Batch Cr(VI) removal by polyacrylamide-grafted sawdust: Kinetics and thermodynamics

Batch sorption studies have been carried out to determine the effect of adsorbent dose, initial sorbate concentration and pH on the adsorption of Cr(VI) on polymer-grafted sawdust. The process was found to be pH, temperature and concentration dependent. An empirical relationship has been obtained to predict the percentage Cr(VI) removal at any time for known values of sorbent and initial sorbate concentration under observed test conditions. The effect of diverse ions has been studied and it is found that there is very little effect on the sorption of Cr(VI). The process was found to be exothermic with a maximum adsorption of 91.0% at 30°C for an initial concentration of 100 mg l⁻¹ at pH 3. The process follows first-order kinetics and the data fits the Freundlich adsorption isotherm. Thermodynamic parameters were also evaluated. Desorption studies confirmed that adsorbent can be effectively regenerated using 0.2 M NaOH and 0.5 M NaCl and can then be reused.     

Immobilization of heavy metals from aqueous solutions using polyacrylamide grafted hydrous tin (IV) oxide gel having carboxylate functional groups

A new adsorbent containing a carboxylate group has been prepared by the surface modification of a polyacrylamide grafted hydrous tin (IV) oxide gel. The product exhibits a very high adsorption potential for Pb(II), Hg(II) and Cd(II). The effect of initial metal ion concentration, adsorbent dose, pH, concentration of light metal ions, and temperature on metal removal has been studied. The process follows a first-order rate kinetics. The intraparticle diffusion of metal ions through pores in the adsorbent was shown to be the main rate limiting step. The equilibrium data fit well with the Langmuir adsorption isotherm. The selectivity order of the adsorbent is Pb(II) > Hg(II) > Cd(II). Adsorption rate constants and thermodynamic parameters were also presented to predict the nature of adsorption. The method was applied on synthetic wastewaters. Acid regeneration has been tried for several cycles with a view to recover the adsorbed metal ions and also to restore the sorbent to its original state.     

Atomic oxygen resistant coating from poly(tetramethyldisilylene‐co‐styrene)

A polydisilahydrocarbon, namely, poly(tetramethyldisilylene‐co‐styrene), synthesized from dimethyldichlorosilane and styrene in 1 : 0.5 mol ratio under dechlorination conditions was evaluated as an atomic oxygen (AO) resistant coating for polyimide film and C‐polyimide composite. Exposure of the polymer coating on a quartz plate to an AO fluence of 2.1 × 10²¹ atoms/cm² resulted in practically no mass loss, indicating the AO resistance of the polymer. Ten percent solution of the polymer in toluene was applied on aluminized Kapton® polyimide film (125 μm thick) to obtain a coating thickness of ～ 5 μm on the unaluminized surface. In a similar way, the coating was applied on a C‐polyimide composite. The coated and uncoated samples of Kapton® film and C‐polyimide composite were exposed to AO in a plasma barrel system. The uncoated aluminized Kapton® film (125 μm) lost 6.35 mg/cm² when exposed to AO fluence of 1.6 × 10²¹ atoms/cm² whereas the corresponding coated film lost only 0.14 mg/cm² even after exposure to AO fluence of 2.1 × 10²¹ atoms/cm². In the case of the C‐polyimide composite, the uncoated sample lost 63.64 mg/cm² on exposure to AO fluence of 1.8 × 10²¹ atoms/cm² whereas the coated one lost only 0.21 mg/cm² even after exposure to AO fluence of 2.1 × 10²¹ atoms/cm². SEM studies suggest that the coating offers good protection to the substrates. Formation of cracks on some portions of the coating was noticed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2368–2375, 2004     

Group delay modulation for pulse position coding based on periodically coupled C-sections

Chipless radio frequency identification (RFID) is an emerging research area nowadays. The recent development in this area proves its efficiency to compete with low cost identification systems like barcodes in the upcoming years. Chipless RFID encodes data using different kinds of spectral signature produced from some planar images as in the case of barcodes, the difference here is those images are made with conductive materials. Among the different ways of information encoding, a powerful way of encoding is time domain approach. This paper incorporates a tag using group delay encoding. The proposed chipless tag is composed of commensurate cascaded transmission line sections coupled at alternative ends (also known as C-sections). It consists of single group of C-sections. However, in order to increase the coding capacity, the proposed tag can allow multi-frequencies also. In addition to this, the tag is also compatible with commercial ultra wide band radar. The proposed tag is validated experimentally. It exhibits a good reading range of 1.2 m.     

Novel fabrication of extremely high aspect ratio and straight nanogap and array nanogap electrodes

Microsystem Technologies - We reported a reproducible, simple and novel method for fabricating electrodes with high aspect ratio and highly straight nanometer size gap. The gap size could be...     

