Inorganic Biocides Research Articles

Anti-bacterial and anti-mold efficiency of silver nanoparticles present in melamine-laminated particleboard surfaces

Laminated surfaces of wooden composites are created from decorative papers and impregnation thermosetting resins, mainly melamine-formaldehyde (MF). This type of surface treatment is not always resistant to microorganisms, especially when polluted with organic substances. Bioactive additives are often needed to improve the microbial resistance. In this study, silver nanoparticles (Ag-NPs), in amounts of 0.15  10-3 wt.%, 0.5  10-3 wt.%, 1.5  10-3 wt.%, 5  10-3 wt.%, 15  10-3 wt.%, and 50  10-3 wt.% were added to MF resin. The presence of Ag-NPs in the laminated surfaces of the particleboards improved their anti-bacterial and anti-mold resistances. Growth of gram-positive bacterium Staphylococcus aureus on the sterilized surfaces decreased by approximately 53.7% at most, while the growth of gram-negative bacterium Escherichia coli decreased by up to 100%. The anti-mold resistance of the polluted laminated surfaces containing Ag-NPs increased against Penicillium brevicompactum by up to 62.5%, but there was almost no improvement against Aspergillus niger. The Ag-NPs did not affect the resistance of the laminated surfaces towards aggressive chemicals and only minimally towards dry heat at 180 °C. This inorganic biocide decreased the abrasion resistance of the laminated surfaces by up to 12.6%.

Copper release and transformation following natural weathering of nano-enabled pressure-treated lumber

Commercially available lumber, pressure-treated with micronized copper azole (MCA), has largely replaced other inorganic biocides for residential wood treatment in the USA, yet little is known about how different outdoor environmental conditions impact the release of ionic, nano-scale, or larger (micron-scale) copper from this product. Therefore, we weathered pressure treated lumber for 18 months in five different climates across the continental United States. Copper release was quantified every month and local weather conditions were recorded continuously to determine the extent to which local climate regulated the release of copper from this nano-enabled product during its use phase. Two distinct release trends were observed: In cooler, wetter climates release occurred primarily during the first few months of weathering, as the result of copper leaching from surface/near-surface areas. In warmer, drier climates, less copper was initially released due to limited precipitation. However, as the wood dried and cracked, the exposed copper-bearing surface area increased, leading to increased copper release later in the product lifetime. Single-particle-ICP-MS results from laboratory prepared MCA-wood leachate solutions indicated that a) the predominant form of released copper passed through a filter smaller than 0.45 micrometers and b) released particles were largely resistant to dissolution over the course of 6 wks. Toxicity Characteristic Leaching Procedure (TCLP) testing was conducted on nonweathered and weathered MCA-wood samples to simulate landfill conditions during their end-of-life (EoL) phase and revealed that MCA wood released <10% of initially embedded copper. Findings from this study provide data necessary to complete a more comprehensive evaluation of the environmental and human health impacts introduced through release of copper from pressure treated lumber utilizing life cycle assessment (LCA).

Effect of hardening parameters of wood preservatives based on tannin copolymers

AbstractAmongst polyphenols, tannins belong to the most effective chemical protection systems against biological attack on trees. Tannins are water-soluble and are thus leached out easily when used for wood protection.In situpolymerized tannin-hexamine wood preservatives have better leaching resistance (LR), but they do not resist weathering. In this study, tannin copolymer formulations were prepared with hexamine, formaldehyde, furfural, glyoxal, furfuryl alcohol and maleic anhydride, impregnated in wood, and cured at higher temperatures. The wood samples treated with these formulations were tested for their anti-swelling efficiency (ASE), leaching behavior, mechanical properties, and their resistance against fire, weathering and biological attack. Several tannin-treated specimens showed improved hardness and enhanced leaching and fire resistance. Some formulations also responded well to artificial weathering cycles, but natural weathering cycles deteriorated their performance. Samples treated with maleic anhydride showed improved leachability and high biological resistances, even without the addition of inorganic biocides. These organic and bio-friendly products can be considered as promising alternatives to heavy metal-based wood preservatives.

