Pyrazine-Based Iodine-Containing Biocidal Materials: Enhanced Energy Performance and Reduced Corrosion Risk.

Biosafety is crucial to the common interests of all humanity. Currently, global biosafety governance is a challenge and poses significant opportunities. With the escalating challenges posed by microorganisms, there is an urgent need to develop advanced biocidal materials. In this work, we introduce a class of iodine-containing high-energy biocidal materials, utilizing pyrazine rings with good thermal stability as nitrogen-rich high-energy backbones, to address the issues of corrosion and hygroscopicity associated with N-H acidic protons in traditional iodine-containing azole compounds. Employing nucleophilic substitution and coupling reactions, we successfully synthesized two distinct series of eight compounds (Series A: BQDI, BQFI, BQDIO; Series B: BBQ3I, BBQ4I, BBQNI, MBQ5I, and MBQDI), which exhibit a high iodine content and enhanced detonation pressure. Notably, compounds BQDIO and BBQNI show detonation pressures of 13.70 and 16.52 GPa, respectively, both exceeding the 10 GPa of traditional iodine-containing biocidal materials. This improvement is crucial for expanding the diffusion range of biocidal substances and enhancing the biocidal efficiency of these materials. Pyrazine-based iodine-containing compounds have revolutionized the performance of biocidal materials, addressing corrosion issues and paving the way for the development of efficient, stable, and safe biocidal materials.

Preparation methods, applications, toxicity and mechanisms of silver nanoparticles as bactericidal agent and superiority of green synthesis method.

Silver nanoparticles (SNPs) are a type of nanomaterial with wide applications in water treatment, medicine, food packaging, and industrial processes. Their unique optical, electrical, thermal conductivity, and biological properties distinguish them from other metal ions and liken them to noble metals like gold and copper. The present review explores the diverse applications, preparation techniques, mechanism of action of SNPs, and properties of SNPs focusing on their bactericidal activities and potential impacts on human health. Different preparation methods, encompassing chemical, physical, and biological techniques, were reviewed and analyzed to comprehend their effect on the properties and applications of SNPs. Studies revealed that the SNPs exhibit excellent antibactericidal properties. Mechanisms underlying their antimicrobial effects were explored, primarily focusing on pathogen-scavenging activities. Despite the promising benefits of SNPs, their potential toxicity to human health must be carefully managed. Regulatory standards, such as those set by WHO and USEPA; establish a maximum tolerable limit of 0.1 mg/L to mitigate health risks associated with SNP exposure. It is recommended to continue research into safer applications and alternative formulations of SNPs to minimize potential health risks while maximizing their beneficial applications across different industries.

Microencapsulation of the Biocide Benzisothiazolinone (BIT) by Inclusion in Methyl-ß-cyclodextrin and Screening of Its Antibacterial and Ecotoxicity Properties.

The excessive use of biocides has considerable environmental and economic impacts; this is why new technologies have been sought to decrease the concentration levels applied in an effort to reduce the use of these substances. Microencapsulation using cyclodextrins has been widely used in the food and pharmaceutical industries as a way of reducing the concentrations of the active substance necessary to achieve a biological effect and/or eliminate its irritating or toxicological effects. In this study, the inclusion complexation behavior and binding ability of benzothiazolinone (BIT) with different ß-cyclodextrins (ß-CD, HP-ß-CD, and Me-ß-CD) was investigated. The intermolecular interactions were examined through UV and FTIR spectroscopy, DSC, 1D 1H NMR, and 2D ROESY. The highest stability constant was observed for the BIT/Me-ß-CD inclusion complex (299.5 ± 2.9 M-1). Antibacterial activity was investigated against Staphylococcus aureus and Escherichia coli, and the results revealed that the BIT/Me-ß-CD inclusion complex displays a higher antibacterial activity than BIT. The acute toxicity of the biocide and inclusion complex was also examined using the photobacterium Aliivibrio fischeri. Although BIT exhibited higher toxicity than the inclusion complex, further investigation is needed due to the quorum quenching effect of ß-CDs. The data found suggest that BIT microencapsulation can increase its aqueous solubility and can be used as an effective tool to improve its chemical, biological, and ecotoxicological properties.

