Cleaning Strategies Research Articles

Automatic cleaning suggestion adapting to real-time soiling status of solar farms

Solar farms are subject to various environmental factors that can affect their performance and output. One of the major factors is soiling. Consequently, it is essential to monitor and mitigate the effects of soiling on solar panels to ensure optimal performance and maximum profitability of a solar farm. In this paper, we present a novel cleaning intervention strategy that adapts to the present solar panel performance status to detect cleaning requirements for maximizing profit. This algorithm works with onsite insolation and panel data to give live feedback on cleaning requirements. Moreover, unlike other models in the literature, this method does not require historical or a priori insolation, weather, or soiling data. We have comprehensively tested the algorithm through experiment and simulation under various conditions (i.e., seasonal rain, few annual rainfall or sandstorms, unpredictable dust accumulation). The results show that the adaptive cleaning algorithm, even with no historical insolation or soiling information, outperforms optimal periodic cleaning strategies in terms of net revenue. The adaptive cleaning suggestion system shows significant advantages especially in locations with high variability in weather and soiling conditions. The algorithm is also suitable for practical deployment in solar farms near industrial or construction zones where sudden dust accumulation can occur. Our adaptive model will maximize profit in such unpredictable soiling scenarios, while in comparison, it is not even possible to utilize historical information-based cleaning cycle model in such cases.

Facile and Environmentally Friendly Synthesis of Ga2O3/MFI Catalysts for Propane Dehydrogenation.

A GaOx-based catalyst is recognized as a promising catalyst for dehydrogenation of light alkanes. Conventionally, impregnation and calcination are necessary processes for the loading of GaOx. However, the incomplete impregnation of gallium salt solution would generate wastewater, and the calcination for the dissociation of gallium salt would release harmful gases, such as SOx, NOx, and HCl. Meanwhile, the high temperature results in an excessive energy cost and undesired GaOx particle aggregation. Here, we report a facile and environmentally friendly method for the synthesis of GaOx-based catalysts. The gallium salt solution was replaced directly with liquid gallium (LG). Through a simple physical mixing method at room temperature, uniform GaOx nanoparticles with diameters of around 3.5 nm were loaded onto the surface of silicalite-1 (S-1). With the optimal GaOx/MFI catalyst, the propane conversion and propylene selectivity reached 22.9 and 90.1%, respectively, in the propane dehydrogenation reaction. The work offers a clean and economical strategy utilizing liquid metal (LM) as an impregnation solution for the preparation of GaOx-based catalysts.

Sustainable enhancement of biogas production from a cold-region municipal wastewater anaerobic digestion process using optimized sludge-derived and commercial biochar additives

Anaerobic digestion (AD) of municipal wastewater sludges produces valuable solid digestate and biogas. Biogas is a source of clean energy and enhancement of its production has been of recent interest for increased electricity generation, among other products. The objective of this study was the development of a novel municipal sludge-derived biochar and its application in a municipal wastewater AD system to increase the biogas production rate. Thickened waste-activated sludge (TWAS) samples were collected from the cold-region municipal wastewater treatment plant and used to synthesize biochar applied in the simulation of AD processes using laboratory-scale reactors. The TWAS-derived biochar was synthesized using the commonly used furnace pyrolysis (sludge-based biochar, SBC), and more novel microwave pyrolysis including phosphoric acid as a microwave activator (activated sludge-based biochar, ASBC). The microwave pyrolysis conditions were optimized using a computational fluid dynamics (CFD) technique. In addition, various commercially available carbon-based additives were assessed for their impacts on the AD process including activated carbon, wood-derived biochar, and forest residue-derived biochar. Results showed that the ASBC increased the cumulative methane production by 50% (333 mL/g VS) versus the control sample (221 mL/g VS) after 30 d. The ASBC showed higher surface area, electrical conductivity, and metal contents versus the other biochars which boosted the AD microbial community growth leading to higher organic matter conversion into biogas. In the ASBC-amended digesters, the bacterial phylum Bacteroidota, which contains a major genus of the dgA-11-gut-group, exhibited a synergy between organic substrate fermentation and volatile fatty acid production, resulting in enhanced biogas production. The TWAS biochar demonstrated promising performance in enhancing the AD process fostering energy and resource self-sufficiency at municipal wastewater treatment plants. This smart sludge management aligns well with sustainable waste management practices and clean energy production strategies, especially considering that the biochar was sourced from a readily available continuous waste-product stream.

