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.
An experimental study of the thermal decomposition of polyethylene in an inert atmosphere has been carried out in the temperature range 300-800°C using Shimadzu PYR-2A pyrolyzer for heating the sample. The method allows the accurate control and measurement of the pyrolysis temperature. The production of hydrocarbons and the corresponding monomers of these polymeric systems were monitored. The effects of variation of temperature, sample size, pyrolysis atmosphere, residence time and catalyst on the distribution of these products were studied. As the carrier gas rapidly swept the primary products from the hot zone into the chromatographic column, so the secondary decomposition is largely eliminated and the pyrolysis products give accurate information about the nature, composition and structure of the pyrolysis material.
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