Development of high strength,porous mullite ceramic hollow fiber membrane for treatment of oily wastewater

Ceramic hollow fiber membranes (CHFMs) are known for their excellent characteristics including high surface area, compact design, and good chemical, thermal, and mechanical stabilities. Despite these interesting attributes, CHFMs are also prone to certain limitations, such as brittleness and high cost that hinder them from being commercialized. To mitigate this drawback, we have developed a high strength, porous ceramic hollow fiber membrane, derived from mullite–kaolinite powder, for efficient oil–wastewater separation. The superhydrophilic, low-cost mullite-based (CHFM) was successfully fabricated through combined phase inversion and sintering techniques. Prior to the fabrication, the as-received mullite–kaolinite was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analyses. Subsequently, operational parameters such as the effect of mullite content, sintering temperature, and air gap were optimized during the fabrication of mullite ceramic hollow fiber membrane. The resulting membranes were systematically characterized and evaluated in terms of morphology, porosity, mechanical strength, water flux, and oil–water separation. Increasing the mullite content, air gap, and sintering temperature enhanced the formation of microvoid structure. It is interesting to note that the mechanical strength of 86 MPa was obtained for the membrane containing 60 wt % of mullite sintered at 1450 °C and an air gap of 5 cm. The membrane induced a stable permeate water flux and oil rejection of mullite CHFM of 182 L/m²?h and 97.1%, respectively. As compared to kaolin ceramic counterparts, this porous mullite ceramic hollow fiber membrane can be used in various water treatment applications, including for the separation of oily wastewater due to its mechanical strength and water flux.     

Thermal properties of processable polyaniline with novel sulfonic acid dopants

Thermal properties of melt processable polyaniline (PANI) synthesized by doping with functionalised novel sulfonic acid dopants have been investigated. Doping of PANI was carried out by using the dopants derived from an inexpensive naturally existing biomonomer, cardanol: sulfonic acid of 3‐pentadecylphenol, sulfonic acid of 3‐pentadecylanisole and sulfonic acid of 3‐pentadecylphenoxyacetic acid. These dopants act as very good plasticizing cum protonating agents for PANI. Doping was carried out either by mechanical mixing of emeraldine base and the dopant or by an in situ doping emulsion polymerization of aniline. Highly conducting free‐standing flexible films of protonated PANI could be prepared by a hot pressing method at different temperatures. The thermal stability and thermal reactions of these protonated PANI were followed by conductivity measurements at different temperatures, wide angle X‐ray diffraction measurements, thermogravimetric analysis and differential scanning colorimetry analysis. © 2001 Society of Chemical Industry     

Smart networks for control

Control networks move small packets of data to a large set of nodes, so as to integrate and automate everything from home appliances to entire factories. This is due to the use of embedded microprocessors. The author discusses the control net architecture, network topology and the fast response of the network     

Characterization of etch pit formation via the Everson-etching method on CdZnTe crystal surfaces from the bulk to the nanoscale

A combination of atomic force microscopy, optical microscopy, and mass spectrometry was employed to study CdZnTe crystal surface and used etchant solution following exposure of the CdZnTe crystal to the Everson etch solution. We discuss the results of these studies in relationship to the initial surface preparation methods, the performance of the crystals as radiation spectrometers, the observed etch pit densities, and the chemical mechanism of surface etching. Our results show that the surface features that are exposed to etchants result from interactions with the chemical components of the etchants as well as pre-existing mechanical polishing.     

Biodegradation of Used Engine Oil by a Methylotrophic Bacterium,Methylobacterium Mesophilicum Isolated from Tropical Hydrocarbon-contaminated Soil

A Gram-negative facultatively methylotrophic bacterium putatively identified as Methylobacterium mesophilicum strain RD1 displayed extensive degradative ability on used engine oil (SAE 40W) in liquid cultures. The rate of degradation of used engine oil (1274.85 mg L^?1) by the isolate, for the first 12 days and the last 9 days were 65 and 40 mg L^?1 d^?1, respectively. Gas chromatographic (GC) analyses of residual used engine oil revealed that 61.2% and 89.5% of the initial concentration of the used engine oil were degraded within 12 and 21 days. GC fingerprints of the used engine oil after 12 days of incubation showed total disappearance of C₁₅, C₂₃, C₂₄, C₂₅, and C₂₆ hydrocarbon fractions as well as drastic reductions of C₁₃, C₁₄, C₁₆, and PAHs fractions such as C₁₉-Anthracene and C₂₂-Pyrene. At the end of 21 days’ incubation, total disappearance of C₁₇-pristane, C₂₂-pyrene, one of the C₁₉-anthracene, and significant reduction of C₁₈-phytane (96.8%) fractions were observed. In addition, less than 10% of Day 0 values of medium fraction ranges C₁₃, C₁₄, and C₁₆ were discernible after 21 days. This study has established the potential of Methylobacterium mesophilicum strain RD1 in degradation of aliphatic, aromatic, and branched alkane components of used engine oils.