Clean label extraction of bioactive compounds from Chenopodium album and their role in the characterization and stability of ostrich meat

The demand for clean-label products continues to rise, as consumers increasingly prioritize natural and transparent ingredient lists. Natural substances are generally deemed safe for consumption by consumers. This study was focused on the development of clean-label ostrich meat patties with Chenopodium album extract and their storage stability. To prepare C. album extract, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) were employed. Ostrich meat patties were prepared using diverse combinations of extract, including 1% UAE, 2% UAE, 1% MAE, 2% MAE, 0.5% UAE+0.5% MAE, and 1% UAE + 1% MAE. The highest pH was observed for MAE in T3 on the 14th day (6.19 ± 0.03). The L* value was observed between 39.12 ± 1.09 and 44.00 ± 1.1. As storage intervals passed, the a* and b* values of ostrich meat patties decreased. After the 14th day of storage, the best results were obtained from 2% UAE (T2), with the lowest TBRAS, Peroxide value (POV), and Total of volatile basic nitrogen (TVBN) readings recorded for T2 (0.74 ± 0.02 MDA/kg, 0.56 ± 0.01 meq peroxide/kg, and 6.28 ± 0.40 mg/100 mL, respectively). At the end of the storage study, the lowest Total Microbial Count (TMC) and coliform count were recorded for T2 (8.08 ± 0.03 and 4.97 ± 0.05 cfu/mL, respectively). At the end of the storage study, T2 exhibited the highest values for total phenolic content (TPC), diphenyl-1-picrylhydrazyl (DPPH), Ferric reducing antioxidant power (FRAP), and azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay, namely of T2 122 ± 0.28 mg GAE/100 g, 73 ± 0.27%, 5.9 ± 0.01 mmol FSE/100 g, and 83 ± 0.08 mmol/L, respectively. The current study concludes that the UAE extract of C. album incorporated into ostrich meat patties manifests improved safety, quality, and storage stability. The implementation of clean label strategies can facilitate food manufacturers to align with consumer preferences for product transparency and sustainability while ensuring product safety and quality.

Peracetic acid enhanced anaerobic co-digestion of excess sludge and food waste: performance and mechanism

ABSTRACT Anaerobic co-digestion of excess sludge (ES) and food waste (FW) has been proven to be a clean and efficient strategy for the resource recovery of organic waste. However, the methane production from the anaerobic co-digestion of ES and FW is not optimal. This study reports a new strategy of using peracetic acid (PAA) pretreatment to enhance the anaerobic co-digestion of ES and FW and reveals the underlying mechanisms. The results confirm that PAA can effectively promote the production of methane from the anaerobic co-digestion of ES and FW, with the maximum methane yield reaching 416 mL/g volatile suspended solids at a PAA content of 9% (w/w). Mechanistic analysis indicates that PAA efficiently facilitates the solubilization of organic matter, promoting the release of soluble proteins and polysaccharides, and accelerating the metabolic conversion of volatile fatty acids (VFAs) to prevent excessive acidification. The maximum output of VFA in the PAA group was 1,511–1,974 mg/L, which was lower than that in the control group. Batch experimental analysis revealed that PAA promoted the hydrolysis and acidification processes, but inhibited the methanogenic process. The PAA pretreatment technique provides a theoretical basis for the efficient treatment of organic matter in urban areas.

