Degradation Of Pollutants In Water Research Articles

Multifunctional Cu:ZnS quantum dots for degradation of Amoxicillin and Dye Sulphon Fast Black-F and efficient determination of urea for assessing environmental aspects

This work is particularly aimed at the preparation of ZnS and Cu doped ZnS (Cu:ZnS) QDs by facile and easy technique, chemical precipitation method for the degradation of water pollutants and a simple scheme was proposed to prepare the urea-sensing system. The morphological and optical properties of the synthesized QDs was studied using high resolution transmission and scanning electron microscopes, X-ray diffraction, energy dispersive X-ray analysis, fluorescence and ultraviolet–visible spectroscopy, differential thermal and thermogravimetric analyses, Brunauer–Emmett–Teller analysis. The photocatalytic performance was systematically assessed by the photodegradation of an important pharmaceutical water pollutant, Amoxicillin (AMX) and a dye Fast Sulphon Black F (SFBF) in aqueous medium under UV light irradiation. Also, a very sensitive system was prepared by depositing the dots over an indium-tin-oxide (ITO) glass substrate for the sensing of biologically active molecule urea as it is an important monitor of public health in water and soil productivity. The results illustrated excellent photocatalytic efficiency (86.46% for AMX and 99.41% for SFBF) with stability up to four cycles of degradation reaction. The optimal photocatalyst dosage for achieving maximum removal of AMX was found to be 70 mg at a pH of 9.5, with a treatment time of 40 min. Similarly, for SFBF, the optimal photocatalyst dosage was determined to be 60 mg at pH 9, with a treatment time of 60 min. Further, the electrochemical analysis was done by fabricating Urease enzyme (UR)/Cu:ZnS QDs/ITO bioelectrode and then the fabricated bioelectrode, was utilized to determine the different concentrations of urea by cyclic voltammetry. Thus, the obtained limit of detection and sensitivity of the fabricated biosensing device for urea detection was obtained to be 0.0092 μM and 12 μA μM−1cm−2, respectively; under the optimized experimental conditions. Hence, it is anticipated that Cu:ZnS QDs can also successfully be applied as a promising material for fabrication of novel bioelectrode for urea determination and the biosensing platform is desirable and viable.

CdS Nanoparticles Supported by Cobalt@Carbon-Derived MOFs for the Improved Adsorption and Photodegradation of Ciprofloxacin.

The design and synthesis of efficient photocatalysts that promote the degradation of organic pollutants in water have attracted extensive attention in recent years. In this work, CdS nanoparticles are grown in situ on Co@C derived from metal-organic frameworks. The resulting hierarchical CdS/Co@C nanostructures are evaluated in terms of their adsorption and photocatalytic ciprofloxacin degradation efficiency under visible-light irradiation. The results show that, apart from offering a large surface area (55.69 m2·g-1), the prepared material can effectively suppress the self-agglomeration of CdS and enhance the absorption of visible light. The CdS/Co@C-7 composite containing 7% wt Co@C has the highest photodegradation rate, and its activity is approximately 4.4 times greater than that of CdS alone. Moreover, this composite exhibits remarkable stability after three successive cycles of photocatalysis. The enhanced photocatalytic performance is largely ascribed to the rapid separation of electron-hole pairs and the effective electron transfer between CdS and Co@C, which is confirmed via electrochemical experiments and photoluminescence spectra. The active substance capture experiment and the electron spin resonance technique show that h+ is the main active entity implicated in the degradation of CIP, and accordingly, a possible mechanism of CIP photocatalytic degradation over CdS/Co@C is proposed. In general, this work presents a new perspective on designing novel photocatalysts that promote the degradation of organic pollutants in water.

