Reduced graphene oxide (rGO) and metal oxide based binary (rGO–TiO 2 /rGO–Fe 3 O 4 ) and ternary (rGO–Fe 3 O 4 –TiO 2 ) nanocomposites with enhanced photocatalytic and adsorption properties are ...successfully synthesized by a simple one-step solvothermal process. The microscopy images of the nanocomposites show that the ferric oxide (Fe 3 O 4 ) and titania (TiO 2 ) nanoparticles are firmly anchored over rGO, which enhances the surface area of the resultant nanocomposites. The as-synthesized nanocomposites are evaluated for the removal of methylene blue dye under UV and visible light irradiation as well as for the adsorption of As( iii ) from aqueous solution. Compared to binary, the ternary (rGO–Fe 3 O 4 –TiO 2 ) nanocomposite exhibits the highest dye degradation efficiency (∼100% within 5 minutes). This enhancement is attributed to the synergetic interaction and increase in the surface area of rGO–Fe 3 O 4 –TiO 2 . For As( iii ) adsorption, the adsorption data are obtained by Langmuir and Freundlich adsorption isotherms. Compared to binary nanocomposites, the maximum monolayer adsorption capacity (147.05 mg g −1 ) is observed for rGO–Fe 3 O 4 –TiO 2 . These results reveal that the rGO–Fe 3 O 4 –TiO 2 nanocomposite has potential application in water/wastewater treatment.
Solar air heater is the cheapest and extensively used solar energy collection device for drying of agricultural products, space heating, seasoning of timber and curing of industrial products. The use ...of an artificial roughness on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the duct of a solar air heater. Use of artificial roughness in solar air heater has been topic in research for the last thirty years. In the present article an attempt has been made to present holistic view of different kinds of roughness geometry used for creating artificial roughness in solar air heater for performance enhancement by experimental approaches. In this article thirty eight experimental studies have been reported on solar air heater, roughened with different kinds of roughness geometry. However, no comprehensive comparative study has been carried out or found in the literature so far, in order to investigate the relative performance of different types of artificially roughened solar air heater. The objective of this article is to perform such a study. In this article twenty known different shapes and orientations of roughness elements are considered for comparative analysis. In order to obtain the results numerically, codes are developed in MATLAB-7. Correlations for heat transfer and friction factor, developed by various investigators for artificially roughened solar air heaters have been reported in this article. The effects of various rib parameters on heat transfer and fluid flow processes are also discussed.
Multi-drug resistant microbes, pathogenic viruses, metals, and pharmaceuticals and personal care products (PPCPs) in water has become the crux of urban sustainability issues. However, vulnerability ...due to pollutant concurrences, source apportionment, and identification of better faecal indicators needs to be better understood. The present study focuses on the vulnerability of urban Guwahati, the largest city in Northeastern India, through analyzing the concurrence of PPCPs, enteric viruses, antibiotic resistant bacteria, metal, and faecal contamination in water. The study strives to identify a relevant marker of anthropogenic pollution for the Indian scenario. Samples from the Brahmaputra River (n = 4), tributary Bharalu River (an unlined urban drain; n = 3), and Ramsar recognized Lake (Dipor Bil; n = 1) indicate caffeine > acetaminophen > theophylline > carbamazepine > crotamiton for PPCPs and pepper mild mottle virus (PMMoV) > aichi > hepatitis A > norovirus GII > norovirus GI for enteric viruses. PMMoV was the better indicator of faecal pollution due to its prevalence, specificity and ease of detection. Antibiotic resistance was neither correlated with the prevalence of PPCPs nor E. coli. As, Co and Mn appear to be inducing antibiotic resistance in E. coli. While the risk quotient of the urban drain (Bharalu River) indicates one order higher magnitude than reported for other Indian rivers, the Lake exhibited the least pollution and better resilience. The concurrence of pollutants and multi-drug resistant E. coli, owing to the complete absence of wastewater treatment, puts the city in a highly vulnerable state. Pollution is being regulated only by the dilution capability of the Brahmaputra River, which needs to be further researched for seasonal variation.
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•Antibiotics resistance was not correlated with the prevalence of PPCPs and E. coli.•Risk quotient in the urban water was higher than reported for other Indian rivers.•PMMoV was a good faecal pollution indicator due to prevalence, specificity and detectability.•As, Co and Mn appear to be inducing antibiotic resistance in E.coli.•Wetland in the urban area exhibited the least pollution and better resilience for ARB.
Artificial water channels (AWCs) are synthetic mimics of biological water channel proteins, aquaporins. They combine the characteristic features of aquaporins, including a transmembrane orientation ...in biomimetic membrane matrices and the possibility of combining high water permeability with high water/solute selectivity, with higher processability and stability compared to protein channels. AWCs have thus emerged as a platform for biomimetic membrane development. During the last few years, remarkable progress has been made in AWC synthesis and characterization but bridging these advances to practical membrane development still remains a significant challenge. In this article, we review some recent concepts regarding permeability in water channels and its relevance to AWCs, common misconceptions and need for better clarity in permeability and selectivity characterization of AWCs, and prospective applications of channel-based membranes beyond desalination.