Top capping of nanosilver-loaded titania nanotubes with norspermidine-incorporated polymer for sustained anti-biofilm effects

Detrimental biofilms in water and wastewater treatment systems have become a great concern. Norspermidine is a potent inhibitor for biofilm growth through a non-biocidal mechanism. Nanosilver is a widely used and efficient inorganic biocide. In this study, using a titania nanotube (TNTs) array as the loading carrier of nanosilver and a norspermidine-incorporated polymer poly(lactic-co-glycolic acid) (PLGA) as the top cap of TNTs, a composite anti-biofilm coating (TNTs-Ag-PLGA/norspermidine) with multiple effects was fabricated, and its anti-biofilm efficiency against biofilms by wastewater mixed culture was investigated. Results showed that the addition of a PLGA/norspermidine cap to the top of TNTs greatly retarded silver ion release and extended antimicrobial validity. The TNTs-Ag-PLGA/norspermidine coating showed a biofilm inhibition of 48.42 ± 2.71% after 16 days of leaching, much higher than that without the PLGA/norspermidine cap (4.10 ± 3.32%). Confocal laser scanning microscopy (CLSM) showed that the biofilm attached to the surface of the TNTs-Ag-PLGA/norspermidine showed a much lower exopolysaccharide/exoprotein ratio (0.44) compared to the control (0.94), indicating that norspermidine incorporated into the PLGA layer could act on biofilm bacteria by reducing exopolysaccharides and destroying the EPS matrix. The TNTs-Ag-PLGA/norspermidine coating inhibited biofilm formation both through a killing mechanism by silver and a non-killing mechanism of norspermidine biofilm disassembly. The combination of nanosilver-loaded TNTs and a norspermidine-incorporated PLGA cap provides a novel and effective strategy to mitigate biofilm formation by wastewater mixed cultures and has potential application in water and wastewater treatment systems.

Corrosion and fouling protection performance of biocide-embedded hybrid organosiloxane coatings on mild steel in a saline medium

This work assessed the anticorrosion and antifouling properties of a novel sol-gel derived hybrid coating functionalized with 5 different organic and inorganic biocides. FTIR and NMR analysis of the newly synthesized polymeric base material confirmed the photo-induced organic polymerization of the allyl groups in the allyltrimethoxysilane precursor of the polymer and the inertness of the allyl groups in the allyl glycidyl ether precursor. The parent coating and biocide-embedded coatings were applied on mild steel sheets, cured with UV light, and subjected to thermal, morphological and electrochemical characterization. The cured coatings were thermally stable, and their hydrophobicity increased after immersion in a saline medium, owing to further polymer crosslinking. According to lab-based electrochemical and visual evaluations of the corrosion protection performance of the different formulations, the coating embedded with Irgarol and MOLY-white 101 had an improved performance, compared with the formulations with the other added biocides. Field testing results from the coated samples were consistent with the lab results; i.e., some biocides positively affected the anticorrosion and antifouling behavior of the hybrid coatings, whereas other biocides negatively affected the newly developed hybrid coating. The methodology reported here holds promise for the development of multifunctional hybrid sol-gel coatings for mild steel substrates with interesting anticorrosion and antifouling activities in saline.

Bonded Joints in Water-Repellent Timber Structures

Water in liquid and gaseous form is the main factor which significantly affects degradation processes in the wood. The mechanism and rate of wooden degradation processes can be effectively influenced by appropriate methods and technologies for its protection. However new knowledge, based on the possibilities of application of modern physical and chemical analytical methods, confirms that most well-known and previously commonly used protective equipment damages wooden structure. Many chemical substances, which are included in preservatives such as organic and inorganic biocides, or also flame retardants, are declared to be environmentally unacceptable. Nowadays, environmentally friendly treatment technologies of wood have increased attention to the above reasons. Wooden treatment by silicones ranks among the technologies which repellent, fire resistant and corrosion effectiveness is demonstrated by many authors. This article presents results of the experimental study that deals with the mechanical properties of bonded joints in the wood treated by silicones.