Interaction of BiVO4 anchored 2D hexagonal boron nitride nanocomposite for photocatalytic water pollutants degradation and phytotoxicity assessment

Water pollution caused by chemical contaminants has become an ongoing issue for society, industry, and government. In comparison to traditional treatment approaches, nanotechnology is currently an ideal medium for microbial and organic pollutant removal from water. This study aims to create BiVO4/h-BN nanocomposites for effective photocatalytic degradation. The nanocomposite was studied using XRD, UV-Vis, FTIR, Zeta potential, SEM, TEM, BET, XPS, PL, EIS, and M-S plot analysis. The morphological analysis showed that the formed boron nitride is a hexagonal structure on which BiVO4 is anchored. The band gap of prepared h-BN is 5.8 eV, whereas the band gap of the binary BiVO4/h-BN nanocomposite is 2 eV. The photocatalytic effectiveness of the nanocomposite was employed to degrade various water-polluting dyes like Rhodamine-B (Rh-B) and Congo red (CR) and antibiotics like Amoxicillin (AMX) and Cephalexin (CPX). Furthermore, under visible light, BiVO4/h-BN nanocomposites decomposed up to 93.3%, 92.9%, 94.1%, and 90.1% against Rh-B, CR, AMX, and CPX after 60 min, according to the photocatalytic treatment study. The degradation efficacy of the catalyst was studied using scavengers to understand the mechanism. The BiVO4/h-BN nanocomposites are a good and inexpensive photocatalyst for degrading techniques. Further phytotoxicity analyses were carried out using the degraded Rh-B dye sample which shows a better result when compared to non-treated dye.

Dissolved organic matter promotes photocatalytic degradation of refractory organic pollutants in water by forming hydrogen bonding with photocatalyst

Removing refractory organic pollutants in real water using photocatalysis is a great challenge because coexisting dissolved organic matter (DOM) can quench photogenerated holes and thus prevent generation of reactive oxygen species (ROS). Herein, for the first time, we develop a hydrogen bonding strategy to avoid the scavenging of photoexcited holes, by which DOM even promotes photocatalytic degradation of refractory organic pollutants. Theoretical calculations combined with experimental studies reveal the formation of hydrogen bonding between DOM and a hydroxylated S-scheme heterojunction photocatalyst (Mo-Se/OHNT) consisting of hydroxylated nitrogen doped TiO2 (OHNT) and molybdenum doped selenium (Mo-Se). The hydrogen bonding is demonstrated to change the interaction between DOM and Mo-Se/OHNT from DOM-Ti (IV) to a hydrogen bonded complexation through the hydroxyl/amine groups of DOM and the OHNT in Mo-Se/OHNT. The formed hydrogen network can stabilize excited-state of DOM and inject its electron to the conduction band rather than the valence band of the OHNT upon light irradiation, realizing the key to preventing hole quenching. The electron-hole separation in Mo-Se/OHNT is consequently improved for generating more ROS to be involved in removing refractory organic pollutants. Moreover, this hydrogen bonding strategy is generalized to nitrogen doped zinc oxide and graphitic carbon nitride and applies to real water. Our findings provide a new insight into handling the DOM problem for photocatalytic technology towards water and wastewater treatment.

Superparamagnetic Zinc Ferrite Nanoparticles as Visible-Light Active Photocatalyst for Efficient Degradation of Selected Textile Dye in Water

Photocatalysis is a promising technology for the degradation of recalcitrant organic pollutants in water. In this study, superparamagnetic zinc ferrite nanoparticles (ZnFe2O4) were synthesized and characterized using scanning electron microscopy, X-ray diffraction, energy dispersive X-ray and Fourier transform infrared spectroscopy. The synthesized nanoparticles (NPs) of ZnFe2O4 were observed to have a photosensitive nature and showed characteristic visible-light-induced activation that was used for the photocatalytic degradation of a textile dye, Remazol brilliant violet 5R (RBV-5R). The effect of different operational parameters such as pH, H2O2, catalyst dosage, concentration of RBV-5R and the reusability of ZnFe2O4 as well as scavengers were investigated under visible irradiation. The almost complete degradation (99.9%) of RBV-5R was observed at pH 10, 0.1 g of ZnFe2O4 and 6 mM of H2O2 in 30 min. The photocatalytic degradation of RBV-5R followed pseudo-first-order kinetics. The mineralization was calculated from total organic carbon (TOC) that was represented by 82% TOC removal in 30 min. The results revealed that visible-light-induced ZnFe2O4 photocatalysis may be a promising technology for the elimination of toxic organic dyes, such as RBV-5R, from water resources.

