Metal adsorption properties of multi-functional PAMAM dendrimer based gels

Metal adsorption studies are getting important and there are many functional adsorbents developed recently. Here, we report the synthesis of multifunctional PAMAM G2 (polyamidoamine) possessing methacryl, amine, hydroxyl and phosphonate groups used in free radical curing gel formulations. UV curable gel is conducted in the presence of acrylamide, bisacrylamide, and polyethylene glycol diacrylate. Adsorption study of the resulting novel sorbents (gels) are carried out with a series of metals. Through a comprehensive study, structure–property relationship of the series gels is conducted by using different amount of amine, hydroxyl, and/or phosphonate ester groups on the PAMAM G2. Selected metals are Cr³⁺, Fe³⁺, Ni²⁺, Cu²⁺, Ag⁺, and Cd²⁺ within a series of hard, intermediate, and soft ionic species. Adsorption study is carried out in pure water environment at neutral pH. Metal ions removal percentages and adsorption capacities of gel adsorbents are calculated by using atomic absorption spectroscopy. There is relationship between the overall functional groups presence in gel formulation and swelling densities for removing the metal ions. Introducing dendrimer into the gel formulation enhanced the metal ions adsorption against to Bare GEL formulation which do not possess dendrimer units. Consequently, the maximum removal efficiency has been obtained for Cr³⁺ and Fe³⁺.     

On the Computation of the Macroscopic Tangent for Multiscale Volumetric Homogenization Problems

For the computation of the macroscopic tangent that is required in multiscale volumetric homogenization techniques, two methods are summarized. First, a condensation approach is followed where the linearity of variational terms associated with the penalty enforcement of boundary conditions is explored in order to extract a macroscopic tangent at any stage of the Newton–Raphson iterations of a microstructural testing procedure. As an alternative approach, a second method is explored that requires only the knowledge of infinitesimally close macroscopic deformation states. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetic adsorption of drugs using carbon nanofibers in simulated gastric and intestinal fluids

Two different classes of drugs were selected to test the adsorption capacity of carbon nanofibers as a greener new generation alternative adsorbent in simulated gastric and intestinal fluids. Kinetics of the promethazine and trimethoprim adsorption were analyzed using Lagergren first order and Pseudo second order models. Intraparticle diffusion graphs were also plotted to discuss the adsorption mechanism. Kinetic data showed the significance of boundary layer effect for both of the drugs and the presence of intraparticle diffusion as the other rate controlling step for the promethazine adsorption. Giles isotherms showed the high affinity of drug molecules to the adsorbent. Maximum adsorption capacity of drugs was calculated using Langmuir model as 18.35 and 41.15 mg/g for trimethoprim and 95.24 and 80.65 mg/g for promethazine in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), respectively. Trimethoprim adsorption was under favor of hydrophobic interaction and π-π dispersion interactions while promethazine adsorption was through cation exchange where the electrostatic attraction is an important force with the contribution of dispersion interactions.