading of Fe
2
O
3
. The zeta potential analysis revealed that the surface of the Fe
2
O
3
/Cu
2
O photocatalyst was negatively charged in neutral solution. The loading of
n
-type Fe
2
O
3
on
p-
type Cu
2
O augments the charge carrier separation at the interface, which was evident from the enhanced photodegradation of organic pollutants (Methylene blue and Rhodamine B dyes) under visible light irradiation.
The ammonia industry plays a crucial role in various aspects of human progress and the global economy, particularly in fields such as fertilizers and the production of emerging clean fuels. The ...Haber-Bosch process, a commercially used method for ammonia production has significant environmental drawbacks and is economically challenging. The conversion of nitrates into ammonia can be considered as an alternative approach to address these challenges. Nitrates represent a prevalent toxic inorganic compound found in groundwater, posing significant health risks when present in high levels in drinking water. An emerging field of research, photocatalysis, harnesses solar energy and catalysts to convert nitrates into ammonia, offering environmentally sustainable and cost-efficient pathways. This review provides a thorough exploration of recent advancements in the reduction of nitrate to ammonia using photocatalytic technology. The discussion comprehends various aspects, including the detailed mechanism of ammonia production based on experimental and theoretical calculations, a detailed analysis of reported catalysts, factors affecting ammonia production, and potential areas for advancement based on previous research. Furthermore, this comprehensive review examines the challenges and prospects for future efforts essential for adopting photocatalysis for ammonia production from nitrate pollution.
•This review discusses photocatalytic conversion of nitrate, a common wastewater contaminant, into valuable ammonia.•It provides a comprehensive analysis of the existing literature on photocatalytic conversion of nitrate to ammonia.•A systematic explanation of the mechanism behind nitrate-to-ammonia conversion through photocatalysis is presented.•The review discusses factors affecting the process and highlights state-of-the-art catalysts for selective ammonia production from nitrates.•The advantages, limitations, and future research directions for this technology are discussed.
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•α-Fe2O3 loaded Cu2O mixed metal oxide photocatalyst shows remarkable photocatalytic activity for the degradation of organic pollutants.•Band gap modification of Cu2O by α-Fe2O3 ...results in enhanced visible light absorption and efficient charge carrier separation in the binary photocatalyst.•Photo excited charge carriers separation occurs via double charge transfer mechanism.
α-Fe2O3/Cu2O mixed oxide photocatalysts were prepared by one step facile hydrothermal method. During the synthesis, the growth of phase pure and highly crystalline polyhedral Cu2O crystals occurred and simultaneously a heterojunction formed between α-Fe2O3 and Cu2O particles. The optical band gap of bare Cu2O was found to be 1.8eV which was less than the reported values and incorporation of 5wt% α-Fe2O3 further reduced the band gap of Cu2O to 1.75eV, indicating an enhanced absorption of visible light by the binary photocatalysts. More importantly, the loading of α-Fe2O3 on Cu2O augmented the charge carriers separation and transfer at the interface, which was evident by the reduced photoluminescence intensity of α-Fe2O3/Cu2O photocatalysts. The influence of different loading amounts of iron oxide (1–10wt%) on Cu2O was evaluated. Among them, 5wt% α-Fe2O3 loaded Cu2O showed the enhanced photodegradation activity due to the formation of an effective p-n heterojunction and exhibited nearly 30% and 95% increase in the photodegradation rate of methyl orange (MO) compare to bare Cu2O and α-Fe2O3, respectively. The photo generated superoxide radicals were found to be the main reactive species responsible for the degradation of MO. The excellent photodegradation activity of α-Fe2O3/Cu2O photocatalyst is mainly attributed to the enhanced visible light absorption, efficient charge carriers separation and transfer. Based on the experimental results, a double charge transfer mechanism was proposed for the separation and transfer of photogenerated charge carriers in the photocatalysts.
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