Self-cleaning Capacity Research Articles

Three birds with one stone: Constructing Janus multilayer carbon fabric to boost solar-driven interfacial evaporation, electrical power generation and inhibit VOCs volatilization

Solar-driven interfacial evaporation technology has great potential to address both the freshwater and energy crises in a low-cost, environmentally friendly, and sustainable method. How to achieve highly efficient freshwater and energy harvesting simultaneously is still challenging. Here, a Janus-structured multilayer carbon fabric (JMCF) solar evaporator is proposed to effectively overcome the bottleneck in the cogeneration of fresh water and electricity. The Janus structure of the multilayer fabric effectively controls water supply upwards, improves light absorption and photothermal conversion, increases evaporation surface area, facilitates water vapor escape and inhibits VOCs volatilization. Accordingly, the optimized JMCF solar evaporator can achieve a high evaporation rate of 3.12 kg m-2h−1 and an output voltage of 0.577 V in 3.5 wt% seawater under 1 sun irradiation. In addition, the JMCF evaporation system also demonstrates good working stability, self-cleaning capacity, environmental adaptability, and economic feasibility. This work provides new ideas and inspiration for the design of high efficiency solar-driven interfacial evaporation system to address the freshwater scarcity, energy crisis, global change problem, etc.

Multienzyme Immobilization on PVDF Membrane via One-Step Mussel-Inspired Method: Enhancing Fouling Resistance and Self-Cleaning Efficiency.

Immobilizing different enzymes on membranes can result in biocatalytic active membranes with a self-cleaning capacity toward a complex mixture of foulants. The membrane modification can reduce fouling and enhance filtration performance. Protease, lipase, and amylase were immobilized on poly(vinylidene fluoride) (PVDF) microfiltration membranes using a polydopamine coating in a one-step method. The concentrations of polydopamine precursor and enzymes were optimized during the immobilization. The higher hydrolytic activities were obtained using 0.2 mg/mL of dopamine hydrochloride and 4 mg/mL of enzymes: 0.90 mgstarch/min·cm2 for amylase, 10.16 nmoltyrosine/min·cm2 for protease, and 20.48 µmolp-nitrophenol/min·cm2 for lipase. Filtration tests using a protein, lipid, and carbohydrate mixture showed that the modified membrane retained 41%, 29%, and 28% of its initial water permeance (1808 ± 39 L/m2·h·bar) after three consecutive filtration cycles, respectively. In contrast, the pristine membrane (initial water permeance of 2016 ± 40 L/m2·h·bar) retained only 23%, 12%, and 8%. Filtrations of milk powder solution were also performed to simulate dairy industry wastewater: the modified membrane maintained 28%, 26%, and 26% of its initial water permeance after three consecutive filtration cycles, respectively, and the pristine membrane retained 34%, 21%, and 7%. The modified membrane showed increased fouling resistance against a mixture of foulants and presented a similar water permeance after three cycles of simulated dairy wastewater filtration. Membrane fouling is reduced by the immobilized enzymes through two mechanisms: increased membrane hydrophilicity (evidenced by the reduced water contact angle after modification) and the enzymatic hydrolysis of foulants as they accumulate on the membrane surface.

Ecofriendly bleaching method for cotton fabric: Development of titanium dioxide doped single wall carbon nanocomposites by photocatalytic treatment for sustainable textile pre-finishing applications

This study aimed to find an eco-friendly substitute method and chemical for conventional hydrogen peroxide (H2O2) bleaching of cotton fabric. We developed diverse functional groups containing titanium dioxide-doped single-wall carbon nanotubes (TiO2-SWCNTs) particles, designed a photocatalytic system, and examined the effects of working conditions and functional group variations on the degree of fabric whitening. Throughout the many phases of the chemical development process, X-ray diffraction (XRD), Fourier transform infrared spectroscopy −Attenuated total reflectance (FTIR-ATR) and the scanning electron microscopy (SEM) tests were conducted. In addition, the color spectrum values, the whiteness indexes, the results of the tearing test, SEM and FTIR-ATR findings of 100% cotton textiles were presented that were treated with TiO2-SWCNTs particles using the photocatalytic technique. The test results demonstrated the successful synthesis of various types of TiO2-SWCNTs, leading to a significant enhancement in the whiteness of the cotton fabrics. This increase reached 21.79% using a small amount of nano-chemicals, surpassing the whiteness index value created by the conventional H2O2 bleaching process. Optimal results were achieved by using minimum quantities of substance and working at moderate temperatures. According to this information, it can be concluded that this approach may serve as a substitute for the conventional H2O2 whitening procedure in terms of both the substance utilized and the application method, specifically for treating cotton fabric. Moreover, the statistical analysis revealed that the fabric’s self-cleaning capacity is significantly influenced by the square of temperature and pH.