Carbohydrate elicitor-induced plant immunity: Advances and prospects.

The perceived negative impacts of synthetic agrochemicals gave way to alternative, biological plant protection strategies. The deployment of induced resistance, comprising boosting the natural defense responses of plants, is one of those. Plants developed multi-component defense mechanisms to defend themselves against biotic and abiotic stresses. These are activated upon recognition of stress signatures via membrane-localized receptors. The induced immune responses enable plants to tolerate and limit the impact of stresses. A systemic cascade of signals enables plants to prime un-damaged tissues, which is crucial during secondary encounters with stress. Comparable stress tolerance mechanisms can be induced in plants by the application of carbohydrate elicitors such as chitin/chitosan, ß-1,3-glucans, oligogalacturonides, cellodextrins, xyloglucans, alginates, ulvans, and carrageenans. Treating plants with carbohydrate-derived elicitors enable the plants to develop resistance appliances against diverse stresses. Some carbohydrates are also known to have been involved in promoting symbiotic signaling. Here, we review recent progresses on plant resistance elicitation effect of various carbohydrate elicitors and the molecular mechanisms of plant cell perception, cascade signals, and responses to cascaded cues. Besides, the molecular mechanisms used by plants to distinguish carbohydrate-induced immunity signals from symbiotic signals are discussed. The structure-activity relationships of the carbohydrate elicitors are also described. Furthermore, we forwarded future research outlooks that might increase the utilization of carbohydrate elicitors in agriculture in order to improve the efficacy of plant protection strategies.

Protection motivation when using biocidal products - A survey study in Germany.

Due to their inherent properties, biocidal products might pose a risk to human and animal health and the environment. In risk management, there exists uncertainty about private users' comprehension of and willingness-to-adhere to use instructions that mitigate these risks (e.g., limit frequency of use or application area). This study aimed at providing insights into the users' perspective by focusing on their attention, comprehension, and the attitudinal predictors of protection motivation. In the online study (N = 957 participants from Germany) were introduced to a hypothetical purchase scenario featuring an insect spray and a realistic set of use instructions. Next, the participants' attention for the use instruction was measured in self-report and by tracking the time spent on the page with the use instruction, while Likert scale-type questions measured the comprehensibility, protection motivation, and predictors. Participants reported higher protection motivation if they spent more time with the use instruction, perceived it as comprehensible, rated the threat to humans, animals, and the environment as more severe, perceived themselves as responsible (i.e., internal locus of control) and capable (i.e., self-efficacy) of adhering to the use instructions, perceived adherence to the use instructions as effective (i.e., response efficacy) and did not perceive biocidal products as inherently safe (i.e., neutral locus of control). These results offer valuable information for an improved regulation of biocidal products and better management of potential risks associated with their use. They also provide concepts for interventions to ensure users of biocidal products follow the instructions for a safe use and better protection of the environment.

Insights into properties, synthesis and emerging applications of polypyrrole-based composites, and future prospective: A review.

Recent advancements in polymer science and engineering underscore the importance of creating sophisticated soft materials characterized by well-defined structures and adaptable properties to meet the demands of emerging applications. The primary objective of polymeric composite technology is to enhance the functional utility of materials for high-end purposes. Both the inherent qualities of the materials and the intricacies of the synthesis process play pivotal roles in advancing their properties and expanding their potential applications. Polypyrrole (PPy)-based composites, owing to their distinctive properties, hold great appeal for a variety of applications. Despite the limitations of PPy in its pure form, these constraints can be effectively overcome through hybridization with other materials. This comprehensive review thoroughly explores the existing literature on PPy and PPy-based composites, providing in-depth insights into their synthesis, properties, and applications. Special attention is given to the advantages of intrinsically conducting polymers (ICPs) and PPy in comparison to other ICPs. The impact of doping anions, additives, and oxidants on the properties of PPy is also thoroughly examined. By delving into these aspects, this overview aims to inspire researchers to delve into the realm of PPy-based composites, encouraging them to explore new avenues for flexible technology applications.

