Filtration Properties Research Articles

Synthesis and performance evaluation of a micron-size silica-reinforced polymer microsphere as a fluid loss agents

A silica-reinforced polymer microsphere was prepared by reverse suspension polymerization using acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and silica nanoparticles modified with methacryloyloxypropyltrimethoxysilane as a filtrate reductant resistant to high temperature and salt contamination. The filtration volume of American Petroleum Institute (API) sodium-based bentonite fluids was reduced by 63.5% after aging with the addition of 3.0 wt% M-SiO2/ZMD at 150 °C. M-SiO2/ZMD also exhibited significant salt resistance when compared to ZMD. The test results demonstrate that M-SiO2/ZMD exhibits excellent rheological and filtration properties even at elevated temperatures. A significant filtration reduction effect was also shown in the water-based drilling fluid system. The filtrate volumes before and after aging at 150 °C were 5.2 mL and 5 mL, respectively, when the addition amount was 1.0 wt%. Finally, the possible filtration loss reduction mechanisms involved in M-SiO2/ZMD are also discussed. This study provides a new heat- and salt-resistant fluid loss reduction material for water-based drilling fluids in oilfields, and provides theoretical support for its practical application.

Characterization and Performance Evaluation of Modified Apatite Ore as a New Acid-Soluble Weighting Agent for Drilling Fluids

Summary Drilling in oil and gas reservoir formations requires the solid weighting agent used in drilling fluids to have good acid solubility to facilitate plugging removal in subsequent operations. Limestone is the most commonly used acid-soluble weighting agent, but its low density and significant thickening effect lead to a low weighting limit. To achieve control of drilling fluid density, rheology, sag stability, and acid solubility, the feasibility of using apatite (AP) ore as an acid-soluble weighting agent for drilling fluids has been discussed after it was modified by the nitrogen-containing organic polybasic phosphonic acid sodium salt. The basic characteristics of AP and modified AP (MAP) were analyzed. After that, the rheological, filtration, and sag stability properties of MAP-weighted water-based drilling fluids with densities of 1.2 g/cm3 and 1.6 g/cm3 were evaluated, and acid solubility, filter-cake permeability, core permeability damage, and plugging removal tests by acid solutions were performed to evaluate the formation protection effect. The results show that the density of AP is 2.98 g/cm3, and the main component is hydroxyapatite. Its negative electricity and hydrophilicity were enhanced after surface modification, so its dispersion stability in water was enhanced, thereby improving the rheology, filtration, and sag stability properties of the MAP-weighted drilling fluid. The solubility of MAP in 10% HCl solution reached 90.13%, and the core contamination experiments show that after being soaked in HCl solution, the return permeability of contaminated cores reached higher than 90%, indicating that the MAP invading the core can be efficiently dissolved and removed in the acidic working fluids used in the subsequent completion and stimulation operations, thus effectively protecting the reservoir formation. The properties of MAP are superior to those of limestone, and it can be used as a new acid-soluble weighting agent for drilling fluids, considering both drilling fluid performance regulation and reservoir formation protection.

Comparative analysis of the effect of single-walled and multi-walled carbon nanotube additives on the properties of hydrocarbon-based drilling fluids

The article presents the results of a comprehensive comparative analysis of the effect of single-walled and multi-walled carbon nanotubes on the main performance characteristics of mineral oil-based drilling emulsions. Such a systematic comparative study of hydrocarbon-based solutions has been performed for the first time. Weight concentration of single-walled nanotubes varied from 0.01 % to 0.1 %, and of multi-walled ones, from 0.1 % to 0.5 %. The formulation and preparation technique of stable drilling emulsions with single-walled and multi-walled nanotube additives were practiced. The effect of nanotube additives on rheology, filtration, and antifriction properties, as well as colloidal stability, and clay inhibition kinetics of hydrocarbon-based drilling fluids has been studied. As a result of the study, it has been successfully demonstrated that adding even very small amount of carbon nanotubes allows significantly controlling the main performance characteristics of drilling fluids. Thus, adding just 0.025 wt% of single-walled nanotubes increases effective viscosity of the drilling fluid by about 45 %, the yield stress – by 1.7 times, colloidal stability – by 36 %, reducing at the same time filtration loss by 55 %, and friction factor – by 20 %. At the same time, it has been shown that using single-walled nanotubes is several times more efficient compared to adding multi-walled nanotubes, and hundreds of times more efficient compared to using spherical metal oxide nanoparticles.

