Bleach Solution Research Articles

Thermal Infrared Enthalpimetry Method for the Determination of Hypochlorite in Bleaching Solutions

Thermal infrared enthalpimetry (TIE) was used for hypochlorite determination in commercial hypochlorite-based bleaching solutions. Experimental parameters were evaluated for the reaction with a hydrogen peroxide solution. The most relevant conditions were 5% H2O2 (m/m) solution, stirring speed of 250 rpm, dispensing rate of 0.57 mL s-1, and 10 s after reaction for the simultaneous temperature readings of four replicates. Agreement to reference method NBR 9425 ranging from 98.2 to 103.2% was achieved, with a low variation among measurements (relative standard deviation < 3.5%). The number of analytical operations was reduced, and only H2O2 solution was required as a greener reagent. A low amount of residues was generated (2.4 and 152.8 mL for each replicate in TIE and official method, respectively), and the application of the green analytical procedure index (GAPI) showed the greenness of the proposed method.

Establishing an energy-saving scouring/bleaching one-step process for cotton/spandex fabric using UVA-assisted irradiation.

To reduce the energy and water consumption from a conventional textile industry, a facile and efficient UVA-assisted scouring/bleaching strategy has been customized for cotton/spandex in this research. The bleaching efficacy under UVA irradiation is explored by comparing diverse processes, i.e., Scouring only (Sc.); Conventional scouring and pad-steam bleaching (Sc/BlConv-PS); Conventional scouring and cold pad-batch bleaching (Sc/BlConv-CPB); and one or two-step scouring and UVA-assisted bleaching (Sc/BlUVA-I, Sc/BlUVA-II). The significance, interactive effect and optimisation of parameters on the whiteness index (WI) of fabric are investigated through mathematical modelling. The bleaching mechanism is analysed by a fluorescence labelling method. The dyeing and tensile properties of fabrics and the energy conservation during processing are also demonstrated. Results show that Sc/BlUVA-I achieves an equivalent scouring and bleaching effect as Sc/BlUVA-II. A superior bleaching effect of Sc/BlUVA-II over that of Sc/BlConv-PS reveals the better function of catalytic UVA than conventional steam. Under the theoretical optimal bleaching conditions (H2O2 conc. 42.96 g L−1, pH 10.24 and irradiation time 3.68 h), a calculated highest WI of 77.19 (1.48 times higher than that of untreated fabric) can be achieved based on the mathematical modelling. Through mechanism studies, hydroxyl radicals are confirmed as the main oxidative species taking part in UVA-assisted bleaching and their concentration in simulated bleaching solution dramatically increases upon the introduction of UVA. The fabric treated by Sc/BlUVA-I exhibits an acceptable strength decrease (<10%) and excellent dyeing performance with reactive dyes. The Sc/BlUVA-I strategy enables more than ca. 70% of energy conservation than the Sc/BlConv-PS process. The encouraging results manifest the practicability and promising prospects of UVA-assisted pre-treatment which contributes to enhancing the sustainability of the textile industry.

Evaluation of the effects of repeated disinfection on medical exam gloves: Part 1. Changes in physical integrity

COVID-19 has created shortages of personal protective equipment. In resource-constrained situations, limited cycles of disinfection and extended use of gloves is recommended by the U.S. Centers for Disease Control and Prevention to conserve supplies. However, these guidelines are based on limited evidence. In this study, serial cycles of hand hygiene were performed on gloved hands using an ethanol-based hand rub (six and 10 cycles), 0.1% sodium hypochlorite (bleach) solution (10 cycles), or soap and water (10 cycles) on latex and nitrile medical exam gloves from the United States and India. A modified water-leak test evaluated glove integrity after repeated applications of these disinfecting agents. When aggregated, dilute bleach demonstrated the lowest difference between treatment and control arms: −2.5 percentage points (95% CI: −5.3 to 0.3) for nitrile, 0.6 percentage points (95% CI: −2.6 to 3.8) for non-powdered latex. For U.S.-purchased gloves tested with six and 10 applications of ethanol-based hand rub, the mean difference in failure risk between treatment and control gloves was within the prespecified non-inferiority margin of five percentage points or less, though some findings were inconclusive since outside the margin. The aggregated difference in failure risk between treatment and control was 3.5 percentage points (0.6 to 6.4) for soap and water, and 2.3 percentage points (−0.5 to 5.0) and 5.0 percentage points (1.8 to 8.2) for 10 and 6 applications of ethanol-based hand rub, respectively. Most leaks occurred in the interdigital webs (35%) and on the fingers (34%). This indicates that some combinations of glove types and disinfection methods may allow for extended use. Ten applications of dilute bleach solution had the least impact on glove integrity. However, the majority of glove and exposure combinations were inconclusive. Additional testing of specific glove and disinfectant combinations may inform future strategies to guide extended use during glove shortages. Additional considerations, not evaluated here, include duration of use, disinfectant chemical permeation, and the effects of hand temperature, movement, and manipulation of instruments on glove integrity.