Impact of artificial accelerated ageing of PVC surfaces and surface degradation on disinfectant efficacy.

BACKGROUND: Standardized efficacy surface tests for disinfectants are performed on pristine surfaces. There is a growing interest in understanding the impact of surface ageing on disinfectant activity, owing for example to the increased usage of ultraviolet (UV) radiation and oxidative chemistries for surface decontamination. This acknowledges that general surface 'wear and tear' following UV radiation and oxidative biocide exposure may impact biocidal product efficacy. METHODS: PVC surfaces were aged through thermal and UV-A radiation (340 nm wavelength) following the use of standard ageing surface protocols to simulate natural surface degradation. Surface roughness, contact angle and scanning electron microscopy were performed to evaluate physical changes in PVC surfaces before and after artificial ageing. The efficacy of five pre-impregnated disinfectant wipes were evaluated using the ASTM E2967-15 on stainless-steel (control) and PVC surfaces (aged and non-aged). RESULTS: The type of formulation and the organism tested remained the most significant factors impacting disinfectant efficacy, compared with surface type. Both thermal ageing and UV-A exposure of PVC surfaces clearly showed signs of surface degradation, notably an increase in surface roughness. Physical changes were observed in the roughness of PVC after artificial ageing. A difference in disinfectant efficacy dependent on aged PVC surfaces was observed for some, but not all formulations. CONCLUSION: We showed that surface type and surface ageing can affect biocidal product efficacy, although in a non-predictable manner. More research is needed in this field to ascertain whether surface types and aged surfaces should be used in standardized efficacy testing.

Novel Biocomposite of Starch and Flax Fiber Modified with Tannic Acid with Biocidal Properties.

The purpose of this paper was to develop novel biocomposites with biocidal properties in microorganisms, with enhanced mechanical strength and hydrophobicity as well as with increased biodegradation rates. The main idea and the novelty of this work was to use cross-linking compounds and, at the same time, biocidal compounds-natural compounds of plant origin with biocidal properties. The authors assumed that the modification of flax fiber by natural plant compound will reduce the hydrophilicity of novel biocompositie. Biopolymer based on thermoplastic starch reinforced with flax fibres modified with tannic acid (TA) was prepared by extrusion and injection molding processes. The effects of TA modification on the mechanical and structural properties of biocomposites were analyzed through DMA, tensile tests, DSC, and TG. The biocidal and wettability properties of the biocomposites were investigated. The article also discusses the outcomes of research conducted on the structural characteristics and rates of the biodegradation of biocomposites.

A Perspective Looking Backward and Forward on the 25th Anniversary of Conjugated Polyelectrolytes.

Conjugated polyelectrolytes are π-conjugated polymers that contain ionic charged groups such as sulfonate (R-SO3-), carboxylate (R-COO-), or ammonium (R-NR3+) combined with a π-conjugated backbone. This perspective provides a summary review of the key developments in the field, starting from the first reports of their synthesis and properties to application-focused developments. The applications include optical sensors for molecular and biomolecular targets, organic electronic applications, and specific biological applications including cellular imaging and photodynamic therapy. This perspective concludes with a discussion of where the field of conjugated polyelectrolytes is expected to lead in the coming years.

A neoteric antibacterial ceria-silver nanozyme for abiotic surfaces.