Investigating the suitability of North Dakota fly ash as fluid loss reducing additive in densified water-based drilling fluid

Fluid loss circulation control during drilling operations is becoming more challenging as exploration moves from conventional to unconventional energy resources. The process of controlling filtrate loss during drilling operation necessitates the right design of drilling fluid that is capable to build an impermeable thin filter cake layer and permit a loss of a reasonable amount of filtrate volume into the formation. It is essential to understand the dynamics that play out between particle morphology of drilling mud additives to assess the sealing efficiency of the loss-reducing additives. As a result, a lot of materials were suggested as fluid loss-reducing materials, which also give thin filter cake thickness. This study investigates the suitability of a coal-fired plant waste (fly ash), as an alternative supplement for filtration agents to improve the quality of the filter cake layer that is built using ilmenite (FeTiO3) derived densified drilling fluid. The ilmenite-derived densified water-based mud samples containing 0, 1, 2, and 3 lb./bbl of fly ash were investigated. To gain an understanding of the pozzolanic influence of class C fly ash on ilmenite-weighted water-based mud, tests were conducted at reservoir conditions according to API specifications. The results from drilling fluid tests were benchmarked against the API standard range of values and contrasted with a control drilling fluid with no-fly ash added. It has been found that mud samples that include fly ash have better filtration properties. The openings in the filter cake were sealed by the amorphous structured fly ash particles, which created an impermeable filter cake. In Mud-4 and Mud-5, where the filtrate volume was reduced by 75% and 79%, respectively, the influence of particle size distribution to form a good sealant and a further reduction in filtrate loss was observed.

Rice husk ash as a sustainable and economical alternative to chemical additives for enhanced rheology in drilling fluids.

Performance evaluation of drilling fluids is essential for a successful drilling project, as they not only remove drill cuttings but also prevent undesired penetration or outflow of formation fluids by sealing off wellbore walls. However, concerns have been raised about the use of chemical additives in drilling fluids due to their toxicity and non-biodegradability. To this end, agricultural waste materials are recognized as a promising alternative as they are cost-effective, environmentally sustainable, and can be used as a substitute for lost circulation materials. Rice husk ash (RHA) has become popular as an additive due to its renewable characteristics, including its large surface area, silica content, and microporous structure. This research article explores the rheological properties of drilling fluid with RHA as a filter control medium. The results showed that increasing concentrations of RHA in the drilling mud significantly improved its rheology, particularly at higher concentrations (15 and 20 wt.%). The addition of RHA modified the filtration and rheological properties of the drilling mud, resulting in improved plastic viscosity, yield point, density, gel strength, and thixotropy. However, filter loss and mud cake thickness increased at elevated RHA concentrations. Furthermore, the pH test revealed that the mud's properties shifted toward the acidic region as the RHA concentration increased. The results indicate that RHA could be used as a sustainable and cost-effective alternative to conventional chemical additives with a positive environmental impact. This study may also provide valuable insights into the use of RHA in water-based bentonite mud and could serve as a guide for future research in the drilling industry.

Photoelectrocatalytic modification of nanofiltration membranes with SrF2/Ti3C2Tx to simultaneously enhance heavy metal ions rejection and permeability

