Vibrational and structural properties of lead-free piezoelectric (1-x)Na0.5Bi0.5TiO3–xCaTiO3 (0 < x < 1.00) solid solutions have been investigated using Raman spectroscopy and X-ray diffraction. Different anomalies were detected and analyzed taking into consideration the phase transition from rhombohedral to orthorhombic phase at room temperature. All Raman bands were interpreted through the variation in the peak positions (frequency) and the corresponding half-widths at half maximum (HWHM) as a function of x. XRD used as a complementary technique to Raman spectroscopy, showed that the rhombohedral – orthorhombic phase transition went gradually through an intermediate phase consisting of a mixture of rhombohedral (R3c) and orthorhombic (Pnma) structures and that the fraction of orthorhombic phase increased with CT composition. The results show that the morphotropic phase boundary (MPB) is located between 0.09 and 0.15.
Arsenic contamination of groundwater is a major public health concern worldwide. The problem has been reported mainly in southern Asia and, especially, in Bangladesh. Slow-sand filters (SSF) augmented with iron were proven to be a simple, low-cost and decentralized technique for the treatment of arsenic-contaminated sources. In this research, three pilot-scale SSF (flowrate 6 L·h−1) were tested regarding their capability of removing arsenic from groundwater in conditions similar to those found in countries like Bangladesh (70 µg As(III) L−1, 26 °C). From the three, two filters were prepared with mixed media, i.e., sand mixed with corrosive iron matter (CIM filter) and iron-coated sand (ICS filter), and a third conventional SSF was used as a reference. The results obtained showed that the CIM filter could remove arsenic below the World Health Organization (WHO) guideline concentration of 10 µg·L−1, even for inlet concentrations above 150 µg·L−1. After 230 days of continuous operation the arsenic concentration in the effluent started increasing, indicating depletion or saturation of the CIM layer. The effluent arsenic concentration, however, never exceeded the Bangladeshi standard of 50 µg·L−1 throughout the whole duration of the experiments.
MULTIFILE
Surface Active Agents, or surfactants, are chemicals which provide a surface (interface) activity when dispersed in liquids. They have different purposes, can be used as herbicides, anti-foaming agents, adhesives, cleaning agents and softeners. For cleaning purposes, their function is to alter (decrease) liquid surface tension. In this function they are ubiquitous in both industrial processes (cleaning of production equipment, storage vats, packaging lines, and cooking units either during the manufacturing process) and domestic applications. ProtoNeat proposes an alternative way to decrease water surface tension without adding chemicals (surfactants). This can be done by charging the water (producing protonically charged water) [2], i.e. positive and negative Bjerrum-defect like charges [3, 4]. This phenomenon was experimentally observed by Fuchs et al [5] in anolyte and catholyte when doing high voltage electrolysis of highly pure water during the so-called ‘floating water bridge’ experiment. The work done by the authors, when working with this “bridge”, showed that, in case of positive excess charge, the hydronium ions migrate to the surface [8] thereby significantly lowering the surface tension [9,10]. However, for how long this effect can be maintained and how effective it is to produce such water is still unknown. ProtoNeat wants to tackle these two questions and investigate whether a continuous production of protonically charged water as an environmentally friendly and sustainable cleaning agent is possible.
