Removal and recovery of lead(II) from single and multimetal (Cd, Cu, Ni, Zn) solutions by crop milling waste (black gram husk)

The study reports removal of heavy metals when present singly or in binary and ternary systems by the milling agrowaste of Cicer arientinum (chickpea var. black gram) as the biosorbent. The biosorbent removed heavy metal ions efficiently from aqueous solutions with the selectivity order of Pb>Cd>Zn>Cu>Ni. The biosorption of metal ions by black gram husk (BGH) increased as the initial metal concentration increased. Biosorption equilibrium was established within 30 min, which was well described by the Langmuir and Freundlich adsorption isotherms. The maximum amount of heavy metals (qmax) adsorbed at equilibrium was 49.97, 39.99, 33.81, 25.73 and 19.56 mg/g BGH biomass for Pb, Cd, Zn, Cu and Ni, respectively. The biosorption capacities were found to be pH dependent and the maximum adsorption occurred at the solution pH 5. Efficiency of the biosorbent to remove Pb from binary and ternary solutions with Cd, Cu, Ni and Zn was the same level as it was when present singly. The presence of Pb in the binary and ternary solutions also did not significantly affect the sorption of other metals. Breakthrough curves for continuous removal of Pb from single, binary and ternary metal solutions are reported for inlet-effluent equilibrium. Complete desorption of Pb and other metals in single and multimetal solutions was achieved with 0.1 M HCl in both shake flask and fixed bed column studies. This is the first report of removal of the highly toxic Pb, Cd, and other heavy metals in binary and ternary systems based on the biosorption by an agrowaste. The potential of application for the treatment of solutions containing these heavy metals in multimetal solutions is indicated.     

Metastable structures of liquid-quenched and vapour-quenched antimony films

Antimony foils/films have been prepared by liquid-quenching and by vapour-quenching. (1) Simple cubic (a=3.16 Å), (2) f c c (a=4.61 Å), (3) tetragonal (a=3.01 Å, c=4.96 Å and c/a=1.64) structures, and (4) a new rhombohedral (a _H=4.12 Å, c _H=10.26 Å and c _H/a _H=2.49) metastable structure have been observed in splat-quenched foils. The metastable rhombohedral phase transforms to the equilibrium rhombohedral phase (a _H=4.30 Å, c _H=11.27 Å and c _H/a _H=2.62) on heating. The simple cubic, f c c and tetragonal phases are converted in to a hexagonal close-packed (a=3.33 Å, c=5.23 Å and c/a=1.57) structure on heating in the electron microscope. The simple cubic and h c p phases correspond to the known high-pressure phases of antimony. The h c p phase does not transform on further heating. Films prepared by vapour deposition on substrates held at room temperature show the same metastable f c c and rhombohedral phases as observed in splat-quenched foils, in addition to the equilibrium rhombohedral phase. On heating, these metastable phases transform in the same way as the splat-quenched specimens. The films deposited at liquid air temperature are amorphous; on electron-beam heating, these crystallize first to an unidentified complicated structure and then to the equilibrium structure.     

Optimization of biodiesel production process in a continuous microchannel using response surface methodology

We assessed the biodiesel production process in a continuous microchannel through preparation of a heterogeneous catalyst (CaO/MgO) from demineralized water plant sediment. This mixed oxide catalyst was used for transesterification of rapeseed oil as feedstock by methanol to produce biodiesel fuel at various conditions. A microchannel, utilized as a novel reactor, was applied to convert rapeseed oil into biodiesel in multiple steps. The effects of the process variables, such as catalyst concentration, methanol to oil volume ratio, n-hexane to oil volume ratio, and reaction temperature on the purity of biodiesel, were carefully investigated. Box-Behnken experimental design was employed to obtain the maximum purity of biodiesel response surface methodology. The optimum condition for the production of biodiesel was the following: catalyst concentration of 7.875 wt%, methanol to oil volume ratio of 1.75: 3, n-hexane to oil volume ratio of 0.575: 1, and reaction temperature of 70 °C.     

Boosting the photovoltaic performance of Zn2SnO4‐based dye‐sensitized solar cells by Si doping into Zn2SnO4

In the present work, Zn₂SnO₄ nanoparticles were doped with silicon to improve their electrical and optical properties by the conventional solid‐state reaction method. The results showed that the minimum electrical resistivity of about 0.09 Ωcm was obtained for Zn₂SnO₄ nanoparticles with 3% Si doping. The decrease in the electrical resistivity can be attributed to the insertion of Si⁺⁴ atoms into the Zn⁺² and/or Sn⁺⁴ sites and also the formation of more oxygen vacancies in the Zn₂SnO₄ lattice. The formation of the more oxygen vacancy defect states in Si‐doped Zn₂SnO₄ nanoparticles was verified by photoluminescence spectroscopy. The efficiency of a dye‐sensitized solar cell based on 3% Si‐doped Zn₂SnO₄ was significantly better, by about 81%, compared to that of a cell based on the undoped Zn₂SnO₄. The enhancement in the efficiency can be ascribed to the facilitation of electron transport throughout a photoelectrode due to increase in the charge carrier concentration which was caused by Si doping.     

