Precise Filtration Research Articles

Innovative ionic liquid pretreatment followed by wet disk milling treatment provides enhanced properties of sugar palm nano-fibrillated cellulose

In order to accommodate the increased demand for innovative materials, intensive research has focused on natural resources. In pursuit of advanced substances that exhibit functionality, sustainability, recyclability, and cost-effectiveness, the present work attempted an alternative study on cellulose nanofibers derived from sugar palm fiber. Leveraging an innovative approach involving ionic liquid (IL) pre-treatment, bleaching, and wet disc mill technique, nano-fibrillated cellulose (NFC) was successfully obtained from the sugar palm fiber source. Remarkably, 96.89% of nanofibers were extracted from the sugar palm fiber, demonstrating the process's efficacy and scalability. Further investigation revealed that the sugar palm nano-fibrillated cellulose (SPNFC) exhibited a surface area of 3.46 m2/g, indicating a significant interface for enhanced functionality. Additionally, the analysis unveiled an average pore size of 4.47 nm, affirming its suitability for various applications that necessitate precise filtration. Moreover, the surface charge densities of SPNFC were found to be −32.1 mV, offering opportunities for surface modification and enhanced interactions with various materials. The SPNFC exhibit remarkable thermal stability, enduring temperatures of up to 360.5 °C. Additionally, the isolation process is evident in a significant rise in the crystallinity index, escalating from 50.97% in raw fibers to 61.62% in SPNFC. These findings shed light on the vast potential and distinct features of SPNFC, opening the path for its application in a wide array of industries, including but not limited to advanced materials, biomedicine, and environmental engineering.

TriboNano shield – Scalable manufacturing anti-smog multi-level structured nanofiber air filter with co-enhanced purification performance towards self-powered window screen

Nanofiber air filter has garnered tremendous attention due to large specific surface area, large porosity, highly interconnected aperture channels, etc. However, its unitary interlayer structural construction encounters limitation of filtration performance with a low yield. Here, we architect a triboelectric-induced multi-level interlaminar composite structure-based nanofiber window screen (T-MLNS), manufactured continuously utilizing free surface electrospinning. Subjoined with triboelectric charges (active type), T-MLNS possesses co-enhanced adsorption capacity of aerosols. Additionally, MLNS is constructed with finer fibrous layers for precise filtration and coarser fibrous layers in the middle facilitating airflow passing, under physical filtration mechanisms (passive type). Significantly, three-dimensional theoretical models are innovatively employed with numerical simulation findings that multi-level structures present superb filtration performance than uni-structure ones. In the synergistic effect of the active and passive typed mechanisms, T-MLNS is prolonged service life for precise capture of ultrafine aerosols (Diameter: 0.26 µm) with enhanced filtration efficiency up to 99.9%. The integrated multi-zone structure design creates a pattern-shape fiber mesh, resulting in prominent air permeability (∼100 mm s−1), optical light transmission (> 60%), and robust mechanical properties. This combination of active and passive filtering self-powered window screens offers a unique concept for revolutionising interior air quality in industrialization.

Photoswitchable and reusable superhydrophobic/hydrophilic TiO2-coated stainless-steel mesh as oil–water separator

This study fabricated a superhydrophobic/hydrophilic stainless-steel mesh with a TiO2-coated surface for efficient oil–water separation. The mesh manifested both hydrophobic and hydrophilic properties upon incorporating fluorine- and amine-containing silanes, respectively. The photoswitching speed and recovery of surface properties were evaluated by adjusting the UV irradiation period. Additionally, the mesh was subjected to ultrasonic treatment to enhance the photoswitching speed. After alternating UV irradiation and ultrasonification treatments, the variations in contact angle confirmed the feasibility of reversible surface conversion: 158° → 15° → 149.4° → 9.1° → 146.8° → 8.4° → 147.3°. Furthermore, the oil–water separation efficiency of the fluorine-modified mesh was assessed using water and n-hexane solutions. Over eight cycles, the hydrophobic/hydrophilic mesh achieved an average separation efficiency of 95.3% and 96.7%, respectively. The separation process occurred within approximately 5 s. Thus, this study proposed a comprehensive approach for developing a single superhydrophobic mesh capable of facile and rapid photoswitching between hydrophilic and hydrophobic properties. The developed mesh offers precise filtration, durability, and reusability, contributing to sustainable oil–water separation processes.