Nanoconfined Catalytic Membranes for EfOM Fouling Mitigation: An Intelligent “Pore-Centric” Cleaning Strategy

This study investigated the effectiveness of the nanoconfined catalytic membrane (NCCM), fabricated by nitrogen-doped carbon nanotubes (NCNT) incorporated with graphene oxide membrane (NCNT@GO-M), in mitigating fouling caused by effluent organic matter (EfOM). Compared to conventional catalytic membranes (NRCM) that lack precise spatial design and prepared with only NCNT, NCCM exhibits a unique advantage by preferentially retaining and adsorbing protein-like substances in EfOM during the fouling formation process, forming a cake layer that effectively mitigates pore blockage from irreversible foulants. Furthermore, the ordered nanoconfined structure of NCCM facilitates an intelligent “pore-centric” hierarchical degradation strategy based on the molecular size of EfOM, preferentially removing irreversible foulants caused by fulvic acid-like and low molecular weight protein-like substances. The results demonstrated effective preservation of catalytic sites by the NCCM’s advanced nanoconfined configuration and a 1.6-fold increase in the mass transfer rate of peroxymonosulfate (PMS) compared to NRCM, synergistically promoting hydroxyl radical (•OH) enrichment, resulting in rapid EfOM degradation kinetics. Additionally, chemical cleaning almost completely eliminated irreversible fouling, restoring the NCCM to near its original flux. Overall, this study sheds light on the fouling mitigation mechanisms of NCCM, aiding their tailored design and application in targeted wastewater treatment.

Making Waves: The Progress of Management Strategies for Cleaning and Rinsing of PFAS-Impacted Fire Suppression Systems

Aircraft rescue firefighting (ARFF) vehicles often contain residual levels of per- and polyfluoroalkyl substances (PFAS) due to the global use of legacy and current use of aqueous film-forming foam (AFFF) for class B firefighting. However, numerous countries are transitioning to fluorine-free foam (F3) alternatives. There is, thus, an urgent need to develop efficient methods to rinse and clean interior ARFF surfaces thereby avoiding expensive replacement costs and preventing further discharge of PFAS to the environment. However, the unique self-assembly behavior of amphiphilic PFAS is a complicating factor that can result in measurable levels of PFAS within replacement F3s following cleanout efforts (i.e., the rebound effect). This Making Waves article aims to elucidate the emerging challenges associated with cleanout of impacted ARFF vehicles and introduce the current efforts for PFAS management of rinsate derived from cleanout of impacted fire suppression infrastructure.

Unveiling the impact of climate diversity on solar PV soiling

ABSTRACT Advanced knowledge of PV soiling can aid in the economic profitability of PV plants and efficient generation. This study introduces a novel approach for evaluating energy losses from soiling deposition on PV modules. Experimental investigations conducted under real outdoor conditions in Jaipur (India) were used to validate the model’s accuracy, demonstrating close agreement (with MAPE < 3.6%). Annual soiling trends were also investigated for seven cities reflecting diverse climatic zones (hot-dry, warm-humid, composite, temperate, and cold) and pollutant (PM10) concentrations. The proposed model was also tested with three different cleaning thresholds using rainfall intensities of 1, 3, and 5 mm/day and energy yield reductions due to soiling were simulated. Consequently, the findings of this study underscore the significance of seasonal variations in soiling profiles for different cities and, thus, highlight the need to develop location-specific cleaning strategies for PV systems that also account for the soiling removal due to rain events. The significant contribution of this research is a simplistic modeling approach that addresses the relationship of PV soiling with the input parameters such as wind speed (WS), relative humidity (RH), rainfall, particulate matter (PM10), and tilt angle. Hence, the proposed method can calculate soiling losses worldwide irrespective of geographical differences.

Chemical Cleaning Techniques for Fouled RO Membranes: Enhancing Fouling Removal and Assessing Microbial Composition.

