Salacca zalacca skin and its modified form as biosorbents for Hg2+ removal from aqueous solution

ABSTRACT

A chemically modified-biosorbent was prepared by attaching dithizone onto Salacca zalacca skin waste for Hg²⁺ bioremoval. The material was synthesized by refluxing dithizone 5% with the Salacca zalacca skin powder followed by drying. The material was characterized through scanning electron microscopy, gas sorption analysis, and Boehm titration. The applicability of the material as biosorbent was tested for Hg²⁺ adsorption at room temperature. Findings suggested that the modification altered the surface properties of the biosorbent as indicated by the increased values for such surface parameters as specific surface area, pore volume, and quantitative functional groups. Particularly, the material demonstrated a high removal efficiency during Hg²⁺ adsorption, which fit the pseudo-second-order kinetics. The removal efficiency of Hg²⁺ was not influenced by the adsorbent dosage of 1–4?g/L.     

Gold nanoparticle mediated method for spatially resolved deposition of DNA on nano-gapped interdigitated electrodes,and its application to the detection of the human <Emphasis Type="Italic">Papillomavirus</Emphasis>

The authors introduce a method for spatially arranged DNA immobilization on 10-nm gold nanoparticles (GNP) deposited on a silicon substrate carrying nanogapped interdigitated electrodes. The GNPs are covalently bound to the surface via silane chemistry, and the single steps of fabrication are monitored by FTIR spectroscopy and atomic force microscopy. This GNP deposition technique is shown to reduce the size of the nanogaps to 130 nm. FTIR also was used to monitor the immobilization of DNA on the surface of the interdigitated electrodes. This method allows DNA to be immobilized in a uniform and homogenous way. The utility of the method is demonstrated by immobilizing probe DNA on the surface and detecting target DNA specific for the human papilloma virus via fluorescence with a detection limit as low as 1 pM. In our perception, this method for GNP-mediated DNA immobilization enables high-performance sensing of a wide range of target (analyte) DNA.

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Graphical abstract Schematic presentation of gold nanoparticle-mediated and spatially resolved deposition of DNA on nano-gapped interdigitated electrodes. The method was applied to the chemiluminescent determination of the human papillomavirus

     

Mixed Convection Boundary-Layer Flow Along a Vertical Cylinder Embedded in a Porous Medium Filled by a Nanofluid

The steady mixed convection boundary-layer flow on a vertical circular cylinder embedded in a porous medium filled by a nanofluid is studied for both cases of a heated and a cooled cylinder. The governing system of partial differential equations is reduced to ordinary differential equations by assuming that the surface temperature of the cylinder and the velocity of the external (inviscid) flow vary linearly with the axial distance x measured from the leading edge. Solutions of the resulting ordinary differential equations for the flow and heat transfer characteristics are evaluated numerically for various values of the governing parameters, namely the nanoparticle volume fraction ${\phi}$ , the mixed convection or buoyancy parameter ?? and the curvature parameter ??. Results are presented for the specific case of copper nanoparticles. A critical value ?? _c of ?? with ?? _c <?0 is found, with the values of | ?? _c| increasing as the curvature parameter ?? or nanoparticle volume fraction ${\phi}$ is increased. Dual solutions are seen for all values of ?? >??? _c for both aiding, ?? >?0 and opposing, ?? <?0, flows. Asymptotic solutions are also determined for both the free convection limit ${(\lambda \gg 1)}$ and for large curvature parameter ${(\gamma \gg 1)}$ .     

Biosynthesis of TiO2 nanoparticles and their superior antibacterial effect against human nosocomial bacterial pathogens

Research on Chemical Intermediates - Antibacterial titanium dioxide nanoparticles (TiO2NPs) were biologically synthesized by microwave irradiation of Cissus quadrangularis extract followed by...     