Precise Filtration of Chronic Myeloid Leukemia Cells by an Ultrathin Microporous Membrane with Backflushing to Minimize Fouling.

A cell filtration platform that affords accurate size separation and minimizes fouling was developed. The platform features an ultra-thin porous membrane (UTM) filter, a pumping head filtration with backflush (PHF), and cell size measurement (CSM) software. The UTM chip is an ultrathin free-standing membrane with a large window area of 0.68 mm2, a pore diameter of 5 to 9 μm, and a thickness of less than 0.9 μm. The PHF prevents filter fouling. The CSM software analyzes the size distributions of the supernatants and subnatants of isolated cells and presents the data visually. The D99 particle size of cells of the chronic myeloid leukemia (CML) line K562 decreased from 22.2 to 17.5 μm after passage through a 5-μm filter. K562 cells could be separated by careful selection of the pore size; the recovery rate attained 91.3%. The method was compared to conventional blocking models by evaluating the mean square errors (MSEs) between the measured and calculated filtering volumes. The filtering rate was fitted by a linear regression model with a significance that exceeded 0.99 based on the R2 value. The platform can be used to separate various soft biomaterials and afford excellent stability during filtration.

A field study of desalination of high-salinity surface brackish water via an RO-NF hybrid system

In this work, a pilot-scale membrane desalination demonstration system for producing drinking water from surface brackish water with a total dissolved solids (TDS) of ≤ 10 g/L was designed and constructed. The production capacity and water recovery were at least 1 m3/h and 50%, respectively. Brackish water was pretreated with microflocculation – precision filtration – ultrafiltration, and the quality of the produced water met the feed water requirements of nanofiltration (NF)/reverse osmosis (RO). The performances of various design configurations, including single NF, single RO, and NF-RO hybrid systems, were evaluated and compared in terms of water recovery and product water TDS. The hybrid RO-NF systems were found to be more effective than either NF or RO alone, and the 4RO-4NF design configuration was most favorable. At a TDS of 10 g/L in the feed, the processing capacity and product water TDS of the 4RO-4NF hybrid system was able to meet the design specs at a feed flow rate of 2 m3/h and an operating pressure of 1.5 MPa. Its long-term stability was examined as well, and it was demonstrated that the desalination performance of the system was mainly affected by seasonal temperature changes and rainfall. The total process cost was estimated to be $1.56/m3, which is considered economically suitable for remote areas where safe drinking water cannot be provided centrally.

Air permeability and tensile properties of novel micron-scale gradient porous plates fabricated by rolling and vacuum sintering

A new type of gradient porous plate (GPP) was successfully fabricated by rolling and vacuum sintering using powders and wire mesh porous plates (WMPPs). The air permeability and tensile strength tests were carried out and the fracture morphology was observed. The results showed that the GPPs with low porosity not only had micron-pore structure with the pore size below 10 μm, and air permeability reached 1.27 × 10−13 m2, but also hold tensile strength with 257.8 MPa. Particularly, its air permeability and tensile strength were significantly superior to nuclear graphite, stainless steel foam, and porous alumina ceramics, equivalent to porous titanium. This study provides an effective method for the fabrication of micron-scale metal GPPs, and is of great significance for expanding the application range (especially in the fields of micron-scale precision filtration and the porous throttles of the aerostatic bearing) of porous materials.

