Water Purification Performance Research Articles

Alignment of MXene based membranes to enhance water purification

Membrane-based separation techniques are crucial for mitigating the pollution of aquatic environments and addressing challenges associated with water scarcity. Controlling the structure and chemical functionality of two-dimensional materials can enable the development of new classes of membranes that overcome the limitations of conventional membrane materials to optimize water purification performance. This work uses supramolecular cyclodextrins to decorate the exterior surface of MXene materials, thereby fabricating a series of hybrid membranes via vacuum-assisted self-assembly. These novel nanofiltration membranes can be used to efficiently separate dyes from wastewater. Compared with pristine MXene membranes, the permeability flux of the best-performing membrane increased 23.3 times, while its rejection of methylene blue exceeded 99.7%, most likely because of charge effects and size-selective molecular sieving features of the membranes. This study offers a promising approach for developing advanced membrane separation technologies for water purification by precisely controlling the two-dimensional membrane structure using supramolecular chemistry. This work uses supramolecular cyclodextrins to decorate the exterior surface of MXene (Ti 3 C 2 T x ) materials, thereby fabricating a series of hybrid membranes via vacuum-assisted self-assembly. These novel nanofiltration membranes can be used to efficiently separate dyes from wastewater, with good selectivity and stability. • We prepared a series of hybrid membranes via the combination of MXene and CM-β-CD. • The hybrid membranes exhibited promising rejection effect toward dyes. • The permeability flux of hybrid membranes increased 23.3 times in contrast to that of the pristine MXene membrane.

Low consumption Fenton-like water purification through pollutants as electron donors substituting H2O2 consumption via twofold cation-π over MoS2 cross-linking g-C3N4 hybrid

A twofold cation-π-assembled catalyst consisting of honeycomb microsphere-like MoS2 cross-linking g-C3N4 hybrid (HM-MS/CN) is first developed to address the bottleneck of excessive resource and energy consumption in Fenton chemistry. A series of modern characterization techniques combined with theoretical calculation are used to reveal and verify the twofold cation-π interaction (Mo-O-C and Mo-S-C bonding bridges). It is found that the electrons of pollutants can be captured by H2O2 and O2 through the twofold cation-π interaction during Fenton-like reaction, which inhibits the oxidative decomposition of H2O2 and promotes its hydroxylation. As a result, HM-MS/CN shows excellent performance for water purification by initiating pollutants as electron donors substituting H2O2 consumption under mild natural conditions, and the actual consumption of H2O2 in this system is only 6–8% of that in the common Fenton systems. This discovery is of great significance for the development of novel water purification technology with high efficiency and low consumption.

A General Route to Flame Aerosol Synthesis and In Situ Functionalization of Mesoporous Silica

AbstractMesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m2 g−1. We show its superior performance in water purification, as a drug carrier, and in thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell‐supported nanocatalysts by in situ decoration with active nanoclusters, including noble metal (Pt/SiO2), transition metal (Ni/SiO2), metal oxide (CrO3/SiO2), and alumina support (Co/Al2O3). As a prototypical application, we perform dry reforming of methane using Ni/SiO2, achieving constant 97 % CH4 and CO2 conversions for more than 200 hours, dramatically outperforming an MCM‐41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to design and produce flexible catalysts for many reactions.

A General Route to Flame Aerosol Synthesis and In Situ Functionalization of Mesoporous Silica.

Mesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m2 g-1 . We show its superior performance in water purification, as a drug carrier, and in thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell-supported nanocatalysts by in situ decoration with active nanoclusters, including noble metal (Pt/SiO2 ), transition metal (Ni/SiO2 ), metal oxide (CrO3 /SiO2 ), and alumina support (Co/Al2 O3 ). As a prototypical application, we perform dry reforming of methane using Ni/SiO2 , achieving constant 97 % CH4 and CO2 conversions for more than 200 hours, dramatically outperforming an MCM-41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to design and produce flexible catalysts for many reactions.