Unsteady mixed convection boundary-layer flow with suction and temperature slip effects near the stagnation point on a vertical permeable surface embedded in a porous medium

The unsteady mixed convection boundary-layer flow near the two-dimensional stagnation point on a vertical permeable surface embedded in a fluid-saturated porous medium with suction and a temperature slip effect is studied numerically. Similarity equations are obtained through the application of a similarity transformation technique. The shooting method is used to solve these similarity equations for different values of the mixed convection, wall mass suction, the unsteadiness and the slip parameters. Results show that multiple solutions exist for certain ranges of these parameters. Some limiting forms are then discussed, namely strong suction, the free convection limit, the situation when there is a large temperature slip and when the time dependence dominates.     

On the Temperature Slip Boundary Condition in a Mixed Convection Boundary-Layer Flow in a Porous Medium

A problem derived previously (Rohni et?al., Transp Porous Media 92:1?C14, 2012) for unsteady mixed convection flow in a porous medium involving a ??temperature slip?? boundary condition and fluid transfer through the boundary is considered. It is shown that the solution to this problem can be directly related to the solution of the corresponding problem for a prescribed surface temperature, involving a mixed convection parameter ??, an unsteadiness parameter A and transpiration parameter s. This latter problem is discussed in detail, particular attention being given to the steady analogue, A?=?0, allowing for fluid transfer through the surface, and to the unsteady problem, A?>?0, for an impermeable surface, s?=?0. Asymptotic results are obtained for large fluid transfer rates, ${s \gg 1}$ and ${s <0 , |s| \gg 1}$ and for large A. Particular attention is given to deriving asymptotic results for the critical points which determine the range of existence of solutions.     

Micropolar fluid flow over a shrinking sheet

An analysis is carried out for the steady two-dimensional flow of a micropolar fluid over a shrinking sheet in its own plane. The shrinking velocity is assumed to vary linearly with the distance from a fixed point on the sheet. The features of the flow and heat transfer characteristics are analyzed and discussed. It is found that the solution exists only if adequate suction through the permeable sheet is introduced. Moreover, stronger suction is necessary for the solution to exist for a micropolar fluid compared to a classical Newtonian fluid. Dual solutions are obtained for certain suction and material parameters.     

Catalytic Transesterification of Coconut Oil in Biodiesel Production: A Review

Catalysis Surveys from Asia - Biodiesel is one of the renewable energy (RE) sources that has received much interest due to its promising properties. Recently, the use of coconut oil as biodiesel...     

Radiation effects on the thermal boundary layer flow over a moving plate with convective boundary condition

The steady laminar boundary layer flow over a moving plate in a moving fluid with convective surface boundary condition and in the presence of thermal radiation is investigated in this paper. Under certain conditions, the present problem reduces to the classical Blasius and Sakiadis problems. The effects of radiation and convective parameters on the thermal field are thoroughly examined and discussed. Dual solutions are found to exist when the plate and the fluid move in the opposite directions.     

The Antiproliferative and Apoptotic Effect of a Novel Synthesized S-Triazine Dipeptide Series,and Toxicity Screening in Zebrafish Embryos

Several derivatives containing morpholine/piperidine, anilines, and dipeptides as pending moieties were prepared using s-triazine as a scaffold. These compounds were evaluated for their anticancer activity against two human breast cancer cell lines (MCF-7 and MDA-MB-231), a colon cancer cell line (HCT-116), and a non-tumorigenic cell line (HEK 293). Tamoxifen was used as a reference. Animal toxicity tests were carried out in zebrafish embryos. Most of these compounds showed a higher activity against breast cancer than colon cancer. Compound 3a—which contains morpholine, aniline, and glycylglycinate methyl ester—showed a high level of cytotoxicity against MCF-7 cells with IC₅₀ values of less than 1 µM. This compound showed a much lower level of toxicity against the non-tumorigenic HEK-293 cell line, and in the in vivo studies using zebrafish embryos. Furthermore, it induced cell cycle arrest at the G2/M phase, and apoptosis in MCF-7 cells. On the basis of our results, 3a emerges as a potential candidate for further development as a therapeutic drug to treat hormone receptor-positive breast cancer.