Removal of sulfide in integrated anaerobic–aerobic wastewater treatment system

In recent years, the stipulations fixed by regulatory bodies have become stringent to keep environmental pollution under control. Normally COD and BOD are the parameters monitored to determine the efficiency of any treatment system. But in many cases, industrial wastewater may contain sulfate along with other organic constituents. Sulfate, if present in the wastewater, will be converted to H₂S under anaerobic conditions and this is hazardous. Subsequently, if the same wastewater is treated under aerobic conditions, a part of the air supplied will be utilized for oxidation of sulfide back to sulfate which leads to reduced efficiency of the aerobic treatment. The released wastewater with high sulfate levels will be going into the environment, which is undesirable. Methods are reported in the literature for the removal of sulfate and sulfide before and after anaerobic treatment respectively. Most of these methods are chemical which are either costly or impracticable. Therefore, a novel approach for removing sulfate or sulfide in the treatment scheme is required. In the present communication, studies are undertaken by designing an innovative stripper system where sulfide is removed to the extent of 60 to 70% before aerobic treatment. The parameters involved in design and operation of the stripper, such as airflow rate, liquid flow rate, liquid to air ratio, and pH profile, are optimized. It is a physical system in which air and waste water are passed as counter currents. The treated wastewater from the stripper, which contains less sulfide, may be post-treated in the aerobic system before final discharge. Hydrogen sulfide can be efficiently removed by coupling this type of stripper to existing anaerobic systems. The system can be efficiently used in existing treatment plants or in new designs to control sulfide (free sulfide generated in an anaerobic reactor in the case of wastewaters having high sulfate inhibits methanogenesis, resulting in reduced performance of the anaerobic process) generated in anaerobic reactors and to optimize the air and oxygen requirements in the aerobic system.     

Growth of carbon nanotubes directly on a nickel surface by thermal CVD

A simple method of growing carbon nanotubes directly on nickel substrate without chemical pretreatment is reported. It is demonstrated that carbon nanotubes growth is directly affected by the roughness on the surface. Carbon nanotubes density is large in each growth zone observed on the surface; these zones being spread sparsely for coarse roughness of the surface. The density of carbon nanotubes decreases and the number of growth zones increases as the roughness on the surface is reduced. The above trend was not affected with C₂H₂ flow time changing from 10 to 2 min. A similar result was obtained using a Ni alloy as substrate, but the effect of surface roughness on the growth of CNTs was less pronounced. The CNTs grown on the Ni alloy were free of amorphous carbon and uniformly distributed.     

Development of nitrendipine controlled release formulations based on SLN and NLC for topical delivery: in vitro and ex vivo characterization

The aim of the investigation is to develop solid lipid nanoparticles (SLN) and nano-structured lipid carrier (NLC) as carriers for topical delivery of nitrendipine (NDP). NDP-loaded SLN and NLC were prepared by hot homogenization technique followed by sonication, and they were characterized for particle size, zeta potential, entrapment efficiency, stability, and in vitro release profiles. Also the percutaneous permeation of NDPSLN A, NDPSLN B, and NDPNLC were investigated in abdominal rat skin using modified Franz diffusion cells. The steady state flux, permeation coefficient, and lag time of NDP were estimated over 24 h and compared with that of control (NDP solution). The particle size was analyzed by photon correlation spectroscopy (PCS) using Malvern zeta sizer, which shows that the NDPSLN A, NDPSLN B, and NDPNLC were in the range of 124-300 nm during 90 days of storage at room temperature. For all the tested formulations (NDPSLN A, NDPSLN B, and NDPNLC), the entrapment efficiency was higher than 75% after 90 days of storage. The cumulative percentage of drug release at 24 h was found to be 26.21, 30.81, and 37.52 for NDPSLN A, NDPSLN B, and NDPNLC, respectively. The results obtained from in vitro release profiles also indicated the use of these lipid nanoparticles as modified release formulations for lipophilic drug over a period of 24 h. The data obtained from in vitro release from NDPSLN A, NDPSLN B, and NDPNLC were fitted to various kinetic models. High correlation was obtained in Higuchi and Weibull model. The release pattern of drug is analyzed and found to follow Weibull and Higuchi equations. The permeation profiles were obtained for all formulations: NDPSLN A, NDPSLN B, and NDPNLC. Of all the three formulations, NDPNLC provided the greatest enhancement for NDP flux (21.485 +/- 2.82 microg/h/cm(2)), which was fourfold over control (4.881 +/- 0.96 microg/h/cm(2)). The flux obtained with NDPSLN B (16.983 +/- 2.91 microg/h/cm(2)) and NDPNLC (21.485 +/- 2.82 microg/h/cm(2)) meets the required flux (16.85 microg/h/cm(2)).     