Fabrication of a Simple and Cheap Screen‐printed Silver/Silver Chloride (Ag/AgCl) Quasi‐reference Electrode

AbstractIn this work, a silver/silver chloride ink is fabricated using two steps. First the silver ink is prepare using silver, nail polish and acetone. Then the silver ink is painted in a paper substrate and a silver chloride layer is deposited using a bleach solution. The result is the silver/silver chloride conductive ink. The silver ink is cheap ($2.49/g), well‐dispersive and very easy to fabricate. The materials were characterized by SEM and XRD. The Ag ink showed the formation of a continuous network throughout the silver ink film with fewer agglomeration. The effective chlorination process was also observed in the Ag/AgCl characterization. Since the Ag/AgCl substrate will be used as a quasi‐reference electrode, it is important to investigate the electrical properties. The Ag ink showed an average ohmic resistance of 2.27 Ω. The addition of the AgCl layer decreases the conductivity, as expected. In summary, the Ag/Ag/Cl ink developed is simple, well‐dispersed, cheap and with good conductivity. Therefore, it can be used as a conductive ink in the fabrication of quasi‐reference electrodes.

Отбелка микрокристаллической целлюлозы, полученной методом газофазного гидролиза

One of the main consumers of microcrystalline cellulose (MCC) is the pharmaceutical industry, where MCC is used as a binder and filler in direct compression of tablets. MCC is produced by acidic hydrolysis of cellulose, which usually results in a decrease in whiteness. This is due to the destruction of sugars formed during hydrolysis and the subsequent formation of colored products. The composition and properties of these products depend on the method of hydrolysis, acid concentration, temperature, and process duration. One of the most promising methods for producing MCC is gas-phase hydrolysis of cellulose with hydrogen chloride gas-air mixtures. The method has a high rate of hydrolysis, low reagent and energy consumption. The requirements of the pharmaceutical industry determine the need to produce MCC with high whiteness. The research purpose is to select bleaching modes for MCC using sodium hypochlorite and hydrogen peroxide as bleaching agents. MCC produced by gas-phase hydrolysis of bleached wood pulp was used during the study. The whiteness and intensity of the yellow tint of MCC in the bleaching process were determined by digital colorimetry on a flatbed scanner. The paper shows that sodium hypochlorite and hydrogen peroxide allow achieving the whiteness not less than 90 % and the intensity of the yellow tint not more than 3 standard units. High-quality bleaching can be carried out even for MCC samples with an initial whiteness of about 40 %. The most effective bleaching agent is sodium hypochlorite when the pH of the bleaching solution is 2–3. Hydrogen peroxide also provides high whiteness of MCC at pH of 10–11. However, the consumption of active oxygen (AO) for bleaching is more than three times higher in comparison with the consumption of active chlorine (ACh). It was found that the dyes of MCC produced by gas-phase hydrolysis consist of two chromophore groups that decolorize at different rates. The easily oxidized group of components makes up about 90 % of the total amount of dyes, and the resistant to oxidation components make up about 10 % and determine the intensity of the yellow tint of MCC. The modes of bleaching MCC with sodium hypochlorite and hydrogen peroxide to product samples with whiteness comparable to that of imported samples were determined. For citation: Sizov A.I., Pimenov S.D., Stroiteleva A.D., Stroiteleva K.D. Bleaching of Microcrystalline Cellulose Produced by Gas-Phase Hydrolysis. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 173–183. DOI: 10.37482/0536-1036-2021-6-173-183