Recyclable solar evaporator based on hollow glass microspheres for water purification and desalination

Solar-driven interfacial steam generation (SISG) has attracted much more attention for its significant potential in water purification and desalination. Herein, we report the fabrication of a novel photothermal material (MHGM/Fe 3 O 4 /TiO 2 –Ag/PPy) by coating Fe 3 O 4 , TiO 2 & Ag, and fluorosilane doped polypyrrole (PPy) on (3-Aminopropyl)triethoxysilane modified hollow glass microspheres (MHGM), respectively, and a certain amount of such hollow microspheres self-float on the water surface as a solar evaporator for efficient SISG. Benefiting from low thermal conductivity (0.0455 W m –1 k –1 ), strong light absorption (about 95%) and the gap between the microspheres provides the channels for water transportation, the as-prepared solar evaporator of MHGM/Fe 3 O 4 /TiO 2 –Ag/PPy shows a high water evaporation rate of 1.5516 kg m –2 h −1 under 1 kW m –2 solar irradiation. Moreover, the evaporator with unique spherical hollow structure exhibits excellent salt resistance, as well as efficient water purification and antibacterial performance. More importantly, the evaporator possesses magnetic property and can be magnetically recovered. Thus, the as-prepared solar evaporator shows great potential for practical applications, including seawater desalination, sterilization and synergistic water purification during freshwater production. • The solar evaporator based on hollow microspheres was reported for the first time. • The evaporator possesses efficient antibacterial and water purification performance. • The evaporator has magnetism and can be magnetically recovered. • The evaporator shows high water evaporation rate of 1.5516 kg m –2 h −1 under 1 sun. • The evaporator shows excellent salt-resistant performance even in 20 wt% NaCl.

Superwetting Ag/α-Fe2O3 anchored mesh with enhanced photocatalytic and antibacterial activities for efficient water purification

Superwetting materials have drawn unprecedented attention in the treatment of oily wastewater due to their preferable anti-fouling property and selective oil/water separation. However, it is still a challenge to fabricate multifunctional and environmentally friendly materials, which can be stably applied to purify the actual complicated wastewater. Here, a Ag/α-Fe 2 O 3 heterostructure anchored copper mesh was intentionally synthesized using a facile two-step hydrothermal method. The resultant mesh with superhydrophilicity and underwater superoleophobicity was capable of separating various oil/water mixtures with superior separation efficiency and high permeation flux driven by gravity. Benefiting from the joint effects of the smaller band gap of Ag/α-Fe 2 O 3 heterojunction, inherent antibacterial capacity of α-Fe 2 O 3 and Ag nanoparticles, favorable conductive substrate, as well as the hierarchical structure with superwettability, such mesh presented remarkably enhanced degradation capability toward organic dyes under visible light irradiation and antibacterial activity against both Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) compared with the pure α-Fe 2 O 3 coated mesh. Impressively, the mesh exhibited bifunctional water purification performance, in which organic dyes were eliminated simultaneously from water during oil/water separation in one filtration process. More importantly, this mesh behaved exceptional chemical resistance, mechanical stability and long-term reusability. Therefore, this material with multifunctional integration may hold promising potential for steady water purification in practice. A facile two-step hydrothermal method is adopted to synthesize a durable Ag/α-Fe 2 O 3 heterostructure anchored copper mesh, which behaves superior oil/water separation capability, enhanced photocatalytic and antibacterial activities for promisingly efficient water purification in practice. • A Ag/α-Fe 2 O 3 heterostructure anchored copper mesh was facilely synthesized. • The superwetting mesh enabled to efficiently separate various oil/water mixtures. • Remarkably enhanced photocatalytic and antibacterial activities were achieved. • Organic dyes degradation and oil removal were realized in one filtration process. • The mesh behaved long-term reusability, superior mechanical and chemical stability.

Enzyme-enhanced adsorption of laccase immobilized graphene oxide for micro-pollutant removal

