Air pollution from household solid fuel combustion in India: an overview of exposure and health related information to inform health research priorities

Environmental and occupational risk factors contribute to nearly 40% of the national burden of disease in India, with air pollution in the indoor and outdoor environment ranking amongst leading risk factors. It is now recognized that the health burden from air pollution exposures that primarily occur in the rural indoors, from pollutants released during the incomplete combustion of solid fuels in households, may rival or even exceed the burden attributable to urban outdoor exposures. Few environmental epidemiological efforts have been devoted to this setting, however. We provide an overview of important available information on exposures and health effects related to household solid fuel use in India, with a view to inform health research priorities for household air pollution and facilitate being able to address air pollution within an integrated rural–urban framework in the future

High-performance and stable photoelectrochemical water splitting cell with organic-photoactive-layer-based photoanode

Considering their superior charge-transfer characteristics, easy tenability of energy levels, and low production cost, organic semiconductors are ideal for photoelectrochemical (PEC) hydrogen production. However, organic-semiconductor-based photoelectrodes have not been extensively explored for PEC water-splitting because of their low stability in water. Herein, we report high-performance and stable organic-semiconductors photoanodes consisting of p-type polymers and n-type non-fullerene materials, which is passivated using nickel foils, GaIn eutectic, and layered double hydroxides as model materials. We achieve a photocurrent density of 15.1 mA cm???2 at 1.23 V vs. reversible hydrogen electrode (RHE) with an onset potential of 0.55 V vs. RHE and a record high half-cell solar-to-hydrogen conversion efficiency of 4.33% under AM 1.5 G solar simulated light. After conducting the stability test at 1.3 V vs. RHE for 10 h, 90% of the initial photocurrent density are retained, whereas the photoactive layer without passivation lost its activity within a few minutes

Photocatalytic Degradation of Poly(ethylene oxide) and polyacrylamide

The photocatalytic degradation of poly(ethylene oxide) (PEO) and polyacrylamide (PAM) was investigated using combustion synthesized nano-sized $TiO_2$ catalyst (CSN-$TiO_2$). The degradation was conducted with two different UV lamps of 125 and 80 W. Degradation of PEO was observed in both the cases, whereas PAM degraded only when exposed to lamp of higher power, even in the presence of catalyst. Gel permeation chromatography was used to determine the molecular weight distribution. Continuous distribution kinetics was applied to determine the kinetics of the photodegradation process. The degradation rate coefficients of the polymers in the presence of combustion synthesized $TiO_2$ were higher than the degradation rate coefficients obtained with commercially available $TiO_2$ (Degussa P-25). The enhanced degradation rate of the polymers when catalyzed by CSN-$TiO_2$ can be due to the nano-size, high surface area, and the presence of hydroxyl groups on the surface of the catalyst

The effect of nature of raw coal on the adhesion of bacteria to coal surface

The surface properties of coal and solution pH play a major role in determining the adhesion of microorganisms. In this study, three Indian coal samples with different compositions have been used and the adhesion of the bacterium Bacillus polymyxa to these coals has been investigated. It was found that due to the high ash content of coal, the zeta-potential was negative over most of the pH range which is close to the values exhibited by pure quartz as well as B. polymyxa. Similarly, the surface free energy components of coal (derived from contact angle measurements) showed that the electron-donor component increased with ash content. Adhesion experiments revealed that maximum adhesion of the bacterium B. polymyxa occurred on to the coal samples around the point-of-zero-charge of the coal and the bacterium i.e. about pH 2. Further, adhesion was found to be dependent on the ash content and the surface free energy of the coals. (C) 2002 Published by Elsevier Science Ltd

Photocatalytic Degradation of Poly(ethylene oxide) and polyacrylamide

The photocatalytic degradation of poly(ethylene oxide) (PEO) and polyacrylamide (PAM) was investigated using combustion synthesized nano-sized $TiO_2$ catalyst (CSN-$TiO_2$). The degradation was conducted with two different UV lamps of 125 and 80 W. Degradation of PEO was observed in both the cases, whereas PAM degraded only when exposed to lamp of higher power, even in the presence of catalyst. Gel permeation chromatography was used to determine the molecular weight distribution. Continuous distribution kinetics was applied to determine the kinetics of the photodegradation process. The degradation rate coefficients of the polymers in the presence of combustion synthesized $TiO_2$ were higher than the degradation rate coefficients obtained with commercially available $TiO_2$ (Degussa P-25). The enhanced degradation rate of the polymers when catalyzed by CSN-$TiO_2$ can be due to the nano-size, high surface area, and the presence of hydroxyl groups on the surface of the catalyst