Slip effect based bimodal nanofibrous membrane for high-efficiency and low-resistance air purification

• The slip effect on nanofibrous was modeled and numerically simulated to determine the optimal membrane structure. • Slip effect was utilized to design the low-resistance bimodal nanofibrous membrane filter. • The bimodal and sandwich structured fibers ware easily prepared via free surface electrospinning. • A sandwich structured fibrous membrane filter with gradient air passageway was fabricated for ultrafine-particle filtration. Nanofiber materials have great potential in air filtration, especially to deal with the micro-/nano-particulate matters (PM). However, there still remains a challenge to reduce pressure drop while maintaining ultra-high filtration efficiency for fibrous membrane filters. In the present article, the high-efficiency and low-resistance bimodal nanofibrous membrane filter based on slip effect was designed and fabricated. By modelling and numerically simulating the air flow field around single fiber, the fiber with diameter of 70 nm was found to be most effective for slip flow to reduce air resistance. To introduce the slip effect into fibrous membrane, bimodal structured fibrous membrane filters which consisted of scaffold fibers (200 nm) and the optimal slip effect functional fibers (70 nm) were designed to increase the gap between the fibers. Furthermore, a sandwich structured fibrous membrane filter was fabricated via one-step free surface electrospinning, in which the bimodal fibers (70 + 200 nm) was in the middle layer, while the upper and lower layers were consisted of unimodal fibers of 110 and 70 nm, separately, to form gradient air passageway. The sandwich structured fibrous membrane presented a filtration efficiency of 99.984% for PM 0.26 , meeting the requirements of precision filtration under the premise of low-resistance (85.02 Pa), with a QF (quality factor) as high as 0.1028 Pa −1 . The results shown in the current work provide an efficient way for the design and fabrication of nanofibrous membrane for high-efficiency and low-resistance air purification against PM.

Filtration efficiency improvement of air filter paper for fine particles by electrospinning technology

Due to great advantages, such as simple operation, high porosity, and good fiber continuity, the working principle and research progress of electrospinning technology was studied and polyvinyl alcohol (PVOH) nanofibers were prepared via this process. Air filter paper was used as the receiving substrate to prepare electrospun nano air filter paper (NAFP). The PVOH concentration, static voltage, and receiving distance, were tested to explore the influence of spinning parameters on the filtration performance. Further, the microfiber morphology of the electrospun NAFP was observed. The performance of filter paper, including air permeability, pore size, initial resistance, filtration efficiency, and dust retention, were tested. The results showed that the electrospun NAFP had better filtration performance compared to the air filter paper, and simultaneously they had lower initial resistance and higher precision filtration efficiency. The nanofiber influenced the surface of the air filter paper, as it sharply reduced the pore size. When the spinning condition was 10%, 21 kV, and 15 cm, the pore size decreased approximately 0.6 times of the original, which meant the electrospun NAFP could capture particles ≥ 0.2 μm in size. Finally, after three repeated uses, the good filtration performance was maintained.

Andritz Group, Austria

Nanofiber materials have great potential in air filtration, especially to deal with the micro-/nano-particulate matters (PM). However, there still remains a challenge to reduce pressure drop while maintaining ultra-high filtration efficiency for fibrous membrane filters. In the present article, the high-efficiency and low-resistance bimodal nanofibrous membrane filter based on slip effect was designed and fabricated. By modelling and numerically simulating the air flow field around single fiber, the fiber with diameter of 70 nm was found to be most effective for slip flow to reduce air resistance. To introduce the slip effect into fibrous membrane, bimodal structured fibrous membrane filters which consisted of scaffold fibers (200 nm) and the optimal slip effect functional fibers (70 nm) were designed to increase the gap between the fibers. Furthermore, a sandwich structured fibrous membrane filter was fabricated via one-step free surface electrospinning, in which the bimodal fibers (70 + 200 nm) was in the middle layer, while the upper and lower layers were consisted of unimodal fibers of 110 and 70 nm, separately, to form gradient air passageway. The sandwich structured fibrous membrane presented a filtration efficiency of 99.984% for PM0.26, meeting the requirements of precision filtration under the premise of low-resistance (85.02 Pa), with a QF (quality factor) as high as 0.1028 Pa−1. The results shown in the current work provide an efficient way for the design and fabrication of nanofibrous membrane for high-efficiency and low-resistance air purification against PM.