One-pot synthesis of Ag-modified SrTiO3: synergistic effect of decoration and doping for highly efficient photocatalytic NOx degradation under LED

Strontium titanate is an ideal cubic-structure perovskite oxide that finds application in hydrogen production and water pollutants degradation field. However, its photocatalytic activity is limited under UV irradiation due to its wide energy band bap (∼ 3.2 eV). To overcome this limitation, different strategies, such as metal-doping or metal-decoration, have emerged. Here, Ag-modified-SrTiO3 photocatalysts were prepared for the first time by a cheap, simple and sustainable approach based on the use of Ag-enriched wastewaters. The Ag-decorated SrTiO3 synthesized by a two steps method photodegraded by nearly 77% of NOx within 3 h. The Ag-modified SrTiO3 prepared by aone-pot synthesis led to a doubly modification of the oxide: Ag+ doping and Ag nanoparticles-decoration. In this case the use of Ag-enriched wastewaters led to poor photocatactivity of the photocatalyst, probably related to the presence of other metals in the waste. However, the use of a pure Ag precursor permitted the fabrication of a highly efficient material achieving complete photodegradation of NOx, exhibiting a photoactivity 4 times higher than bare SrTiO3 and 1.3 times more active than Ag-decorated material. The photocatalytic enhancement was attributed to the combined effect of Ag-doping and Ag-decoration on SrTiO3, which contributed to a narrow band gap (2.80 eV), as well as the formation of heterojunctions that promotes the separation of photogenerated charges, respectively. This material showed good stability during recycling tests, maintaining high performances after five cycles. Eventually, active species were identified using various scavengers by trapping holes and radicals generated during the photocatalytic degradation process.

Harnessing Evanescent Waves in UV-Irradiated TiO2-Coated Quartz Optical Fibers Improves Pollutant Degradation in Water

Coupling TiO2-coated quartz optical fibers (TiO2-QOFs) with LEDs shows potential in degrading organics in water. Conventional TiO2-QOFs with thick and compact coatings are inefficient to degrade organic pollutants due to refraction losses. The research focuses on manipulating coating strategies to increase the generation of evanescent waves, which react more efficiently with the coated TiO2, which shows a crystal structure at anatase/rutile of 85/15. Through the use of dip-coating methods, TiO2 can be effectively deposited on quartz optical fibers, leveraging the principle of electrostatic attraction. By decreasing TiO2 dip-coating concentrations from 200 to 10 mg/L, dip-coating duration from 2 to 0.5 h, and coating cycles from 3 to 1, TiO2 patchiness on quartz fibers was reduced by 50–60%, enhancing the formation of more interspaces between the fiber surfaces and the coatings, which in turn allowed over 90% of evanescent waves in the TiO2-QOFs. The evanescent wave-dominated TiO2-QOFs irradiated by 275 nm UV-LED exhibited methylene blue degradation rate constants at around 0.03 h−1 and quantum yields greater than unity, indicating a highly efficient interaction between the evanescent wave and the surface coatings. These findings offer significant insights into optimizing the utilization of evanescent waves in TiO2-QOFs for pollutant degradation by regulating the coating structures.