Gold nanoparticles decorated hydrogen-bonded organic frameworks (HOFs) as self-cleaning SERS substrates

The development of efficient trace sensing and green photodegradation synergetic system for antibiotics has become increasingly significant in ecological environmental risk prevention. Herein, a recyclable self-cleaning surface-enhanced Raman scattering (SERS) hybrid system was developed by in-situ deposition of gold nanoparticles (Au NPs) on hydrogen-bonded organic framework (HOF) nanorods. The hybrid system possessed excellent trace SERS detection performance (10−13 M for rhodamine 6G), attributed to the considerable molecular enrichment capacity of HOFs and the intense local surface plasmon resonance (LSPR) effect of Au NPs. The hot-electron transfer pathway activated by the deposition of Au NPs extremely inhibited the hot carrier recombination and therefore induced a self-cleaning capacity of the hybrid system. Notably, the Au NPs decorated HOFs accomplished trace SERS sensing (10−10 M) for ciprofloxacin with good self-cleaning and reusable capabilities. This work provides a new material construction strategy for the reusable trace monitoring and green removal of antibiotics, possessed with an enormous application potential in ecological environmental risk prevention.

Robust and repairable PET superwicking surfaces: A simple two-step fabrication approach for enhanced liquid transport

Superwicking surfaces stand out for their superior wicking abilities that expedite liquid flow across their structural form. The surface has attracted significant attention due to its promising applications in water harvesting, thermal management, biomedical fields, and more. However, minimizing manufacturing costs while ensuring long-term stability remains a challenge in the production of superwicking surfaces and enhancing their applications. This study presents the development of polyethylene terephthalate (PET) superwicking surfaces using a straightforward two-step technique with sandpaper abrasion and nanocomposite coating of TiO2-SiO2. Superwicking performance was evaluated through droplet spread analysis, contact angle measurements, and water drying tests. Results exhibited a more than 100% rise in absorbed water film thickness on the 180-grit abraded superwicking surface versus the coating on raw PET. Additionally, a 10μl droplet displayed more than triple the spreading diameter. Sandpaper abrasion, high-pressure water impact, and outdoor stability tests appraised surface durability. The PET superwicking surface showed enhanced mechanical durability and outdoor stability, attributed to protective microgrooves and photocatalytic self-cleaning capacity. The findings of this study clearly address the high cost, instability, and extreme lack of durability associated with conventional superwicking surface preparation. More importantly, the developed self-repairing capability of the surface allows it to be restored by reapplying the spray coating after the nanoparticles have been worn away due to heavy use. This advancement will significantly promote the use of such surfaces in heat transfer and self-cleaning applications.

Optimizing open-pit coal mining operations: Leveraging meteorological conditions for dust removal and diffusion

Dust pollution from Chinese open-pit coal mines (OPCMs) threatens the coexistence of resource development and environmental protection. This research introduces a new approach to designing OPCMs based on meteorological indicators for dust removal and diffusion. It analyzes the production, distribution, and dust emission features of large-scale OPCMs in China. The factors affecting dust dispersion and atmospheric pollution characteristics were also examined. The findings reveal a surge in the number and output of OPCMs, intensifying the conflict between resource development and environmental protection. Notably, over 80% of OPCMs are in arid and semi-arid regions, exacerbating the challenge. Microclimate effects, including circulation and inversion effects, further amplify dust pollution. Regional and seasonal dust pollution patterns were identified, with the southern region experiencing the highest pollution levels, followed by the northern and central regions. Seasonally, dust pollution exhibits the following pattern: winter > autumn > spring > summer. An alarming decline in atmospheric self-cleaning capacity over the past two decades underscores the pressing challenges ahead for dust control. The increase in air stagnation days/events highlights the urgency for effective dust prevention and control measures. This research suggests considering meteorological elements in OPCM design for dust control. Optimizing mining operations based on weather forecasts enables the utilization of natural conditions for effective dust prevention and control. The results provide insights for dust prevention and control in open-pit mines to foster green and climate-smart mining.

