Ni Nano-particle Encapsulated in Hollow Carbon Sphere Electrocatalyst in Polymer Electrolyte Membrane Water Electrolyzer

The present study evaluates the synthesis by solvo-thermal method and electrocatalytic activity of nickel nano-particles encapsulated in hollow carbon sphere, in hydrogen and oxygen evolution reaction in PEM water electrolyzer. The XRD patterns have ascertained the formation of nickel metal with different planes in face centered cubic (fcc) and hexagonal closed pack (hcp) form. SEM and TEM images have confirmed the nickel nano-particles with diameter of 10-50 nm inside the 0.2 mu m sized hollow carbon spheres. The BET surface area values gradually decreased with greater encapsulation of nickel; although the electrochemical active surface area (ECSA) values have been calculated as quite higher. It confirms the well dispersion of nickel in the materials and induces their electrocatalytic performance through the active surface sites. The cyclic voltammetric studies have evaluated hydrogen desorption peaks as five times more intense in nickel encapsulated materials, in comparison to the pure hollow carbon spheres. The anodic peak current density value has reached the highest level of 1.9 A cm(-2) for HCSNi10, which gradually decreases with lesser amount of nickel in the electrocatalysts. These electrocatalysts have been proved electrochemically stable during their usage for 48 h long duration under potentiostatic condition. (C) 2015 Elsevier Ltd. All rights reserved.

Reliability Assessment of a Storm Water Drain Network

Most of the cities in India are undergoing rapid development in recent decades, and many rural localities are undergoing transformation to urban hotspots. These developments have associated land use/land cover (LULC) change that effects runoff response from catchments, which is often evident in the form of increase in runoff peaks, volume and velocity in drain network. Often most of the existing storm water drains are in dilapidated stage owing to improper maintenance or inadequate design. The drains are conventionally designed using procedures that are based on some anticipated future conditions. Further, values of parameters/variables associated with design of the network are traditionally considered to be deterministic. However, in reality, the parameters/variables have uncertainty due to natural and/or inherent randomness. There is a need to consider the uncertainties for designing a storm water drain network that can effectively convey the discharge. The present study evaluates performance of an existing storm water drain network in Bangalore, India, through reliability analysis by Advance First Order Second Moment (AFOSM) method. In the reliability analysis, parameters that are considered to be random variables are roughness coefficient, slope and conduit dimensions. Performance of the existing network is evaluated considering three failure modes. The first failure mode occurs when runoff exceeds capacity of the storm water drain network, while the second failure mode occurs when the actual flow velocity in the storm water drain network exceeds the maximum allowable velocity for erosion control, whereas the third failure mode occurs when the minimum flow velocity is less than the minimum allowable velocity for deposition control. In the analysis, runoff generated from subcatchments of the study area and flow velocity in storm water drains are estimated using Storm Water Management Model (SWMM). Results from the study are presented and discussed. The reliability values are low under the three failure modes, indicating a need to redesign several of the conduits to improve their reliability. This study finds use in devising plans for expansion of the Bangalore storm water drain system. (C) 2015 The Authors. Published by Elsevier B.V.

High photoconductive combustion synthesized TiO2 derived nanobelts for photocatalytic water purification under solar irradiation