A small molecule norspermidine in combination with silver ion enhances dispersal and disinfection of multi-species wastewater biofilms.

Detrimental biofilms have become a great concern in many areas due to their strong resistance and insensitivity to traditional antimicrobial agents. Norspermidine is a potent small molecule for biofilm dispersal. In this study, silver ion, a conventional inorganic biocide, was combined with norspermidine and used for control and removal of multi-species biofilms formed by a mixed culture from wastewater treatment systems. Results showed that silver ion (0.01-1mg/L) treatment alone failed to remove the existing wastewater biofilms. Norspermidine at the concentrations of 500-1000μM was capable to disrupt and disperse the existing biofilms with a biofilm reduction of 21-34% after 24-h exposure. The combined treatment with norspermidine (500μM) and silver ion (0.01mg/L) increased biofilm reduction to 48% (24-h exposure). The combined treatment also enhanced biofilm disinfection ratio (82%, 2-h exposure) by 2.0- and 2.6-folds compared to norspermidine (27%) or silver ion (23%) treatment alone, respectively. Confocal laser scanning microscopic (CLSM) observations found that norspermidine could disrupt biofilm matrix and promote biofilm dispersal via breaking down exopolysaccharides. The combined treatment increased the reduction in biofilm cell density and viability, possibly due to the damage of biofilm matrix, enhanced silver ion diffusion in biofilms, and increased biofilm sensitivity. These findings indicate that the combination of a small molecule norspermidine with a traditional biocide silver ion presents a novel strategy to remove and kill biofilms, which have a potential application in addressing wastewater biofilm-related issues.

Antimicrobial polycarbonates for biomedical applications

BackgroundPolycarbonate (PC) is one of the most widely used engi-neering polymers due to its unusual combination of opti-cal clarity, heat resistance,high impact strength anddimensional stability over wide thermal range [1]. Lowwater absorption, ease of sterilization and biocompatibilityof PC have led to its use in a wide range of medical equip-ment, including critical medical devices [2]. The preven-tion of biofilm formation on the internal medical devicesis of great importance since it can initiate a degradationprocess of the material, as well as cause infections andhealth related problems [3]. In order to obtain antimicro-bial properties, polymers are usually compounded withorganic or inorganic biocides [4,5]. However, the use oforganic biocides as additives for PC is significantly limiteddue to their insufficient thermal stability in the tempera-ture range used for PC processing (300 – 320 °C).The aimof research was to develop novel low toxic biocides forPC having sufficient thermal stability for the joint meltprocessing with PC resin.Materials and methodsTwo kinds of potential antimicrobial additives for PC havebeen synthesized: imidazolium and guanidinium ionenes,as well as imidazolium based ionic liquids. PC films con-taining from 1 to 10 wt% of biocides were prepared by sol-vent casting or by compression molding methods. Thethermal stability of novel biocides as well as modified PCwas investigated by using thermogravimetric analysis(TGA). Antimicrobial testing of PC composites were per-formed using a model bacteriaPseudomonas fluorescensSBW25 with a help of classical microbiological methodsfor bacterial suspension as well as a live-dead assay forbiofilms [6].ResultsAccording to TGA data, the thermal stability of PC sam-ples containing biocidal additives was found to be in therange of 350-425

Mechanism of synergistic toxicity between organic pesticides and copper/zinc-containing inorganic pesticides

Current knowledge on the toxicity of chemicals comes primarily from studies conducted on individual chemicals at relatively high concentrations. However, throughout their lifetimes, people are more commonly exposed to a range of chemicals at low concentrations. From a public health perspective, a major concern is whether toxicity could result from the interaction of two or more chemicals. Both organic pesticides (such as pentachlorophenol and metam sodium) and copper- and zinc-containing inorganic compounds are used as general biocides and wood preservatives. They are commonly found together in the soil and ground water near the wood-preserving and wood-disposing facilities, and in bodily fluids and human tissue. Recently, we have found that combinations of pentachlorophenol and copper, each at non-toxic concentrations, resulted in an enhanced cytotoxic effect, via a synergistic mechanism, in a bacterial model. Similar synergistic effects were observed with metam sodium and copper or zinc. This synergism, observed for organic and inorganic biocides, was found to be related to the formation of lipophilic complexes, which facilitate metal transport into bacterial cells. We propose that interactions between organic and inorganic biocides, and the formation of lipophilic complexes, that lead to a synergistic toxicity, may serve as a new mechanism for toxicity. This hypothesis needs to be further investigated, both experimentally and theoretically.

