Virus removal in ceramic depth filters based on diatomaceous earth

Ceramic filter candles, based on the natural material diatomaceous earth, are widely used to purify water at the point-of-use. Although such depth filters are known to improve drinking water quality by removing human pathogenic protozoa and bacteria, their removal regarding viruses has rarely been investigated. These filters have relatively large pore diameters compared to the physical dimension of viruses. However, viruses may be retained by adsorption mechanisms due to intermolecular and surface forces. Here, we use three types of bacteriophages to investigate their removal during filtration and batch experiments conducted at different pH values and ionic strengths. Theoretical models based on DLVO-theory are applied in order to verify experimental results and assess surface forces involved in the adsorptive process. This was done by calculation of interaction energies between the filter surface and the viruses. For two small spherically shaped viruses (MS2 and PhiX174), these filters showed no significant removal. In the case of phage PhiX174, where attractive interactions were expected, due to electrostatic attraction of oppositely charged surfaces, only little adsorption was reported in the presence of divalent ions. Thus, we postulate the existence of an additional repulsive force between PhiX174 and the filter surface. It is hypothesized that such an additional energy barrier originates from either the phage's specific knobs that protrude from the viral capsid, enabling steric interactions, or hydration forces between the two hydrophilic interfaces of virus and filter. However, a larger-sized, tailed bacteriophage of the family Siphoviridae was removed by log 2 to 3, which is explained by postulating hydrophobic interactions.     

Sustainable colloidal-silver-impregnated ceramic filter for point-of-use water treatment

Cylindrical colloidal-silver-impregnated ceramic filters for household (point-of-use) water treatment were manufactured and tested for performance in the laboratory with respect to flow rate and bacteria transport. Filters were manufactured by combining clay-rich soil with water, grog (previously fired clay), and flour, pressing them into cylinders, and firing them at 900 degrees C for 8 h. The pore-size distribution of the resulting ceramic filters was quantified by mercury porosimetry. Colloidal silver was applied to filters in different quantities and ways (dipping and painting). Filters were also tested without any colloidal-silver application. Hydraulic conductivity of the filters was quantified using changing-head permeability tests. [3H]H2O water was used as a conservative tracer to quantify advection velocities and the coefficient of hydrodynamic dispersion. Escherichia coli (E. coli) was used to quantify bacterial transport through the filters. Hydraulic conductivity and pore-size distribution varied with filter composition; hydraulic conductivities were on the order of 10(-5) cm/s and more than 50% of the pores for each filter had diameters ranging from 0.02 to 15 microm. The filters removed between 97.8% and 100% of the applied bacteria; colloidal-silver treatments improved filter performance, presumably by deactivation of bacteria. The quantity of colloidal silver applied per filter was more important to bacteria removal than the method of application. Silver concentrations in effluent filter water were initially greater than 0.1 mg/L, but dropped below this value after 200 min of continuous operation. These results indicate that colloidal-silver-impregnated ceramic filters, which can be made using primarily local materials and labor, show promise as an effective and sustainable point-of-use water treatment technology for the world's poorest communities.     

Filter and electrostatic samplers for semivolatile aerosols: physical artifacts

Adsorptive and evaporative artifacts often bias measurements of semivolatile aerosols. Adsorption occurs when the sampling method disrupts the gas-particle partitioning equilibrium. Evaporation occurs because concentrations of semivolatiles are rarely constant over time. Filtration is subject to both adsorptive and evaporative artifacts. By comparison, electrostatic precipitation reduces these artifacts by minimizing the surface area of collected particles without substantially disrupting the gas-particle equilibrium. The extent of these artifacts was determined for filter samplers and electrostatic precipitator samplers for semivolatile alkane aerosols in the laboratory. Adsorption of gas-phase semivolatiles was lower in electrostatic precipitators by factors of 5-100 compared to the filter method. Particle evaporation from the electrostatic sampler was 2.3 times lower than that from TFE-coated glass-fiber filters. Use of a backup filter to correct for compound-specific adsorption artifacts can introduce positive or negative errors to the measured particle-phase concentration due to competition among the adsorbates for available adsorption sites. Adsorption of evaporated particles from the front filter onto the backup filter increased the measured evaporative artifact by a factor of 1.5-2.     

负载金属改性活性碳纤维材料制备及吸碘性能

以活性碳纤维（ACF）为原料,采用浸渍法制备了负载金属银的改性活性碳纤维（Ag-ACF）,并通过测定吸附材料在77 K的氮气吸附等温线对改性前后材料的比表面积和孔结构进行了表征.研究并比较了活性碳纤维在负载金属银后对碘的吸附性能,结果表明,在活性碳纤维上负载适量的金属银,可以显著地提高活性碳纤维对碘的吸附容量,原因是由于金属银对活性碳纤维比表面积和表面化学性质的修饰,并提高了活性碳纤维对碘的吸附势.     