Widely used charcoal analysis method in paleo studies involving NaOCl results in loss of charcoal formed below 400°C

This study investigated the effects a dilute solution of bleach (4% sodium hypochlorite), has on charcoal. We were particularly interested in considering if charcoal formed under different conditions of pyrolysis was differentially affected by this treatment, which is commonly used for the quantification of charcoal in sediments. We first produced a series of charcoal samples, under laboratory conditions (at temperatures between 250°C and 800°C and under oxygen limited conditions) and then measured total surface area of charcoal before and after treatment in a solution of 4% bleach. We found that charcoal formed ⩽400°C showed nearly complete bleaching after 24 h, while high temperature charcoal (&gt;400°C) was much more resistant. These results indicate this treatment bleaches charcoal formed at lower temperatures: this means particles charred at low temperature may not be quantified in common optical counting or image analysis methods. This could have serious ramifications for sediment-based paleofire research as low intensity fire may be lost from a record, and the resulting fire history biased towards high intensity (high temperature) fires. Our findings suggest the need for a new, non-destructive method for extracting charcoal from sediment.

Effects of consumer surface sterilization on diet DNA metabarcoding data of terrestrial invertebrates in natural environments and feeding trials.

DNA metabarcoding is an emerging tool used to quantify diet in environments and consumer groups where traditional approaches are unviable, including small‐bodied invertebrate taxa. However, metabarcoding of small taxa often requires DNA extraction from full body parts (without dissection), and it is unclear whether surface contamination from body parts alters presumed diet presence or diversity.We examined four different measures of diet (presence, rarefied read abundance, richness, and species composition) for a terrestrial invertebrate consumer (the spider Heteropoda venatoria) both collected in its natural environment and fed an offered diet item in contained feeding trials using DNA metabarcoding of full body parts (opisthosomas). We compared diet from consumer individuals surface sterilized to remove contaminants in 10% commercial bleach solution followed by deionized water with a set of unsterilized individuals.We found that surface sterilization did not significantly alter any measure of diet for consumers in either a natural environment or feeding trials. The best‐fitting model predicting diet detection in feeding trial consumers included surface sterilization, but this term was not statistically significant (β = −2.3, p‐value = .07).Our results suggest that surface contamination does not seem to be a significant concern in this DNA diet metabarcoding study for consumers in either a natural terrestrial environment or feeding trials. As the field of diet DNA metabarcoding continues to progress into new environmental contexts with various molecular approaches, we suggest ongoing context‐specific consideration of the possibility of surface contamination.

ECO-DESIGN: IMPACTS OF BLEACHING CHEMICALS AND VARNISHES ON THE AMOUNT OF CARBON DIOXIDE IN THE COMBUSTION OF ORIENTAL BEECH (FAGUS ORIENTALIS LIPSKY)

This study was carried out to determine the effects of bleaching chemicals and varnishes on the amount of carbon dioxide (CO2) in the combustion of oriental beech (Fagus orientalis Lipsky). For this purpose, samples of Oriental beech prepared according to ASTM D 358 contain 18% R1 = (NaOH + H2O2), R2 = (NaOH + Ca(OH)2 + H2O2), R3 = (Na2S2O5 + H2C2O4), R4 = (NaSiO3 + H2O2), R5 = (KMnO4 + Na2S2O5 + H2O2) solution groups, after bleaching with solution groups, water based, synthetic, polyurethane and acrylic varnish were applied according to ASTM D 3023 and combustion tests were carried out in accordance with ASTM E 160-50. Gas measurements were made with the SIGMA 74172 NSU flue gas device during the combustion process. As a result, in respect to the burning types; the highest amount of CO2 (ppm) was found in the self-combustion (8.468 ppm) while the lowest was obtained from the flame combustion source (4.599 ppm). In respect to the types of bleaching; the highest in R5 (7.458 ppm) and the lowest in R3 (4.059 ppm) were found. According to the varnish types; the highest value was found in the synthetic varnish (8.261), and the lowest value was found in the acrylic varnish (4.772 ppm). According to combustion type + bleaching solution + varnish type interaction, the highest values were found for without flame combustion (II) + R3 + Sn (18.40 ppm) and lowest for flame source combustion (I) + R5 + Pu (0.600 ppm). Consequently, the highest values for combustion gases were found in samples of oriental beech wood samples treated with water-based varnish with R1 solution. According to this, in terms of human health and life safety, possibility of fire in places, R3 solution and acrylic varnish may be used in the related industries.