A short review of recent discoveries in montmorillonite‐based photocatalysts for organic dye water pollutant degradation

AbstractOrganic dye pollutants are the most common type of pollutant found in water and wastewater as a result of various industrial activities. In particular, one of the largest contributors is the textile industry, which uses a lot of organic dyes to produce its goods. Organic dyes that remain in the effluents are typically permanent and difficult to detoxify using traditional wastewater treatment strategies. Photocatalysis using semiconductors have emerged as an attractive wastewater treatment method for resolving the major drawbacks of traditional methods. Montmorillonite has been presented as a conceivable dye adsorbent. When a semiconductor is incorporated, its adsorptive capability assists in imposing heterogeneous photoactivity. It is widely employed in a variety of applications due to fundamental characteristics such as high flexibility, swelling, ion exchange ability, acidity, usage in catalytic amounts, milder reaction conditions, benefit in reusability, selectivity, high yield, cheap cost, and so on. In this review, we specifically describe the last 3 years' development of dye degradation employing recently developed montmorillonite (MMT)‐based materials, as well as their preparation methods. In addition, the photocatalytic degradation of various types of organic dye pollutants, such as anionic and cationic dyes, was also studied in this review. The findings reveal that MMT‐based materials have a wide range of applications in the photocatalytic degradation of contaminants existing in the environment.

Confinement of cobalt phosphides in nitrogen-doped carbon hosts for efficient peroxymonosulfate activation: Understanding charge-imbalance induced coordinative radical/non-radical oxidation

Development of a new catalytic system with synergistic multiple active sites to effectively promote the activation of peroxymonosulfate (PMS) is crucial for the control of emerging organic pollutants in water, but it is still challenging. Herein, we explore robust CoPx-implanted porous N-doped carbon frameworks (CoPx@NC) to effectively activate PMS and eliminate tetracycline (TC). The cobalt phosphides in CoPx@NC spontaneously create the distinctive charge imbalance to form asymmetrically charged Coδ+ and Pδ− as dual active sites to efficiently enhance catalytic activity, while the positively polarized carbon induced by neighboring electronegative N atoms in CoPx@NC contributes to high catalytic efficiency in parallel. As an advanced catalyst, CoPx@NC displays excellent catalytic performances in PMS activation toward efficient TC degradation with an improved rate constant of 0.137 min−1 and a favorable k-value of 1.43 μmol s−1 g−1. Mechanistic analysis clearly unveils that the non-radical pathway (singlet oxygen 1O2 and direct electron transfer) in CoPx@NC/PMS system dominantly governs the TC degradation along with cooperative radical (SO4·− and ·OH) pathway. This study enriches the charge imbalance strategy for catalyst design and highlights a new catalytic platform to activate PMS for efficient pollutant degradation in water.

Synthesis and characterization of zinc oxide nanoparticles using peppermint tea (Mentha piperita) dregs extract and their photocatalytic performance

AbstractZinc oxide (ZnO) is a n‐type semiconductor with a wide band gap of 3.37 eV and a large excitation binding energy of 60 meV. ZnO nanoparticles (ZnO NPs) is considered as one of the best photocatalyst for the degradation of pollutants in water since it has large surface area to enhance the photocatalytic activity. This article aims to study the feasibility of using the agricultural waste of peppermint tea dregs extract with zinc nitrate hexahydrate as salt precursor to synthesis ZnO NPs through a simple, low cost, greener and environmentally friendly method. The qualitative phytochemical screening of peppermint tea dregs extract revealed the presence of flavonoids which can be served as the reducing and stabilizing agent in the synthesis of ZnO NPs. Various analytical techniques such as FTIR, UV–vis, XRD, FESEM, EDX and PSA confirmed the presence of ZnO NPs. The photocatalytic performance of the synthesized ZnO NPs showed a 95.03% degradation of crystal violet dye within 4 h of sunlight exposure.