Influence of the Addition of TiO2 Nanoparticles on the Self-Cleaning Capacity of Cementitious Composites.

This study evaluated the potential of incorporating TiO2 nanoparticles (NT) into cementitious composites to provide self-cleaning and self-sanitising properties, as well as the partial replacement of natural aggregates with recycled glass (RGA), ceramic brick (RBA), granulated blast furnace slag (GBA), and textolite waste (RTA) from electronic equipment on these properties. Based on the research results, the addition of NT to cementitious composites led to a significant reduction in contact angle, which means an increase in surface hydrophilicity. At the same time, Rhodamine B stain fading was highlighted, with the degree of whiteness recovery of NT composites exceeding that of the control by up to 11% for natural aggregate compositions, 10.6% for RGA compositions, 19.9% for RBA compositions, 15% for GBA compositions, and 13% for RTA compositions. In a mould-contaminated environment, it was shown that the introduction of NT allowed the material to develop a biocidal surface capacity which is also influenced by the nature of the aggregates used. Furthermore, the study revealed that, under controlled conditions, certain recycled waste aggregates, such as textolite, promoted mould growth, while others, such as brick and slag, inhibited it, highlighting not just the effect of the addition of NT, but also the significant influence of the aggregate type on the microbial resistance of cementitious composites. These improvements in the performance of cementitious composites are particularly advantageous when applied to prefabricated elements intended for the finishing and decorative surfaces of institutional (schools, administrative buildings, religious structures, etc.) or residential buildings.

Hydrochemical characteristics of abandoned coal mines derived acid mine drainage in a typical karst basin (Wuma river basin, Guizhou China)

The hydrochemical characteristics of acid mine drainage (AMD) were investigated in Wuma River Basin, China. AMD was sampled from nine closed coal mine (CCM) sites to study the temporal and spatial evolution of pH, dissolved oxygen (DO), electrical conductivity (ED), total hardness (THR), total dissolved salt (TDS), and trace elements. The surface water (river) and groundwater surrounding mine sites were sampled to evaluate the potential pollution derived from AMDs. The TDS content of AMD was higher than that of surface water and groundwater. The dominant factors influencing TDS were the pH, temperature, and wet or dry season (which played a role in controlling microbial activity), HCO3− balance, and REDOX during the evolutionary process. The hydrochemical type of AMD was dependent on the evolutionary stage. From observations, most AMDs were in the form of the SO42--Ca2+•Mg2+ type that was characterized by a low pH, low [HCO3−], high [SO42−], and high [Fe]. In addition, the AMD samples were undergoing stage I and II processes, in which SO42− and trace elements were generated. The surface water and groundwater were primarily classified as the HCO3−-Ca2+•Mg2+ type, which accounted for their self-cleaning capacity, as indicated by the high [HCO3−]. The surface water and groundwater could be affected by the surrounding AMD depending on the geographical location. The surface water and groundwater sites that were located downstream of subsurface and surface runoff were obviously affected by AMD. After being polluted by AMD, surface water and groundwater contained higher levels of trace elements and emerged as the HCO3−•SO42--Ca2+•Mg2+ type.