OPTIMIZATION OF DITHIONITE BLEACHING OF HIGH YIELD BAGASSE PULP

Non-wood raw materials are an essential fiber source in regions where forest resources are limited. Therefore, chemi-mechanical high-yield bagasse pulp was prepared and then bleached with a dithionite bleaching agent. One- and two-stage bleaching of the pulp was carried out by using sodium dithionite (Y) as a sole bleaching agent, or after bleaching with hydrogen peroxide to achieve high brightness for the prepared pulp. Different parameters, such as consistency, concentration, temperature, time and pH were investigated. The effect of various additives, such as diethylenetriaminepentaacetic acid (DTPA) as chelating agent or Zn compounds and hexamethylenetetramine to stabilize the bleaching solution, was studied. The effect of dissolved oxygen in liquor was also considered.

Rapid Biocidal Activity of N-Halamine-Functionalized Polydopamine and Polyethylene Imine Coatings.

Microorganisms easily adhere to the surface of substrates and further form biofilms, which present problems in various fields. Therefore, the development of surfaces with antimicrobial adhesion or viability is a promising approach. In this study, we were committed to develop a rapid sterilizing coating. First, polyester fibers were immersed into a mixing solution of dopamine (PDA) and polyethyleneimine (PEI) for forming the co-deposition of PDA and PEI coatings. After this, the co-deposition of PDA and PEI coatings was immersed in a solution of household bleach for chlorination. We found that the nitrogens of PDA and PEI could be chlorinated repeatedly and that the oxidative chlorine content increased with the increasing PEI concentration upon co-deposition. Next, the efficacy of the co-deposition of chlorinated PDA and PEI coatings in eliminating Staphylococcus aureus and Escherichia coli was investigated. We found that the antibacterial ability of the coatings increased with increasing PEI content. In addition, the chlorinated co-deposition coatings had significantly improved antibacterial properties compared to the unchlorinated ones. The chlorinated co-deposition coatings inactivated >99.99% of S. aureus and >99.9% of E. coli after contact of less than 10 min. Therefore, chlorination of a PDA/PEI co-deposition surface is a feasible method for use in antibacterial coatings.

Bird-feeder cleaning lowers disease severity in rural but not urban birds

Animals inhabiting urban areas often experience elevated disease threats, putatively due to factors such as increased population density and horizontal transmission or decreased immunity (e.g. due to nutrition, pollution, stress). However, for animals that take advantage of human food subsidies, like feeder-visiting birds, an additional mechanism may include exposure to contaminated feeders as fomites. There are some published associations between bird feeder presence/density and avian disease, but to date no experimental study has tested the hypothesis that feeder contamination can directly impact disease status of visiting birds, especially in relation to the population of origin (i.e. urban v. rural, where feeder use/densities naturally vary dramatically). Here we used a field, feeder-cleaning experimental design to show that rural, but not urban, house finches (Haemorhous mexicanus) showed increased infection from a common coccidian endoparasite (Isospora spp.) when feeders were left uncleaned and that daily cleaning (with diluted bleach solution) over a 5-week period successfully decreased parasite burden. Moreover, this pattern in rural finches was true for males but not females. These experimental results reveal habitat- and sex-specific harmful effects of bird feeder use (i.e. when uncleaned in rural areas). Our study is the first to directly indicate to humans who maintain feeders for granivorous birds that routine cleaning can be critical for ensuring the health and viability of visiting avian species.