Modelling inorganic biocide emission from treated wood in water

The objective of this work is to develop a chemical model for explaining the leaching behaviour of inorganic biocides from treated wood. The standard leaching test XP CEN/TS14429 was applied to a commercial construction material made of treated Pinus sylvestris (Copper Boron Azole preservative). The experimental results were used for developing a chemical model under PHREEQC ® (a geochemical software, with LLNL, MINTEQ data bases) by considering the released species detected in the eluates: main biocides Cu and B, other trace biocides (Cr and Zn), other elements like Ca, K, Cl, SO 4 −2, dissolved organic matter (DOC). The model is based on chemical phenomena at liquid/solid interfaces (complexation, ion exchange and hydrolysis) and is satisfactory for the leaching behaviour representation. The simulation results confronted with the experiments confirmed the hypotheses of: (1) biocide fixation by surface complexation reactions with wood specific sites (carboxyl and phenol for Cu, Zn, Cr(III), aliphatic hydroxyl for B, ion exchange to a lesser extent) and (2) biocide mobilisation by extractives (DOC) coming from the wood. The maximum of Cu, Cr(III) and Zn fixation occurred at neutral pH (including the natural pH of wood), while B fixation was favoured at alkaline pH.

Glass Powders with a High Content of Calcium Oxide: A Step Towards a “Green” Universal Biocide

AbstractIt is shown that soda‐lime glass powders (d &lt; 100 µm) with a content of CaO ranging from 15 to 20 wt‐% are strong inorganic biocide agents, with a logarithm of reduction &gt; 4, versus Gram‐positive and Gram‐negative bacteria, and yeasts. First, the glass particles are attached to the cell membrane; then, the Ca2+ lixiviated from the glass particles surface brings about membrane depolarization and subsequent death of the cells.

Potentials of Liquefied CCB Treated Waste Wood for Wood Preservation

Recovered wood is frequently contaminated with biocides and therefore its use is limited. Even more, wood, impregnated with classical chromated copper arsenate (CCA) preservatives is classifi ed as a hazardous waste, therefore solutions for reuse or recovery of this material are sought. One of the options, discussed in this paper is liquefaction and further applications of liquefi ed wood containing biocide remainings. In order to elucidate this possibilty, spruce and beech wood was impregnated with liquefi ed CCB treated and untreaded spruce wood of various concentrations and exposed to wood decay fungi according to the EN 113 procedure. In paralel, the leaching experiments (ENV 1250-2) were performed as well. The results do not clearly show that liquefi ed wood is bio-inactive. In most cases the mass loss by fungal attack is decreased compared to the untreated controls. On the other hand, copper leaching from spruce wood, impregnated with the liquefi ed CCB treated wood was signifi cantly reduced. Thus, there are indications that the liquefi ed wood could be utilized as a binding agent for inorganic biocides.

Biocide activity of diatom-silver nanocomposite

Diatom-nAg composites containing 1 wt.% of metallic silver nanoparticles (≤ 20 nm) have been obtained by a colloidal route and chemical reduction. This nanostructured powder has proved to be a selective green inorganic biocide which reduces the starting concentrations of Escherichia coli and Micrococcus luteus cultures by at least 5 orders of magnitude, while completely inactive against yeast. Diatom-nAg can be considered as a selective inorganic biocide particularly suitable for the food and pharmacological sectors. The silver nanoparticles are released from the diatom surface to the liquid media in a controlled manner, reaching a concentration (< 11 ppm) far below the toxicity limit for human cells.

