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Abstract : Evaluation of Kinetics of Leaching of Lignins and Tannins in Batch Adsorption of Cr (VI) by Emblica officinalis Leaf Powder (EOLP)
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Abstract: The present paper is aimed to assess the contents of lignin and tannin leached in the batch adsorption test filtrate and to evaluate the kinetics of leaching of lignin and tannins. For the purpose, raw Emblica officinalis leaf powder (EOLP) has been used as adsorbent for removal of Cr (VI) from aqueous solution in batch mode of operation. Test results indicate that EOLP imparts lignin and tannin in batch test filtrate. Both lignin and tannin contents are related to pH, chemical oxygen demand (COD), initial Cr(VI) concentration (C0) residual Cr(VI) concentration in batch test filtrate (C),amount of adsorbent (Wad) and the time of contact (t). Dimensionless parameters are developed and the lignin and tannin contents are well correlated with dimensionless parameters. From the studies conducted on rate of leaching of both soluble lignin and tannins, the kinetics of leaching of soluble lignin and tannin follow a pseudo second order type rate kinetics. Linear regression models are developed based on pseudo second order kinetics for determination of lignin and tannin contents in batch test filtrate. However, these findings need further verification in future investigations. Keywords: Emblica officinalis leaf powder (EOLP), batch test filtrate, chromium (VI), leaching, kinetics.a.Download Full Article |
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Abstract: Biotechnological production of chemical building blocks is one important step towards a more sustainable production. Unfortunately, the products to be separated are often highly diluted. Pervaporation has received increasing attention for the separation of small amounts of organic compounds from aqueous solutions, especially in the separation of butanol from water or from fermentation broth. To evaluate the potential of pervaporation for biobutanol recovery a consistent database is required, describing the dependency of permeate fluxes and selectivities on process variables like temperature, permeate pressure as well as feed concentrations and compositions. Therefore, within this work we investigated the separation behaviour of a commercially available polydimethylsiloxane (PDMS) membrane and membranes based on poly(ether block amide) (PEBA) fabricated in our own laboratory. The membranes were tested under varying operating conditions. Fermentation by-products or impurities may affect the pervaporation separation performance. Therefore, in addition, the permeate fluxes and the influence of acetone, ethanol, acetic and butyric acid and 1,3-propanediol have been investigated in detail as well. Several differences in the permeability and selectivity of PDMS and PEBA were observed during the experimental study. Swelling experiments were applied to further analyse the separation behaviour of PDMS and PEBA more in detail. Finally the influence of the observed separation performances on the overall butanol pervaporation process is discussed. It was found that especially well permeating by-products like acetone can drastically influence the subsequentdownstreaming process. Keywords: Polydimethylsiloxane (PDMS), PervapTM, poly(ether block amide) (PEBA), swelling, organic acid, Hansen Solubility Parameter.Download Full Article |
Abstract : Heparin-Mimicking Polymer Modified Polyethersulfone Membranes - A Mini Review
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Abstract: Recent studies on the modification of polyethersulfone (PES) membranes using heparin-mimicking polymers are reviewed. The general conception of heparin-mimicking polymersis defined as the syntheticpolymers (including the biopolymer derivates and synthetic sulfated artificial polymers) with similar biologically functionalities as heparin, such as the anticoagulant, growth factor binding, and also disease mediation. In the review, heparin-mimicking polymers is briefly reviewed; then heparin-mimicking polymer modified PES membranes, including blended, coated, and grafted membranes are discussed respectively. Keywords: Heparin-mimicking, polyethersulfone, blood compatibility, blending, coating.Download Full Article |
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Abstract: Photovoltaic-powered membrane was taken to filter brackish water. Effect of ammonia concentration, pressure and salinity on ammonia and total dissolved solids (TDS) removal, water recovery and energy consumption had been investigated. Results show that ammonia concentration did not influence ammonia and TDS removal, water recovery, and energy consumption obviously. Results of ammonia concentration of 10, 20 and 35 mg/l were similar to that of 5 mg/l. For salinity, the better filtration was achieved when the concentration of salinity was lower. With increment of pressure, ammonia and TDS removal increased simultaneously. The ammonia and TDS removal of more than 98% attained with the water recovery of 40.6% at the energy consumption of 2.0 kWh/m3. It illustrates that salinity and pressure were definitely crucial to brackish water filtration with photovoltaic-powered membrane. Keywords: Photovoltaic-powered membrane, Reverse osmosis, Brackish water, Salinity, Total dissolved solids (TDS), Energy consumption. Download Full Article |
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Abstract: H2 permselective silica hybrid membranes were successfully prepared by using a counter diffusion chemical vapor deposition (CVD) method. Hexyltrimethoxysilane (HTMOS), phenyltrimethoxysilane (PhTMOS) or diphenyldimethoxysilane (DPhDMOS) were used as silica precursors. The oxidants were O3 or O2. These reactants were provided at the opposite side of the γ-alumina substrates, and the deposition occurred in the pores of the substrates. The HTMOS/O3 derived membrane deposited at 450°C showed the highest H2 permselectivity. The H2 permeace was 2.1×10-6 mol m-2 s-1 Pa-1 with the H2/SF6 permeance ratio of 5.9×106. H2 permeances through the HTMOS derived membranes increased with increasing the deposition temperatures. While the H2 permeance through the PhTMOS and DPhDMOS derived membranes decreased with increasing the deposition temperatures. The PhTMOS derived membrane prepared at 150°C showed the H2 permeance of 1.7×10-6 mol m-2 s-1 Pa-1 with the H2/SF6 permeance ratio of 13. The PhTMOS membrane prepared at 320°C showed the highest H2/SF6 permeance ratio of 1.8×104among the PhTMOS derived membranes. However, the H2/SF6 permeance ratio through the DPhDMOS membranes showed the different trend. Higher H2/SF6 permeance ratio was found through the DPhDMOS derived membranes deposited at 180°C and 360°C. The maximum H2/SF6 permeance ratio was 4.2×104 through the DPhDMOS membrane deposited at 180°C. The decomposition properties of organic groups on silica surface are investigated by using hydrolysis powders derived from the each silica precursor. The HTMOS powders showed O3 stability after the high temperature treatment. Thus, high H2 permselective membranes were prepared by the HTMOS at 450 °C. Keywords: Silica hybrid membrane, counter diffusion CVD method, H2permselective membrane, pore size control, silica precursors. Download Full Article |