Selective removal of chromium (VI) from sulphates and other metal anions using an ion-imprinted polymer

A linear copolymer was prepared from 4-vinylpyridine and styrene. An ion-imprinted polymer (IIP) specific for Cr (VI) adsorption was prepared by copolymerisation of the quaternised linear copolymer (quaternised with 1,4-chlorobutane), 2-vinylpyridine functional monomer and ethylene glycol dimethacrylate (EGDMA), as the cross-linking monomer, in the presence of 1,1’-azobis(cyclohexanecarbonitrile) as initiator. Ammonium dichromate and aqueous methanol were used as a template and porogenic solvent, respectively. Leaching of the chromate template from the polymer particles was achieved with successive stirring of the ion-imprinted polymer (IIP) particles in 4 M HNO3 solutions to obtain leached materials, which were then used for selective rebinding of Cr (VI) ions from aqueous solutions. Similarly, the non-imprinted polymer/ control polymer (NIP/CP) material was also prepared under exactly the same conditions as the IIP but without the chromate anion template. Various parameters, such as solution pH, initial concentration, aqueous phase volume, sorbent dosage, contact time and leaching solution volumes, were investigated. Scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, BET surface area and pore size analysis were used for the characterisation of IIP (both unleached and leached) and CP materials. Optimal parameters were as follows: solution pH, 3; contact time, 120 min; eluent, 20 mℓ of 0.1 M NaOH; and sorbent amount, 125 mg. Maximum retention capacity of IIP and CP was 37.58 and 25.44 mg∙g-1, respectively. The extraction efficiencies of the IIP and CP were compared using a batch and SPE mode of extraction. In the absence of high concentrations of ions, especially sulphate ions, both CP and IIP demonstrated no differences in binding of Cr (VI), which was almost 100%. However, in the presence of high concentrations of sulphate ions, the selectivity on the CP completely collapsed. The study clearly demonstrates the suitably of the developed IIP for selective extraction of Cr (VI) in complex samples such as those from acid mine drainage. The selectivity was also compared by direct injection of the real-world sample, both spiked and non-spiked, into that obtained after IIP selective extraction. Despite the method’s very low detection limits for direct injection (below 1 μg∙ℓ-1), no Cr (VI) was obtained. However, after IIP selective extraction, spiked Cr (VI) was detected in the spiked sample

Elucidation of the complex Baylis-Hillman reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone

DABCO-catalyzed reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone (MVK) affords a mixture of products, comprising the ‘normal’ Baylis-Hillman adduct, theMVKdimer and a pair of diastereomeric bis-(MVK)Baylis-Hillman adducts. 1HNMRspectroscopy-based kinetic studies have provided clear insights into the competing pathways and product distribution in this complex reaction

Transport properties of zinc-bismuth oxide glasses

28-32<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Zinc-bismuth oxide glasses of 10-25 mol% of zinc oxide are prepared having thickness between 0.35-0.42 cm and diameter 0.60-0.95 cm. Physical properties such as density (d), molar volume <span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:arial;mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa;mso-bidi-font-style:="" italic"="">(V),<span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"=""> hopping distance <span style="font-size:11.0pt;line-height:115%;font-family: " calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:arial;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa;mso-bidi-font-style:italic"="">(R), number of ions per cc (N) and polaron radius <span style="mso-bidi-font-style: italic">(rp) are also reported. Polaron radius is found around 1.85 <span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">Å<span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"=""> which shows formation of small polarons. Measurements of de electrical conductivity are reported in the temperature range 443-573K. - Log σ<span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"=""> versus 1/T and –log µ versus 1/T plots exhibited linearity. Hopping condition given by Holstein was applied. Polaron band-width (J) satisfies the inequality which shows adiabatic hopping conduction. The density of Fermi level and the density of localized states are found to be close to each other.</span

Effect of Past Electric Field on Transport Properties of 8Ov<Sub>2</Sub>O<Sub>5</Sub>-2Op<Sub>2</Sub>O<Sub>5</Sub> Semiconducting Glass

The effect of past electric field on transport properties such as dc-conductivity, activation energy etc. of 8Ov2O5-2Op2O5 semiconducting glass has been considered. The various parameters N,rp,N (EF) etc. Are calculated from Mou T1/4 analysis, and the results are discussed on the basis of the polaron model

<span style="font-size:11.0pt;line-height:115%; font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family: "Times New Roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font: minor-latin;mso-bidi-font-family:Arial;mso-ansi-language:EN-US;mso-fareast-language: EN-US;mso-bidi-language:AR-SA">Thermal conductivity of V₂O₅-P₂O₅ glasses</span>