Sulfonated cobalt phthalocyanine/NH2-MIL-125 heterojunction modified electrospun nanofiber membrane for emulsion separation and PMS-photocatalysis synergistic degradation

Membrane technology for wastewater remediation has generated significant interest, however, the single functionality, dull wettability and easy fouling property of the membrane hinder its practical application. Herein, a self-cleaning and multi-use superwetting nanofiber membrane was prepared by electrospinning and subsequent spraying technique. The sulfonated cobalt phthalocyanine/NH2-MIL-125 (CoPcS/NMIL) heterojunction was uniformly enrobed over polyethylene terephthalate (PET) electrospun membrane derived from waste PET bottles. The unique CoPcS/NMIL heterojunction exhibited a dual driving effect in photocatalytic activity and membrane wettability. Therefore, the fabricated CoPcS/NMIL@PET composite membrane demonstrated its capability to address complex water pollution issues effectively. The composite membrane exhibited notable flux permeation ability (538–3180 L m−2 h−1) and achieved excellent separation efficiency of over 99 % for diverse oil-in-water emulsions under the gravity filtration condition. Notably, the membrane can efficiently deal with stubborn high-viscosity crude oil fouling profiting from the photocatalytic self-cleaning function. A high flux recovery ratio of 93.6 % and a low irreversible fouling resistance ratio of 6.4 % can be obtained after 30 min of visible light irradiation. Impressively, CoPcS/NMIL@PET membrane exhibited enhanced permeation flux, separation efficiency and self-cleaning capacity compared to NMIL@PET membrane. Meanwhile, the CoPcS/NMIL@PET-activated peroxomonosulfate (PMS) system exhibited extremely high degradation performance for RhB under visible light with the degradation efficiency of 98 % within 10 min, suggesting its potential in the rapid purification of water-soluble organic pollutants. In addition, the CoPcS/NMIL@PET membrane has good chemical stability and mechanical properties for potential long-term use. Moreover, the demulsification mechanism in oil-water separation and PMS-photocatalysis synergetic mechanism over the fabricated CoPcS/NMIL@PET membrane were also investigated in detail. The research offers a promising approach for the design and fabrication of novel nanofiber membranes that incorporate photosensitizers and MOFs functional surfaces to address the challenges associated with such wastewater treatment.

Filling up the water quality database to assess the water quality levels and self-cleaning capacities

The one of water resource’s functions is the self-renewable capacity about quality, quantity and energy. To assess the level or fluctuat trend of water resource functions, a complete set of continuous and representative data is needed. The water quality monitoring of environment management is implementing continuous in Ho Chi Minh City. Because of many causes, the water quality data set is asynchronous by years and observation locations. It causes the many difficulties to researches, studies as the assessment of water’s self-cleaning capacity. With the support of two interpolations equations (the Highest order polynomial fitting Curve Function (HopCEF) and Multivariable Regression Correlative Function (MrCEF)) and GIS tool, the water quality and self-cleaning capacity distributions are zoned/mapped with the fully and continuously data set. The research of water quality and self-cleaning capacity is implemented with the filled quality data set period 2012 – 2022 for urban inner canal system in HCMC. Based on the assessment’s results and the mapped distribution of levels, the fluctuations the quality and self-cleaning capacity of inner canal system are made high visualization. And they are a valuable basis for planning and decision making on the solutions of management agencies in HCMC.

Arrays of Triangular Au Nanoparticles with Self-Cleaning Capacity for High-Sensitivity Surface-Enhanced Raman Scattering

Arrays of Triangular Au Nanoparticles with Self-Cleaning Capacity for High-Sensitivity Surface-Enhanced Raman Scattering

The Influence of TiO2 Nanoparticles on the Physico–Mechanical and Structural Characteristics of Cementitious Materials

The urgent need for sustainable construction that corresponds to the three pillars of sustainable development is obvious and continuously requires innovative solutions. Cementitious composites with TiO2 nanoparticles (NT) addition show potential due to their improved durability, physico–mechanical characteristics, and self-cleaning capacity. This study aimed to evaluate the influence of NT on cementitious composites by comparing those with 2%–5% nanoparticles with a similar control sample without nanoparticles, as well as an analysis of cost growth. The experimental results showed an increase in bulk density of the material (4.7%–7.4%), reduction in large pore sizes by min. 12.5%, together with an increase in cumulative volume and cumulative specific surface area of small pore sizes, indicating densification of the material, also supported by SEM, EDS, and XRD analyses indicating acceleration of cement hydration processes with formation of specific products. The changes at microstructural level support the experimental results obtained at macrostructural level, i.e., modest but existent increases in flexural strength (0.6%–7.9%) and compressive strength (0.2%–2.6%) or more significant improvements in abrasion resistance (8.2%–58%) and reduction in water absorption coefficient (37.5%–81.3%). Following the cost–benefit analysis, it was concluded that, for the example case considered of a pedestrian pavement with a surface area of 100 m2, using 100 mm thick slabs, if these slabs were to be made with two layers, the lower layer made of cementitious composite as a reference and the upper layer with a thickness of 10 mm made of cementitious composite with 3% NT or 4% NT, the increase in cost would be acceptable, representing less than 15% compared to the cost for the exclusive use of cementitious composite without NT.

