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

Organisational Management III : ORM3022

Examination on Organizational Management III : ORM3022, November 201

Organisational Management 111: ORM3022

Examination on Organisational Management 111: ORM3022, Nov 201

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