Particles in filter effluent: the roles of deposition and detachment

Particles in the effluent of granular media filters can be classified as influent particles that were never removed or as particles that detached after prior deposition. To determine the effects of particle size, filter media depth and filter run duration on the relative fraction of each class, laboratory experiments were performed using suspensions of four sizes of polystyrene particles (0.2, 1.2, 2.5, and 4.0 microm diameters) that were destabilized with 0.04 M calcium chloride and continuously supplied to filters after flocculation. To investigate particle attachment alone, three sizes (1.4, 4.0, and 9 microm) of fluorescent microspheres (FM) were periodically pulse injected immediately ahead of the filter media. Detachmentwas assessed as the difference between net removal (particle counts) and deposition (FM counts). FM deposition followed theory, while results show that particle detachment was significant from an early phase of filtration (100 minutes). The detached fraction of effluent particles increased with particle size (1 to 12 microm range) and filter depth. These model system results suggest that detachment plays a significant role in the origin of filter effluent particles in full-scale water treatment systems.     

Electrical conductivity and physiological comfort of silver coated cotton fabrics

The objective of present study was to develop multifunctional and wearable electrically conductive fabrics with acceptable comfort properties by in-situ deposition of silver particles. The effect of silver nitrate concentration and number of dips was investigated for change in electrical conductivity, EMI shielding, and antimicrobial properties of coated fabrics. The dynamic light scattering and SEM analysis were employed to study the morphology of deposited silver particles. The EMI shielding was found to increase with increase in concentration of silver particles. Later, the comfort and mechanical properties were studied. No significant decrease in air permeability and water vapor permeability was observed due to partial coverage of fabric pores by coating of silver particles. Moreover, the coated fabrics also showed promising behavior toward antimicrobial properties. When the durability of coated fabrics was examined against washing, the application of binder provided good retention of silver particles without loss of electrical conductivity of coated fabrics.     

含银海藻酸纤维的制备方法和性能

为了结合银的抗菌性能和海藻酸纤维的高吸湿性,可将银离子加入海藻酸纤维后制备含银的海藻酸纤维和医用敷料。介绍了在海藻酸纤维中加入银离子的各种方法,并分析了含银海藻酸纤维和医用敷料的性能。结果表明:把银的磷酸锆钠化合物颗粒混入海藻酸纤维后可以制备具有白色外观的抗菌性能很好的纤维,与伤口渗出液接触后,这种纤维可以持续地释放出银离子。实验结果显示含银海藻酸纤维有很好的抗菌性能。     

Use of Lactobacillus paracasei isolated from whey for silver nanocomposite synthesis: Antiradical and antimicrobial properties against selected pathogens

The present research emphasizes the use of safe, inexpensive, and available whey using Lactobacillus paracasei as a source in silver nanocomposite synthesis as an alternative bioactive agent for dairy and biomedical applications. Through the multiinstrumental approach used in this study based on spectroscopic and microscopic methods as well as spectrometric techniques, the characterization and evaluation of silver composites and their antimicrobial and antiradical properties were enabled. Synthesized silver nanocomposites have been found in form of nanocrystals, naturally coated by an organic surface with high antimicrobial and antiradical properties. Furthermore, this work also presents an innovative approach regarding the organic surface (naturally secreted by the bacteria isolated from whey) of the core of nanoparticles, which has already been explored and therefore is starting to supplement the scientific approach concerning biologically synthesized nanoparticles. This work also presents a general frame on the resistance subject by performing the trial interaction of commercially available antibiotics (kanamycin and ampicillin) with new bioactive compounds that can create novel knowledge on complementing their action. Moreover, synthesized silver nanocomposites have shown great antioxidant and antimicrobial effects against various foodborne pathogens from dairy products and drug resistance pathogens found in the medical area to rank on the top of mortality rate.     