Influence of microwave-assisted chemical treatment on delignification of rice straw biomass

Lignocellulosic biomass (like rice straw) provides an alternative for depleting non-renewable energy sources through its value-added utilization (like production of biofuels and nanocellulose) owing to its abundance, renewability, polymer presence and environmental friendliness. Prior to its utilization, any lignocellulosic biomass is subjected to a time-consuming delignification process for lignin free biomass recovery. The present study aims to reduce the time of delignification of rice straw along with enhancing the delignification percentage of biomass by use of microwave assisted sodium chlorite method. The experiments were done at two microwave power levels (640, 800 W), three bleaching solution concentrations (0.4, 1.7, 3.0 %) and three microwave treatment times (4, 8, 12 min). The delignification percentage of the rice straw for the whole experimentation varied from 24.7 to 90.12%. The results revealed that the time of delignification was greatly reduced (12 min) with a very high delignification (90.12%) percentage. The morphology of the delignified samples also revealed the deconstruction of the lignin structure. The improved method can thus be applied for the delignification of other biomasses as well for quick and effective delignification

Laboratory Efficacy of Locally Available Backwashing Methods at Removing Fouling in Hollow-Fiber Membrane Filters Used for Household Water Treatment.

Hollow-fiber membrane filters (HFMFs) for household water treatment (HWT) can efficaciously remove disease-causing organisms in laboratory settings. However, lower effectiveness in use in low- and middle-income countries (LMICs) and humanitarian contexts (HCs) has been observed and attributed to membrane fouling and the associated cleaning. In LMICs/HCs, it is not possible to prevent and control fouling using commonly known methods (e.g., testing influent water, maintenance regimes), and the literature on fouling/cleaning of HFMFs distributed in LMICs is scarce. As such, controlled laboratory experiments were conducted to determine the efficacy of locally available (in LMICs/HCs) backwashing solutions at removing fouling using different influent waters and HFMF types. Four commonly distributed HFMFs were selected; fouling layers were developed by filtering three influent water compositions, representing LMIC/HC waters, for 10-days, and bleach, water, or vinegar backwashing solutions were used for daily backwashing. Filter performance indicators included: fiber mechanical properties (strain at break, break force), water quantity performance (flow), water quality performance (turbidity, E. coli), and imaging. The study found fouling developed rapidly and altered mechanical properties and water quantity indicators within 200 h of filtration. Fouling did not decrease water quality indicators. Backwashing improved the filter’s mechanical properties and water quantity performance, but it did not fully recover the initial performance. Additionally, recovery differed between backwashing solutions, and no universal cleaning recommendation appropriate for HFMFs in LMICs/HCs was identified. Overall, fouling development and control depended on HFMF type, influent water quality, and backwashing solution type; thus, caution before distributing HFMFs for long-term use in LMICs/HCs is recommended.

Measurement of the Effects of Metals on Taxis-to-Food Behavior in Caenorhabditis elegans.

Chemosensation in nematodes is linked to processes that affect their ability to survive, such as the search for food and the avoidance of toxic substances. Since the 1970s, numerous studies have assessed chemotaxis in the nematode species Caenorhabditis elegans, focusing on a multitude of agents, including bacteria (food), ions, salts, hormones, volatile organic compounds, and, to a lesser extent, metal-contaminated medium/food. The few studies evaluating metal exposure have reported a variety of responses (neutral, attraction, avoidance), which generally appear to be contaminant and/or concentration specific. Differences in experimental designs, however, hinder appropriate comparison of the findings and attainment of firm conclusions. Therefore, we herein propose and describe a detailed protocol for the assessment of the effects of metals on taxis-to-food behavior in C. elegans. Distinct approaches are proposed in two innovative stages of testing to (1) screen metals' effects on taxis-to-food behavior and (2) classify the behavioral response as attraction/avoidance/indifference or preference. Use of such a standard protocol will allow for easy comparison across studies and direct interpretation of results. Findings using this model system can contribute to a deeper understanding of the real risks of metal contamination to nematodes and how such contaminants could impact ecosystems in general, given the key environmental roles that these organisms play. © 2021 Wiley Periodicals LLC. Basic Protocol: Assessing the effects of metal contamination on taxis-to-food behavior in Caenorhabditis elegans Support Protocol 1: Synchronization of C. elegans by hand-picking gravid worms Support Protocol 2: Synchronization of C. elegans by using a bleaching solution.

