Water-based technologies for improving water quality at the point of use: A review.

Water safety concerns are increasing tremendously as a result of the rising population and environmental pollution. As a result, viable water treatment approaches need to be designed to meet the water consumption demands of the population, particularly in developing countries. The recent technological advances in water treatment and purification are well articulated in this review. The efficiency of the materials used for purification and their affordability for people living in rural and remote settlements in various parts of the world have been discussed. Water treatment techniques prior to the rapid advancement of science and technology included a variety of strategies such as coagulation/flocculation, filtration, disinfection, flotation and pH correction. The use of nanotechnology in water treatment and purification has modernized the purification process. Therefore, efficient removal of microbes such as bacteria and viruses are exquisitely accomplished. These technologies may include membrane filtration, ultraviolet irradiation, advanced oxidation ion-exchange and biological filtration technologies. Thus, nanotechnology allows for the fabrication of less expensive systems, allowing even low-income people to benefit from it. Most developing countries find these technologies particularly valuable because access to clean and safe water for drinking and residential needs is critical. This is because access to municipal water supplies is also difficult. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Evaluating the potential applications of brewers' spent grain in biogas generation, food and biotechnology industry: A review.

Breweries, as the major users of fossil fuels, are constantly under economic and environmental pressure to minimize energy consumption and residual management costs. Biogas generation from brewing wastes is a realistic solution for significantly reducing fossil fuel use. Brewers' spent grain (BSG) forms about eighty per cent of the total wastes from a brewing plant. BSG has a high cellulose and non-cellulosic polysaccharides content which makes it potential for biogas production. This paper reviews the potential applications of BSG as an alternative substrate for production of biogas and the recent achievements which have been attained in anaerobic digestion (AD) technology. The usability of BSG in diverse technologies including production of animal and human food and as a medium for growing microorganisms and enzymes is reviewed. The chemical processes involved in producing biogas from BSG are discussed.

Inexpensive sol-gel synthesis of multiwalled carbon nanotube-TiO2 hybrids for high performance antibacterial materials.

This study reports an inexpensive sol-gel method to synthesize TiO2-CNT hybrid materials. Synthesized TiO2-CNT materials show strong antibacterial activity in the absence of light. Cheap TiO2 source TiOCl2 is used during synthesis in the absence of high temperatures, high pressures and organic solvents. TiO2-CNT materials with 0, 2, 5, 10, 15 and 20wt% of CNT were synthesized and compared for antibacterial activity, surface area, porosity, crystalline structure, chemical state, and HaCaT cell proliferation. The antibacterial strength of hybrid materials increased significantly with the increase in CNT loading amount, and the TiO2-CNT samples with a CNT loading of 10wt% or more nearly removed all of the E.coli bacteria. HaCaT cell proliferation studies of synthesized hybrid materials illustrated that prepared TiO2-CNT systems exhibit minimum cytotoxicity. The characteristics of prepared materials were analyzed by means of XRD, FTIR, Raman spectroscopy, XPS, TEM, and nitrogen gas physisorption studies, compared and discussed.

Investigation of the influence of vanadium, iron and nickel dopants on the morphology, and crystal structure and photocatalytic properties of titanium dioxide based nanopowders.

Photoactive V, Fe and Ni doped TiO2 (M-TiO2) nanopowders were synthesized by a modified two-step sol-gel process in the absence of additives. Titanium oxychloride, which is a rarely-used TiO2 precursor was used to yield M-TiO2 photocatalysts with preferential photochemical performance in the presence of natural solar irradiation. The obtained samples were calcined at different calcination temperatures ranging from 450 to 800°C to evaluate the influence of the sintering on the physicochemical properties. The properties of the obtained samples were examined by XRF, XRD, Raman spectroscopy, UV-visible DRS, XPS, nitrogen gas physisorption studies, SEM-EDAX and HRTEM analyses. Structural characterization of the samples revealed the incorporation of these transition metal element into TiO2. It was also depicted that the morphology, crystal structure, optical and photochemical properties of the obtained samples were largely dependent on the calcination temperature and the type of dopant used during the preparation process. The photochemical performance of the samples was investigated in the photodegradation of methylene blue in the presence of natural sunlight. The experimental results indicated that the VT600 sample possessed the highest activity due to its superior properties. This study provides a systematic preparation and selection of the precursor, dopant and calcination temperature that are suitable for the formation of TiO2-based heterogeneous photocatalysts with appealing morphology, crystal structure, optical and photochemical properties for myriad of applications.

Aminated polyethersulfone-silver nanoparticles (AgNPs-APES) composite membranes with controlled silver ion release for antibacterial and water treatment applications.

The present study reports the antibacterial disinfection properties of a series of silver nanoparticle (AgNP) immobilized membranes. Initially, polyethersulfone (PES) was functionalized through the introduction of amino groups to form aminated polyethersulfone (NH2-PES, APES). AgNPs were then coordinately immobilized on the surface of the APES composite membrane to form AgNPs-APES. The properties of the obtained membrane were examined by FT-IR, XPS, XRD, TGA, ICP-OES and SEM-EDAX analyses. These structural characterizations revealed that AgNPs ranging from 5 to 40 nm were immobilized on the surface of the polymer membrane. Antibacterial tests of the samples showed that the AgNPs-APES exhibited higher activity than the AgNPs-PES un-functionalized membrane. Generally, the AgNPs-APES 1 cm × 3 cm strip revealed a four times longer life than the un-functionalized AgNPs polymer membranes. The evaluation of the Ag(+) leaching properties of the obtained samples indicated that approximately 30% of the AgNPs could be retained, even after 12 days of operation. Further analysis indicated that silver ion release can be sustained for approximately 25 days. The present study provides a systematic and novel approach to synthesize water treatment membranes with controlled and improved silver (Ag(+)) release to enhance the lifetime of the membranes.

Sol-gel synthesis of mesoporous anatase-brookite and anatase-brookite-rutile TiO2 nanoparticles and their photocatalytic properties.

TiO2 photocatalysts with a mixture of different TiO2 crystal polymorphs have customarily been synthesized hydrothermally at high temperatures using complicated and expensive equipment. In this study TiO2 nanoparticles with a mixture of TiO2 crystals were synthesized using a modified sol-gel method at low temperature. In order to form nanoparticles with different polymorphs a series of samples were obtained at pH 2, 4, 7 and 9. Raw samples were calcined at different temperatures ranging from 200 to 800°C to evaluate the effect of the calcination temperature on the physico-chemical properties of the samples. XRD results revealed that a mixture of anatase and brookite can be obtained in the as-synthesized samples and in those calcined up to 800°C depending on the pH used to obtain the final product. Indeed, a mixture of anatase brookite and rutile; or a sample with only rutile phase can be yielded through further calcination of the as-prepared samples at temperatures ⩾600°C due to phase transformation. The photocatalytic performance of the samples with a mixture of anatase-brookite; anatase-brookite-rutile; and anatase-rutile (Degussa P25 TiO2) was exquisitely investigated in the degradation of methylene blue solutions. The samples obtained at pH 2 and calcined at 200°C possessed the highest activity of all due to its superior properties. This study elucidates a facile method suitable for the synthesis of TiO2 with different mixtures of TiO2 polymorphs with desirable properties for various applications.