Characterization of vertical Bridgman grown Cd0.9Zn0.1Te0.97Se0.03 single crystal for room-temperature radiation detection

We report a modified vertical Bridgman method to grow Cd_0.9Zn_0.1Te_0.97Se_0.03 (CZTS) single crystals using in-house zone-refined 7 N (99.99999%) purity elemental precursors for room-temperature radiation detection. CZTS is an economic yet high performance alternative to expensive CdZnTe (CZT) detectors for room-temperature gamma-ray detection. Radiation detector in planar geometry has been fabricated on an 11.0?×?11.0?×?3.0 mm³ CZTS single crystal. A bulk resistivity of 10¹⁰ Ω.cm has been achieved without using any compensating dopant. The elemental composition of the grown crystal has been examined using energy-dispersive X-ray (EDX) analysis. Powder X-ray diffraction (XRD) showed formation of zincblende phase with a lattice constant of 6.447 Å, and sharp peaks confirmed the formation of highly crystalline single-phase CZTS crystals. A modified Vegard’s law has been applied to calculate the atomic percentage of Se in the grown crystals from the XRD patterns and compared with the intended and the measured stoichiometry. The electron mobility-lifetime (μτ) product and the drift mobility have been calculated to be 1.5?×?10^–3 cm²/V and 710 cm²/V.s, respectively, using alpha spectroscopy. The presented vertical Bridgman growth method uses a single pass through the controlled heating zone in contrast to the previously reported multiple pass growth techniques, thus, reducing the growth duration by two third which would help to further reduce the cost of production of CZTS-based room-temperature detectors.

     

Corrosion and erosion behavior of iron aluminide (FeAl(Cr)) coating deposited by detonation spray technique

The electrochemical corrosion and erosion behavior of FeAlCr coating was reported in this article. The FeAlCr coatings were deposited by detonation spray coating system (DSC) by utilizing the gas atomized powder with a nominal composition of Fe-12Al-5Cr at two different pulse frequencies on mild steel (MS) substrate. Feedstock and coatings were characterized using XRD, SEM and elemental mapping. Nanoindentation tests using a Berkovich indenter indicate a hardness of 5.5 GPa and 4.9 GPa for the coatings deposited at 3 Hz and 6 Hz respectively as compared to 1.5 GPa of the substrate. Electrochemical corrosion tests were performed on coated samples in 3.5 wt% NaCl and 2 N H₂SO₄ media and are compared with the bulk MS substrate. Detonation pulse frequency significantly influenced the coating microstructure and corrosion performance. The coating deposited at a frequency of 6 Hz exhibited higher resistance against electrochemical corrosion in 3.5 wt% NaCl medium than the coating that was deposited at 3 Hz frequency. Solid particle erosion tests performed at room temperature (25 °C) and an impingement angle of 90° (normal incidence) using Al₂O₃ as the erodent medium demonstrate a higher erosion loss of the coatings than the bulk MS. On the contrary, at a temperature of 400 °C, the coatings exhibited notably better erosion resistance than the MS substrate, illustrating the potential of FeAlCr coatings for high temperature wear-corrosion resistant applications.     

Studies on void coalescence analysis of nanocrystalline cryorolled commercially pure aluminium formed under different stress conditions

Cryorolling was performed on commercially pure aluminium sheet from an initial thickness of 7 mm to 0.25 mm with a total true strain of around 3.33. Cryorolling was performed in many passes with only 5% reduction in each pass to avoid adiabatic heating during rolling process. Detailed Transmission Electron Microscopic studies showed increased dislocation density and distributed dislocation cell structure. Streaks along with ring pattern in selected area electron diffraction of transmission electron microscopy evidenced the existence of texture component on the surface of rolled sheet along with nanocrystalline sub-structure. Studies on fracture behavior of the cryorolled sheets were performed using specimen of double edge-notch tensile geometry. Compared to the conventionally rolled sheet metal, the strain triaxiality ratio value in the case of cryorolled sheets is insensitive to the void growth analysis due to the presence of nano-sized grains. The ratio of length to the width of voids varies from 1.6 to 2.4 in the case of conventionally rolled sheet. In contrast, length to width ratio is very close to 1.0 in the case of cryorolled sheet. Thus no oblate or prolate voids were observed during cryorolling compared with conventionally rolled sheets and it is observed the formation of equiaxed nanostructured grains. In the case of cryorolled sheets, minimal variation in length to width ratio was observed with the variation in the shear strains, due to the presence of nanostructured grains. Whereas, in the case of conventionally rolled material, wide variation in the length to width ratio with the variations in the shear strains was observed.     

Synthesis of CdZnTeSe single crystals for room temperature radiation detector fabrication: mitigation of hole trapping effects using a convolutional neural network

Journal of Materials Science: Materials in Electronics - In this article, we report the growth of Cd0.9Zn0.1Te0.97Se0.03 (CZTS) wide bandgap semiconductor single crystals for room temperature...     

Experimental and theoretical investigation of forming limit diagram for Ti-6Al-4 V alloy at warm condition

Forming limit diagram (FLD) is an important performance index to describe the maximum limit of principal strains that can be sustained by sheet metals till to the onset of localized necking. It is useful tool to access the forming severity of a drawing or stamping processes. In the present work, FLD has been determined experimentally for Ti-6Al-4 V alloy at 400 °C by conducting a hemispherical dome test with specimens of different widths. Additionally, theoretical FLDs have been determined using Marciniak Kuczynski (M-K) model. Various yield criteria namely: Von Mises, Hill 1948, Hill 1993 and Cazacu Barlat in combination with different hardening models viz., Hollomon power law (HPL), Johnson-Cook (JC), modified Johnson-Cook (m-JC), modified Arrhenius (m-Arr.), modified Zerilli–Armstrong (m-ZA) have been used in M-K analysis for theoretical FLD prediction. The material properties required for determination of yield criteria and hardening models constants have been calculated using uniaxial tensile tests. The predicted theoretical FLDs results are compared with experimental FLD. It can be observed that influence of yield criterion in M-K analysis for theoretical FLD prediction is predominant than the hardening model. Based on the results; it is observed that the theoretical FLD using Cazacu Barlat and Hill 1993 yield criteria with m-Arr. hardening model has a very good agreement with experimental FLD.