• Laccase immobilization introduced enzymatic degradation for micropollutant removal. • Adsorption and enzymatic degradation had synergy effect for micropollutant removal. • Enzyme-enhanced adsorption improved the adsorption capacity and adsorption rate. • Laccase immobilization promoted the diffusion rate and reduced diffusion resistance. Laccase immobilization has been proven to improve the adsorption efficiency for promoting the micro-pollutant removal performance. However, the enzyme-enhanced adsorption mechanism remains poorly investigated. The main objective of this work is to examine the water purification performance of laccase immobilized graphene oxide (Lac-GO), to reveal the enzyme-enhanced adsorption mechanism and to explain the synergy of adsorption and enzymatic degradation, from the views of theory and experiment. Above all, by the appropriate laccase immobilization, the enzyme-enhanced adsorption process formed, and enzymatic degradation was introduced by the change of micromorphology. Then, the laccase immobilization did not affect the GO adsorption behavior, which was dominated by monolayer and homogeneous adsorption, based on the analysis of adsorption thermodynamics and adsorption kinetics theories. Nevertheless, the enzyme-enhanced adsorption showed higher adsorption capacity and greater adsorption rate, because the enzyme is able to degrade the micro-pollutant adsorbed on GO surface, releasing the occupied active sites and delaying the adsorption saturation. Moreover, the calculation of particle diffusion dynamic model clarified that the micro-pollutant diffusion process accelerated after laccase immobilization, since the enzymatic degradation eliminated the diffusion resistance. Afterwards, the GO adsorption and enzymatic degradation exhibited the clear synergy mechanism for micro-pollutant removal, because of the enzymatic degradation enhancement, diffusion resistance elimination and adsorption saturation reduction. In addition, at the optimal operating conditions (laccase concentration of 333.3 mg L −1 , Malachite Green concentration of 100 mg L −1 , adsorbent concentration of 200 mg L −1 , rotation rate of 150 rpm, and temperature of 40 °C), the enzyme-enhanced adsorption process displayed a significant equilibrium adsorption capacity and high micro-pollutant diffusion rate. In final, this study provides an in-depth understanding to improve the adsorption processes for water purification by the unique advantages of enzyme-enhanced adsorption process.

Self-assembly hierarchical binary gel based on MXene and montmorillonite nanosheets for efficient and stable solar steam generation

Solar steam generation is an environment-friendly, low-cost, efficient and sustainable approach to produce fresh water, which has been widely researched recently as a promising technology. However, practical application of solar steam generation is always restricted by the photothermal conversion efficiency and long-term stability. Herein, the self-assembly hierarchical binary gel (HBG) containing a MXene (Ti 3 C 2 ) gel as the upper structure and montmorillonite (MMT) gel as based materials was designed to achieve the efficient solar desalination toward water purification applications . The result indicated that Ti 3 C 2 gel exhibited high light absorption efficiency (over 94%) in a wide solar spectrum range, meanwhile, MMT gel showed remarkable thermal isolation with a low conductivity of 0.04366 (W/m·K) as well as quick water supply ability. In addition, the HBG achieved the evaporation rate of 1.37 kg m −2 h −1 with the high photothermal conversion efficiency of 93.7%. This hierarchical design also performed an excellent stability in cycle tests and salt-rejecting experiments as well as achieved remarkable water purification performance by rejecting organics and metal ions . In a word, the HBG is proved to be an efficient and advanced design with excellent stability for solar steam generation. • A novel hierarchical binary gel was designed for efficient solar desalination. • Porous MXene gel as upper structure with high light absorption efficiency. • MMT gel as based materials with low conductivity and quick water supply. • High photothermal conversion efficiency was achieved with 93.7%.

Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification Performance.

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as FeIII and CoIII, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO2 and CoO2 metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm. By monitoring of the redox reaction kinetics, the pore area density can be also tuned from ∼0.9 × 104 to ∼3.3 × 105 μm-2. The universality of this method to produce much smaller pores and higher area density than the previously reported ones has been proven in different oxide nanosheets. To demonstrate their potential applications, ultrasmall metal organic framework particles were grown inside the pores of perforated titania oxide nanosheets. The optimized hybrid film showed ∼100% rejection of methylene blue (MB) from the water. Its water permeance reached 4260 L m-2 h-1 bar-1, which is 1-3 orders of that for reported 2D membranes with good MB rejections.

Chemical treatment of biomass wastes as carbon dot carriers for solar-driven water purification

A purely chemical method is demonstrated to treat a variety of biomass wastes for extracting cellulose nanofibrils (CNFs) with a consistent property. By hydrothermal reaction, carbon dots (CDs) can be easily grafted on the surface of CNFs to act as photo-thermal agents and enable fast water evaporation rate at 2.5kgm-2h-1 with about 96.45% solar-to-vapor efficiency under one sun irradiation. This derives from good hydration ability of this system, which lowers the evaporation enthalpy. Moreover, this system not only adsorbs dye contaminants effectively by the formation of hydrogen bonds, but also possesses long-term antifouling solar desalination by means of rationally drilled millimeter-sized channels. Given the sustainable biomass resources and scalable fabrication process, this work offers a promising strategy towards construct low-cost evaporators with the excellent water purification performance.