Biogenic Fe(III) minerals lower the efficiency of iron-mineral-based commercial filter systems for arsenic removal

Millions of people worldwide are affected by As (arsenic) contaminated groundwater. Fe(III) (oxy)hydroxides sorb As efficiently and are therefore used in water purification filters. Commercial filters containing abiogenic Fe(III) (oxy)hydroxides (GEH) showed varying As removal, and it was unclear whether Fe(II)-oxidizing bacteria influenced filter efficiency. We found up to 10(7) Fe(II)-oxidizing bacteria/g dry-weight in GEH-filters and determined the performance of filter material in the presence and absence of Fe(II)-oxidizing bacteria. GEH-material sorbed 1.7 mmol As(V)/g Fe and was ~8 times more efficient than biogenic Fe(III) minerals that sorbed only 208.3 μmol As(V)/g Fe. This was also ~5 times more efficient than a 10:1-mixture of GEH-material and biogenic Fe(III) minerals that bound 322.6 μmol As(V)/g Fe. Coprecipitation of As(V) with biogenic Fe(III) minerals removed 343.0 μmol As(V)/g Fe, while As removal by coprecipitation with biogenic minerals in the presence of GEH-material was slightly less efficient as GEH-material only and yielded 1.5 mmol As(V)/g Fe. The present study thus suggests that the formation of biogenic Fe(III) minerals lowers rather than increases As removal efficiency of the filters probably due to the repulsion of the negatively charged arsenate by the negatively charged biogenic minerals. For this reason we recommend excluding microorganisms from filters (e.g., by activated carbon filters) to maintain their high As removal capacity.     

Effects of food components on the antimicrobial activity of polypropylene surfaces containing silver ions (Ag+)

The aim of this study was to investigate the influence of food components on the antimicrobial properties of surfaces containing silver. The antimicrobial activity of a polypropylene compound with a zirconium phosphate–based ceramic ion exchange resin containing silver was investigated by comparing the surface count of bacteria on sample and reference surfaces. Different food components were added to the inocula to investigate their influence on the extent of antimicrobial activity in comparison with pure inoculum (Pseudomonas fluorescens in saline solution). In the experiments with pure inoculum, a marked reduction in bacterial counts on samples containing silver was observed (7.4 log₁₀ units). However, protein‐rich food strongly reduced or completely inhibited the antimicrobial activity of silver. Almost all other tested components from the carbohydrate or lipid group did not affect the antimicrobial activity. Overall, the effect and the risks of materials containing silver needs to be analysed individually for the respective application.     

Sampling atmospheric carbonaceous aerosols using an integrated organic gas and particle sampler

Measurement of particle-bound organic carbon (OC) may be complicated by sampling artifacts such as adsorption of gas-phase species onto particles or filters or evaporation of semivolatile compounds off the particles. A denuder-based integrated organic gas and particle sampler (IOGAPS), specifically designed to minimize sampling artifacts, has been developed to sample atmospheric carbonaceous aerosols. IOGAPS is designed to first remove gas-phase chemicals via sorption to the XAD-coated denuder, and subsequently particles are trapped on a quartz filter. A backup sorbent system consisting of sorbent- (XAD-4 resin) impregnated filters (SIFs) was used to capture the semivolatile OC that evaporates from the particles accumulated on the upstream quartz filter. A traditional filter pack (FP) air sampler, which uses a single quartz filter to collect the particles, was employed for comparison in this study. Elemental and organic carbon were determined from filter punches by a thermal optical transmittance aerosol carbon analyzer. Field measurements show that there was no significant difference between the elemental carbon concentrations determined by the FP and IOGAPS, indicating that particle loss during the transit through the denuder tube was negligible. Compared with the OC determined by FP (3.9-12.6 microg of C/m3), the lower OC observed on the quartz filter in the IOGAPS (2.2-6.0 microg of C/m3) was expected because of the removal of gas-phase organics by the denuder. Higher semivolatile organic carbon (SVOC) on the backup SIFs during the night (1.24-8.43 microg of C/m3) suggests that more SVOC, emitted from primary sources or formed as secondary organic compounds, partitions onto the particles during the night because of the decreased ambient temperature. These data illustrate the utility of an IOGAPS system to more accurately determine the particle-bound OC in comparison to FP-based systems.     

Antimicrobial effects of silver nanoparticles against bacterial cells adhered to stainless steel surfaces