291-296<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:arial;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">The thermal conductivity of V2O5-P2O5 glass system has been experimentally determined in the temperature range 303-422 K. The data covered the glass composition range from 60 to 80 mol% of V2O5. It has been observed that the thermal conductivity increases linearly with temperature. The results obtained confirmed that the major contribution to the thermal conductivity of this glass system is due to lattice vibrations. The values of density, molar volume, lattice thermal conductivity (λL) band gap energy, melting temperature, electronic (λe) and bipolar component of thermal conductivity (λbp) are also reported.</span

Comparative accounts of chromium accumulation in three ferns under hydroponic system

553-558Hydroponic experiments were carried out to demonstrate the chromium bioaccumulation potential of three ferns viz. <i style="mso-bidi-font-style: normal">Diplazium esculentum (Retz.) Sw., Pteris cretica L. and Polystichum squarossum (D. Don) J. Sm. Plants were exposed to seven levels of Cr (0, 25, 50, 100, 300, 600 and 100 µg ml-1) for 10 days. All three test species accumulated significant Cr content in comparison to control. The result showed the increasing trends in fresh biomass (25-30%) up to 600 µg ml-1 concentration in P. cretica and P. squarossum. Although, D. esculentum showed necrosis even after 1 day exposure; necrosed biomass contained significant Cr than control but significant decrease in chlorophyll and carotenoid content indicates its least tolerance capacity. It has also been revealed that chlorophyll content was not affected by Cr exposure up to 300 µg ml-1 concentrations in P. cretica and <i style="mso-bidi-font-style: normal">P. squarossum and the carotenoid content showed the significant increase of 35 to 74% at higher dose from 300 and 1000 µg ml-1 in comparison to the control. Therefore, it has been observed that P. cretica and P. sqarossum are new Cr hyperaccumulator with efficient tolerance capacity. It also revealed that <i style="mso-bidi-font-style: normal">P. cretica has highest tolerance capacity to Cr ions amongst the three test species which often grows rapidly, densely and easily adapt to artificial cultivation and can be exploited for treatment of tannery and other Cr contaminated wastelands. </span

Hopping Conduction Mechanism in Amorphous CuO-Bi2\text{}_{2}O3\text{}_{3} Pellets

The transport properties of CuO-Bi$\text{}_{2}$O$\text{}_{3}$ pellets (pressed at room temperature 303 K) like dc electrical conductivity etc. are measured. The activation energy, dielectric constant etc. are reported. The hopping conduction is examined. Non-adiabatic hopping conduction is observed. The plot of -log σ versus 1/T is found to be linear. Activation energy of pellets containing CuO (80, 70, 60 mol%) shows electronic conduction while the pellet containing CuO (50 mol%) shows ionic conduction. The effect of content of CuO (mol%) and frequency on dielectric constant is also studied. The variation of dielectric constant with CuO (mol%) shows zigzag nature and may be due to the relaxation effects

<span style="font-size:11.0pt;line-height:115%; font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family: "Times New Roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font: minor-latin;mso-bidi-font-family:Arial;mso-ansi-language:EN-US;mso-fareast-language: EN-US;mso-bidi-language:AR-SA">Effect of pellet pressing temperature on transport properties of amorphous CuO-Bi₂O₃ pellets</span>

231-235<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:arial;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">The results of transport properties of CuO-Bi2O3 pellets pressed at different temperatures are reported. The data of electrical properties such as dc-electrical conductivity, dielectric constant and activation energy are discussed. Similarities between CuO-Bi2O3 pellets and oxide glasses are emphasized. New results of pellet pressing temperature are reported. The hopping conduction phenomenon in three sets of pellets is discussed. All the three pellets exhibited non-adiabatic electronic conduction. The results of dc-conductivity are discussed on the basis of growing of small crystallities in the pellets.</span

<span style="font-size:11.0pt;line-height:115%; font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family: "Times New Roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font: minor-latin;mso-bidi-font-family:"Times New Roman";mso-ansi-language:EN-US; mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Transport properties of amorphous CuO-Bi₂O₃ semiconducting pellets</span>

33-37<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The results of measurement of de-electrical conductivity and activation energy have been reported for four different composition of CuO-Bi2O3 glass powder pellets pressed at 50°C in the temperature range of 300 - 493 K. A plot of -log σ<span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:arial;mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"=""> versus 1/T shows two different regions of conduction suggesting two types of conduction mechanisms switching from one type to another occurring at Rnee temperature. The de-conductivity increases with increase in temperature of the sample and also with increase of mol% of CuO. Activation energy calculated for both regions (LTR and HTR) is below 1 eV, thus the electrical conduction is electronic. Activation energy decreases with increase of mol% of CuO. Non-adiabatic hopping conduction was observed in the sample. A plot of dielectric constant versus log of frequency shows zig-zag nature. Dielectric constant decreases with increase in mol% of CuO.</span