Heavy metal pollution can significantly harm water systems and human health. Combining photoelectrocatalytic (PEC) and nanofiltration (NF) membrane separation technologies can effectively remove heavy metal ions from wastewater. In this study, a water bath method was used to form SrF2/Ti3C2Tx (ST) nanoparticles on the surface of polyvinylidene fluoride (PVDF) membranes and an additional polyamide (PA) functional layer was formed at the interface by crosslinking. ST@PA composite NF membranes (STPP) with good photocatalytic performance were obtained. The separation and catalytic properties of the STPP membranes were controlled by the ST content, which modifies the surface structure and properties of the membranes. The membrane with optimal ST crosslinking exhibited a water contact angle of 50.8°, pure water flux of 24.6 L·m−2·h−1·bar−1, and rejection rates of Mn2+, Ni2+, Cu2+, and Zn2+ of 98.8%, 95.3%, 95.7%, and 97.3%, respectively, under PEC-assisted separation with visible light illumination from a Xe lamp (300 W) and an applied voltage (2 V). The STPP membranes showed improved rejection rates of heavy metal ions under PEC-assisted operation. The mechanism for the improved membrane performance under PEC conditions was preliminarily clarified considering the relationship between the photocatalytic and filtration properties of STPP membranes along with the influence of light irradiation and an external voltage on the heavy metal ions. The generation of electrons, holes, superoxide radicals, and hydroxyl radicals during membrane operation enhances the rejection rates of heavy metal ions. Based on these results, STPP membranes are considered a promising technology for industrial applications in heavy metal removal.

An estimation of gas volume in the water-saturated part of Cenomanian gas reservoirs: a case study of the Medvezhye oil and gas condensate field

The amount of remaining recoverable natural gas reserves is affected by the pinching of gas reserves by infiltrating water and degassing of formation water in the Cenomanian water-pressure complex. It is necessary to reliably determine the volume of gas-saturated water in order to estimate the volume of gas dissolved in produced water. The area of the gas-oil contact is determined by known methods, but the height of the reservoir zone, represented by gas-saturated water (transition zone), must be specified.The fluid distribution and the structure of the transition zone depend on gravitational and capillary forces. These forces depend on the physical and chemical properties of the gas and formation water, as well as the composition and filtration properties of the reservoir. To calculate the thickness of the reservoir in which the process of gas dissolution in water takes place, it is proposed to consider it from the point of view of molecular diffusion processes.The authors of the article propose an adapted VNIIGAZ method for determining the transition zone and the volume of water in which gas from underground gas storages is dissolved (a case study of the Medvezhye oil and gas condensate field). The proposed method for calculating the volume of gas dissolved in formation waters of Cenomanian gas deposits, taking into account diffusion, showed an acceptable result. The proposed method for calculating the volume of gas dissolved in formation waters of Cenomanian gas deposits, taking into account diffusion, gave an acceptable result.

Promotion of thermochromic luminous polysulfone membrane towards smart high-temperature PM2.5 filtration and fire alarming

Particulate matter 2.5 (PM2.5) has become a major threat to human lives. To minimize the adverse effect of high temperature PM2.5, the best way is to alert and filter out the PM2.5 simultaneously. However, it remains a challenge to design filters with combined merits of high-performance, fire-retardancy and thermal response. In this work, we prepare the thermochromic luminous polysulfone membrane with high-temperature PM2.5 filtration and alarming property. The dual luminous center containing covalent donor–acceptor (DA) structure and metal–ligand interaction are incorporated and electrospun into structure unified nanofibers. And different thermal responsiveness is observed for the dual luminous center. The high PM2.5 filtration efficiency (99.1%), low pressure drops (98 Pa) and heat-resistant (Tg > 236 °C) membrane can be directly applied on an in-situ high-temperature PM2.5 filtration and monitoring device, with the emission color variable from red to cyan in a wide range. More importantly, PBN composite filters show excellent flame retardancy in comparison with the commercial PE fabrics, and the color indicating property functions well even under fire. Therefore, the PBN composite membrane holds great potential in the fields of high-temperature PM2.5 filtration and fire alarming.

Photocatalytic membrane coated with α-Fe2O3/Fe3O4 for enhanced filtration performance and antifouling property in surface water treatment

