Kinetic and equilibrium isotherm studies for the adsorptive removal of Brilliant Green dye from aqueous solution by rice husk ash

The present study deals with the adsorption of Brilliant Green (BG) on rice husk ash (RHA). RHA is a solid waste obtained from the particulate collection equipment attached to the flue gas lines of rice husk fired boilers. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH0), contact time, adsorbent dose and initial concentration (C0) on the removal of BG. Optimum conditions for BG removal were found to be pH0 approximately 3.0, adsorbent dose approximately 6 g L(-1) of solution and equilibrium time approximately 5 h for the C0 range of 50-300 mg L(-1). Adsorption of BG followed pseudo-second-order kinetics. Intra-particle diffusion does not seem to control the BG removal process. Equilibrium isotherms for the adsorption of BG on RHA were analyzed by Freundlich, Langmuir, Redlich-Peterson (R-P), Dubnin-Radushkevich (D-R), and Temkin isotherm models using a non-linear regression technique. Langmuir and R-P isotherms were found to best represent the data for BG adsorption onto RHA. Adsorption of BG on RHA is favourably influenced by an increase in the temperature of the operation. Values of the change in entropy (DeltaS0) and heat of adsorption (DeltaH0) for BG adsorption on RHA were positive. The high negative value of change in Gibbs free energy (DeltaG0) indicates the feasible and spontaneous adsorption of BG on RHA.     

A comparative study on the dissipation and microbial metabolism of organophosphate and carbamate insecticides in orchaqualf and fluvaquent soils of West Bengal

An experiment has been conducted under laboratory conditions to investigate the effect of phorate (an organophosphate insecticide) and carbofuran (a carbamate insecticide) at their recommended field rates (1.5 and 1.0 kga.i.ha-1, respectively) on the growth and multiplication of microorganisms as well as rate of dissipation and persistence of the insecticidal residues including their metabolites in laterite (typic orchaqualf) and alluvial (typic fluvaquent) soils of West Bengal. Application of phorate and carbofuran in general, induced growth and development of bacteria, actinomycetes, fungi, N2-fixing bacteria and phosphate solubilizing microorganisms in both the soils and the stimulation was more pronounced with phorate as compared to carbofuran. Application of phorate recorded highest stimulation of fungi in laterite and actinomycetes in alluvial soil. Carbofuran on the other hand, augmented fungi and N2-fixing bacteria in laterite and actinomycetes in alluvial soil. Bacterial population was inhibited due to the application of carbofuran in alluvial soil. Phorate sulfoxide and phorate sulfone, the two metabolites of phorate and 3-hydroxycarbofuran and 3-ketocarbofuran, the two metabolites of carbofuran isolated were less persistent in both the soils. Phorate persisted in laterite and alluvial soils up to 45 and 60 days, respectively depicting the half-life (T1/2) 9.7 and 11.5 days, respectively while the T1/2 of carbofuran for the said soils were 16.9 and 8.8 days, respectively. No metabolite of carbofuran was detected in soils after 30 days of incubation while phorate sulfone persisted in alluvial soil even after 60 days of application of the insecticide.     

ZnO nanophotocatalysts coupled with ceramic membrane method for treatment of Rhodamine-B dye waste water

In the present investigation, hybrid treatment process has been developed for the treatment of synthetic dye wastewater. Photocatalysis and ceramic nanoporous membrane are mainly used for process integration to minimize the fouling and increase the flux. Commercial ZnO powder has been used as a nano-photocatalyst for the degradation of rhodamine-B dye in the hybrid system. Commercial ceramic nanoporous tubular membranes have been used for the rejection of dye and suspended catalysts. Photocatalysis process alone has shown the 33% of decolorization, whereas ceramic nanofiltration has shown the 50% of decolorization. Integration of photocatalysis and ceramic nanofiltration were shown 96% of dye decolorization over 90 min of operation.     

