EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES ON REMOVAL OF Cd(II), Pb(II) AND As(V) FROM WASTEWATER USING CARP (CYPRINUS CARPIO) SCALES

Unmodified farming carp (cyprinus carpio) scales were used as a biosorbent for the removal of Cd(II), Pb(II) and As(V) ions from aqueous solutions. The adsorption studies were conducted as a function of pH, contact time and temperature. The best sorption of cadmium, lead and arsenate ions was achieved for pH between 6.0 and 8.0. The adsorption data for cadmium, lead and arsenate at 20, 30 and 40 °C are fitted to Langmuir, Freundlich, Sips, Dubinin-Radushkevich (D-R), Jovanovic, Jovanovic-Freundlich (J-F), Temkin, Toth and Koble-Corrigan (K-C) isotherm models. Experimental data were used to model adsorption kinetics using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. The results showed that the adsorption of Cd(II), Pb(II) and As(V) ions onto carp scale followed the pseudo-second-order kinetic model. Thermodynamic parameters, including the Gibbs free energy (Δ

Synthesis and characterization of nanocrystalline polyhedral oligo silsesquioxanes (POSS) with cross-linkable functionalities

A facile synthesis was employed for three polyhedral oligo silsequioxanes (POSS), obtaining incompletely condensed structures with fern-like and cubic morphologies. Proton nuclear magnetic resonance spectroscopy (H-1 NMR) indicated the successful synthesis of the proposed POSS structures. The hydroxyl groups affected the manner and type of POSS morphology, as seen under a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Fourier-transform infrared spectroscopy (FTIR) showed the availability of surface hydroxyl groups that contributed to the formation of a higher amount of char residue, as found from TGA analysis. The highest decomposition temperature (281 degrees C) and the least char residue were found for a cross-linkable POSS, obtained by esterification of the hydroxyl groups with methacryloyl chloride

Immobilization of horseradish peroxidase onto kaolin

Kaolin showed as a very perspective carrier for the enzyme immobilization and it was used for the adsorption of horseradish peroxidase (HRP). The effects of the enzyme concentration and pH on the immobilization efficiency were studied in the reaction with pyrogallol and anthraquinone dye C.I. Acid Violet 109 (AV 109). In addition, Fourier transform infrared spectroscopy, scanning electron microscopy and analysis by Brunauer-EmmettTeller were performed for kaolin, thermally activated kaolin and the immobilized enzyme. It has been shown that 0.1 IU of HRP-kaolin decolorized 87 % of dye solution, under the optimal conditions (pH 5.0, temperature 24 degrees C, dye concentration 40 mg/L and 0.2 mM of H2O2) within 40 min. The immobilized HRP decolorization follows the Ping Pong Bi-Bi mechanism with dead-end inhibition by the dye. The biocatalyst retained 35 +/- 0.9 % of the initial activity after seven cycles of reuse in the decolorization reaction of AV 109 under optimal conditions in a batch reactor. The obtained kinetic parameters and reusability study confirmed improvement in performances of k-HRP compared to free, indicating that k-HRP has a great potential for environmental purposes