A photocatalytic membrane coated with α-Fe2O3/Fe3O4 nanoparticles has been developed to address the challenges of membrane fouling and organic removal in the treatment of natural surface water. The photocatalytic and filtration properties of the membranes were investigated through a variety of methods. The successful preparation of iron oxide was confirmed by UV–vis diffuse reflectance spectra and X-ray diffractometry, with α-Fe2O3 identified as the primary photocatalytic agent. A commercial ultrafiltration (UF) membrane was employed as a comparison to evaluate the photocatalytic performance and filtration properties of the modified membrane. Results showed that the photocatalytic membrane achieved better removal rates for UV254 (22.0%) and specific fluorescent organic compounds, such as component 2 (19.38%) and component 3 (16.89%), compared to the control group. Furthermore, both irreversible and reversible fouling resistances of the prepared membranes were significantly lower than that of the control group, with reductions of 39.4% and 50.2%, respectively. The membrane coated with α-Fe2O3/Fe3O4 nanoparticles exhibited moderate removal of protein-like and terrestrially derived humic-like fluorescent organics while controlling membrane fouling. Although the α-Fe2O3/Fe3O4 nanoparticles-coated photocatalytic membrane demonstrated good anti-fouling properties, the removals of organic matters were not as effective as anticipated due to the shorter hydraulic retention time. This study provides valuable insights for enhancing pollutant degradation and anti-fouling properties of membranes through the utilization of solar photocatalytic α-Fe2O3/Fe3O4 surface-modified membranes in the treatment of natural surface water.

Modification of nonwoven polymer materials for increasing of their filtration and antibacterial properties

AbstractPolytetrafluoroethylene (PTFE), octenidine dihydrochloride (OCT), and zinc oxide (ZnO) were used to modify the polypropylene nonwoven material by the methods of “wet chemistry” and low‐energy electron beam deposition (EBD). The influence of nonwoven material modification on the morphology, chemical composition, filtration, and antibacterial properties was established. The modified material has antibacterial activity against the gram‐positive strain Staphylococcus aureus and against gram‐negative strains of Escherichia coli and Klebsiella pneumoniae (suppression of bacterial growth for materials with OCT was 100%, with ZnO—70%). PTFE application to Aquaspun leads to a significant increase in the contact angle (from 141.3° to 152.7°) and air filtration efficiency (from 78.3% to 83.4%), which provides the barrier properties of the material. It was established that the material obtained using low‐energy EBD demonstrated a more pronounced antimicrobial potential against the tested strains of St. aureus.Highlights The influence of polypropylene nonwoven materials surface modification methods is systematically investigated. Low‐energy electron beam deposition increases antibacterial and filtration properties of nonwoven materials. Surface modification methods increase barrier properties of polypropylene nonwoven materials.

Modyfikacja właściwości filtracyjnych ośrodków porowatych z wykorzystaniem micelarnej cieczy zabiegowej Multizol

The need for the modification of filtration properties of rock media (most frequently porous rocks) appears frequently, e.g., in hydrocarbon exploitation. Exploitation of crude oil and natural gas is frequently accompanied by an excessive and uncontrolled inflow of reservoir water to the production well, which often results in a significant reduction of hydrocarbon production in the late period of reservoir exploitation. The control of water inflow, through modification treatments of rock filtration properties of the near wellbore zone, is the solution to this problem. The use of dedicated treatment fluids is the basis of such success, which, after the injection and change of original physicochemical properties, create local insulation barriers, enabling the control of the flow of fluids in the geological formation. This paper presents the results of the laboratory assessment of the technological effectiveness of Multizol micellar treatment fluid, which is used for selective blocking of the reservoir water inflow to gas wells. Tests performed, at a preliminary stage, comprised the development of a procedure, the obtaining of samples of the treatment fluid, and the performance of flow tests in test glass tubes, which allow for a swift determination of the technological range of the fluid's capability to form gel and emulsion. Flood tests were the main element of testing, related to the measurement of pressure drops of fluids flowing through the sample under the simulated reservoir conditions. The tests were carried out using two types of media, porous rocks (Szydłowiec sandstone) and sand packs. The determination of the modification degree of filtration properties, both in individual zones and in the entire sample/model, was based on the value of the FRR (Residual Resistance Factor) coefficient, being the measure of their permeability reduction. Two types of tests were performed to assess the effect of Multizol treatment fluid on the initial filtration properties of gas and water-bearing zones.