Membrane fouling, a major challenge in desalination, is addressed in this study by investigating three different chemical cleaning protocols (A, B, and C) targeting fouled reverse osmosis (RO) membranes and microbial community composition. Cleaning protocols A and B involve different chemical treatments selected based on preliminary tests and literature review, while protocol C follows the manufacturer's standard recommendation. Membrane morphology, foulant composition, and microbial community variability in fouled, virgin, and cleaned membranes are studied. Effective biofilm removal is observed across all protocols using scanning electron microscopy (SEM), while spectroscopic techniques highlight interactions between foulants and membranes. Importantly, a critical gap in understanding how cleaning strategies influence microbial communities on membranes is addressed. Shifts in dominant bacterial phyla (Proteobacteria, Firmicutes, and Actinobacteria) after cleaning are identified through 16S rRNA amplicon sequencing. Cleaning A showed the best results in reducing microbial counts and restoring composition similar to virgin membranes. Additionally, chemical treatment increased dominance of resistant genera such as Staphylococcus, Bacillus, Citrobacter, and Burkholderia. This study emphasizes the necessity for tailored fouling cleaning strategies for RO membranes, with Cleaning A is a promising solution, paving the way for enhanced water purification technologies.

Electrolyzed water combined with ozone treatment for efficient removal of mancozeb residues from grapes.

Existing cleaning methods mainly focus on removing free-state pesticides. However, mancozeb can bind to the wax layer of grapes, forming bound-state residues that are difficult to remove. This study aims to develop an effective cleaning strategy to eliminate both free and bound mancozeb residues from grapes. Compared with the untreated mancozeb aqueous solution, the concentration of free mancozeb significantly decreased (p<0.05) after treatment with ozonated water (OW), electrolyzed water (EW), and their combination (OW+EW) for 60min. The combined treatment synergistically promoted mancozeb degradation, thus reducing its half-life to 38% and 75% of that observed when OW and EW were used alone, respectively. To investigate the effect of the waxy layer on mancozeb removal, oleanolic acid (OLA) was selected as a representative component. The binding effect of OLA limited the degradation of mancozeb in OW and EW, extending its half-life by 1.27 and 1.20 times, respectively. Density functional theory elucidated the mechanism by which the binding of OLA affects the degradation of mancozeb. Interestingly, the decomposition of mancozeb in OW + EW was almost unaffected by the introduction of OLA, indicating that the combined treatment could effectively remove bound-state mancozeb. The combined treatment was then successfully applied to remove mancozeb from grapes. After exposure to OW + EW for 10 min, the removal efficiency of mancozeb reached up to 80.61% with minimal risks of ethylene thiourea formation. There was no obvious change in the surface color of grapes after treatment. The findings provide valuable guidance for removing mancozeb from fresh fruits rich in waxy coatings.

Forecast of Foreground Cleaning Strategies for AliCPT-1

We report the test results of several independent foreground cleaning pipelines used in the Ali CMB Polarization Telescope experiment (AliCPT-1), a high-altitude cosmic microwave background (CMB) imager in the Northern Hemisphere with thousands of detectors dedicated to the search for a primordial CMB polarization B-mode signature. Based on simulated data from four detector modules and a single season of observation, which we refer to as Data Challenge 1 (DC1), we employ different and independent pipelines to examine the robustness and effectiveness of estimates on foreground parameters and primordial B-mode detection. The foreground cleaning strategies used in the pipelines include the parametric method of template fitting (TF) and the nonparametric methods of constrained internal linear combination (cILC), analytical blind separation (ABS), and generalized least squares (GLS). We examine the impact of possible foreground residuals on the estimate of the CMB tensor-to-scalar ratio (r) for each pipeline by changing the contamination components in the simulated maps and varying the foreground models and sky patches for various tests. According to the DC1 data with the simulation input value r true = 0.023, the foreground residual contamination levels in the TF/ABS/cILC/GLS pipelines are well within the corresponding statistical errors at the 2σ level. Furthermore, by utilizing the tension estimator, which helps identify significant residual foreground contamination in the detection of the primordial B-mode signal by quantifying the discrepancy between various r measurements, we conclude that the presence of small foreground residuals does not lead to any significant inconsistency in the estimation of r.