Drinking water scarcity is a major issue that needs to be addressed seriously. Water needs to be purified from organic pollutants and bacterial contamination. In this study, sunlight driven photocatalysis for the degradation of dyes and bacterial inactivation has been conducted over TiO2 nanoparticles (CST) and TiO2 nanobelts (CSTNB). TiO2 nanoparticles were synthesized by a solution combustion process using ascorbic acid as a fuel. Acid etched TiO2 nanobelts (CSTNB) were synthesized using combustion synthesized TiO2 as a novel precursor. The mechanism of formation of TiO2 nanobelts was hypothesized. The antibacterial activity of combustion synthesized TiO2 and acid etched TiO2 nanobelts were evaluated against Escherichia coli and compared against commercial TiO2. Various characterization studies like X-ray diffraction analysis, BET surface area analysis, diffused reflectance measurements were performed. Microscopic structures and high resolution images were analyzed using scanning electron microscopy, transmission electron microscopy. The extent of photo-stability and reusability of the catalyst was evaluated by conducting repeated cycles of photo degradation experiments and was compared to the commercial grade TiO2. The reactive radical species responsible for high photocatalytic and antibacterial activity has been determined by performing multiple scavenger reactions. The excellent charge transfer mechanism, high generation of hydroxyl and hole radicals resulted in enhanced photocatalytic activity of the acid etched TiO2 nanobelts compared to commercial TiO2 and nanobelts made from commercial TiO2.

Effect of catchment characteristics on the relationship between past discharge and the power law recession coefficient

This study concerns the relationship between the power law recession coefficient k (in - dQ/dt = kQ(alpha), Q being discharge at the basin outlet) and past average discharge Q(N) (where N is the temporal distance from the center of the selected time span in the past to the recession peak), which serves as a proxy for past storage state of the basin. The strength of the k-Q(N) relationship is characterized by the coefficient of determination R-N(2), which is expected to indicate the basin's ability to hold water for N days. The main objective of this study is to examine how R-N(2) value of a basin is related with its physical characteristics. For this purpose, we use streamflow data from 358 basins in the United States and selected 18 physical parameters for each basin. First, we transform the physical parameters into mutually independent principal components. Then we employ multiple linear regression method to construct a model of R-N(2) in terms of the principal components. Furthermore, we employ step-wise multiple linear regression method to identify the dominant catchment characteristics that influence R-N(2) and their directions of influence. Our results indicate that R-N(2) is appreciably related to catchment characteristics. Particularly, it is noteworthy that the coefficient of determination of the relationship between R-N(2) and the catchment characteristics is 0.643 for N = 45. We found that topographical characteristics of a basin are the most dominant factors in controlling the value of R-N(2). Our results may be suggesting that it is possible to tell about the water holding capacity of a basin by just knowing about a few of its physical characteristics. (C) 2015 Elsevier B.V. All rights reserved.

Use of Sr isotopes as a tool to decipher the soil weathering processes in a tropical river catchment, southwestern India

River water composition (major ion and Sr-87/Sr-86 ratio) was monitored on a monthly basis over a period of three years from a mountainous river (Nethravati River) of southwestern India. The total dissolved solid (TDS) concentration is relatively low (46 mg L-1) with silica being the dominant contributor. The basin is characterised by lower dissolved Sr concentration (avg. 150 nmol L-1), with radiogenic Sr-87/Sr-86 isotopic ratios (avg. 0.72041 at outlet). The composition of Sr and Sr-87/Sr-86 and their correlation with silicate derived cations in the river basin reveal that their dominant source is from the radiogenic silicate rock minerals. Their composition in the stream is controlled by a combination of physical and chemical weathering occurring in the basin. The molar ratio of SiO2/Ca and Sr-87/Sr-86 isotopic ratio show strong seasonal variation in the river water, i.e., low SiO2/Ca ratio with radiogenic isotopes during non-monsoon and higher SiO2/Ca with less radiogenic isotopes during monsoon season. Whereas, the seasonal variation of Rb/Sr ratio in the stream water is not significant suggesting that change in the mineral phase being involved in the weathering reaction could be unlikely for the observed molar SiO2/Ca and Sr-87/Sr-86 isotope variation in river water. Therefore, the shift in the stream water chemical composition could be attributed to contribution of ground water which is in contact with the bedrock (weathering front) during non-monsoon and weathering of secondary soil minerals in the regolith layer during monsoon. The secondary soil mineral weathering leads to limited silicate cation and enhanced silica fluxes in the Nethravati river basin. (C) 2015 Elsevier Ltd. All rights reserved.