Given the increasing number of antibiotic-resistant bacteria and the need to synthesize new antimicrobials, silver has attracted interest in the scientific community because of its recognized antimicrobial activity. This study aimed to evaluate the antimicrobial effects of silver nanoparticles (NP) obtained by a new method and tested at concentrations of 6 μg/ml and 60 μg/ml against the species Staphylococcus aureus, Listeria innocua, Salmonella Choleraesuis, Pseudomonas aeruginosa, Escherichia coli, and Bacillus cereus. The ability of these nanoparticles to remove or kill vegetative cells adhered to stainless steel surfaces was also evaluated. We observed that the NP obtained with the new method, concentrated silver nanoparticles (CNP), and silver nanoparticles with added sodium chloride (NPNaCl) had high antimicrobial activities (P < 0.05). We also verified that the most effective condition for the removal of P. aeruginosa cells on stainless steel coupons (10 by 10 mm) was immersion of the surfaces in CNP. The CNP treatment produced a 5-log reduction of the microbial population after 30 to 60 min of immersion. The CNP treatment also performed better than water and sodium carbonate, a compound commonly applied in clean-in-place procedures in the food industry, in removing adherent B. cereus cells from stainless steel cylinders. Therefore, these results suggest that NP synthesized by a new procedure may be used as antimicrobials in the food industry, for example, for the sanitization of utensils that come into contact with foods.     

Antimicrobial activity of the surface coatings on TiAlZr implant biomaterial

This study is devoted to antimicrobial activity of new surface coatings on TiAlZr. Ti alloys such as TiAlZr are used as implant biomaterials, but, despite the good behavior of such alloys in simulated conditions, bacterial infections appear after the introduction of an implant into the body. The infections are typically caused by the adherence and colonization of bacteria on the surfaces of the implants. The study presents preparation and surface morphology characterization of coatings obtained via anodizing, as well as biomimetic coatings with hydroxyapatite and silver ions with and without antibiotic. The percentage inhibition of Escherichia coli bacteria growth was evaluated for each of the studied coating, and a Trojan-horse model of silver nanoparticles (nAg) antibacterial activity at interface was proposed. Such coatings could be more important taking into account that antibacterial treatments with antibiotics are becoming less effective due to their intensive use.     

Cysteine-induced modifications of zero-valent silver nanomaterials: implications for particle surface chemistry, aggregation, dissolution, and silver speciation

The persistence of silver nanoparticles in aquatic environments and their subsequent impact on organisms depends on key transformation processes, which include aggregation, dissolution, and surface modifications by metal-complexing ligands. Here, we studied how cysteine, an amino acid representative of thiol ligands that bind monovalent silver, can alter the surface chemistry, aggregation, and dissolution of zero-valent silver nanoparticles. We compared nanoparticles synthesized with two coatings, citrate and polyvinylpirrolidone (PVP), and prepared nanoparticle suspensions (approximately 8 μM total Ag) containing an excess of cysteine (400 μM). Within 48 h, up to 47% of the silver had dissolved, as indicated by filtration of the samples with a 0.025-μm filter. Initial dissolution rates were calculated from the increase of dissolved silver concentration when particles were exposed to cysteine and normalized to the available surface area of nanoparticles in solution. In general, the rates of dissolution were almost 3 times faster for citrate-coated nanoparticles relative to PVP-coated nanoparticles. Rates tended to be slower in solutions with higher ionic strength in which the nanoparticles were aggregating. X-ray absorption spectroscopy analysis of the particles suggested that cysteine adsorbed to silver nanoparticles surfaces through the formation of Ag(+I)--sulfhydryl bonds. Overall, the results of this study highlight the importance of modifications by sulfhydryl-containing ligands that can drastically influence the long-term reactivity of silver nanoparticles in the aquatic environment and their bioavailability to exposed organisms. Our findings demonstrate the need to consider multiple interlinked transformation processes when assessing the bioavailability, environmental risks, and safety of nanoparticles, particularly in the presence of metal-binding ligands.     

Investigation of antibacterial and antifungal properties of tufting carpets containing metal composite yarns

In this research, antimicrobial (antibacterial and antifungal) properties of tufting carpets containing metal/texturized polyester composite yarns were investigated. Carpet contains different yarn groups such as pile yarns, ground warps and wefts. Backing fabric’s warp and weft yarns are suitable for gaining antimicrobial activity because of their placement and low usage amount. Thus, textured polyester yarns were commingled with copper, stainless steel metal wires and silver metalized polyamide yarn. Backing fabrics were produced with four different placements by composite yarns. Antibacterial activity tests were applied to carpet samples according to AATCC 100 standard against K. pneumoniae and S. aureus bacteria. AATCC 30 – Part 3 standard was used for determining antifungal activity against A. niger. Results show that the antibacterial activity increases with increasing in the amount of metal composite yarn in unit area. Carpet samples which include copper or metalized silver composite yarn in all warps showed antibacterial activity about 99%. Moreover, antifungal activity can be provided against A. niger when copper and metalized silver composite yarn is used in all warps of carpet samples.     