Spatial variability of cake layer in membrane fouling of full-scale MBR: New insights and implications

The spatial variability of the cake layer formed on the hollow fiber membranes during the operation of a full-scale membrane bioreactor (MBR) has been thoroughly investigated, samples from the bulk phase of the reactor and cakes formed on the membrane surface with different locations (i.e., inner layer of the cake (Cake-I), central layer of the cake (Cake-C), and outer layer of the cake (Cake-O)) were collected. The results showed that the viscous nature of proteins, the main component of extracellular polymeric substances (EPS),as well as the hydrophobicity of the protein secondary structure, were factors that led to variations in particle size (Cake-I = 566 μm > Cake-C = 283 μm > Cake-O = 92.2 μm > Bulk sludge = 59.7 μm) and total interaction energy (Cake-I = −216.39 × 104 KT > Cake-C = −68.35 × 104 KT > Cake-O = −30.42 × 104 KT > Bulk sludge = −30.08 × 104 KT) between the spatially varying cake layers. Numerous filamentous bacteria were found in the MBR, and genes related to membrane plugging processes (such as polysaccharide synthesis, surface attachment, and amino acid degradation) of the microbial community composition were regulated within the cake layers. These new insights could be beneficial to developing fouling control and membrane cleaning strategies.

Data-driven approach to evaluate the impact of hull roughness on main engine load of river-sea ships

Hull roughness increases the ship's resistance during navigation, significantly increasing fuel consumption and emissions. The study proposed the hull fouling factors (HFFs) to evaluate the time-varying impact of hull roughness on main engine load (MEL) for the three bulk carriers. Initially, ships' Automatic Identification System data, operational data, and weather and sea state data were fused to develop predictive models for MEL. Specifically, the Random Forest (RF) model outperformed others in predicting MEL. Then, by adopting a controlled variable experiment, the RF model was utilized to evaluate the impact of hull roughness on MEL as the days since clean (DSC) increased. Hull roughness analysis results showed that the HFFs of ship operated primarily on sea routes showed an increasing trend with the increasing DSCs. In contrast, the HFFs of ships primarily operated on the river-sea routes did not change significantly. The approach revealed significant temporal variations in hull roughness for ships operating in different routes. Besides, the proposed HFFs could capture the impact of sea temperature, salinity, current velocity and ship speed on hull roughness. Overall, the finding provides new insights into the time-varying hull roughness impacts on sea-to-river ships, and supports hull cleaning strategies, energy management and emission estimates.

Boron-doping tunes nitrogen species to abundant edge-N and B-N matrix for efficient phosphate removal in capacitive deionization: Additional accessible sites and defective centers

The elimination of eutrophication necessitates the implement of a clean and efficient phosphate removal strategy. Capacitive deionization (CDI) is recently regarded a promising approach for removing pollutants from aqueous environment with high-efficiency, facile operation, and low-energy consumption. Development of electrode materials with good properties is crucial for CDI. In this study, novel edge-N-modified boron-doped hierarchical carbon composites (MBCNs) were prepared via a hard template strategy for phosphate electrosorption. According to the pseudo-second-order kinetic, the MBCN2 electrode exhibited a dynamic capacity of 196.02 mg PO43− g−1 in 150 min with an initial concentration of 100 mg PO43− L−1 at 1.2 V. And it also demonstrated an exceptional saturation capacity of 399.70 mg PO43− g−1 under the Langmuir model. Based on theoretical analysis and experimental results, the incorporation of boron atoms in the carbon framework indicated a dual reinforcement. This included an enhanced proportion of edge-N modifications for defective centers and sufficient high-polarity B-N matrix for additional available active sites. The joint contribution of edge-N and B-N matrix revealed favorable electrical double layer capacitance, which resulted in good phosphate removal performance. This work disclosed the synergistic impact of dual nonmetallic atom doping, providing insights into the efficient phosphate removal anode for CDI.

Early Experience With a Novel Super-Hydrophilic Laparoscopic Scope Cleaning Device and Narrative Review of Available Cleaning Strategies.

