Removal of cobalt ions from aqueous solutions by using poly(N,N‐dimethylaminopropyl methacrylamide/itaconic acid) hydrogels

In this study, N,N‐dimethylaminopropyl methacrylamide (DMAPMAm) homopolymer and DMAPMAm/itaconic acid (DMAPMAm/IA) copolymers were obtained from ⁶⁰Co‐γ radiation polymerization. Gel fraction and percentage of swelling values were calculated through gravimetrical calculations. In order to increase the swelling of the hydrogel, the amount of IA in initial copolymer composition was gradually increased, but it was observed that gelation values were low. The structural and morphological assessments of homopolymer and copolymers were made by means of several techniques including Fourier Transform Infrared Spectroscopy (FT‐IR), Scanning Electron Microscopy (SEM), and Energy‐Dispersive X‐ray Spectroscopy (EDS). The cobalt ion (Co²⁺) removal capacities of hydrogel were investigated by taking into account of the initial metal ion concentration and pH of aqueous medium. When it came to the maximum capacity of values obtained from adsorption experiments by using Co²⁺ solutions at pH 5, they changed between 220 and 245 mg Co²⁺/g dry hydrogel. FT‐IR, SEM, EDS, and XRD analyses were carried out for enlightening the mechanism of Co²⁺ removal by hydrogels after the completion of adsorption. Also, desorption studies were conducted using ethylenediaminetetraacetic acid (EDTA). Finally, within approximately 5 days, all adsorbed Co²⁺ ions were released from hydrogels at pH 5 using 0.1M EDTA solution. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39569.     

Pyrolysis Kinetics of Asphaltite by Thermal Analysis

Abstract

Pyrolysis properties and kinetic analysis of asphaltite were investigated by means of thermogravimetry (TG) and derivative thermogravimetry (DTG). Thermal experiments were carried out from ambient temperatures to 1000°C in nitrogen atmosphere at different heating rates. TG/DTG curves showed that the decomposition proceeds through two steps with DTG peaks corresponding to the weight loss obtained. Kinetic analysis of the asphaltite decomposition steps was carried out under non-isothermal conditions. Coats-Redfern method was used to analyze the TG data for determination of kinetic parameters. Activation energies (E _a ) and pre-exponential factors (k _o ) were calculated for different heating rates and compared.     

Bio-Liquefaction/Solubilization of Lignitic Humic Acids by White-Rot Fungus (Phanerochaete chrysosporium)

Humic acid samples obtained from lignite were liquefied/solubilized by using white-rot fungus, and chemical characterization of the products was investigated by FTIR and GC-MS techniques. Prior to the microbial treatment, raw lignite was oxidized with hydrogen peroxide and nitric acid separately, and then humic acids were extracted by alkali solution. The prepared humic acid samples were placed on the agar surface of the fungus and liquid products formed by microbial affects were collected. The products were analyzed and the chemical properties were compared. The results show that oxidation agent and oxidation degree affect composition of the liquid products formed by microbial attack.     

Some generalizations of comparison results for fractional differential equations

In this paper, by using the technique of upper and lower solutions together with the theory of strict and nonstrict fractional differential inequalities involving Riemann–Liouville differential operator of order q, 0<q<1, some necessary comparison results for further generalizations of several dynamical concepts are obtained. Furthermore, these results are extended to the finite systems of fractional differential equations.     

Electrochemical synthesis of polypyrrole on aluminium in different anions and corrosion protection of aluminium

In this study, polypyrrole was deposited on the aluminium in different anions (CO₃²⁻, NO₂⁻, CrO₄²⁻, DBS⁻). The contribution of anions to formation of polypyrrole film was investigated by using cyclic voltammetry (CV) technique. The effect of polypyrrole film on the corrosion of aluminium was searched in 0.1 M HCI solution by using potentiostatic method. For this purpose, polarization curves were obtained, corrosion current density (icorr), corrosion potential (Ecorr), polarization resistance (Rp) were determined from the polarization curves. Moreover, the percent efficiency of coating was calculated. The complexes of pyrrole pentamers and different anions (CO₃²⁻, NO₂⁻, CrO₄²⁻, DBS⁻) were studied using ab initio quantum chemical at the Hartree-Fock (HF) levels with STO-3G, 3-21G, 6-31G(d,p) [13] basis sets and HOMO-LUMO energy gap is calculated by B3LYP method with 3-21G* and 6-31G(d,p) basis sets. The polypyrrole film obtained in CrO₄²⁻ anion is determined to be the most effective in prevention to pitting corrosion of aluminium as experimental and theoretical.