Community-associated and hospital-acquired infections caused by bacteria continue to yield major global challenges to human health. Bacterial contamination on abiotic surfaces is largely spread via high-touch surfaces and contemporary standard disinfection practices show limited efficacy, resulting in unsatisfactory therapeutic outcomes. New strategies that offer non-specific and broad protection are urgently needed. Herein, we report our novel ceria-silver nanozyme engineered at a molar ratio of 5:1 and with a higher trivalent (Ce3+) surface fraction. Our results reveal potent levels of surface catalytic activity on both wet and dry surfaces, with rapid, and complete eradication of Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin resistant S. aureus, in both planktonic and biofilm form. Preferential electrostatic adherence of anionic bacteria to the cationic nanozyme surface leads to a catastrophic loss in both aerobic and anaerobic respiration, DNA damage, osmodysregulation, and finally, programmed bacterial lysis. Our data reveal several unique mechanistic avenues of synergistic ceria-Ag efficacy. Ag potentially increases the presence of Ce3+ sites at the ceria-Ag interface, thereby facilitating the formation of harmful H2O2, followed by likely permeation across the cell wall. Further, a weakened Ag-induced Ce-O bond may drive electron transfer from the Ec band to O2, thereby further facilitating the selective reduction of O2 toward H2O2 formation. Ag destabilizes the surface adsorption of molecular H2O2, potentially leading to higher concentrations of free H2O2 adjacent to bacteria. To this end, our results show that H2O2 and/or NO/NO2-/NO3- are the key liberators of antibacterial activity, with a limited immediate role being offered by nanozyme-induced ROS including O2•- and OH•, and likely other light-activated radicals. A mini-pilot proof-of-concept study performed in a pediatric dental clinic setting confirms residual, and continual nanozyme antibacterial efficacy over a 28-day period. These findings open a new approach to alleviate infections caused by bacteria for use on high-touch hard surfaces.

Micro-Addition of Silver to Copper: One Small Step in Composition, a Change for a Giant Leap in Biocidal Activity.

The use of copper as an antimicrobial agent has a long history and has gained renewed interest in the context of the COVID-19 pandemic. In this study, the authors investigated the antimicrobial properties of an alloy composed of copper with a small percentage of silver (Cu-0.03% wt.Ag). The alloy was tested against various pathogens, including Escherichia coli, Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa, and the H1N1 virus, using contact exposure tests. Results showed that the alloy was capable of inactivating these pathogens in two hours or less, indicating its strong antimicrobial activity. Electrochemical measurements were also performed, revealing that the small addition of silver to copper promoted a higher resistance to corrosion and shifted the formation of copper ions to higher potentials. This shift led to a slow but continuous release of Cu2+ ions, which have high biocidal activity. These findings show that the addition of small amounts of silver to copper can enhance its biocidal properties and improve its effectiveness as an antimicrobial material.

GC-MS profiling, antifeedant, nematicidal and phytotoxic effects of essential oils of two subspecies of Eucalyptus flocktoniae (Maiden) Maiden.

This work presents the biocidal effects and chemical compositions of two essential oils (EOs) obtained by hydrodistillation of Eucalyptus flocktoniae subsp. flocktoniae and E. flocktoniae subsp. hebes. The two subspecies studied had different chemical composition, when analysed by gas chromatography coupled to mass spectrometry with 1,8-cineole (56.98%), trans-pinocarveol (20.38%) and α-pinene (5.86%) being the major components of E. flocktoniae subsp. flocktoniae and spathulenol (25.09%), p-cymene (21.20%), 1,8-cineole (10.74%) and α-pinene (8.93%) are the major components of E. flocktoniae subsp. hebes. These oils were evaluated for their insect antifeedant, nematicidal and phytotoxic activities. The biocidal tests showed that E. flocktoniae subsp. hebes was the most active against Myzus persicae and Rhopalosiphum padi. While, E. flocktoniae subsp. flocktoniae was not antifeedant. None of the investigated EOs were active against both Spodoptera littoralis and Meloidogyne javanica root-knot nematode. Moreover, the EOs extracted from these two subspecies showed a significant phytotoxic effect.

Magnesium and manganese induced changes on chemical, nutritional, antioxidant and antimicrobial properties of the pansy and Viola edible flowers.