Photodegradation of Poly(vinyl alcohol) Under UV and Pulsed-Laser Irradiation in Aqueous Solution

The photodegradation of poly(vinyl alcohol) (PVA) in aqueous solution was investigated under UV exposure and pulsed-laser irradiation. The degradation under UV exposure was studied at different pH values and with the addition of potassium chloride and potassium dichromate. The pulsed- laser degradation of PVA was investigated with a Nd : YAG laser, operating at a wavelength of 266 nm with about 6-ns pulses. The pulsed-laser degradation was studied at different polymer concentrations and light intensities. Samples were analyzed by gel permeation chromatography. The degradation rate coefficients were determined by the application of a continuous distribution model. The photodegradation rates under UV exposure were highest at extremes of pH and were greatly enhanced by the addition of potassium chloride and potassium dichromate. The pulsed-laser degradation of the polymer decreased with increasing polymer concentration, although a threshold light intensity was required to initiate the degradation process

Effect of initial molecular weight and solvents on the ultrasonic degradation of poly(ethylene oxide)

The ultrasonic degradation of poly(ethylene oxide) (PEO) of different initial molecular weights was studied at a fixed temperature. The time variation of the number average molecular weight was determined using Gel Permeation Chromatography (GPC). The ultrasonic degradation rate,\chi, was assumed to be of the form, $\kappa = k_d(\chi - \chi_{lim})^\lambda$, where $k_{d}$ represents the rate coefficient, while \chi and $\chi_{lim}$, represent the molecular weight and limiting molecular weight, respectively. A continuous distribution model assuming midpoint chain scission and two different expressions for the rate coefficient was developed to satisfactorily model the experimental data. In the first method, the model was solved numerically and the values of $k_{d}$ and \chi were determined by fitting the model to the experimental data. However, when \chi is assumed to be unity, an analytical solution to the model was determined and fitted the experimental data for the degradation of PEO.To confirm this model, the effect of initial molecular weight on the degradation of other polymers (polyacrylamide (PAM), poly(butylacrylate) (PBA), poly(methyl acrylate) (PMA)) was also investigated.The assumption of $\chi = 1$ fitted the experimental data for the ultrasonic degradation of these polymers indicating that this is a reasonable approximation for the ultrasonic degradation of polymers.The effect of various solvents on the degradation of poly(ethyleneoxide) was also investigated. No degradation was observed when PEO was degraded in acetone, acetonitrile or methanol but degradation occurred in mixtures of water and the above solvents. Thus, it was concluded that the degradation of PEO was dependent more on the vapor pressure of the solvent than on polymer-solvent interactions

Thermal Degradation of Water Soluble Polymers and their Binary Blends

The effect of five different metal oxides on the pyrolysis of poly(ethylene oxide) (PEO), polyacrylamide (PAM), and poly(vinyl alcohol) (PVA) was investigated using thermogravimetry. The presence of metal oxide did not influence the degradation of PEO while the order of metal oxide on the degradation rate of PAM and PVA was PbO > $Co_3O_4$ > CuO > ZnO > $Al_2O_3$. The miscibility and the decomposition of PEO-PAM and PVA-PAM blends were also investigated. The blends were found to be immiscible and the presence of one polymer did not influence the degradation of the other polymer in the polymer blend

The utility of Bacillus subtilis as a bioflocculant for fine coal

The application of Bacillus subtilis as a flocculant for fine coal has been reported here. Zeta-potential measurements showed that both the coal and bacteria had similar surface charge as a function of pH. Surface free energy calculations showed that the coal was hydrophobic while the bacterium was hydrophilic. The adhesion of the bacteria to coal and subsequent settling was studied in detail. Adhesion of bacteria to coal surface and subsequent settling of coal was found to be quick. Both adhesion and settling were found to be independent of pH, which makes the process very attractive for field applications. The presence of an electrolyte along with the bacterium was found to not only enhance adhesion of bacteria, but also produce a clear supernatant. Further, the settled fraction was more compact than with bacteria alone. Interaction energy calculations using the extended DLVO theory showed that the electrical forces along with the acid-base interaction energy play a dominant role in the lower pH range. Above pH 7, the acid-base interaction energy is the predominant attractive force and is sufficient enough to overcome the repulsive forces due to electrical charges to brine about adhesion and thus settling of fine coal. With increase in electrolyte concentration, the change in total interaction energy with pH is minimal which probably leads to better adhesion and hence settling. (C) 2003 Elsevier Science B.V. All rights reserved