IN-VIVO CONTROL OF FUSARIUM MONILIFORME CAUSING ROOT ROT OF JATROPHA THROUGH CHEMICAL AND AQUEOUS PLANT EXTRACTS

Jatropha (Jatropha curcas) is a plant of the Euphorbiaceae family that grows fast and able to be cultivated in tropical and subtropical regions. It is also known as Jamalghota and Jangli in different regions of the world and reported to be grown along with other crops such as wheat, sunflower, cluster bean, and pearl millet.Jatropha seeds were collected from the field of a project run by the Department of Agronomy, Sindh Agriculture University, Tando Jam. In the isolation process, seeds of jatropha were surface sterilized in a 5% bleach solution for 1-2 minutes to remove contamination.The experiment was carried in nursery bags to seethe effect of different doses of plant extracts on root rot of jatropha. The aqueous extract of different plant species was prepared by grinding freshly collected leaves of Neem, Ginger, Basil, Acasia, Garlic, Toothbrush plant, Eucalyptus, Giant milkweed, Mint, and Aloe vera separately. These extracts were then stained with a muslin cloth and a piqued solution was stored. Later it was used at the dose of 10ml, 20ml, and 30ml per bag containing disease-free (sterilized in soil sterilizer) soil. For comparison, two treatments (untreated, inoculated, and untreated, un-inoculated) bags were placed.The results of the experiment showed a significant growth of shoot length and weight in inoculated plants treated with the highest dose of Aliette, followed by Carbendazim, and Metalyxl+Mancozeb. Whereas minimum shoot length and weight was observed in control. Similarly, maximum root length and weight were recorded in plants treated with Aliette, followed by Carbendazim and Metalyxl+Mancozeb as compared to control.

Testing and evaluation of web bearing capacity of corroded steel bridge girders

Aging bridges have become an important issue in the United States. One of the most dominant forms of deterioration for steel bridges is corrosion, which is typically due to moisture exposure and water leakage through deck joints. In cold regions, frequent use of deicing chemicals during the winter season further contributes to the corrosion process. Over the years, corrosion can become serious enough to disconnect the girder’s web from its flanges. This excessive rust accumulation and metal area loss pose significant concerns for the reduction of the structural capacity of a girder, especially at its ends. In this paper, new corroded sample preparation and testing procedures were developed and implemented to study the residual web bearing capacity of corroded steel beam specimens in the lab. The laboratory testing results were used to extend the study to evaluate the residual web bearing capacity of corroded steel bridge girders. Corroded steel beam specimens were approximated in two forms in laboratory testing. In the first form, web thinning was achieved by prolonged submersion in bleach solution, to develop surface corrosion and section loss. In the second form, web holes were cut out of specimens with a plasma torch. Loading tests were performed on scaled steel beam specimens to investigate the consequent reduction in web bearing capacity due to web thinning and web area losses. The reaction at girder ends was simulated by a compression force exerted on the top flange of the steel beam specimens through a loading plate of the Material Testing System. The residual strengths of the steel beam specimens, varying in levels of corrosion, were analyzed and compared with the 3-D finite element modeling results. A quantitative relationship between corrosion condition and residual web bearing strength of I-plate steel girders is developed based on the laboratory testing and numerical modeling results. The findings in this study align with the observations from the real-world bridge practice. The proposed table of web bearing strength reduction factors can be used as a reference for evaluating residual web bearing capacity of corroded steel girders in bridge loading rating.

Effect of pH of H2O2 solutions on the morphology and wear resistance of human dental enamel: an AFM study

Introduction Teeth whitening is a highly demanded aesthetic dental procedure to remove teeth stains and get a whiter and perfect smile. This type of treatment is usually performed by the application on the teeth surface of hydrogen or carbamide peroxides which diffuse through the external layer of the teeth, enamel [1]. Although whitening treatments improve teeth appearance, they can impair teeth health, due to the eventual degradation of the teeth tissues. This may lead to abnormal wear and weaken the tooth structure. The aim of this work is to study the effect of the pH of 30% H2O2 solutions on the surface of human enamel. Materials and methods Human molars were collected for the study with informed consents of the patients. Teeth were bleached in 30% H2O2 solution with different pH values (2, 4 and 6). All samples were submitted to 11 bleaching sessions of 10 min each with alternate periods (2 min) of exposition to blue light. Microhardness, surface roughness and topography/morphology were characterised by microindentation tests, atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively, before and after the whitening treatments. AFM scratching tests (10 × 10 µm2) were performed, using a diamond probe. After the nanowear tests, topographical images of larger areas (20 × 20 µm2) which include the scratched squares were obtained with a silicon probe. The wear mechanisms were evaluated by SEM. Acceptance of the study protocol was obtained from a local ethics committee. Results The most significant changes on enamel surface were obtained for pH = 2: the microhardness decreases, and the surface roughness significantly increases as confirmed by the SEM image analysis. A higher wear rate was observed for pH = 2 in the AFM scratching tests. SEM observation of the wear zone showed differences in the wear mechanisms, which depend on the pH. Discussion and Conclusions Enamel microhardness, surface roughness and wear resistance are affected by the pH of the bleaching solution: pH = 2 led to the most adverse effects, which was attributed to hydroxyapatite demineralisation. The study of the effect of pH in the bleaching treatments is crucial to optimise this type of procedures and avoids enamel damage.

