The presence of organic dyes in the aquatic environment is a serious global problem because of the serious negative consequences on the quality of ecosystems. Among various physico-chemical methods, the adsorption could be considered a promising alternative for removing dyes from aqueous media, due to its efficiency, high selectivity, low cost, ease of operation, simplicity, and availability in a wide range of experimental conditions. However, all these advantages are closely related to the nature of adsorbent material used in the adsorption processes of dyes. The adsorbent materials available in large quantities requiring a simple preparation will enhance the benefits of the adsorption processes, in agreement with the concepts of green chemistry. This review is focused on the use of leaf-based materials, in raw or modified forms, as adsorbents for the removal of dyes from aqueous effluents, with applications in the wastewater treatment. This review addresses characterization of leaf-based adsorbents, possible utilization of leaf-based adsorbents (raw and activated forms) for dye removal and possible applications in pilot and full scale systems. Also, thermodynamics, equilibrium and kinetic parameters of dye adsorption on leaf-based adsorbents are discussed. The practical utility of leaf-based adsorbents for dye removal, and their possible uses in the treatment of industrial wastewater are copiously highlighted.

ABSTRACT:The chelation properties of the addition-type polymers poly(amidoxime-hydroxamic acid) and poly(Nmethyl amidoxime-N-methyl hydroxamic acid) toward some trivalent lanthanide metal ions [La(III), Nd(III), Sm(III), Gd(III), and Tb(III)] were studied by a batch equilibration technique as a function of contact time, pH, and counterion. The effect of the crosslinker, divinylbenzene, was also studied. The selectivity and binding capacity of the resins toward various lanthanide metal ions are discussed.

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This study represented a novel conducting poly (p-nitroaniline-co-p-aminophenol) (P(p-NAn-co-p-APh)) material, obtained by electrocopolymerization of para-nitroaniline (p-NAn) and para-aminophenol (p-APh) in aqueous sulfuric acid solution. Copolymerization was carried out using cyclic voltammetry technique on gold electrode with different monomer feed concentrations. The obtained polymer and copolymer films had been characterized by scanning electron microscopy (SEM), in situ conductivity measurements, in situ UV-Vis, and FT-IR spectroscopy. Initial cyclic voltammograms of p-NAn, p-APh and p-NAn + p-APh showed that the peak potentials were located at different values. The in situ conductivity of the copolymers measured between −0.20 V< E SCE < 0.70 V increased with decreasing the [p-NAn]/[p-APh] concentration ratio. In situ UV-Vis. spectra of the obtained samples revealed strong absorption bands at different applied potentials and wavelengths. The structure and morphology characterizations of homo and copolymer films were studied by FT-IR spectroscopy and SEM analysis. Fundamental differences between the morphology of the homo-and copolymers were observed. The mechanism of the electrochemical copolymerization reaction was discussed as well.In the past few years much attention has been paid to conducting polyaniline (PAn) and its substituted derivatives such as poly (N-methyl aniline), poly nitroaniline, poly amino phenols and etc. because of their many potential applications, redox reversibility and good environmental stability. 1-5 PAn and its substituted derivatives have received a great interest due to its large field of applications such as electrocatalysis, 6,7 sensors and biosensors, 8,9 batteries, 10 corrosion inhibitors, 11 high electrical conductivity when it is doped in acidic medium. 12,13 Many of the problems associated in applying these polymers are their poor processibility by solvent. Most of those polymer materials are insoluble in common solvents and undergo degradation before reaching the melting point. However, in several methods, e.g. doping polyaniline and block copolymers were used to overcome this problem by many researchers during the past two decades. 14-18 The processibility of PAn may improved by copolymerization. The type of substitution groups (e.g. electron donating and etc.) on PAn can be changed the properties of polymers. Nitro anilines and amino phenols are interesting members of the classes of substituted aniline. The reported electrochemical properties of the three positional isomers (ortho, meta and para) of nitro anilines and amino phenols are strongly different. 19,20 Copolymers of aniline with ortho, metaor para-nitro aniline were synthesized in various molar ratios of the comonomers by various methods. [18][19][20][21][22] The copolymers show comparatively different properties than the homopolymers. The conductivity and solubility of PAn and PAn derivatives in organic solvents depend on the degree of protonation, nature of dopants and oxidation state. Electrocopolymerizati...