Boosting charge separation in graphdiyne quantum dots/hollow tubular carbon nitride heterojunction for water pollutant degradation

Non-desirable solar energy absorption and poor charge transfer efficiency are two problems that limit the peroxymonosulfate (PMS) photocatalytic techniques. Herein, a metal-free boron-doped graphdiyne quantum dot (BGDs) modified hollow tubular g-C3N4 photocatalyst (BGD/TCN) was synthesized to activate PMS and achieved effective space separation of carriers for degradation of bisphenol A. With 0.5 mM PMS, the degradation rate of bisphenol A (20 ppm) was 0.0634 min−1, 3.7-fold higher than that of TCN itself. The roles of BGDs in the distribution of electrons and photocatalytic property were well identified by experiments and density functional theory (DFT) calculations. The possible degradation intermediate products of bisphenol A were monitored by mass spectrometer and demonstrated to be nontoxic using ecological structure activity relationship modeling (ECOSAR). Finally, this newly-designed material was successfully applied in actual water bodies, which further renders its promising prospect for actual water remediation.

Acetic acid mediated fabrication of highly exposed Fe(III)/Fe(II) sites in Fe2O3/MA for enhanced peroxymonosulfate activation

The design and synthesis of efficient heterogeneous catalysts with the accessible and mixed-valence metal centers for the activation of peroxymonosulfate (PMS) is an important research topic in water pollution control. In this work, the highly efficient catalysts Fe2O3/MA have been successfully synthesized with acetate acid as an important regulating agent. Methylene blue (MB) has been applied as the organic pollution for catalysis experiments and Fe2O3/MA-1.5 can achieve 98% catalytic degradation of MB at a concentration of 10 mg/L in 100 min, showing much higher catalytic efficiency than those of single MA (acetate modified MIL-53(Fe)) (60%) and Fe2O3 (57%). Electron paramagnetic resonance (EPR) spectroscopy and radical scavenging experiments have shown that hydroxyl radical (•OH), sulfate radical (•SO4ˉ), and singlet oxygen (1O2) all participate and contribute to the degradation process. The efficient catalytic mechanisms have been carefully studied. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and pyridine Fourier transformed infrared (py-FT-IR) have successfully proved the construction of highly exposed coordinatively unsaturated sites and the coexistence of Fe(III)/Fe(II) double catalytic centers in Fe2O3/MA-1.5, which function together with the high dispersion of Fe2O3 on MA to realize the final high activation activity for PMS. Further research shows that the initial coordination of acetic acid with Fe sites and the departure of acetic acid after vacuum treatment help construct highly exposed Fe(III)/Fe(II) double catalytic sites in Fe2O3/MA-1.5. Eventually, the intermediates produced in the reaction were analyzed by gas chromatography mass spectrometry (GC-MS), and the degradation pathway has been tentatively proposed. This study has proposed a new route to build active sites in catalysis, which shows high application potential for the effective degradation of organic pollutants in water.

Direct synthesis of TiO2 nanoparticles without heat treatment: Effect of order of addition and precursor/reducing ratio

Titanium dioxide (TiO2) is the most used semiconductor for heterogeneous photocatalysis. However, there is a limitation on its application since TiO2 works as catalyst only under ultraviolet radiation. Therefore, the synthesis of high-performance TiO2 NPs by a direct method without further calcination could improve the use of this catalyst. The current work aimed to obtain anatase/rutile TiO2 nanoparticles for photocatalysis under UV light by a direct method without further heat treatment. A 2k factorial design was used to evaluate the effect of the order of addition and ratio of the precursor/reducing agents on the synthesis of the NPs. TiO2 nanoparticles with large surface area were synthesized via the controlled precipitation method. The NPs were characterized by the XRD, DSC/TG, FTIR, BET, DLS, ELS, UV–Vis, FESEM-EDS techniques, and by the photocatalytic activity test. The commercial TiO2 NP P25 Evonik was used as standard photocatalyst for comparison with the obtained samples. The specific surface area (BET) of the TiO2 NP samples was three to five times higher in comparison to P25. The photoactivity of the TiO2 NP samples and P25 was determined as the discoloration of methylene blue and rhodamine B dyes under UVA radiation (330 nm, 12 W/m2) for 180 min. The results showed that the discoloration efficiency of the synthesized TiO2 NP samples is equivalent to that of the P25 sample. The synthesis of TiO2 nanoparticles via the controlled precipitation method using only two reagents proved to be a viable and promising route. The method does not require heat treatment for titanium dioxide crystallization and is still capable of producing a mixture of ideal phases to delay the recombination of the photogenerated electron-hole pair, contributing to the increase of the photocatalytic efficiency. The TiO2 NP samples will be used to the degradation of recalcitrant pollutants in water as textile dyes and pharmaceutical byproducts.

