Investigation of polyaniline processibility using GPC/UV–vis analysis

In this work, we characterized the molecular weight and UV–vis spectra of polyaniline (PANI) simultaneously using a gel permeation chromatography (GPC) system equipped with a photodiode array (PDA) detector. Therefore, we constructed correlations between weight average molecular weight (M_w) values and UV–vis spectral features such as the ratio of quinoid units/benzenoid units (Q/B ratio), and the B peak positions for the continuum of discrete chromatographic fractions of PANI emeraldine base (EB). The correlation is further verified by electrochemical techniques. Using this correlation, we analyzed newly synthesized PANIs and investigated how the synthesis and post-treatment conditions impact the quality, uniformity, and processibility of the PANIs. The study also reveals that the portions with low molecular weights of PANI are more sensitive to the process conditions than those with high molecular weights.     

Technology learning for renewable energy: Implications for South Africa's long-term mitigation scenarios

Technology learning can make a significant difference to renewable energy as a mitigation option in South Africa's electricity sector. This article considers scenarios implemented in a Markal energy model used for mitigation analysis. It outlines the empirical evidence that unit costs of renewable energy technologies decline, considers the theoretical background and how this can be implemented in modeling. Two scenarios are modelled, assuming 27% and 50% of renewable electricity by 2050, respectively. The results show a dramatic shift in the mitigation costs. In the less ambitious scenario, instead of imposing a cost of Rand 52/t CO₂-eq (at 10% discount rate), reduced costs due to technology learning turn renewables into negative cost option. Our results show that technology learning flips the costs, saving R143. At higher penetration rate, the incremental costs added beyond the base case decline from R92 per ton to R3. Including assumptions about technology learning turns renewable from a higher-cost mitigation option to one close to zero. We conclude that a future world in which global investment in renewables drives down unit costs makes it a much more cost-effective and sustainable mitigation option in South Africa.     

Pressure dependence of the electric conductance of aqueous solutions of LiCl,KCl and (CH3)4NCl. Correlation of kinetic parameters

The electrical conductivity and the compression of solutions of LiCl, KCl, and (CH₃)₄NCl have been measured as a function of pressure up to 2 kbar at the temperatures 25°, 35° and 45°C in the concentration range 0·1–1 molal. The results are discussed in terms of the transition state theory in relation to kinetic parameters for viscous flow and partial molal volume.     

XRF-analysis of fine and ultrafine particles emitted from laser printing devices

In this work, the elemental composition of fine and ultrafine particles emitted by ten different laser printing devices (LPD) is examined. The particle number concentration time series was measured as well as the particle size distributions. In parallel, emitted particles were size-selectively sampled with a cascade impactor and subsequently analyzed by the means of XRF. In order to identify potential sources for the aerosol's elemental composition, materials involved in the printing process such as toner, paper, and structural components of the printer were also analyzed. While the majority of particle emissions from laser printers are known to consist of recondensated semi volatile organic compounds, elemental analysis identifies Si, S, Cl, Ca, Ti, Cr, and Fe as well as traces of Ni and Zn in different size fractions of the aerosols. These elements can mainly be assigned to contributions from toner and paper. The detection of elements that are likely to be present in inorganic compounds is in good agreement with the measurement of nonvolatile particles. Quantitative measurements of solid particles at 400 °C resulted in residues of 1.6 × 10(9) and 1.5 × 10(10) particles per print job, representing fractions of 0.2% and 1.9% of the total number of emitted particles at room temperature. In combination with the XRF results it is concluded that solid inorganic particles contribute to LPD emissions in measurable quantities. Furthermore, for the first time Br was detected in significant concentrations in the aerosol emitted from two LPD. The analysis of several possible sources identified the plastic housings of the fuser units as main sources due to substantial Br concentrations related to brominated flame retardants.