Pansy and viola edible flowers were grown hydroponically with different levels of Mg and Mn. The nutritional composition was determined using standard methods. Free sugars, fatty acids, organic acids, tocopherols, and phenolic compounds were analyzed using various HPLC and GC devises. The extract's antimicrobial, antioxidant, cytotoxicity, and anti-inflammatory activity were assessed. The results indicated that Mg enrichment negatively affected plant growth and mineral accumulation but improved photosynthetic performance. The edible flowers contained significant amounts of protein, low levels of fat, and varying sugar contents, such as glucose and fructose. Various fatty acids and phenolic compounds were identified, with different concentrations depending on the treatment. The flowers exhibited antioxidant potential, antimicrobial activity, cytotoxic effects, and anti-inflammatory properties. The correlations between the investigated parameters not only expand knowledge on Mg and Mn interaction but also catalyze significant advancements in sustainable agriculture and food health, fostering a healthier and more conscious future.

Biocidal products: Opportunities in risk assessment, management, and communication.

In the coronavirus disease 2019 era, biocidal products are increasingly used for controlling harmful organisms, including microorganisms. However, assuring safety against adverse health effects is a critical issue from a public health standpoint. This study aimed to provide an overview of key aspects of risk assessment, management, and communication that ensure the safety of biocidal active ingredients and products. The inherent characteristics of biocidal products make them effective against pests and pathogens; however, they also possess potential toxicities. Therefore, public awareness regarding both the beneficial and potential adverse effects of biocidal products needs to be increased. Biocidal active ingredients and products are regulated under specific laws: the Federal Insecticide, Fungicide, and Rodenticide Act for the United States; the European Union (EU) Biocidal Products Regulation for the EU; and the Consumer Chemical Products and Biocide Safety Management Act for the Republic of Korea. Risk management also needs to consider the evidence of enhanced sensitivity to toxicities in individuals with chronic diseases, given the increased prevalence of these conditions in the population. This is particularly important for post-marketing safety assessments of biocidal products. Risk communication conveys information, including potential risks and risk-reduction measures, aimed at managing or controlling health or environmental risks. Taken together, the collaborative effort of stakeholders in risk assessment, management, and communication strategies is critical to ensuring the safety of biocidal products sold in the market as these strategies are constantly evolving.

Synthesis, spectral characterisation, biocidal investigation, in-silico and molecular docking studies of 4-[(2-chloro-4-methylphenyl)carbamoyl]butanoic acid derived triorganotin(IV) compounds.

Three triorganotin(IV) compounds, R3Sn(L), with R = CH3 (1), n-C4H9 (2) and C6H5 (3), and LH = 4-[(2-chloro-4-methylphenyl)carbamoyl]butanoic acid, were prepared and confirmed by various techniques. A five-coordinate, distorted trigonal-bipyramidal geometry was elucidated for tin(IV) centres both in solution and solid states. An intercalation mode was confirmed for the compound SS-DNA interaction by UV-visible, viscometric techniques and molecular docking. MD simulation revealed stable binding of LH with SS-DNA. Anti-bacterial investigation revealed 2 to be generally the most potent, especially against Sa and Ab, i.e. having the lowest MIC values (≤0.25 µg/mL) compared to the standard anti-biotics vancomycin-HCl (MIC = 1 µg/mL) and colistin-sulphate (MIC = 0.25 µg/mL). Similarly, the anti-fungal profile shows 2 exhibits 100% inhibition against Ca and Cn fungal strains and has MIC values (≤0.25 µg/mL) comparatively lower than standard drug fluconazole (0.125 and 8 µg/mL for Ca and Cn, respectively). Compound 2 has the greatest activity with CC50 ≤ 25 µg/mL and HC50 > 32 µg/mL performed against HEC239 and RBC cell lines. The anti-cancer potential was assessed against the MG-U87 cell line, using cisplatin as the standard (133 µM), indicates 2 displays the greatest activity (IC50: 5.521 µM) at a 5 µM dose. The greatest anti-leishmanial potential was observed for 2 (87.75 at 1000 µg/mL) in comparison to amphotericin B (90.67). The biological assay correlates with the observed maximum of 89% scavenging activity exhibited by 2. The Swiss-ADME data publicised the screened compounds generally follow the rule of 5 of drug-likeness and have good bioavailability potential.