3D-printing has the potential to deliver ceramic membranes with transformational performance gains

In the UK, Evove is working with a company that specialises in 3D printing to develop a way of producing ceramic membranes using additive manufacturing. It says the work marks a milestone in the commercialisation of additive manufacturing of membranes and anticipates it will result in a transformational increase in performance for water purification and suspended solids separation, as this brief focus article reveals.

Graphene nanofiltration membrane intercalated with AgNP@g-C3N4 for efficient water purification and photocatalytic self-cleaning performance

A novel graphene nanofiltration membrane intercalated with AgNP@g-C 3 N 4 as pillars and photocatalysts was fabricated through a mixed-dimensional assembly strategy, which paves the way for sustainable water purification under solar radiation. • A novel graphene membrane was fabricated by intercalating AgNP@g-C 3 N 4 as photocatalysts. • The membrane owned excellent flexibility and structural stability. • The membranes exhibit high water permeability and superior self-cleaning properties. • Water flux and molecular separation remain stable under photocatalytic flowing device. • Membrane separation, in-situ regeneration, and photodegradation is proposed as a whole. Low water flux and heavy membrane fouling hinder the use of graphene-based membranes for water purification and molecular sieving. To the end, a novel graphene-based membrane, intercalated with Ag nanoparticles anchored g-C 3 N 4 (AgNP@g-C 3 N 4 ) as pillars and photocatalysts, was fabricated through a mixed-dimensional assembly strategy. The uniform loading of Ag nanoparticles on g-C 3 N 4 can greatly improve the photocatalytic ability of g-C 3 N 4 while creating more water transport channels between reduced graphene oxide (rGO) and g-C 3 N 4 laminates. The resultant rGO/AgNP@g-C 3 N 4 nanofiltration membrane displayed efficient water permeability, superior photocatalytic self-cleaning performance, and owned excellent flexibility and structural stability. The water permeability of the rGO/AgNP@g-C 3 N 4 membrane was considerably improved (210.9 L∙m −2 ∙h −1 ∙bar −1 ) compared to the pure rGO membrane (78.4 L∙m −2 ∙h −1 ∙bar −1 ) due to the larger interlayer spacing and rough surface. After 1 h of visible light irradiation, the decrease of flux produced by pollutant molecule adsorption can recover with a ultrahigh flux recovery ratio (FRR) of 98.1%. Moreover, the high flux of the rGO/AgNP@g-C 3 N 4 membrane remained stable in a cross-flow photocatalytic nanofiltration device. Membrane separation, photocatalytic regeneration, and pollutant degradation by ·OH and ·O 2 − radicals are proposed as effective cooperation mechanisms.

Modeling and optimization of metal-organic frameworks membranes for reverse osmosis with artificial neural networks

Metal-organic frameworks (MOFs) have recently attracted tremendous attention as membrane materials for desalination owing to their diversified structures, permselectivity, and tunable functionalities. However, the structure-performance relationship of MOF membranes still has not been elucidated. Herein, artificial neural networks (ANN) were developed to form prediction model of MOF thin film nanocomposite (TFN) membrane performances in reverse osmosis applications. Key parameters including MOF size, MOF pore diameter, MOF loading, selective layer thickness, salt concentration, and pressure were collected from literature to predict the water permeability and salt rejection. 5-fold cross-validation and hyperparameter tuning method were employed to acquire a better performing model. When the node structure was 6–9–9–8–2 with the learning rate of 0.001, the developed ANN model attained a remarkable prediction R 2 of 90.62%. By introducing mean impact value algorithm into the model, the feature importance of each factor on the membrane performance was also calculated. Rather than the MOF loading and size, proper control of selective layer thickness and MOF pore diameter was key to breaking the permeability-selectivity tradeoff. Finally, ANN proved its ability to predict the membrane performance for water purification and further provide guidance for MOF-based membrane design, or even other TFN membrane design. • Artificial neural networks are used to optimize and predict MOF TFN membranes. • 5-fold cross-validation and hyperparameter tuning were employed. • R 2 of 98.08% and 90.62% were achieved for training and prediction. • MIV algorithm was used for variable screening of the BP neural network. • PA thickness, MOF pore diameter, and MOF sizes were the key factors.