In-situ implantation of BiVO4 QDs into NH2-mil-125 to construct Z-scheme heterojunction for photocatalytic degradation of organic pollutants in water

Organic pollutants in water seriously destroy the ecological environment and endanger human health. The photocatalyst composed of a metal-organic framework (MOF) and quantum dots (QDs) allows stable and efficient degradation of organic pollutants. A novel BiVO4 QDs/NH2-MIL-125 (BM) photocatalyst has been prepared by depositing of BiVO4 QDs in the Ti-based MOF (NH2-MIL-125(Ti)). The results indicate that the BiVO4 QDs/NH-MIL-125 sample has a porous structure with a concentrated pore size distribution and a large specific surface area. The decoration of BiVO4 QDs effectively broadens the optical response range of NH2-MIL-125 (NM). It is worth noting that 1%BiVO4 QDs/NH2-MIL-125 displays high photocatalytic activity in the degradation of 30 mg/L Rhodamine B (RhB) solution, and the degradation rate constant is 2.337 × 10−2 min−1, which is 4.2 and 5.4 times higher than NH2-MIL-125 and BiVO4 QDs, respectively. In the process of degrading RhB, h+ and ⋅O2− play the major roles in the RhB degradation. The construction of heterojunction between BiVO4 QDs and NH2-MIL-125 is favorable for photogenic carrier migration and inhibits electron and hole recombination. In addition, proposed a Z-Scheme reaction mechanism based on the band potential, where the structure favors carrier migration without photoelectron energy loss. This work is expected to promote the QD-MOF composites in water treatment.

Augmented photocatalytic degradation of Acetaminophen using hydrothermally treated g-C3N4 and persulfate under LED irradiation

Photocatalytic degradation of organic pollutants in water using graphitic carbon nitride and persulfate under visible light (g-C3N4/PS system) has been studied. Here, we demonstrate augmentation of photocatalytic degradation of Acetaminophen (AAP) using hydrothermally treated g-C3N4 and PS under 400 nm LED irradiation (HT-g-C3N4/PS system). A pseudo-first-order rate constant (kobs, 0.328 min−1) for degradation of AAP using HT-g-C3N4/PS system was determined to be 15 times higher compared to g-C3N4/PS system (kobs, 0.022 min−1). HT-g-C3N4 showed a higher surface area (81 m2/g) than g-C3N4 (21 m2/g). Photocurrent response for HT-g-C3N4 was higher (1.5 times) than g-C3N4. Moreover, Nyquist plot semicircle for HT-g-C3N4 was smaller compared to g-C3N4. These results confirm effective photoelectron-hole separation and charge-transfer in HT-g-C3N4 compared to g-C3N4. AAP degradation using HT-g-C3N4/PS system was significantly inhibited with O2.− and h+ scavengers compared to 1O2,SO4.− and HO. scavengers. ESR results revealed O2.− formation in HT-g-C3N4/PS system. Moreover, photocurrent measurements reveal AAP oxidation by h+ of HT-g-C3N4 was effective than g-C3N4. HT-g-C3N4 was reused for five cycles in HT-g-C3N4/PS system. Augmented photocatalytic degradation of AAP by HT-g-C3N4/PS system compared to g-C3N4/PS is attributed to effective photoelectron hole separation of HT-g-C3N4 that generates O2.− and h+ for oxidation of pollutant. Importantly, electrical energy per order (EEO) was 7.2 kWh m−3 order−1. kobs for degradation of AAP in simulated groundwater and tap water were determined as 0.029 and 0.035 min−1, respectively. Degradation intermediates of AAP were proposed. AAP ecotoxicity against marine bacteria Aliivibrio fischeri was completely removed after treatment by HT-g-C3N4/PS system.