Antimicrobial coatings on textiles–modification of sol–gel layers with organic and inorganic biocides

Antimicrobial textile materials were produced by sol–gel coatings with embedded biocidal compounds. For preparation a sol–gel procedure was used, starting from pure silica sols and 3-glycidyloxypropyltriethoxysilane (GLYEO) containing silica sols. These sols were modified with silver compounds, hexadecyltrimethyl-ammonium-p-toluolsulfonat (HTAT) and copper compounds, respectively. The investigations were performed on viscose fabrics as function of the concentration of biocidal compounds and of thermal treatment of textile after dip-coating between 80 up to 180 °C. The use of modified silica coatings leads to a decreased growth of fungi (Aspergillus niger) and bacteria (Bacillus subtilis and Pseudomonas putida) with increasing amount of the biocide embedded in the coating. The addition of GLYEO supports the biocidal effect of the coatings and enhances the stability of the coating solutions. For preparation of antimicrobial silica coatings the biocides silver, copper or HTAT can be used alone but the combination of these compounds leads to enhanced results against both fungi and bacteria. Therefore silica sols containing a combination of different types of biocides may be used for antimicrobial modification of textiles in some practical applications. For industrial applications the here presented coating solutions are especially advantageous, because of 90% water content in the solvent.

Occurrence of organic and inorganic biocides in the museum environment

In the museum environment organic and inorganic chemicals can be found, which originate from both outside and inside the building. Many of the contaminants may cause adverse effects on works of art and human health, but in the past, pollution research in museums has focused on the protection of artifacts, while the risk assessment for humans has been neglected. Especially, the application of biocides leads to a conflict of interest: on the one hand cultural assets have to be protected against microorganisms, insects and rodents while on the other hand it is essential to provide healthy conditions for museum staff and visitors. It has recently been shown that the release of organic indoor pollutants from building products is one of the main reasons for deterioration of artifacts. In this work, we present the results of screening measurements on biocides in different locations of German museums. The major components that could be identified were DDT, PCP, lindane, methoxychlor, naphthalene, chlorinated naphthalenes, 1,4-dichlorobenzene, PCBs and arsenic. It is demonstrated that the application of chlorinated organic compounds and arsenic for preventive conservation is one of the prime reasons for indoor pollution in museums and provides a potential for exposure. However, the concentrations in air, dust and material are widely different and a health risk for humans has to be evaluated case by case.

Partitioning of marine antifoulants in the marine environment.

The partitioning behaviour of the organic biocides, Irgarol 1051 and diuron and two inorganic biocides (copper and zinc) was investigated using six sediments of differing physico-chemical properties collected from unimpacted sites along the south coast of England. The kinetics of sorption and equilibrium partitioning between the sediments and seawater were investigated over a period of 20 days. Resulting organic carbon/water partition coefficients (log Koc) were related to suspended sediment concentration and ranged from 2.28 to 5.20 for diuron; and from 2.41 to 4.89 for Irgarol 1051. Sediment/water partition coefficients (log Kp) for copper and zinc varied from 2.46 to 5.08 l/kg and from 2.49 to 4.97 l/kg, respectively. Kinetic data indicated that there were significant interactions between the dissolved and particulate phases at the start of the experiments, just after mixing. This is thought to be a result of redistribution of organic carbon between the two phases.

An inorganic biocide using a novel presentation of silver

Synopsis A silver-based preservative system has been developed which overcomes difficulties often associated with metals, namely solubility, dispersion and toxicity. It comprises a silver chloride titanium dioxide composite which allows the controlled release of silver ions. Microbiological data has shown the composite to be active at concentrations less than 25 ppm against a wide range of micro-organisms, including Gram-negative non-fermentative bacteria, yeasts and moulds. The composite has satisfactory preservative activity against bacteria and fungi at application concentrations of between 50 ppm and 500 ppm, depending on the formulation. At high concentrations (>300 ppm) there may be some grey discoloration of the product, but the composite remains effective. To overcome this problem, a system of enhancing antimicrobial activity was devised, based on a sulphosuccinate salt dispersing agent. This allows lower concentrations of composite to be used whilst maintaining equivalent antimicrobial activity.