Wastewater treatment plants (WWTPs) are being debated for being the hot spots for the development of antibiotic resistance in pathogenic microbial communities. We observed the prevalence of ...antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARG), and multidrug resistance (MDR) in two municipal WWTPs and one hospital WWTP in Western and Southern Sri Lanka, and compared the results with particular reference to Indian and the World scenario to trace the imprints of treatment on ARB and ARG. Result suggests that although wastewater treatment resulted in higher than 1.06 log Escherichia coli (E. coli) reduction at all WWTPs, yet the percent of E. coli resistant to most of the antibiotics increased from influent to effluent. Higher prevalence of ARB, ARG, and MDR were noted in hospital WWTP owing to the higher antibiotic concentrations used and excreted by the patients. With reference to India, the WWTPs in Sri Lanka showed more ARB and a consistent increase in its percentages after the treatment but were less resistant to Fluoroquinolone (FQ). E. coli strains isolated from each location of both countries showed multidrug resistance, which has increased after the treatment and was strongly correlated with FQ in every WWTP. Resistant genes for Fluoroquinolone (FQ) (aac-(6′)-1b-cr, qnrB, qnrS), β-lactams (ampC), and sulphonamides (sul1) were common in all the wastewaters except additional parC gene in the hospital effluent of Sri Lanka, implying much higher resistance for quinolones, especially for Ciprofloxacin. Multivariate statistical treatments suggest that effluent showed higher loadings and association for MDR/ARB, where pH change and more extensive interaction with metals during the treatment processes seem to have profound effects.
•Antibiotic resistance of E. coli was found increasing after treatment process.•The resistance genes aac-(6′)-1b-cr, qnrB, qnrS, ampC, sul1 were detected in WWTPs.•Cross-resistance within fluoroquinolones was stronger than non-fluoroquinolones.•Sri Lankan WWTPs exhibit more and consistent increase in resistance after the treatment than India.
An elastic organic crystal, 2,6-dichlorobenzylidine-4-fluoro-3-nitroaniline (DFNA), which also shows thermosalient behavior, is studied. The presence of these two distinct properties in the same ...crystal is unusual and unprecedented because they follow respectively from isotropy and anisotropy in the crystal packing. Therefore, while both properties lead from the crystal structure, the mechanisms for bending and thermosalience are quite independent of one another. Crystals of the low-temperature (α) form of the title compound are bent easily without any signs of fracture with the application of deforming stress, and this bending is within the elastic limit. The crystal structure of the α-form was determined (P21/c, Z = 4, a = 3.927(7) Å, b = 21.98(4) Å, c = 15.32(3) Å). There is an irreversible phase transition at 138 °C of this form to the high-temperature β-form followed by melting at 140 °C. Variable-temperature X-ray powder diffraction was used to investigate the structural changes across the phase transition and, along with an FTIR study, establishes the structure of the β-form. A possible rationale for strain build-up is given. Thermosalient behavior arises from anisotropic changes in the three unit cell parameters across the phase transition, notably an increase in the b axis parameter from 21.98 to 22.30 Å. A rationale is provided for the existence of both elasticity and thermosalience in the same crystal. FTIR studies across the phase transition reveal important mechanistic insights: (i) increased π···π repulsions along 100 lead to expansion along the a axis; (ii) change in alignment of C–Cl and NO2 groups result from density changes; and (iii) competition between short-range repulsive (π···π) interactions and long-range attractive dipolar interactions (C–Cl and NO2) could lie at the origin of the existence of two distinctive properties.
The present study demonstrates potential utilization of lime-stabilized sewage sludge (SS) for construction purposes. SS samples were constituted using 0, 2, 4, 6 and 8% of lime by weight of the SS ...and cured for 7, 14 and 28 d. Stability of the lime-modified SS was evaluated through determination of geotechnical, microstructural and mineralogical properties. A large improvement in unconfined compressive strength (UCS) from 207 kPa to 1102 kPa was achieved after 28 d of curing SS with 6% lime. The improvement in UCS is attributed to formation of cementing compounds as a result of pozzolanic reactions. Marked reductions in swell pressure of 47, 51, 54 and 58% were obtained with the 2, 4, 6 and 8% lime treatments. Also, the plasticity index decreased with increasing lime content for different curing periods, indicating the SS becomes much more workable and less expansive. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) after lime treatment confirmed formation of the new compounds responsible for the improved engineering properties of SS. The study concludes that lime treatment can be an alternative to stabilize SS for potential use as a construction material for subbase of flexible pavement as per IRC (Indian Road Congress) 37–2012 guidelines.
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•Sewage sludge (SS) exhibited expansive behaviour due to high content of Montmorillonite.•Lime (CaO) treatment improved SS strength, swelling and plasticity characteristics.•CaO induced cementation via gyrolite and hydrates of Ca and Ca–Al–OH silicates.•Unconfined compressive strength increased to 1102 kPa after 28 d of lime treatment.•SS treated with 6% CaO and cured 28 d found suitable for subbase pavement construction.
Rainfall is a principal element of the hydrological cycle and its variability is important from both the scientific as well as practical point of view. Wavelet regression (WR) technique is proposed ...and developed to analyze and predict the rainfall forecast in this study. The WR model is improved combining two methods, discrete wavelet transform and linear regression model. This study uses rainfall data from 21 stations in Assam, India over 102 years from 1901 to 2002. The calibration and validation performance of the models is evaluated with appropriate statistical methods. The root mean square errors (RMSE), N-S index, and correlation coefficient (R) statistics were used for evaluating the accuracy of the WR models. The accuracy of the WR models was then compared with those of the artificial neural networks (ANN) models. The results of monthly rainfall series modeling indicate that the performances of wavelet regression models are found to be more accurate than the ANN models.
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