The promising solar‐powered water purification based on graphene functional architectures

AbstractSolar‐powered water purification is able to gain freshwater from nonedible water by harnessing inexhaustible and pollution‐free sunlight energy, which is undergoing booming development to address the global water shortage. Due to the fascinating properties, numerous graphene‐based materials were devoted to the solar‐powered system from interfacial solar‐steam generation, towards solar pollutants degradation and even atmospheric water harvesting. Therefore, manipulations on graphene including chemical regulation and structural engineering were first introduced in this review, followed by the recent advancements in three main aspects of graphene‐based solar‐powered water purification concerning rapid steam generation, efficient pollutants degradation and significant atmospheric water harvesting. And the relationships between the designs of the materials with water purification performances were discussed in detail. Finally, a summary of challenges as well as the corresponding possible solutions were also suggested, aiming to provide scientific and technical inspirations to the flourishing solar‐powered water purification based on graphene functional architecturesimage

Constructing oxidized carbon spheres-based heterogeneous membrane with high surface energy for energy-free water purification

Producing affordable freshwater becomes increasingly essential. Membrane separation technology offers an unprecedented opportunity, but they typically use fuel energy during the separation process. Therefore, it is a severe challenge to construct an advanced membrane for energy-free water purification. Herein, for the first time, we reported a heterogeneous membrane for pressure-free water purification. Oxidized carbon spheres (OCS) membrane was optimized by the coordinated modification of polydopamine (PDA) and tetrakis(hydroxymethyl)phosphonium chloride (THPC). Remarkably, the [email protected] membrane was progressively hydroxylated due to the THPC’s superb water-binding ability. Therefore, the [email protected]/THPC membrane demonstrated higher surface free energy and better hydrophilic capacity than the other membranes. Under the combined effect of abundant porous geometry and strong charge interaction, this membrane presented a splendid screening performance for various dye molecules without extra pressure. In addition, its separation throughput can be improved by regulating the external temperature. This work may offer a straightforward manner to handle the relationship between membrane structure and performance for pressure-free water purification.

Enhanced catalytic performance of Cu-doped MnFe2O4 magnetic ferrites: Tetracycline hydrochloride attacked by superoxide radicals efficiently in a strong alkaline environment

It is important to develop a catalyst that can maintain good activity in alkaline environment for Fenton or Fenton-like reactions. In order to achieve stable Fenton catalytic degradation in a wide pH range, this study reports Cu-doped MnFe2O4 heterogeneous catalysts still has excellent effect when the pH is extended to 11 for removing organic pollutants, such as tetracycline hydrochloride (TC-HCl). The synergistic effect among Fe, Mn and Cu ions has been proved to enhanced the catalytic activity in this work. When the molar ratio of Cu/Mn=4:1, the porous Cu0·8Mn0·2Fe2O4 materials had the highest photo-Fenton catalytic activity compared with pure MnFe2O4, CuFe2O4 and other CuxMn1-xFe2O4. The XPS showed that Cu0·8Mn0·2Fe2O4 formed oxygen vacancies, which exposed more active sites to attract more H2O2 for TC-HCl degradation. Results indicated 94.3% of TC-HCl was efficiently degraded by 0.1g/L Cu0·8Mn0·2Fe2O4 with 50mM H2O2 at pH=11 under 30min visible light irradiation, and the corresponding apparent rate constant was 0.08286 min-1. With free radicals quenching experiment, O2- was responsible for the high catalytic degradation and OH was participated in the photo-Fenton reaction. To sum up, Cu0·8Mn0·2Fe2O4 exhibited high activity, great stability and easily recyclable, which eliminated the pH limitation of the Fenton reaction and provided practical application performance for water purification.

Effects of Benzalkonium Chloride Contents on Structures, Properties, and Ultrafiltration Performances of Chitosan-Based Nanocomposite Membranes.

The effects of benzalkonium chloride (BKC) contents on the structure, properties, and ultrafiltration performance of chitosan-based nanocomposite membranes containing poly(ethylene glycol) and multi-walled carbon nanotube (chitosan/BKC/PEG/CNT) were examined. The membranes were prepared by a mixing solution method and phase inversion before being characterized with microscopic techniques, tensile tests, thermogravimetric analysis, water contact angle, and porosity measurements. The performance of the nanocomposite membranes in regard to permeability (flux) and permselectivity (rejection) was examined. The results show that the incorporation of BKC produced nanocomposite membranes with smaller pore structures and improved physico-chemical properties, such as an increase in porosity and surface roughness (Ra = 45.15 to 145.35 nm and Rq = 53.69 to 167.44 nm), an enhancement in the elongation at break from 45 to 109%, and an enhancement in the mechanical strength from 31.2 to 45.8 MPa. In contrast, a decrease in the membrane hydrophilicity (water contact angle increased from 56.3 to 82.8°) and a decrease in the average substructure pore size from 32.64 to 10.08 nm were observed. The membrane rejection performances toward Bovine Serum Albumin (BSA) increased with the BKC composition in both dead-end and cross-flow filtration processes. The chitosan/BKC/PEG/CNT nanocomposite membranes have great potential in wastewater treatments for minimizing biofouling without reducing the water purification performance.