ASSESSMENT OF THE CURRENT ECOLOGICAL AND HYDROGEOLOGICAL STATE AND FORECAST OF ITS CHANGES IN THE CHITA TPP-1 ASH DUMP TERRITORY (EASTERN TRANSBAIKALIA)

The article provides an assessment of the current state of groundwater and shows the dynamics of its transformation based on the analysis of geoenvironment monitoring results for 2008–2022. The geological environment monitoring program included hydrodynamic and hydrogeochemical observations on the Chita thermal power plant № 1 ash dump territory placed in the west of the city. Regime observations were carried out over the aquifer of the Lower Cretaceous sediments of the Doronin formation using hydrogeology boreholes. The hydrodynamic data correlation analysis indicates the relationship of groundwater levels in boreholes located at a considerable distance from the ash dump with the water level in the nearest borehole. The expansion of technogenic object influence zone in the southwest direction is confirmed by this circumstance, together with the appearance of an ascending spring and the previous studies results of the filtration properties of soils which lie at the ash dump bowl base. As revealed earlier, the ash dump appeared to be the source of significant contamination of groundwater in this area. Nowadays, the polluted area is estimated approximately at 12 km2. The concentrations of sulfates, boron, total dissolved solids, as well as total hardness exceed the norms for drinking water within the area of about 12 km2 in the boreholes on the filtration flow route in the southeast direction from the ash dump. The chemical composition of water taken from boreholes in the southwest direction is currently close to the background values of the water quality indices for the Chita-Ingoda intermountain artesian basin. Meanwhile, the composition of the spring located 1 km southwest from the third ash dump bowl indicates worsening of groundwater quality. As proceeds from the study performed, the operation of the third ash dump bowl will create conditions for the spread of the groundwater contamination front in a new direction with flooding of previously unaffected areas.

Novel filter material by glass fiber foam laying for nonwoven fabrics

The needle punched nonwoven fabrics are widely used as the flue gas filter materials while continuous efforts have been made to improve the filtration efficiency in order to meet the low emission requirement. In this study, filter materials with high filtration efficiency were developed via glass fiber foam laying and PTFE (polytetrafluoroethylene) emulsion coating process. Influences of surfactant type, fiber diameter and fiber content on the foam-ability and foam stability of glass fibers were analyzed. The resulting filter materials, obtained here for the first time with glass fiber foam laden and PTFE emulsion coated needle punched nonwoven fabrics, were characterized for morphology, pore size, air permeability, wear resistance and filtration properties. The results were compared against structures obtained from needle punched nonwoven fabrics before and PTFE emulsion coating. Remarkably, compared to untreated and PTFE emulsion coated needle punched nonwoven fabrics, the glass fiber foam laden and PTFE emulsion coated fabrics displayed higher filtration efficiency and lower outlet particle concentration. Overall, glass fiber foam laying is found to be effective to improve the filtration performance of needle punched nonwoven fabrics and is promising to be commercialized after optimizing the foam composition and PTFE emulsion coating process.

ZIF-8-90 @ graphene oxide reinforced porous hollow fiber coupled with deep eutectic solvent for hollow fiber solid-phase microextraction of selected phthalate esters followed by quantification through high-performance liquid chromatography-ultraviolet detection

The present study was conducted to synthesize hybrid MOFs with a high effective surface area consisting of ZIF-8 and ZIF-90 on the surface of Graphene Oxide (GO). The hybrid ZIF-8-90@GO was finally placed inside the Hollow Fiber (HF) pores to use the substrate filtration properties. Then, the extraction device was used to extract three selected phthalate esters including DiMethyl Phthalate (DMP), DiEthyl Phthalate (DEP) and DiButyl Phthalate (DBP) (as the model analytes) followed by back extraction using Deep Eutectic Solvent (DES). Herein, the DES was utilized as a suitable and effective alternative to common toxic desorption solvents, and it led to the greening of the method. In order to achieve maximum efficiency and sensitivity, the parameters influencing on extraction and desorption processes were optimized. In the obtained optimum situation, the method linearity, Limits Of Detection (LODs), Limits Of Quantification (LOQs), Relative Standard Deviations (RSDs%), Enrichment Factors (EFs) were equal to 0.1–500 µg/L, 0.026–0.058 µg/L, 0.089–0.194 µg/L, 1.8 to 4.7% and 45.4–47.1, respectively. The obtained coefficients of determination (r2) were also higher than 0.9990. The Extraction Recovery (%ER) values were also 90, 87 and 91%, respectively for DMP, DEP and DBP. The above-mentioned method was used for the analysis of water and juice samples and acceptable results were obtained. The obtained relative recoveries in the real samples were in the range of 90–103%. Moreover, due to the presence of aldehyde and methyl groups with hydrophilic and hydrophobic properties in the structure of the synthesized hybrid sorbent, the possibility of interaction increased between sorbent and the studied species, and it per se, led to the increase of extraction efficiency.