Impaired visibility is a challenge in laparoscopic surgery. Frequent scope removal increases operative time, reduces efficiency, and potentially compromises patient safety. We examine our initial experience with a novel cleaning device that applies cold plasma to the scope lens and review current available laparoscope cleaning methods. The novel device was used in a variety of laparoscopic general surgery cases from April to November 2023. Primary outcome was number of scope removals per case. Secondary outcomes were time spent cleaning and number of times the scope became smudged or dirty with blood/tissue debris (debris events). An existing device that utilizes heated anti-fogging solution was used for comparison. 97 cases were included (31 with novel device and 66 with existing device). Scope removal rate for the novel device was lower compared to the existing device (0.87 ± 1.02 vs 0.97 ± 1.20 removals/case, P = 0.69), but not statistically significant. Average number of debris events was also lower for the novel device, but not statistically significant (0.90 ± 0.94 vs 1.0 ± 1.18 debris events/case, P = 0.69). Average total time spent cleaning per case was similar between devices (16.9 ± 24.0 vs 15.9 ± 18.7 seconds, P = 0.82). This study demonstrates that a hydrophilic scope cleaning device has comparable performance to heated anti-fogging solution and may reduce scope removals and debris events. Direct comparisons between cleaning products are lacking. Surgeons are most likely to be successful with the cleaning strategy that best suits one's surgical practice.

Impact of carbon quota policy on clean energy investment strategies with financial constraints

The actions of electricity enterprises investing in clean energy are mainly affected by national policies and financial constraints. However, their joint impact on corporate decision-making for clean energy investment (CEI) is unclear. This study develops a game model to study the impact of carbon quota policies on corporate decision-making under financial constraints, including the grandfathering quota policy and benchmarking quota policy. A series of interesting conclusions were obtained. (1) With the goal of CEI, irrespective of financial constraints, the benchmarking quota policy is the best option. (2) With total carbon emissions (TCEs), consumer surplus, or enterprise profit as the goal, financial constraints will have an impact on optimal carbon quota policies. (3) In addition to TCEs, an increase in the financial constraints cap will enhance CEI, consumer surplus, and enterprise profit. These conclusions provide new insights for government policy-making and business decision-making, requiring comprehensive consideration of financial constraints.

Multifunctional Power Generators beyond Moisture Limitation

AbstractThe moisture‐enabled electricity generators (MEGs) represent an appealing clean power strategy within the realm of hydrovoltaic technology. However, their stable operation under all‐weather conditions is still challengeable due to the effect of ambient humidity. Herein, a self‐water‐storage MEGs with multifunctionality was developed. Gel textiles are employed as the proton‐release layer, while graphite fibers loaded with tin‐bismuth alloy liquid metal serve as water‐storing electrode. The gel textiles absorb water permeating down from the electrodes, releasing protons, which then react with the active electrode to enhance output performance. The experiment demonstrates that a device can generate a voltage of 0.55 V and a current of 7.08 μA after water storage, with a maximum power density of 1.14 μW·cm‐². The device's performance output can remain stable within a wide temperature range. The experiment confirms that the electrical output of the device originates from ionic diffusion, while density functional theory (DFT) and molecular dynamics (MD) calculations reveal the importance of the strong hydrolysis ability of the polymer and the high adsorption energy of the liquid metal for H3O+ on the output performance of the device. Furthermore, the integrated device has demonstrated effective applications in driving microelectronic devices, charging capacitors and, self‐powered health monitoring.

Stratified structure of membrane clogs observed in full scale cross-flow tubular ultrafiltration (UF) system: Fouling characterization and a proposed two-stage formation mechanism

Membrane fouling remains a significant challenge in wastewater treatment, hindering both efficiency and lifespan. This study reports a distinct phenomenon of stratified membrane clogging observed in a full-scale cross-flow tubular ultrafiltration (UF) system treating sludge anaerobic digestion (AD) reject water. The distinct stratified structure, comprising inner and outer layers within the cake layer, has not been previously described. This research involved characterizing the filtration performance, analyzing membrane clog composition, and proposing a two-stage formation mechanism for the stratified clogs. It was revealed that higher inorganic and lower organic content in the outer layer compared to the inner layer. Acid and alkali treatments demonstrated the effectiveness of combined cleaning strategies. A mathematical model was developed to determine the critical conditions for stratified clog formation, influenced by membrane flux and cross-flow velocity (CFV). It is proposed that outer layer forms through long-term selective deposition, while the inner layer results from short-term dewatering within limited tubular space. High CFV (>2.5 m/s) prevents inner layer formation. Critical conditions for stratification occur at a flux of 18 L/m2/h with a CFV of 0.1 m/s or 65 L/m2/h with a CFV of 0.35 m/s. This study contributes a novel understanding of stratified membrane clogging, proposing a two-stage formation mechanism and identifying critical conditions, which provides insights for effective fouling control strategies and maintenance of operational efficiency for membrane systems.