Biocidal and synergistic effect of three types of biologically synthesised silver/silver chloride nanoparticles.

Three types of silver/silver chloride nanoparticles were obtained by green synthesis from three types of microbial biomass. Their biocidal capacity was tested against six microorganisms. Two filamentous fungi were used that had previously demonstrated the ability to synthesise nanoparticles, Penicillium sp. 8L2 and Botryosphaeria rhodina MAMB-05. Also, the synthesis capacity of a yeast, Rhodotorula mucilaginosa 1S1, was evaluated. The original protocols underwent slight modifications. At the same time, the fractional inhibitory concentration was obtained. The interaction between specific antibiotics and the nanoparticles that showed the greatest biocidal capacity came from Penicillium sp.8L2, and it was studied further. All nanoparticles were characterised by UV-vis spectrophotometry and transmission electron microscopy (TEM). Also, their size distribution was analysed, which was in the range of 4 to 34 nm. The biocidal capacity of the nanoparticles for a group of bacteria and fungi was studied, presenting very low values in the range of 2.5-10 µg/mL for bacteria and 4-256 µg/mL for fungi. The interactions between the nanoparticles synthesised by Penicillium sp. 8L2 and a group of specific antibiotics for the tested microorganisms were also studied, proving that there was a synergistic interaction with vancomycin and ciprofloxacin and Staphylococcus epidermidis CECT 4183 and Escherichia coli CECT 101 bacteria, respectively.

Green Hydrogels Loaded with Extracts from Solanaceae for the Controlled Disinfection of Agricultural Soils.

The UN 2030 Agenda for Sustainable Development established the goal of cutting the use of pesticides in the EU by 50% by 2030. However, a ban on pesticides could seriously affect the productivity of agriculture, resulting in severe issues due to global hunger and food deficiency. Controlled release (CR) of bioactive chemicals could play a valid alternative in this context. To this aim, two biodegradable polymers, namely sodium alginate (AL) and sodium carboxymethylcellulose (CMC), were employed to obtain crosslinked hydrogel beads for the encapsulation and CR of glycoalkaloids extracted from tomato and potato leaves to be used as biocompatible disinfectants for agricultural soils. The physico-chemical characterization of the controlled-release systems was carried out by means of Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, Scanning Electron Microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC) (FWI > 80%) and drying kinetics. The plant extracts and the encapsulation efficiency (~84%) were, respectively, characterized and evaluated by High-performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). Finally, preliminary microbiological tests were conducted to test the efficacy of the most promising systems as biocidal formulations both in the lab and on a model soil, and interesting results were obtained in the reduction of bacterial and fungal load, which could lead to sustainable perspectives in the field.

Cellulose-Based Metallogels-Part 3: Multifunctional Materials.

The incorporation of the metal phase into cellulose hydrogels, resulting in the formation of metallogels, greatly expands their application potential by introducing new functionalities and improving their performance in various fields. The unique antiviral, antibacterial, antifungal, and anticancer properties of metal and metal oxide nanoparticles (Ag, Au, Cu, CuxOy, ZnO, Al2O3, TiO2, etc.), coupled with the biocompatibility of cellulose, allow the development of composite hydrogels with multifunctional therapeutic potential. These materials can serve as efficient carriers for controlled drug delivery, targeting specific cells or pathogens, as well as for the design of artificial tissues or wound and burn dressings. Cellulose-based metallogels can be used in the food packaging industry to provide biodegradable and biocidal materials to extend the shelf life of the goods. Metal and bimetallic nanoparticles (Au, Cu, Ni, AuAg, and AuPt) can catalyze chemical reactions, enabling composite cellulose hydrogels to be used as efficient catalysts in organic synthesis. In addition, metal-loaded hydrogels (with ZnO, TiO2, Ag, and Fe3O4 nanoparticles) can exhibit enhanced adsorption capacities for pollutants, such as dyes, heavy metal ions, and pharmaceuticals, making them valuable materials for water purification and environmental remediation. Magnetic properties imparted to metallogels by iron oxides (Fe2O3 and Fe3O4) simplify the wastewater treatment process, making it more cost-effective and environmentally friendly. The conductivity of metallogels due to Ag, TiO2, ZnO, and Al2O3 is useful for the design of various sensors. The integration of metal nanoparticles also allows the development of responsive materials, where changes in metal properties can be exploited for stimuli-responsive applications, such as controlled release systems. Overall, the introduction of metal phases augments the functionality of cellulose hydrogels, expanding their versatility for diverse applications across a broad spectrum of industries not envisaged during the initial research stages.