Removal of chlorine and monochloramine from tap water using graphene oxide membranes

Residual levels of chlorine and monochloramine (chlor(am-)ine) in water not only cause unpleasant odour and taste but also pose a challenge for chlor(am-)ine sensitive applications such as polymeric membranes used in reverse osmosis for desalination. Current solutions to remove chlor(am-)ine have their limitations and it is thus desirable to develop an alternative technology that can remove chlor(am-)ine in a simple filtration process. In this study, we show that graphene oxide (GO) membranes can be used to remove chlor(am-)ine from tap water. The tested feed chlorine and monochloramine concentrations are up to 50 ppm and 9 ppm respectively. For all tested feed concentrations, the permeate chlor(am-)ine concentration is < 0.1 ppm after passing through GO membranes. We show that both flat sheet and hollow fibre GO membranes filter out chlor(am-)ine over days of continuous operation. Especially our hollow fibre GO membranes offer a great opportunity for easy scalability. Thus our study highlights not only the filtration properties of GO membranes but also its feasibility as an excellent contender for next-generation membrane technology.

The Effects of Different Concentrations of Nanoclay in Polyvinyl Alcohol (PVA) nanofibres- Polyester Bilayer on Morphological Structure, Mechanical Properties, and Filtration of Direct Red Dye

Nanofibres produced by electrospinning have high porosity, low basis weight, high surface area, and controllable pore size, which can be applied in various applications such as solar cells, supercapacitors, tissue engineering and regenerative medicine, wound dressing, chemical and gas sensing and photocatalysis. However, nanofibres have poor filtration properties, particularly in textile wastewater due to the poor colour adsorption by the fibres. Hence, the study aimed to improve the filtration properties of the nanofibres by developing a bi-layer membrane of polyvinyl alcohol (PVA) nanofibres-polyester woven with different concentrations of nanoclay. In this study, the nanoclay was added to polyvinyl alcohol (PVA) solution, which was electrospun using electrospinning to make PVA/nanoclay with polyester bi-layer. The analysis shows that the addition of nanoclay resulted in good adsorption of direct red dyes since direct dyes are often used in textile industry, indicating an improvement in the filtration properties. The tensile strength and Young’s modulus of samples decreased with an increase in the nanoclay concentration due to the fibre becoming stiffer in the bi-layer sample.

SUBSTANTIATION OF SELECTION OF DRILLING MUD TYPE FOR INITIAL OPENING OF KHAMAKINSKY HORIZON TERRIGENOUS RESERVOIR

Most of the explored and estimated oil reserves of the East Siberian oil and gas province are located in the Republic of Sakha (Yakutia), and in particular, the field is located on the territory of the Lensky district, the development object of which is the formation of the Hamakinsky horizon. The reservoir is characterized by high reservoir properties, oil-saturated thickness, medium permeability, abnormally low pressures, low temperature, the presence of carbonate, terrigenous, chemogenic and karst rocks in the geological section, tectonic deformations, reservoir intrusions and salt-saturated interlayers. These factors create problems in the process of its initial opening, and during further operation cause the deterioration of its filtration and capacitance properties compared to those stated in the design documentation. The use of highly mineralized or anhydrous drilling fluids recommended for drilling wells in the considered oil and gas zone does not allow to overcome the instability of rheological properties, an increase in the values of the filtration index, deep clogging of the reservoir, the accumulation of fluid density and the risk of high repression on the reservoir.&#x0D; The article theoretically substantiates the expediency of using invertemulsion solutions (IES) for the initial opening, the effectiveness of which, compared with aqueous solutions, is expressed in the exclusion of the formation of sludge crusts, stable formation oil-water emulsions and swelling of anhydrite, and the reduction of clogging effect in the near-wellbore part collector.&#x0D; Nevertheless, in order to justify the introduction of one or another composition (type) of IES at the stage of theoretical research, various compositions based on mineral oil, diesel fuel, oil obtained in the course of earlier laboratory tests were considered for comparison with water-based solutions, taking into account required density and clogging action of the flushing fluid, physical and chemical inertness of the dispersed phase of the solution, low formation temperature.&#x0D; The substantiation of the most effective type of fluid was carried out using a methodology based on the method of analysis of hierarchies, the optimality criterion in which is the largest weighted average value of the superiority (priority) of one of the drilling fluid options over others simultaneously in all parameters, taking into account the degree of importance of the latter. Based on estimates of normalized and ideal priorities, it has been established that its highest value, both in the case of a distributed synthesis method and in the ideal one, belongs to oilbased IES.