Elastomeric Silicone Sponges for Bleach Delivery

Topical disinfection protocols to inactivate organisms, particularly on high contact surfaces, have become increasingly important. A classical oxidative agent, sodium hypochlorite (bleach), has many benefits, but can be problematic during applications because of its ability to oxidize the organic polymers in which it is contained. We demonstrate that bleach-containing elastomeric sponges are readily created in one step at room temperature from thiopropyl-modified silicone oils; sodium hypochlorite induces disulfide cross-linking and a foam structure due, in part, to the concomitant formation of sulfonates. No surfactants are required. The morphology of the bleach-containing silicone sponge is tunable by the aqueous bleach solution concentration and the water/silicone ratio used. The resulting silicone sponge contains excess bleach that can be released gradually, as shown by its ability to oxidize organic molecules in aqueous solution, either directly or after dehydration/rehydration; the latter process provides a way to store the bleach-containing material in dry form. Such foams exhibit enhanced sustainability as, we show, they can be converted back to thiopropylsilicone oils by reduction using hydrosilicones. The resulting oils can be re-cross-linked, completing the life cycle.

Chlorine Rechargeable Halamine Biocidal Alginate/Polyacrylamide Hydrogel Beads for Improved Sanitization of Fresh Produce.

Traditional fresh produce washing systems mainly rely on mechanical forces and usage of chlorine bleach solutions to aid in removal and sanitization of microorganisms attached on surfaces of fresh produce during washing processes. Frequent outbreaks of foodborne diseases from ready-to-eat produce indicate insufficient sanitization of the washing processes. Herein, we present a scalable methodology for creating antimicrobial and chlorine rechargeable hydrogel beads using an in situ formed network of polyacrylamide and natural polysaccharide alginate through an emulsion polymerization. The resulting hydrogel beads exhibited robust mechanical strength, rechargeable chlorination capability, rapid up to 99.99% bacterial killing efficiency, and high produce sanitizaiton efficiency, enabling the hydrogel beads as a promising additive in chlorine sanitization to effectively sanitize the produce and automatically being recharged and reused.

Enhancing antibacterial and flame-retardant performance of cotton fabric with an iminodiacetic acid-containing N-halamine

This research focused on preparing antibacterial and flame-retardant multifunctional cotton fabric to decrease the threat of harmful microorganism and fire, which might have huge potential application in household textiles. A water-soluble N-halamine precursor based on s-triazine (TIAPC) was synthesized by introducing iminodiacetic acid (IDA), which can chelate with metal ions to obtain flame retardancy. After coating with TIAPC, the cotton fabric was chlorinated in dilute bleach solution and chelated in metal salt solution to achieve antibacterial and flame-retardant properties. The surface morphology and chemical state of TIAPC-coated cotton fabric were characterized by FT-IR, XPS, SEM and EDX. The chlorinated TIAPC-coated cotton fabric displayed high-efficacy and rapid bactericidal effect against S. aureus and E. coli O157: H7 with 100% bacterial reduction in 1 min. Meanwhile, the chelated TIAPC-modified cotton fabric presented good thermal stability and char-forming capability. The hydrophobic property of modified cotton fabric was greatly improved after chlorination. Besides, this multifunctional coating had little effect on the cytotoxicity, tensile strength, air permeability, whiteness and drape of cotton fabric.