This study aims to use the tissues of Cyclamen persicum tubers to prepare activated carbon (CTAC) by different methods then to set up a thermodynamic study of the pharmaceutical diclofenac sodium (DCF) adsorption from aqueous solution onto this activated carbon. Optimum percent of DCF removal was 72% when CTAC dosage was 0.25 g and DCF concentration 50 mg/L. Percentage removal of DCF increases when the concentration of DCF increases as the maximum percentage removal reached 81% when DCF concentration was 70 mg/L and 0.7 g CTAC and pH ranging from 6 to 2.Freundlich model describes efficiently adsorption isotherm of DCF onto CTAC with n equal to 1.398 whose value indicates a favorable adsorption. This finding validates the assumption of multilayer physical adsorption process of DCF. The results showed that DCF was physically adsorbed onto CTAC, as confirmed by the values of DH°minor than 40 kJ/mol. As DG°had negative charge, the adsorption process is exothermic, and the adsorption process of the DCF onto CTAC is spontaneous, depending on temperature. ª 2014 The Authors. Production and hosting by Elsevier B.V. on behalf of University of Bahrain. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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Natural based composites of hydroxyapatite/Gum Arabic designed for removal of toxic metal arsenic (III) from waste water were synthesized and evaluated. Several composites with various compositions were prepared by the wet chemical method and analyzed using various spectroscopic and analytical methods such as: Fourier transform infrared spectroscopy, total organic carbon production, XRD analysis and scanning electron microscope. The rates of weight loss and water absorption of the HAp/GA composites as a function of time were evaluated in phosphate-buffered saline solution at 37 °C and a pH of 7.4. The effects of several variables on adsorption of arsenic (III) by HAp/GA composites were evaluated. The variables include arsenic (III) concentration, contact time (t) and complex surface nature of HAp/GA composite. Three surface complexation models were used to study the mechanisms controlled the adsorption. The models were Langmuir, Freundlich and Dubinin Radushkevich. The adsorption kinetic of arsenic (III) on the composite surface was described by three modes: pseudo first order, pseudo second order and the intra particle diffusion. The results revealed that, the rate of adsorption of arsenic (III) by HAp/GA composites was controlled by two main factors: the initial concentration of arsenic (III) and the contact time. The kinetic studies also showed that, the rate of adsorption is a second order. The results indicate that, composite offered in this study could be a valuable tool for removing toxic metals for contaminated water by adsorption.Graphical abstract.

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