Facile Fabrication of Highly Hydrophobic Onion-like Candle Soot-Coated Mesh for Durable Oil/Water Separation.

Although sundry superhydrophobic filtrating materials have been extensively exploited for remediating water pollution arising from frequent oil spills and oily wastewater emission, the expensive reagents, rigorous reaction conditions, and poor durability severely restrict their water purification performance in practical applications. Herein, we present a facile and cost-effective method to fabricate highly hydrophobic onion-like candle soot (CS)-coated mesh for versatile oil/water separation with excellent reusability and durability. Benefiting from a superglue acting as a binder, the sub-micron CS coating composed of interconnected and intrinsic hydrophobic carbon nanoparticles stably anchors on the surface of porous substrates, which enables the mesh to be highly hydrophobic (146.8 ± 0.5°)/superoleophilic and resist the harsh environmental conditions, including acid, alkali, and salt solutions, and even ultrasonic wear. The as-prepared mesh can efficiently separate light or heavy oil/water mixtures with high separation efficiency (>99.95%), among which all the water content in filtrates is below 75 ppm. Besides, such mesh retains excellent separation performance and high hydrophobicity even after 20 cyclic tests, demonstrating its superior reusability and durability. Overall, this work not only makes the CS-coated mesh promising for durable oil/water separation, but also develops an eco-friendly approach to construct robust superhydrophobic surfaces.

Study on properties of metakaolin-based cement paste coating and its application of adsorbing methylene blue in water

Cement paste coating is closely related to the water purification performance of porous concrete. The properties of metakaolin (MK) based cement paste coating and the effects of the metakaolin on removing methylene blue in water were investigated. The results showed the fluidity of the cement paste decreased and the cohesiveness increased with increase of the content of MK. It is found that the MK promoted the hydration of cement, which not only refined the pore structure of the cement paste, but also improved the interface transition zone. Besides, MK increased the adsorption capacity of the cement paste coating to methylene blue in water. The results showed that the content of MK is an important factor for affecting the methylene blue removal rate of the cement paste coating. Under the same MK content, the thickness of the cement paste coating had little positive effect on the methylene blue removal rate of the cement paste coating. The study is expected to provide a new approach for preparing cement paste coating with good methylene blue removal.

Biofilm development under different pipe materials and water quality conditions in raw water transportation system: Bacterial communities and nitrogen transformation

Pipe wall biofilm plays a vital role in water quality purification in raw water transportation system (RWTS). This study investigated the pollutants removal, bacterial community (abundant, rare and functional taxa) variations, and their correlations during biofilm development process under different pipe materials and raw water quality. Polyethylene pipe had higher removal efficiency on ammonia nitrogen (NH4+-N) and dissolved organic carbon (DOC), while stainless steel pipe achieved a better total nitrogen (TN) degradation performance. Increasing influent DOC promoted the removal of nitrogen pollutants. Compared with water quality, pipe material showed a greater influence on bacterial diversity and community structure. Pseudomonas and Planctopirus were the dominant genera in abundant and rare taxa, respectively. There were complex interactions within the abundant and rare taxa, with Haliscomenobacter and Reyranella as the hub genera, respectively, and many abundant genera co-occurred with rare genera. Serratia of abundant taxa and Filomicrobium of rare taxa had positive correlations with the influent NH4+-N and DOC concentration, respectively. Complete ammonia oxidation and ammonia assimilatory contributed to the great NH4+-N transformation, while limited denitrification resulted in the undesirable TN removal. Functional bacteria and genes displayed statistically strong correlations with water quality. Abundant and rare taxa were significantly affected by environmental conditions and organic matter, respectively, while the variations in functional taxa were mainly explained by organic matter, nitrogen and their interactions. These findings provide novel insights into the evolution of abundant, rare and functional taxa during biofilm development in RWTS, and highlight their correlations with water purification performance and environmental factors.