An empirical relationship between PM(2.5) and aerosol optical depth in Delhi Metropolitan

Atmospheric remote sensing offers a unique opportunity to compute indirect estimates of air quality, which are critically important for the management and surveillance of air quality in megacities of developing countries, particularly in India and China, which have experienced elevated concentration of air pollution but lack adequate spatial-temporal coverage of air pollution monitoring. This article examines the relationship between aerosol optical depth (AOD) estimated from satellite data at 5 km spatial resolution and the mass of fine particles ≤2.5 μm in aerodynamic diameter (PM(2.5)) monitored on the ground in Delhi Metropolitan where a series of environmental laws have been instituted in recent years.PM(2.5) monitored at 113 sites were collocated by time and space with the AOD computed using the data from Moderate Resolution Imaging Spectroradiometer (MODIS onboard the Terra satellite). MODIS data were acquired from NASA's Goddard Space Flight Center Earth Sciences Distributed Active Archive Center (DAAC). Our analysis shows a significant positive association between AOD and PM(2.5). After controlling for weather conditions, a 1% change in AOD explains 0.52±0.202% and 0.39±0.15% change in PM(2.5) monitored within ±45 and 150 min intervals of AOD data. This relationship will be used to estimate air quality surface for previous years, which will allow us to examine the time-space dynamics of air pollution in Delhi following recent air quality regulations, and to assess exposure to air pollution before and after the regulations and its impact on health.     

Hygroscopic organic aerosols during BRAVO?

The hygroscopic properties of the organic fraction of aerosols are poorly understood. The ability of organic aerosols to absorb water as a function of relative humidity (RH) was examined using data collected during the 1999 Big Bend Regional Aerosol and Visibility Observational Study (BRAVO). (On average, organics accounted for 22% of fine particulate matter with an aerodynamic diameter less than 2.5 microm (PM2.5) mass). Hourly RH exceeded 80% only 3.5% of the time and averaged 44%. BRAVO aerosol chemical composition and dry particle size distributions were used to estimate PM2.5 light scattering (Bsp) at low and high ambient RH. Liquid water growth associated with inorganic species was sufficient to account for measured Bsp for RH between 70 and 95%.     

Carcinogenic and co-carcinogenic potential of 2,3,7,8-tetrachlorodibenzo-p-dioxin in a host-mediated in vivo/in vitro assay

In an in vivo/in vitro assay system (Massa et al., 1990) we have detected the carcinogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The carcinogenic potential measured in this system is concentration-dependent. Experiments with other carcinogenic compounds have revealed that TCDD at low doses can act as co-carcinogen. At higher concentrations TCDD induces TNF-α production.     

Simulating impacts,potential adaptation and vulnerability of maize to climate change in India

Climate change associated global warming, rise in carbon dioxide concentration and uncertainties in precipitation has profound implications on Indian agriculture. Maize (Zea mays L.), the third most important cereal crop in India, has a major role to play in country’s food security. Thus, it is important to analyze the consequence of climate change on maize productivity in major maize producing regions in India and elucidate potential adaptive strategy to minimize the adverse effects. Calibrated and validated InfoCrop-MAIZE model was used for analyzing the impacts of increase in temperature, carbon dioxide (CO₂) and change in rainfall apart from HadCM3 A2a scenario for 2020, 2050 and 2080. The main insights from the analysis are threefold. First, maize yields in monsoon are projected to be adversely affected due to rise in atmospheric temperature; but increased rainfall can partly offset those loses. During winter, maize grain yield is projected to reduced with increase in temperature in two of the regions (Mid Indo-Gangetic Plains or MIGP, and Southern Plateau or SP), but in the Upper Indo-Gangetic Plain (UIGP), where relatively low temperatures prevail during winter, yield increased up to a 2.7°C rise in temperature. Variation in rainfall may not have a major impact on winter yields, as the crop is already well irrigated. Secondly, the spatio-temporal variations in projected changes in temperature and rainfall are likely to lead to differential impacts in the different regions. In particular, monsoon yield is reduced most in SP (up to 35%), winter yield is reduced most in MIGP (up to 55%), while UIGP yields are relatively unaffected. Third, developing new cultivars with growth pattern in changed climate scenarios similar to that of current varieties in present conditions could be an advantageous adaptation strategy for minimizing the vulnerability of maize production in India.     

Use of artificial roughness for performance enhancement of solar air heaters—a review

The performance characteristics of a solar air heater can effectively be improved by providing artificial roughness in the form of protrusions and dimples of various shapes, sizes, and orientations on the underside of heated surface. An extensive literature review on artificial roughness elements has been carried and the correlations developed for heat transfer and friction factor for roughened solar air collector have been discussed and presented in this paper. The performance parameter has also been computed and compared with various kinds and shapes of roughness geometries using correlations developed by various investigators. The optimum values of the roughness parameters obtained by several investigators have also been discussed.