Enhancement of sewer sediment control and disruption of adhesive gelatinous sediment structure using low-dose calcium peroxide

Large quantities of sediments in urban sewer systems pose significant risk of pipe clogging and corrosion. Owing to their gel-like structure, sewer sediments have strong resistance to hydraulic shear stress. This study proposed a novel approach to weaken the erosion resistance of sewer sediments by destroying viscous gel-like biopolymers in sediments with low doses of calcium peroxide (CaO2). After treatment with 10–50 mg g−1 TS of CaO2, the critical erosion shear stress was significantly reduced by 25.7%–59.9%. The sediment aggregates gradually disintegrated into small diameter particles with increasing CaO2 dosage. Further analysis showed that the strong oxidizing and alkaline environment induced by CaO2 treatment led to cell lysis and changes in the composition and property of extracellular polymeric substances (EPS). After CaO2 treatment, aromatic proteins and humic acid-like substances associated with adhesion translocated from the inner EPS layers to outer layers while being disintegrated into small organic molecules. Concomitantly, CaO2 treatment disrupted the main functional groups (–OH, COO−, C–N, CO, and CN) in inner EPS layers, thus weakening EPS adhesion. Analysis of protein secondary structure and zeta potential reflected the reduced aggregation capacity of sediment microorganisms and loosening of sediment structure after CaO2 treatment. Thus, CaO2 treatment facilitated fragmentation and disaggregation of the gelatinous structure of sewer sediments. Such green strategy decreased the cost of sewer sediment disposal by 42.10–68.95% when compared to water flushing, and it would improve the self-cleaning capacity of sewer system and efficiency of dredging equipment.

Optimal waste load allocation in river systems based on a new multi-objective cuckoo optimization algorithm.

Water pollution escalates with rising waste discharge in river systems, as the rivers' limited pollution tolerance and constrained self-cleaning capacity compel the release of treated pollutants. Although several studies have shown that the non-dominated sorting genetic algorithm-II (NSGA-II) is an effective algorithm regarding the management of river water quality to reach water quality standards, to our knowledge, the literature lacks using a new optimization model, namely, the multi-objective cuckoo optimization algorithm (MOCOA). Therefore, this research introduces a new optimization framework, including non-dominated sorting and ranking selection using the comparison operator densely populated towards the best Pareto front and a trade-off estimation between the goals of discharges and environmental protection authorities. The suggested algorithm is implemented for a waste load allocation issue in Jajrood River, located in the North of Iran. The limitation of this research is that discharges are point sources. To analyze the performance of the new optimization algorithm, the simulation model is linked with a hybrid optimization model using a cuckoo optimization algorithm and non-dominated sorting genetic algorithms to convert a single-objective algorithm to a multi-objective algorithm. The findings indicate that, in terms of violation index and inequity values, MOCOA's Pareto front is superior to NSGA-II, which highlights the MOCOA's effectiveness in waste load allocation. For instance, with identical population sizes and violation indexes for both algorithms, the optimal Pareto front ranges from 1.31 to 2.36 for NSGA-II and 0.379 to 2.28 for MOCOA. This suggests that MOCOA achieves a superior Pareto front in a more efficient timeframe. Additionally, MOCOA can attain optimal equity in the smaller population size.

