The demand for access to clean water will continue to increase as the world population increases. For sustainable development and embracement of technological advancement, it is plausible to consider a filter material development approach that uses locally abundant natural resources as the raw material and nanotechnology techniques for material fabrication. The review and research paper will present a perspective of the authors on how to embrace nanotechnology for filter media development with key focus on the remediation of arsenate. Drinking water contaminated with arsenic is an emerging global challenge. Continuous exposure to drinking water with high levels arsenic could result in several types of cancer. With this in mind, the US EPA in 2001 set 10 ppb as the maximum contaminant level of arsenic from the initial 50 ppb. Therefore, arsenic remediation is key in mitigating these health risks in people residing near water bodies with elevated arsenic levels. Adsorption is considered to be the cheapest. However, from literature, majority of the adsorbents cannot be used in field applications due to challenges associated with low adsorption capacity and a high level of particle leaching into purified water thus posing health dangers. Therefore, it means that many of these adsorbents are economically non-viable. A new chitosan, aluminium, titanium, iron and zirconium (CTS-Al-Ti-Fe-Zr) hybrid was fabricated through the sol-gel process. The material was characterized by scanning electron microscopy, Brunauer-Emmett-Teller and Fourier Transform Infrared spectroscopy before and after adsorption. Batch adsorption properties towards As(V) were separately studied as a function of the effect of adsorbent dose, pH, initial concentration, contact time and competing ions. Characterization results show that the material is a polycrystalline with a specific surface area of 56.4 m2g-1. Further, FTIR and SEM-EDAX showed adsorption of arsenate on the surface of the nanocomposite. Research findings suggest that with only 100 mg of the adsorbent arsenate can be reduced to less than 10 ppb from an initial concentration of 300 ppb respectively. The maximum adsorption capacity for arsenate removal was recorded as 123 mg/g. The presence of SiO3 2-, CO3 2-, and HCO3 - ions resulted in a slight decline in the adsorption efficiency of arsenate. The equilibrium data fitted well with the Langmuir isotherm 0.99518. Data from the fabricated prototype Point-of-use filter showed that with 60.0 g of the nanocomposite, it is possible to reduce 650 L of drinking water with an arsenate initial concentration of 300 ppb to less 10 ppb. In conclusion, the research findings suggest that the nanocomposite material is capable of removal of arsenate from contaminated drinking water to WHO acceptable levels with a potential to be up scaled for commercial applications.

In this work, polyethylene (PE) composites were prepared with a series of completely condensed silsesquioxanes (SSQ), as well as with open-cage hepta(isobutyl)trisilanol silsesquioxane. The effect of the additives on the thermal, mechanical, rheological, and crystalline properties of the composites obtained was determined. The dispersion of trisilanol derivative within polymer matrix was slightly better than that of the other isobutyl compounds, suggesting condensation of the additive to less polar products of different structure, which was confirmed by thermogravimetry (TG) and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry analysis. The additives improved the thermal stability of polyethylene and formed composites of higher rigidity than the neat polyolefin. The results were compared to the literature data, with aminopropylhepta(isobutyl)silsesquioxane and vinylhepta(isobutyl)silsesquioxane being used partially as references, as PE composites thereof were reported earlier, but lacked some analytical results and required further investigation. It was proven that the practical upper loading limit for such silsesquioxane compounds as processing and functional additives for polyethylene should be fixed at around 1%.

The linear photochemical response of materials depends on two critical parameters: the size of the optical band gap determines the onset of optical excitation, whereas the absolute energetic positions of the band edges define the reductive or oxidative character of photo-generated electrons and holes. Tuning these characteristics is necessary for many potential applications and can be achieved through changes in the bulk composition or particle size, adjustment of the surface chemistry or the application of electrostatic fields. In this contribution the influence of surface chemistry and fields is investigated systematically with the help of standard DFT calculations for a typical case, namely composites prepared from ZnS quantum dots and functionalized carbon nanotubes. After comparing results with existing qualitative and quantitative experimental data, it is shown conclusively, that the details of the surface chemistry (especially defects) in combination with electrostatic fields have the largest influence. In conclusion, the development of novel or improved photoresponsive materials therefore will have to integrate a careful analysis of the interplay between surface chemistry, surface charges and interaction with the material environment or substrate.

Background. Use of hearing protection devices has become necessary when other control measures cannot reduce noise to a safe and standard level. In most countries, more effective hearing protection devices are in demand. Objective. The aim of this study was to examine the effects of titanium dioxide (TiO2) nanoparticles on noise reduction efficiency in a polyvinyl chloride (PVC) earplug. Methods. An S-60 type PVC polymer as the main matrix and TiO2 of 30-nm size were used. The PVC/TiO2 nanocomposite was mixed at a temperature of 160 °C and 40 rpm and the samples were prepared with 0, 0.2 and 0.5 wt% of TiO2 nanoparticle concentrations. Results. Earplug samples with PVC/TiO2 (0.2, 0.5 wt%) nanoparticles, when compared with raw earplugs, showed almost equal noise attenuation at low frequencies (500-125 Hz). However, at high frequencies (2-8 kHz), the power of noise reduction for earplugs containing TiO2 nanoparticles was significantly increased. Conclusions. The results of the present study showed that samples containing nanoparticles of TiO2 had more noticeable noise reduction abilities at higher frequencies in comparison with samples without the nanoparticles.