Biodegradable Water-Soluble Matrix for Immobilization of Biocidal 4-Hexylresorcinol.

Biocidal coatings have been used in biomedicine, cosmetology and the food industry. In this article, the coatings are described as being composed of non-stoichiometric polycomplexes, products of electrostatic coupling of two commercial biodegradable ionic polymers, anionic sodium alginate and cationic quaternized hydroxyethyl cellulose ethoxylate. Non-stoichiometric polycomplexes with a 5-fold excess of the cationic polymer were used for immobilizing hydrophobic biocidal 4-hexylresorcinol (HR). Being dispersed in water, the polycomplex particles were capable of absorbing a tenfold excess of HR in relation to the polycation. After deposition onto the plastic surface and drying, the aqueous polycomplex-HR composite formulation forms a transparent homogeneous coating, which swells slightly in water. The interpolyelectrolyte complex (IPEC) is substantially non-toxic. The incorporation of HR in the IPEC imparts antimicrobial activity to the resulting composite, in both aqueous solutions and coatings, against Gram-negative and Gram-positive bacteria and yeast. The polysaccharide-based polycomplexes with embedded HR are promising for the fabrication of biocidal films and coatings.

Peracetic acid activated by ferrous ion mitigates sulfide and methane production in rising main sewers.

Iron-based peracetic acid (PAA) advanced oxidation process (AOP) is widely used in water purification because of its high efficiency and low toxicity. In this study, for the first time, ferrous iron (Fe2+) and PAA were dosed jointly into the rising main sewer reactor, to verify the feasibility of sulfide and methane control as well as investigate the comprehensive mechanism of Fe2+/PAA on sewer biofilm. Results demonstrated the superior biocidal effect of Fe2+/PAA dosing than that of PAA alone. Intermittent Fe2+/PAA dosing showed that the average inhibitory rate of sulfide production rate (SPR) and methane production rate (MPR) was 52.0% and 29.9%, respectively, at a Fe2+/PAA molar ratio of 1:1 and PAA concentration of 3 mmol/L (i.e., the mass-based concentrations of Fe2+ and PAA were 6.79 mg-Fe/L and 228 mg/L, respectively). Beside, sewer biofilm was found to be resistant to PAA during repeated dosing events. However, resistance could be alleviated by introducing sulfide in situ in the Fe2+/PAA process, and SPR and MPR were further reduced to 27.39% and 67.32% of the control, respectively. LIVE/DEAD Staining showed that Fe2+/PAA exhibited a strong destructive effect on microbial cells, with the proportion of viable cells being 26.34%. Electron paramagnetic resonance (EPR) and free radical quenching results indicated that the inhibitory order was R-O• > •OH > Fe(IV), which led to the disruption of cellular integrity (i.e., 17.24% increase in LDH) and intracellular enzyme system (i.e., cellular metabolic disorders). Microbial analysis revealed that long-term Fe2+/PAA dosing decreased the sulfate-reducing bacteria (SRB) abundance, and the dominant genus of methanogenic archaea (MA) shifted from Methanofastidiosum, Methanobacterium to Methanosaeta. The cost of Fe2+/PAA dosing on methane and sulfide control in rising main sewers was $1.81/kg-S, economically and environmental-friendly attractive for practical applications.