Kinetic, Isotherm and Thermodynamic Analysis on Adsorption of Cr(VI) Ions from Aqueous Solutions by Synthesis and Characterization of Magnetic-Poly(divinylbenzene-vinylimidazole) Microbeads

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53–212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin–Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol−1, which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field

The use of polyethyleneglycolmethacrylate-co-vinylimidazole (PEGMA-co-VI) microspheres for the removal of nickel(II) and chromium(VI) ions.

The polyethyleneglycolmethacrylate-co-vinylimidazole (PEGMA-VI) copolymers, that can be used in heavy metal removal applications, were synthesized and characterized; and their use as sorbents in heavy metal removal was investigated. It was determined that the ligand vinylimidazole was successfully inserted into the polymer structure. Then, chromium (Cr(VI)) and nickel (Ni(II)) ions were used as model species to investigate the usability of the obtained microspheres in heavy metal removal. The effects of pH of the adsorption medium, initial concentration of the metal ions and VI content of PEGMA-VI microspheres were investigated as the effective parameters on the adsorption capacities of the microspheres. The adsorption rate of the microspheres was also investigated for determination of the optimum adsorption time which is the required time for maximum adsorption capacity. The adsorption capacities under optimum conditions were also determined. The order of adsorption affinities of PEGMA-VI microspheres with respect to the used metals was determined by competitive adsorption studies. According to the obtained results, the highest adsorption affinity of the PEGMA-VI microspheres was towards Cr(VI) ions, the adsorption affinity was less for Ni(II) and the least affinity was towards Cu(II) ions. The adsorption-desorption studies showed that the microspheres were reusable without a significant decrease in the ion adsorption capacities

Preparation and characterization of polyethyleneglycolmethacrylate (PEGMA)-co-vinylimidazole (VI) microspheres to use in heavy metal removal.

Polyethyleneglycolmethacrylate (PEGMA) and vinylimidazole (VI) were used in order to obtain microspheres of PEGMA-VI copolymers that can be used in heavy metal removal applications. The obtained copolymers were characterized and their use as sorbents in heavy metal removal was investigated. In the first part of the study, PEGMA-VI microspheres were prepared by suspension polymerization method. The obtained swellable microspheres with 10-50 microm average diameter did not have permanent porosity according to the morphological and physicochemical determinations. The sizes of microspheres became smaller with increasing VI and cross-linker ethyleneglycoldimethacrylate (EGDMA) contents and increasing agitation rate. The VI content, EGDMA ratio, pH and ionic strength were determined as the effective parameters on the swelling behavior of PEGMA-VI microspheres. In the second part of the study, Cu(II) ions were used as a model species in order to investigate the usability of the obtained PEGMA-VI microspheres in heavy metal removal. Adsorption capacities under optimum conditions were determined. The Cu(II) ion adsorption capacity increased by increasing the initial Cu(II) ion concentration, and it reached the maximum value (i.e., 30 mg Cu(II)/g PEGMA-VI microspheres) at 400 mg Cu(II)/L initial Cu(II) ion concentration under the determined optimum conditions. Microspheres were found to be reusable after desorption for several times

Mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)

The mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) functionalized by reaction of the pendant epoxy groups with diethylene triamine (PGME-deta) was studied using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis. Atomic force microscopy (AFM) and scanning energy-dispersive X-ray spectroscopy (SEM-EDX) were used for the determination of surface morphology of the copolymer particles. The sorption behavior of heavy metals Cu(II), Cd(II) and Pb(II) ions sorption was investigated in batch static experiments under non-competitive conditions at room temperature (298 K). The obtained results were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion kinetic model. The kinetics studies showed that Cu(II), Cd(II) and Pb(II) sorption obeys the pseudo-second-order model under all investigated operating conditions with evident influence of pore diffusion