Innovative DIY drinking water disinfection for underserved communities.

Waterborne pathogens threaten 2.2 billion people lacking access to safely managed drinking water services, causing over a million annual diarrheal deaths. Individuals without access to chlorine reagents or filtration devices often resort to do-it-yourself (DIY) methods, such as boiling or solar disinfection (SODIS). However, these methods are not simple to implement. In this study, we introduced an innovative and easily implemented disinfection approach. We discovered that immersing aluminum foil in various alkaline solutions produces alkali-treated aluminum foil (ATA foil) that effectively adsorbs Escherichia coli (E. coli), Salmonella, and Acinetobacter through the generated surface aluminum hydroxide. For example, a 25 cm2 ATA foil efficiently captures all 104E. coli DH5α strains in 100 mL water within 30 min. Using a saturated suspension of magnesium hydroxide, a type of fertilizer, as the alkaline solution, the properties of the saturated suspension eliminate the need for measuring reagents or changing solutions, making it easy for anyone to create ATA foil. ATA foils can be conveniently produced within mesh bags and placed in household water containers, reducing the risk of recontamination. Replacing the ATA foil with a foil improves the adsorption efficiency, and re-immersing the used foil in the production suspension restores its adsorption capacity. Consequently, ATA foil is an accessible and user-friendly alternative DIY method for underserved communities. Verification experiments covering variations in the water quality and climate are crucial for validating the efficacy of the foil. Fortunately, the ATA foil, with DIY characteristics similar to those of boiling and SODIS, is well-suited for testing under diverse global conditions, offering a promising solution for addressing waterborne pathogens worldwide.

Sorbent-embedded sheets for safe drinking water in developing countries: a case study of lead(II) removal by a zeolite-embedded sheet.

Although many kinds of materials for water purification are known, easy-to-use methods that ensure the safety of drinking water for rural populations are not sufficiently available. Sorbent-embedded sheets provide methods for the easy removal of contaminants from drinking water in the home. As an example of such a sorbent-embedded sheet, we prepared a Linde type A (LTA) zeolite-embedded sheet (ZES) and examined its Pb(II) removal behaviour. Different amounts of LTA were added either as powder or as ZES to 0.3 mM Pb(NO3)2 solutions containing 2.5 mM Ca(NO3)2, in which the ratio of the negative charges in LTA to the positive charges in Pb(II) (LTA/Pb ratio) ranged from 1 to 20. After shaking, the mixtures were centrifuged to remove the powder, while the ZES was simply removed from the mixture by hand. The LTA powder removed more than 99% of the Pb(II) from the solution at all LTA/Pb ratios within 1 h, while the ZES removed >99% of the Pb(II) at LTA/Pb ratios of 2 and higher; at the highest LTA/Pb ratio of 20, the ZES removed >99% of the Pb(II) in 30 s. Therefore, the use of appropriate sorbent-embedded sheets enable the facile removal of contaminants from water.

One-Step Synthesis of Calcium Sulfate Hemihydrate Nanofibers from Calcite at Room Temperature.

In recent years, researchers have made significant progress in the development of inorganic nanofibers (including nanowires). Typically, inorganic nanofibers are synthesized via crystal growth in solution; however, a limited number of studies have focused on their preparation directly from solid raw materials (with no examples of synthesis conducted at room temperature and atmospheric pressure). In this work, we successfully synthesized nanofibers of calcium sulfate hemihydrate (bassanite, CaSO4·0.5H2O) at 20 °C and 1 atm by mixing calcite and dilute sulfuric acid in methanol. The bassanite nanofibers are concluded to be synthesized by the formation of calcium sulfate on the calcite surface and its simultaneous reaction with the generated H2O. Because bassanite exhibits useful physical properties that include high mechanical strength, high thermal stability, and excellent chemical stability, its nanofibers can be widely applied to rubber, plastics, antifriction materials, and paper as a strengthening agent, for heat-resistance, or as a flame retardant, or for creep resistance.

Proton Adsorption Selectivity of Zeolites in Aqueous Media: Effect of Si/Al Ratio of Zeolites.

In addition to their well-known uses as catalysts, zeolites are utilized to adsorb and remove various cations from aqueous system. The adsorption of the cations is ascribed to the negative charge of zeolites derived from isomorphous substitution of Si by Al. The amount of Na+ adsorption on 4A, X, Y, Na-P1 and mordenite type zeolites were determined in aqueous media, in a two-cation (Na+ and H+) system. Although each zeolite has a constant amount of negative charge, the amount of Na+ adsorption of each zeolite decreased drastically at low pH-pNa values, where pH-pNa is equal to log{(Na+)/(H+)}. By using the plot of the amount of Na+ adsorption versus pH-pNa, an index of the H+ selectivity, which is similar to the pKa of acids, of each zeolite was estimated, and the index tended to increase with decreasing Si/Al ratio of zeolites. These indicate that zeolites with lower Si/Al and higher negative charge density have higher H+ adsorption selectivity, and in fact, such a zeolite species (4A and X) adsorbed considerable amount of H+ even at weakly alkaline pH region. The adsorption of H+ results in the decrease of cation adsorption ability, and may lead to the dissolution of zeolites in aqueous media.

Synthesis of Linde type A zeolite-goethite nanocomposite as an adsorbent for cationic and anionic pollutants.

Linde type A zeolite (LTA)-goethite nanocomposite was synthesized by adding sodium orthosilicate solution to goethite, followed by addition of sodium aluminate and NaOH solutions at 100 degrees C. Optimum condition at the Si addition step required for nanocomposite formation was pH 10.0 and Si/Fe=2.7. The final product composed mainly of LTA and goethite crystals. Formation of LTA-goethite nanocomposites in the final product was suggested by differences in IR spectra and SEM images between the final product and a mixture of LTA and goethite. The mixture separated into LTA and goethite components after washing with water, but the final product did not show such separation. Precipitation of silica on the surface of goethite and subsequent formation of Si-O-Fe bonds at the Si addition step contributed to formation of the LTA-goethite nanocomposite. The amount of adsorption of phosphate on the final product was more than 1.6 times the amount adsorbed on the mixture, indicating generation of synergistic effect in the LTA-goethite nanocomposite.