Selective recovery of vanadium from chloride titanium dioxide effluent and preparation of high-purity thermotropic vanadium dioxide(M): An ammonia-free process

Vanadium recovery is critical for the hazard-free treatment and resourceful utilization of chloride titanium dioxide effluent (CTDE). Traditional ammonia precipitation vanadium recovery process from chloride titanium dioxide effluent suffered issues of the long process, high cost, and severe ammonia pollution risk. To solve these issues, an ammonia-free method consisting of V extraction from chloride titanium dioxide effluent by D2EHPA, direct VO2+ hydrolysis precipitation, and vacuum calcination was designed to produce VO2(M). The effect of conditions on V recovery, impurities behaviors, and vacuum dehydration mechanisms in each step was systematically investigated. Experimental results demonstrated that over 96.50% of vanadium was precipitated in the form of VO2∙xH2O by mixing CaO powder at 25 °C for 5 min until pH reached 4.20. And then, high purity VO2(M) (VO2 >99.50%) was prepared by vacuum calcined at 500 °C for 2 h in the tube furnace. Further characterizations revealed that the crystal structure of the calcined product was a monoclinic crystal structure with the space group of P21/c (VO2(M)), and the phase transition temperature was 57.8 °C. This demonstrated that the produced VO2(M) had met the established market standards and exhibited stable thermotropic degeneration, making it suitable for use in thermistors and other related fields. Compared with the conventional ammonia precipitation V recovery process, the proposed process exhibits a promising industrial application due to the short flow, near-zero wastes, higher economic efficiency, and superior product performance. In conclusion, it provides a clean and efficient vanadium recovery strategy from chloride titanium dioxide effluent.

Bimetallic Ag/Fe-MOG derived flake-like Ag2O/Fe2O3 p-n heterojunction for efficient photodegradation organic pollutants within a wide pH range

In this paper, we reported a facile and clean strategy to prepare the flake-like Ag2O/Fe2O3 bimetallic p-n heterojunction composites for photodegradation organic pollutants. The surface morphology, crystal structure, chemical composition and optical properties of Ag2O/Fe2O3 were characterized by SEM, high-resolution TEM images with EDX spectra, XRD, XPS, FT-IR and UV–vis DRS spectra respectively. The formation of Ag2O/Fe2O3 p-n heterojunction facilitated the interfacial transfer of electrons as well as the separation of charge carries. Hence, the as-synthesized Ag2O/Fe2O3-3 composites exhibited ultra-high photocatalytic activity. Under the experimental conditions of catalyst dosage of 0.4 mg mL−1 and irradiation time of 60 min, the degradation conversion rate of rhodamine B reached 96.1 %, which was 5.0 and 2.8 times of pure phase Ag2O and Fe2O3, respectively. Meanwhile, the degradation performance of Ag2O/Fe2O3-3 was not limited by pH, and it can achieve high degradation efficiency under 3–11. In addition, Ag2O/Fe2O3-3 also showed superb degradation ability for other common anionic dyes, cationic dyes and antibiotics. XPS and FT-IR spectra showed that Ag2O/Fe2O3-3 retained a carbon skeleton that facilitated electron transport and light absorption conversion. And the analyses of quenching experiment and EPR demonstrated •O2−, •OH and h+ were crucial reactive oxidant species contributing to the rapid organic pollutant degradation. This work provides new insights into obtaining p-n photocatalysts heterojunction with excellent catalytic activity for removing organic pollutants from wastewater.