Characterization of a chlorine resistant and hydrophilic TiO2/calcium alginate hydrogel filtration membrane used for protein purification maintaining protein structure

The development of membranes for protein purification has stringent requirement of disinfection resistance, low protein adsorption and anti-fouling, without changing protein structure. In this study, hydrophilic titanium dioxide (TiO2)/calcium alginate (TiO2/CaAlg) hydrogel membranes were prepared by a simple ionic cross-linking method. The effects of the porogenic agent polyethylene glycol (PEG) concentration, the molecular weight of PEG, and the concentration of TiO2 on the filtration properties were systematically investigated. The TiO2/CaAlg membrane exhibited excellent bovine serum albumin (BSA) rejection and anti-fouling properties. The mechanical properties and surface energy of the TiO2/CaAlg membrane were significantly improved. The chemical bonding mechanism of TiO2 and NaAlg was investigated by molecular dynamic simulation. The TiO2/CaAlg membrane had good chlorine resistance and could be disinfected or cleaned with sodium hypochlorite. The TiO2/CaAlg hydrogel membrane loaded with polyhydroxybutyrate (PHB) nanofibers maintained high flux (136.7 L/m2h) and high BSA rejection (98.0 %) at 0.1 MPa. The results of circular dichroism and synchronous fluorescence indicated that the secondary structure of BSA was maintained after membrane separation. This study provides one method for the preparation of green and environmentally friendly membrane for protein purification.

Photodynamic antibacterial micro/nanofiber composite membrane with high efficiency and low resistance filtration performance for medical protective materials

Bacterial infection is one of the major threats to human health worldwide, posing a great challenge to the development of medical protective materials with efficient filtration and long-lasting antimicrobial properties. In this study, electrospinning technology and non-woven fabrics were combined to construct a micro/nano-structured photodynamic rechargeable and storable antibacterial filtration composite membrane. The filtration efficiency of the composite membrane is as high as 99.99% for 0.5–5 μm particles, and the resistance pressure drop is 85 Pa. In addition, the release of OH and H2O2 from the composite film reached 5326.16 μg/g and 711.93 μg/g, respectively. After 7 cycles of quenching, the charging capacity retains more than 70 % of the original. It showed good antimicrobial properties even when stored under dark conditions for one month. The bactericidal efficiency of the composite membrane against E. coli and S. aureus exceeded 99% under both dark and light conditions. The development of this simple and clean micro/nanofiber membrane provides a new idea for exploring photoactive antimicrobial and filtration materials for medical protection.

Incorporating charged Ag@MOFs to boost the antibacterial and filtration properties of porous electrospinning polylactide films

Faced with the pollution caused by particulate matter (PM) in the air, the prevalence of infectious diseases, and the environmental burden by use of nondegradable polymers, the existing filter materials such as meltblown cloth of polypropylene cannot satisfactorily meet people's requirements. In this study, Ag nanoparticles were loaded onto ZIF-8 particles by impregnation reduction to prepare the positively charged Ag@ZIF-8. The porous fibrous membranes of Ag@ZIF-8 with polylactide (PLA) were manufactured by electrostatic spinning technology. Due to the inherently charged feature of Ag@ZIF-8 particles and the presence of pores on fibers, the prepared membranes showed a stable good filtration efficiency of over 97 % at different humidity (30–90%RH, relative humidity). Meanwhile, the presence of charge on Ag@ZIF-8 and the synergistic effects of Ag and ZIF-8 particles made the membranes exhibit good antibacterial effects. The width of the inhibition zone of 3 wt%Ag@ZIF-8/PLA membrane reached 1.33 mm for E. coli and 1.35 mm for S. aureus, respectively.