Immobilization of a molybdenum-glycine Schiff base complex within the nanocages of zeolite Y with flexible ligand method

Immobilization of a molybdenum-glycine Schiff base complex onto the supercages of zeolite Y was achieved through the flexible ligand method. The prepared material was characterized by different physicochemical techniques. FT-IR spectroscopy confirmed the immobilization of the complex onto the nanocages of zeolite Y. X-ray diffraction analysis revealed that textural properties of zeolite Y support were preserved during the immobilization process. Nitrogen adsorption–desorption analysis demonstrated the decrease in surface area of the prepared material in comparison with parent zeolite Y. Inductively coupled plasma optical emission spectroscopy showed the presence of 0.75 mmol g^?1 molybdenum in the final material. The obtained material exhibited high catalytic activity, stability, and recyclability in the epoxidation of olefins with tert-butylhydroperoxide as oxidant.     

Increasing Lifetime and Fault Tolerance Capability in Wireless Sensor Networks by Providing a Novel Management Framework

The main application of wireless sensor networks is to monitor remote and dangerous areas that are inaccessible or difficult and or costly to reach by humans. This characteristic makes these networks be self-managed, face the challenges of fault tolerance and energy and network lifetime constraints due to non-renewable energy sources. In this paper, a management framework capable of providing and increasing network fault tolerance is introduced. To design such a framework, fault detection and recovery mechanisms for various fault levels including network nodes and communications between them have been used. The proposed management framework and protocols increase network’s fault tolerance capability in network nodes and in the communications between them. Also, the network lifetime increases three to five times more. On the one hand, it’s expected that the provision of network fault tolerance would decrease network’s lifetime and since it increases information exchange, it would increase energy consumption and cause reduced network life time, however the final results suggest a several-fold increase of network lifetime.     

Synthesis of clay-supported nanoscale zero-valent iron using green tea extract for the removal of phosphorus from aqueous solutions

This study addresses the synthesis of nanoscale zero-valent iron (nZVI) in the presence of natural bentonite (B-nZVI) using green tea extract.The natural bentonite and B-nZVI were then applied for the removal of phosphorus from aqueous solutions at various concentrations,pH levels and contact time.The desorption of phosphorus (P) from adsorbents was done immediately after sorption at the maximum initial concentration using the successive dilution method.The characterization of FTIR,SEM,and XRD indicated that nZVI was successfully loaded to the surface of natural bentonite.The sorption of phosphorus on B-nZVI was observed to be pH-dependent,with maximum phosphorus removal occurring at the pH range of 2 to 5.The results demonstrate that the maximum sorption capacities of natural bentonite and B-nZVI were 4.61 and 27.63 mg·g-1,respectively.Langmuir,Freundlich,and Redlich-Peterson models properly described the sorption isotherm data.For either adsorbent,desorption isotherms did not coincide with their corresponding sorption isotherms,suggesting the occurrence of irreversibility and hysteresis.The average percentages of retained phosphorus released from natural bentonite and B-nZVI were 80％ and 9％,respectively.The results indicated that sorption kinetics was best described by the pseudo-second-order model.The present study suggests that B-nZVI could be used as a suitable adsorbent for the removal of phosphorus from aqueous solutions.     

A study on cell association in heterogeneous networks with joint load balancing and interference management

This paper presents the characteristic analysis of channel gain for two conductor type power line communication (PLC) system using analytical transient model. The analysis of frequency responses is presented by incorporating various lengths of transmission lines and loads at terminal side. It is suggested that variations in the frequency responses of PLC channel, especially under transient condition within the transmission line (TL) can be investigated more effectively by using the transient model. Performance of transient model is found to be significantly better than the previously available work in the literature. More accurate results are achieved in simulation as compared to results obtained from typical \(\pi \) model of lumped circuit.     

Effect of 10 wt% VC on the Friction and Sliding Wear of Spark Plasma–Sintered WC–12 wt% Co Cemented Carbides

The effect of 10 wt% VC addition on the friction and sliding wear response of WC–12 wt% Co cemented carbides produced by spark plasma sintering (SPS) was studied. The SPS of WC–12 wt% Co alloys with and without 10 wt% VC, at 1100 and 1130°C, respectively, yielded dense materials with minimal porosity. No eta phase was found in any of the alloys. The WC–12 wt% Co–10 wt% VC alloy showed the formation of a hard WV₄C₅ phase, which improved the alloy's hardness. Friction and dry sliding wear tests were done using a ball-on-disk configuration under an applied load of 10 N and sliding speed of 0.26 m.s^?1, and a 100Cr-steel ball was used as the counterface. A significant improvement in the sliding wear response of the harder and more fracture tough WC–12 wt% Co–10 wt% VC alloy compared to the WC–12 wt% Co alloy was found. Analysis of the worn surfaces by scanning electron microscopy showed that the wear mechanisms included plastic deformation, preferential binder removal, adhesion, and carbide grain cracking and fragmentation.