Background: Dyes are one of the most important industrial pollutants, especially in textile industries. Many methods have been proposed in order to remove color from wastewater among which, adsorption is more acceptable due to the ability for its use in the large scale. Objectives: The objective of this study was to investigate pumice as an inexpensive adsorbent for removal of Methylene Blue from aqueous solutions. Materials and Methods:In this work the Modified Pumice Stone has been applied for removal of the Methylene Blue dye from aqueous environments. The effect of pH, contact time, initial concentration and amount of adsorbent were considered. In order to investigate the mechanism of the adsorption process, several kinetic models including pseudo-first order, pseudo-second order and intra-particle diffusion were used. In addition, equilibrium data was fitted on to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. Results: Results showed that the adsorption of the Methylene Blue was enhanced with increasing initial dye concentration, pH and contact time. The optimum pH was 10. The q max for adsorption of methylene blue dye from the Langmuir model was 15.87 mg/g. Considering the values of R 2 (0.999) and χ 2 , Freundlich isotherm model and pseudo-second order kinetic model had the best fitness. Conclusions:This study has demonstrated that the modified Pumice stone with HCl can be employed as effective and inexpensive adsorbent for the removal of Methylene Blue from aqueous environments.

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In this study Ziziphus nummularia (ZPN) as a good, available and inexpensive adsorbent has been introduced and used for the removal of Bromocresol Green (BCG) from several water solutions successfully. The effect of various parameters such as pH, dye concentration, amount of adsorbent, size of adsorbent particles, and contact time on removal processing was investigated.To investigate the mechanism of adsorption, several kinetic models were tested including Lagergren, pseudosecond-order, particle diffusion, film diffusion, and Elovich models. Adsorption isothermal data could be interpreted by the Langmuir, Freundlich, Tempkin, and DubininÀRudushkevich (DR) isotherm models. Thermodynamic parameters like free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) of the system were calculated.' EXPERIMENTAL SECTION Materials. BCG with the molecular formula C 12 H 14 Br 4 O

The complexes [pyda.H]2[Co(pydc)2]·H2O (I) and [pyda·H]2[La2(pydc)4(H2O)4].2H2O (II) were prepared from the complexation of a novel pyridine containing self-assembling system LH2, ([pyda·H2]2+[pydc]2–) (pyda = 2,6-pyridinediamine and pydc·H2 = 2,6-pyridinedicarboxylic acid), with cobalt(II) and lanthanum(III) salts in 82% and 74% yields, respectively. The characterizations were performed using elemental analysis, ESI mass spectroscopy as well as 1H and 13C solution NMR spectroscopy, and X-ray crystallography. The crystal systems I and II are monoclinic and triclinic with space groups P21/n and P[Formula: see text] respectively. Coordination number around each Co atom is six with distorted octahedral geometry, while coordination number around each La atom is nine with highly distorted tricapped trigonal prism geometry. The paramagnetic Co(II) and diamagnetic La(III) complexes show 1H NMR resonances of both anionic [pydc]2- and cationic counter ion [pyda·H]+ in DMSO-d6. The complexation reactions of the complex I in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of pH. The results revealed that at a pH range 4.0–4.5 the major complex species is [(pyda·H)]2[Co(pydc)2].Key words: self-assembly, X-ray crystal structure, Co(II) complex, La(III) complex, 2,6- pyridinedicarboxylic acid, 2,6-pyridinediamine, hydrogen bonding.

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