Influence of exogenous risk-inducing factors on the incidence of intestinal infections in the population of the territory of intensive tourism

Introduction. The development of tourism in regions with an insufficient level of social infrastructure and a low self-cleaning capacity of the environment poses a danger due to the gain in infectious diseases. The level of water in Lake Baikal may determine the potential for dilution of chemical and microbiological contaminants in the coastal zone.
 Materials and methods. The incidence of acute intestinal infections (AII) was studied in the area located on the south-eastern shore of the lake. Baikal (2016–2022). There were assessed risk-inducing factors including climate, water level of the lake, number of tourists, water quality. The values of relative risk, etiological share, economic damage were calculated. 
 Results. The incidence was 630.8 (455.9–781.9) in 0–14 years children, 16.0 (4.8–48.5) cases per 100 thousand population in people over 15 years old. The relative risk in children in the year of low water content of the lake. Baikal RR=1.498 (CI 1.067–2.102). The total level of economic damage caused by additional cases of rotavirus infection in children amounted to 4,528.960 of rubles with high water content, and 5,625.740 of rubles with low water content. 
 Limitations of the study relate to the inability to accurately estimate the number of tourists visiting the region; the inflation rate is not taken into account when calculating the economic damage. 
 Conclusion. The AII incidence in the children’s population of the coastal region is characterized by an increase in the years of water content in Lake Baikal, which differs from the optimal level, with changes in risk-inducing factors.

OXIDATION METHODS FOR PHENOLE-CONTAINING WASTEWATER TREATMENT

One of the most complex environmental problems generated by the development of human economic activity is the problem of the negative impact of chemically polluted territories on the objects of the hydrosphere. A lot of toxic compounds, getting into water reservoirs, cause the water area deterioration, the death of their flora and fauna, make the water unusable either for drinking nor for cultural and household needs. Recently, the attention of specialists has been attracted by a group of persistent organic pollutants. All these substances belong to the class of organochlorine pollutants, as well as by-products of hydrocarbon production (for example: dioxins, furans, formaldehydes, phenols). These substances are resistant to decomposition and toxic. Among the most dangerous water pollutants, along with heavy metal ions, petroleum products, surfactants and polyaromatic compounds, are phenol and its derivatives. Phenol-containing wastewater is generated at enterprises of the pulp and paper, woodworking, food industries, leather, chemical, coke, petrochemical industries, etc. When even a small amount of phenolic compounds gets into a water body, the reservoir self-cleaning capacity decreases. In this regard, the problem of an objective assessment of hydrosphere pollution by phenols and its derivatives and the search for new effective methods of wastewater treatment are urgent tasks. The paper describes oxidation methods for wastewater treatment from phenol.

An eco-friendly building coating with high self-cleaning capacity: Synergetic effect of super-hydrophobicity and photocatalytic degradation

Photocatalytic super-hydrophobic coating is highly appealing due to its exceptional self-cleaning capacity. In this study, recycled concrete powder (RCP) was used to support TiO2, and RCP@TiO2 composites (RCPT) were incorporated into polydimethylsiloxane (PDMS) to fabricate an exterior wall self-cleaning coating. The super-hydrophobicity and photocatalytic activity of the resulting coating were modulated by adjusting the dosage of RCPT. The surface roughness was determined through fractal analysis. The findings indicated that the incorporation of RCPT generated micro-/nano-scale structures on the coating surface, which significantly enhanced its hydrophobicity. The water contact angle (WCA) of the coating surface increased with the content of RCPT. When the mass ratio of RCPT to PDMS reached 1, the sliding angle (SA) sharply decreased, resulting in a super-hydrophobic surface with WCA greater than 150° and SA less than 10°. According to the surface roughness, critical points of wetting state transition can be accurately identified. Meanwhile, the coating with the same addition of RCPT exhibited the highest photocatalytic activity. The synergistic effect of super-hydrophobicity and photocatalytic degradation contributed to the enhanced self-cleaning capacity. Due to the lotus effect, the coating exhibited high stain resistance and water repellency. Most pollutants adhering to the coating surface can be removed by rainwater rolling off. In case of fouling by organic pollutants, photocatalytic degradation can decompose adsorbed pollutants, thus restoring the lotus effect. The coating also demonstrated exceptional stability against photo-thermal erosion, mechanical abrasion, and water impact. Our research has unveiled the correlation between surface structure and properties of coating, providing valuable insights for the development of building self-cleaning coatings.