High permeability sub-nanometre sieve composite MoS2 membranes

Two-dimensional membranes have gained enormous interest due to their potential to deliver precision filtration of species with performance that can challenge current desalination membrane platforms. Molybdenum disulfide (MoS2) laminar membranes have recently demonstrated superior stability in aqueous environment to their extensively-studied analogs graphene-based membranes; however, challenges such as low ion rejection for high salinity water, low water flux, and low stability over time delay their potential adoption as a viable technology. Here, we report composite laminate multilayer MoS2 membranes with stacked heterodimensional one- to two-layer-thick porous nanosheets and nanodisks. These membranes have a multimodal porous network structure with tunable surface charge, pore size, and interlayer spacing. In forward osmosis, our membranes reject more than 99% of salts at high salinities and, in reverse osmosis, small-molecule organic dyes and salts are efficiently filtered. Finally, our membranes stably operate for over a month, implying their potential for use in commercial water purification applications.

Polyacrylonitrile/polyimide composite sub-micro fibrous membranes for precise filtration of PM0.26 pollutants

Particulate matter (PM) pollution has enormously threatened ecosystem and public health. Among various air filtration medium, fibrous ones are very attracting and promising, with an array of advantages such as high specific surface area, and good internal connectivity. Even so, the large-scale fabrication of fibrous filtration materials still remains challenging. Here, three-dimensional polyacrylonitrile/polyimide (PAN/PI) composite sub-micro fibrous membranes were fabricated facilely via free surface electrospinning for precise filtration of PM0.26 pollutants, where the waste PI short fibers were utilized as raw material. The resultant composite fibrous membranes, featuring thin fiber diameter (~150 nm), low areal density (<0.8 g m−2), large porosity, and highly tortuous airflow channels with uniform poresize distribution, possessed excellent mechanical property with tensile strength of 4.95 MPa (twice that of pristine PAN), high thermal durability as well as remarkable filtration performance for ultrafine NaCl aerosol particles (≤0.26 µm) even after multiple filtration tests at high airflow velocity of 14.1 cm s−1. The deepened aperture channels inside three-dimensional sub-micro fibrous membranes are tortuous enough for capturing ultrafine PMs from the airstream mainly via diffusion, interception, and impaction mechanisms, and the reported large-scale fabrication of cost-effective homogeneous PAN/PI fibrous filter media is promising for industrial production and commercial applications.

Edge-effect-mediated microfluidics for fabrication of microporous membrane with well-defined size and shape

Microporous membranes of well-defined porous size, shape, and distribution are significantly important for environmental engineering and biomedical treatment applications, where high-throughput precise filtration is required. However, efficient manufacturing of desired microporous membranes remains a great challenge. In this study, an cost-effective method, based on edge-effect-mediated microfluidics, is proposed for the fabrication of polymeric microsieves with well-defined micropore arrays. This method refers to a lateral spreading of a liquid prepolymer between the protruding parts of a template and the flat surface of a substrate. The edge effect enables the liquid prepolymer to bypass, instead of filling the microholes of the template. Based on the proposed method, two types of monodisperse SiO2 microspheres were separated by solution filtration.

Gelcasting of through-pore hydroxyapatite ceramics

Although the near-net-shape forming ability of gelcasting has been well demonstrated, current attention mainly was focused on manufacturing compact ceramics. In this work we demonstrated that the combination of the gelcasting technique and the ceramic sintering process could prepare the near-net-shape through-pore hydroxyapatite (HAP) ceramics, in which the pore diameter at the range of < 2 μm could be adjusted by changing the content of HAP in green bodies and with the aid of alcohol immersion. Experiments demonstrated that the gels in green bodies and alcohol immersion played important roles in improving the strength of green bodies and decreasing the shrinkage and deformation of green bodies, and thus improving the through-pore and near-net-shape forming of HAP ceramics. Such method reported here possibly extends the gelcasting technique to manufacture other through-pore ceramics for precise filtration, protein separation, or high performance liquid chromatography.

Lydall buys Precision Custom Coatings' filtration business

Lydall Inc, through its wholly-owned subsidiary Lydall Performance Materials Inc, has acquired the Precision Filtration division of Precision Custom Coatings.