银离子的释放及敷料的抗菌性能

为了确定不同的含银医用敷料在银的释放量和释放速度上的区别,分析了几种含银医用敷料释放银离子的性能。介绍了测试抗菌性能的3种方法,并总结了含银医用敷料的抗菌性能及临床疗效。结果显示,不同的伤口对银离子的释放量有不同的要求。烧伤病人的伤口特别容易受感染,因此在烧伤伤口上使用的含银医用敷料的银离子释放量高,在伤口上可以维持较高浓度的银。在高吸湿性的医用敷料中,细菌和伤口渗出液一起被吸进敷料,从敷料上释放出少量的银离子即可达到抗菌的目的。     

Electrochemical multiwalled carbon nanotube filter for viral and bacterial removal and inactivation

Nanotechnology has potential to offer solutions to problems facing the developing world. Here, we demonstrate the efficacy of an anodic multiwalled carbon nanotube (MWNT) microfilter toward the removal and inactivation of viruses (MS2) and bacteria (E. coli). In the absence of electrolysis, the MWNT filter is effective for complete removal of bacteria by sieving and multilog removal of viruses by depth-filtration. Concomitant electrolysis during filtration results in significantly increased inactivation of influent bacteria and viruses. At applied potentials of 2 and 3 V, the electrochemical MWNT filter reduced the number of bacteria and viruses in the effluent to below the limit of detection. Application of 2 and 3 V for 30 s postfiltration inactivated >75% of the sieved bacteria and >99.6% of the adsorbed viruses. Electrolyte concentration and composition had no correlation to electrochemical inactivation consistent with a direct oxidation mechanism at the MWNT filter surface. Potential dependent dye oxidation and E. coli morphological changes also support a direct oxidation mechanism. Advantages of the electrochemical MWNT filter for pathogen removal and inactivation and potential for point-of-use drinking water treatment are discussed.     

后处理工艺对聚苯硫醚滤料清灰性能的影响

为研究滤料清灰性能的不同影响因素,选取４种聚苯硫醚（PPS）纤维滤料,即未经后处理、烧毛、聚四氟乙烯（PTFE）乳液浸渍和PTFE 微孔膜覆膜处理的滤料为试样,采用滤料动态过滤性能测试仪测试了４种聚苯硫醚纤维滤料的清灰性能,通过扫描电镜观察了过滤前后滤料的表观形貌。测试结果表明：在试验周期内,这４种滤料中,覆膜滤料经粉尘过滤后剩余压差最低,清灰周期最长,清灰性能最为优异;未经处理滤料清灰性能次之;PTFE乳液浸渍滤料由于表面纤维间充满着PTFE 乳液固状物,其清灰性能较差;烧毛处理滤料表面留有面积较大的PPS 纤维烧焦物质,其清灰性能最差。     

Model simulations of NOx and ultrafine particles close to a Swedish highway

Based on the results from a 6-week monitoring campaign in an area close to a major highway north of Stockholm, Sweden, NOx emission factors representative for vehicle speeds of 100-120 km per h were determined to 0.61 g/veh,km for light duty and to 7.1 g/veh,km for heavy duty vehicles. The corresponding factors for particle number were 1.4 x 10(14) and 52 x 10(14) particles/veh,km, determined for an ambient temperature interval of +7 to +17 degrees C. The removal effects of coagulation and dry deposition on total number concentrations were assessed by numerical model simulations. Velocity and turbulence fields, including those produced by the vehicles, were simulated in a Computational Fluid Dynamics (CFD) model. Coagulation was found to be of little importance over the first 100 m downwind of the highway. The high friction velocities over the road surface created by vehicle movements enhanced deposition locally, contributing to the removal of approximately 10% of the particles originally emitted. Beyond a point 10 m downwind of the highway the removal rate was low and the ultrafine particles were almost inert while being advected over the next hundred meters. As a consequence, it seems reasonable to use monitored data from stations close to highways to estimate emission factors for particle number, assuming that the particles are inert. Those "effective" emission factors should be applicable for urban models with a larger spatial resolution.     

雪莲果叶酚酸提取物抑菌活性研究

以食品中常见的3种病原微生物为供试菌,采用滤纸片法和两倍稀释法研究了雪莲果叶中酚酸提取物的抑菌活性,结果表明:雪莲果叶酚酸对革兰氏阳性细菌和革兰氏阴性细菌均有良好抑制生长作用,对于供试的3种菌,雪莲果叶酚酸对金黄色葡萄球菌抑制作用最强,其次为大肠杆菌,经纯化后的酚酸对金黄色葡萄球菌、大肠杆菌和枯草芽孢杆菌的最小抑菌浓度分别为1.25 mg/mL、2.5 mg/mL、10 mg/mL。