Environmental Assessment of Shakkar and Pench River of Chhindwara District & Photodegradation of River Water by Nano Catalyst

In this research paper deals with work discussing about photo-degradation of river water by nano catalyst. This review discusses the utilization of photocatalysis for the degradation of water pollutants. Emphasis is placed on TiO2 nanoparticles as a benchmark photocatalyst for the destruction of microorganisms and the degradation of a wide variety of organic compounds like phenolics, dyes, pesticides and pharmaceuticals. The mechanism of photocatalytic degradation is elucidated, underlining the importance of reaction kinetics for the efficient design of the processes. The effects of different reaction parameters on photocatalytic degra-dation are discussed. Surface modification of TiO2 for visible light response doping and heterostructuring is outlined. Finally, the challenges in the implementation of this technology for ‘‘real’’ waste water systems are summarized. Photo-degradation is the process of alteration of materials by light, refers to the combined action of light and air. It is usually oxidation and hydrolysis. Nano Catalyst is used for water purification. In this research paper work we are going to discuss about water purification of Shakkar & Peach river of Chhindwara District, Mphilisi M. Mahlambi (2015). The South African National Water Act (Act number 36 of 1998) specifically states that water resources must remain fit for use on a sustainable basis and that their quality must be constantly monitored. Therefore the availability of water should be based not only on the quantity but also on the quality of the available water. However, due to agricultural, industrial, and domestic activities the quality of river water or groundwater continues to deteriorate due to pollution by hazardous materials.

Preparation of direct Z-scheme hierarchical MoS2/MnO2 composite for efficient adsorption and wide spectrum photocatalytic degradation of organic pollutants in water

Developing semiconductor-based heterogeneous photocatalysts with high adsorption performance and wide light response range is a significant technology for removing organic pollutants from water. Herein, a novel hierarchical dendritic-like direct Z-scheme MoS2/MnO2 composite with MoS2 hollow tubular decorated by MnO2 nanosheets was successfully fabricated by vacuum freeze-drying. When the mass ratio of MoS2/MnO2 is 3:1, the highest adsorption-photocatalytic removal rate of 94.5% and 95.1% in 120 min for RhB was attained under visible (Vis) and ultraviolet (UV) light irradiation, respectively. After three repeated uses, the removal rate of RhB still reached 91.1%. The enhanced adsorption-photocatalytic performance of the composite can be well illustrated according to the hierarchical composite structure, production of •OH, •O2− and h+ active species, oxygen-doping in the MoS2 and the direct Z-scheme photocatalytic mechanism. This work gives a good strategy to frame hierarchical Z-scheme photocatalysts for efficient adsorption and wide-spectrum photocatalytic removal of organic pollutants from water.

Cs2SnI6 perovskites nanostructures as excellent photocatalytic degradation of organic dye pollutants in water under visible light: Synthesis and characterization