The Usage of Crumb Rubber Filtration and UV Radiation for Ballast Water Treatment

This research is aimed to build ship’s ballast water treatment prototipe that used to inactivate microbial water patogen in ballast water to produce unpolluted ballast water that can be standardised by IMO Ballast Water Management Convention. A simple concept that used in the development of this prototype is by draining ballast water with capacity at 5 lpm, 10 lpm and 20 lpm into alternative filtration crumb rubber and UV reactor. In the filtration process using crumb rubber, ballast water will be filtered with the precision filtration up to 50 micron, while in the UV reactor ballast water will be illuminated by UV-C with maksimum dose 16,58 mW/cm2. Finally,the study shows the performance of alternative filtration of crumb rubber and UV-C irradiation on microbial water phatogen, and at what UV-C dose ballast water treatment prototipe can inactivate microbial water phatogens, which are complying with IMO Ballast Water Management Convention ANNEX D. This research is aimed to build ship’s ballast water treatment prototipe that used to inactivate microbial water patogen in ballast water to produce unpolluted ballast water that can be standardised by IMO Ballast Water Management Convention. A simple concept that used in the development of this prototype is by draining ballast water with capacity at 5 lpm, 10 lpm and 20 lpm into alternative filtration crumb rubber and UV reactor. In the filtration process using crumb rubber, ballast water will be filtered with the precision filtration up to 50 micron, while in the UV reactor ballast water will be illuminated by UV-C with maksimum dose 16,58 mW/cm2. Finally,the study shows the performance of alternative filtration of crumb rubber and UV-C irradiation on microbial water phatogen, and at what UV-C dose ballast water treatment prototipe can inactivate microbial water phatogens, which are complying with IMO Ballast Water Management Convention ANNEX D. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi; mso-ansi-language:IN;}

An Intelligent Adaptive Filter for Elimination of Power Line Interference From High Resolution Electrocardiogram

Electrocardiogram (ECG) is a non-invasive method to monitor electric activities inside the heart. The signals observed on the surface of human body have very low amplitude, and thus, ECG is highly vulnerable to noise. One of the most devastating noise is power line interference (PLI) and its harmonics, which are interlaced with ECG signal even if the ECG equipment is operated on battery. The problem is further complicated when the frequency of PLI is not static, making the conventional notch filter completely ineffective. High-resolution electrocardiogram (HRECG) is a specialized technique in which higher frequency components present in the ECG signal are observed; here, we need to eliminate the harmonics of PLI as well. In this paper, we propose an intelligent adaptive noise rejection filter, which tracks and eliminates PLI as well as its harmonics. The proposed system can estimate the frequency of PLI and tune the adaptive filter for precise elimination of PLI as well as its harmonics without the requirement of an auxiliary reference input. The proposed system is based on recursive state space model, inherited with less computational complexity and performs well in a non-stationary environment. The proposed system responds well to the ongoing variations in amplitude and frequency of PLI present in the HRECG signal as well as intracardiac signal. The proposed system does not require any reference signal for tracking the PLI and its harmonics, and it is capable to self-adjust its tracking frequency for highly precise filtration of first, third, and fifth harmonics of PLI.

Tracking inorganic foulants irreversibly accumulated on low-pressure membranes for treating surface water