Phenyl-modified silica aerogels with high-temperature hydrophobicity for self-cleaning and thermal insulation under extreme circumstances

Silica aerogels tend to be employed as thermal insulating materials, however their properties are inevitable to deteriorate in humid conditions owing to the hydrophilic nature, especially above 200 °C. Herein, phenyl modified silica aerogels with superhydrophobicity, self-cleaning capacity, and ultra thermal insulation are prepared. Phenyltriethoxysilane (PTES) working as the modifier condenses with tetraethyl orthosilicate (TEOS), forming a three-dimension network containing ladder polyphenylsilsesquioxane structure, where the introduction of bulk phenyl groups decreases free energy and fabricates hierarchical regime, leading to distinctive water repellency. The water contact angles are larger than 150° with low hysteresis (less than 2°), rendering droplet bouncing and self-cleaning capacities. As the molar ratio of PTES to TEOS rises to 1, the superhydrophobicity can be preserved at temperatures as high as 500 °C. In addition, hot-steam resistance and excellent thermal insulation are achieved. When subjected to a direct impact of 200 °C steam for 5 h, the hybrid aerogel demonstrates a reversible rise of thermal conductivity around 34%. The maximum back-surface temperature keeps 55.9 °C after exposure to hot steam for 10 min. The modification can broaden the application area of silica aerogels in high-temperature thermal insulation.

Nitrogen retention in stream biofilms – A potential contribution to the self-cleaning capacity

Surface waters are under increasing pressure due to human activities, such as nutrient emissions from wastewater treatment plants (WWTPs). Using the retention of nitrogen (N) released from WWTPs as a proxy, we assessed the contribution of biofilms grown on inorganic and organic substrates to the self-cleaning capacity of second-order streams within the biosphere reserve Vosges du Nord/Palatinate forest (France/Germany). The uptake of N from anthropogenic sources, which is enriched with the heavy isotope 15N, into biofilms was assessed up- and downstream of WWTPs after five weeks of substrate deployment. Biofilms at downstream sites showed a significant positive linear relationship between δ15N and the relative contribution of wastewater to the streams' discharge. Furthermore, δ15N substantially increased in areas affected by WWTP effluent (∼8.5‰ and ∼7‰ for inorganic and organic substrate-associated biofilms, respectively) and afterwards declined with increasing distance to the WWTP effluent, approaching levels of upstream sections. The present study highlights that biofilms contribute to nutrient retention and likely the self-cleaning capacity of streams. This function seems, however, to be limited by the fact that biofilms are restricted in their capacity to process excessive N loads with large differences between individual reaches (e.g., δ15N: −3.25 to 12.81‰), influenced by surrounding conditions (e.g., land use) and modulated through climatic factors and thus impacted by climate change. Consequently, the impact of WWTPs located close to the source of a stream are dampened by the biofilms’ capacity to retain N only to a minor share and suggest substantial N loads being transported downstream.

In-situ constructing cellulose/PVA hydrogel with confinement capillarity for efficient solar interfacial evaporation

Solar-driven interfacial evaporation technology, a potential method of solving freshwater scarcity without any fossil energy consumption and environmental impact, is limited by its core component of photothermal materials. Herein, we fabricated a cellulose/PVA hydrogel with interconnected pores structure via an in-situ method to improve its working capacity in seawater desalination and wastewater purification. The results show that adding hydroxypropyl cellulose and changing light absorbers (CNTs and Chinese ink) can efficiently regulate the evaporation enthalpy to accelerate the evaporation. Integrating the interconnected pores structure with an indirect water supply can achieve confinement capillarity, i.e., upward water transportation along the inner surface of the porous hydrogel instead of being full of all pores, thus obtaining a sharp increase in evaporation interface. Compared to Chinese ink, CNTs particles exhibit an obvious promotion to the mechanical properties and evaporation capacity. Eventually, the evaporation rate of the hydrogel containing CNTs with optimized structure can reach 3.16 kg m−2 h−1 under 1 sun. Besides, the as-prepared hydrogel has impressive performance in working stability and self-cleaning capacity under harsh environmental conditions, such as high-concentration brine, strong acid, and alkaline solution. The regulation strategy will arouse new inspiration from numerous researchers about designing and manufacturing high-performance solar-driven evaporators.