Pollution of surface waters containing chemical dye combinations and/or biological materials can have adverse effects on human health and other organisms, even in small quantities. The photocatalytic oxidation procedure has been widely regarded as a commercially viable method of removing environmental pollutants. In recent research, Caesium-hexaiodostannate nanostructures (Cs2SnI6) were prepared through a co-precipitation approach and their photocatalytic performance was analyzed. A number of surfactants were examined for their influence on the structure, purity, and morphology of the sample. It was found in the SEM data that the presence of surfactants has a negative impact on the morphology, which may be due to the inability to remove surfactants by calcination at high temperatures. Photocatalytic activity of Cs2SnI6 catalysts was demonstrated over a variety of organic dyes, including methylene blue (MB), rhodamine b (RhB), methyl orange (MO), and methyl violet (MV). Upon exposure to visible light for 180 min, 5 ppm methylene blue showed the greatest degradation (84.0%). Cs2SnI6 nanostructures are being applied for the first time in photocatalytic applications. Due to their wide bandgap (1.7 eV) in the visible region, they may be a suitable candidate for water purification. Moreover, the results indicated that the efficiency of photocatalysis was affected by various parameters, including pH, dye concentration, dye types, catalyst dosages, and surfactants. In the recyclability test, Cs2SnI6 nanostructures were found to be stable, and the removal efficiency was reduced by 6.9% after the fifth run.

Advanced Oxidation Processes for Degradation of Water Pollutants—Ambivalent Impact of Carbonate Species: A Review

Advanced oxidation processes (AOPs) hold great promise in the removal of organic contaminants. Reactive oxygen species (ROS) produced in AOPs react with target pollutants to initially form several intermediate compounds that finally undergo complete mineralization. Such observations are reported, especially for laboratory-scale experiments performed in pure water. On the other hand, while considering real contaminated wastewater matrices, particularly industrial effluents, there are many co-existing ions. Carbonate ions are one of the major inorganic ions commonly existing in water resources. Hence, these ions have a significant impact on the respective water treatment processes. This review focused on the effect of carbonate ions on the degradation of pollutants in AOPs. In AOPs, carbonate radicals are formed by the scavenging reaction of the respective ions with ROS. The reactivity of these radicals towards the pollutant varies with respect to the structure and functionality. Therefore, depending on the functionalities of the contaminants, these ions show both positive and negative effects. Thus, this review aims to summarize the effects of carbonate species on the degradation of organic contaminants during AOPs and their environmental impacts. The carbonates enhanced the degradation of several emerging organic pollutants, including aniline, bisphenol A, rhodamine B, acid orange 7, naphthalene, and phenol derivatives. Carbonate presence was also revealed to have a positive contribution in cases of drug degradation, including sulfamethoxazole, propranolol, sulfamethazine, salbutamol, trimethoprim, azithromycin, naproxen, oxcarbazepine, and oxytetracycline.

Heterogeneous activation of persulfate using delafossite AgFeO2/α-MnO2 for efficient degradation of tartrazine under visible light

For the first time, delafossite AgFeO2/α-MnO2 nanocomposites were successfully synthesized and used as heterogeneous persulfate (PS) activators for degradation of water pollutants. The potential of several systems, such as AgFeO2/α-MnO2/light, AgFeO2/α-MnO2/PS/light, etc., as well as reaction conditions, stability, and radicals involved, were all assessed for degradation of tartrazine (TZ). The exceptional activity of optimal AgFeO2/α-MnO2 (AFM50) nanocomposite was attained because of improved redox cycling between Ag0/Ag+, Fe2+/Fe3+, Mn3+/Mn4+ cycles, enhanced electron transfer, reduced e−/h+ pair recombination, long electron lifetime, high charge transfer and mobility, and electron density, which facilitated efficient PS activation and subsequent generation of various reactive oxidizing species. Interestingly, AFM50 showed exceptional degradation efficiency (67.4%) under dark conditions. The AFM50/PS/Vis system also demonstrated excellent stability and activity for degrading several dyes (rhodamine B (97.8%), methyl orange (94.5%), methylene blue (100%), and congo red (97.7%)). Based on quenching experiments, active radicals (•OH, SO4•-, O2•-), and non-radical (h+, 1O2), all contributed towards efficient degradation of TZ. Following that, a reasonable PS activation mechanism was proposed. This study propounds insightful synergistic activation of PS using delafossite AgFeO2/α-MnO2 nanocomposite under visible light and dark conditions, as well as its potential application in wastewater treatment plants.