While low-pressure membrane filtration processes (i.e., microfiltration and ultrafiltration) can offer precise filtration than sand filtration, they pose the problem of reduced efficiency due to membrane fouling. Although many studies have examined membrane fouling by organic substances, there is still not enough data available concerning membrane fouling by inorganic substances. The present research investigated changes in the amounts of inorganic components deposited on the surface of membrane filters over time using membrane specimens sampled thirteen times at arbitrary time intervals during pilot testing in order to determine the mechanism by which irreversible fouling by inorganic substances progresses. The experiments showed that the inorganic components that primarily contribute to irreversible fouling vary as filtration continues. It was discovered that, in the initial stage of operation, the main membrane-fouling substance was iron, whereas the primary membrane-fouling substances when operation finished were manganese, calcium, and silica. The amount of iron accumulated on the membrane increased up to the thirtieth day of operation, after which it reached a steady state. After the accumulation of iron became static, subsequent accumulation of manganese was observed. The fact that the removal rates of these inorganic components also increased gradually shows that the size of the exclusion pores of the membrane filter narrows as operation continues. Studying particle size distributions of inorganic components contained in source water revealed that while many iron particles are approximately the same size as membrane pores, the fraction of manganese particles slightly smaller than the pores in diameter was large. From these results, it is surmised that iron particles approximately the same size as the pores block them soon after the start of operation, and as the membrane pores narrow with the development of fouling, they become further blocked by manganese particles approximately the same size as the narrowed pores. Calcium and silica are assumed to accumulate on the membrane due to their cross-linking action and/or complex formation with organic substances such as humic compounds. The present research is the first to clearly show that the inorganic components that contribute to membrane fouling differ according to the stage of membrane fouling progression; the information obtained by this research should enable chemical cleaning or operational control in accordance with the stage of membrane fouling progression.

Pseudobrookite-type MgTi2O5 water purification filter with controlled particle morphology

Pseudobrookite-type oxide-based ceramics, such as Al2TiO5 and MgTi2O5, have recently been studied as porous ceramic membranes. Here, the effect of LiF doping on the morphology of MgTi2O5 particles is presented in detail. Water purification filters were produced using porous MgTi2O5, with different particle morphologies. MgCO3 (basic) and TiO2 powders with various LiF contents were wet-ball milled, dried, and then, calcined in air at 1100 °C to obtain the MgTi2O5 powders. The powder compacts were sintered at 1000–1200 °C to produce the MgTi2O5 disk filters. The 0.5 wt.% LiF-doped MgTi2O5 disk filter, with elongated grains, showed well-balanced performance removing boehmite particles with diameter of 0.7 μm. Non-doped MgTi2O5 disk filter with equiaxed grains was suitable for precise filtration.

Investigation of Lyocell Fibrillated Nanofibers and Papermaking Characteristics

The nanofiber based filtering media, made up of fibers of diameter less than 1000 nm, have been discovered as new filtering media for effective filtrations. The present study has been made of the influence of various process parameters on the fibrillation characteristics of Lyocell fibers which focuses on how the Lyocell fiber changes with the intensity of beating. Meanwhile the drainage properties and media properties of Lyocell fiber with different beating degree are characterized. The results show that the length, diameter, distortion and degree of fibrillation of Lyocell fiber changes obviously by beating, and a mass of nano-fibril appeared after intensive beating. The Lyocell fiber is cut off rapidly at first, and then fibrillateion starts to appear during the process of beating. At the same time, comparing with the length of the fiber, the beating degree of Lyocell fiber is more sensitive to the degree of fibrillation. What’s more, the drainage time of Lyocell fiber with strongly beating is over ten times than that of the original or ratherish beaten one; Comparing with the media made from original or light beaten pulp, media thickness made from the strongly beaten fiber decreases almost two times, tensile strength increases nearly four times, and air permeability decreases about seventy times.This study has shed some light on the major properties of Lyocell fiber and paves the way for further application of Lyocell fiber in filed of high precision filtration media.

Meso- and Macroporous Ceramics by Phase Separation and Reactive Sintering Methods

AbstractControlled pore glasses are formed through selective etching of one phase of a spinodally decomposed borosilicate glass, an old technique that is the basis of the porous Vycor synthesis technique developed in the 1920s. This technique is receiving renewed attention as these glasses find new applications as substrates for biosensing, bioreactors, precise filtration, and chromatography. Analogous techniques are being applied to crystalline ceramics, such as directed cooling of ZrO2/MgO and MgAl2O4/Al2O3 eutectics to drive phase separation with the subsequent dissolution of one phase. Pyrolytic reactive sintering is a combination of the phase separation method and the reactive sintering method to obtain a 3D porous structure network. For example, dolomite (CaMg[CO3]2) and ZrO2 yield a uniformly porous CaZrO3/MgO composite that utilizes evolved CO2 as a “pore-forming agent.” This article gives an overview of recent developments on meso- and macroporous ceramics based on phase separation and reactive sintering technologies.