Use of Ponkan mandarin peels as biosorbent for toxic metals uptake from aqueous solutions.

Waste Ponkan mandarin (Citrus reticulata) peel was used as biosorbent to extract Ni(II), Co(II) and Cu(II) from aqueous solutions at room temperature. To achieve the best adsorption conditions the influence of pH and contact time were investigated. The isotherms of adsorption were fitted to the Langmuir equation. Based on the capacity of adsorption of the natural biosorbent to interact with the metallic ions, the following results were obtained 1.92, 1.37 and 1.31 mmol g(-1) for Ni(II), Co(II) and Cu(II), respectively, reflecting a maximum adsorption order of Ni(II)>Co(II)>Cu(II). The quick adsorption process reached the equilibrium before 5, 10 and 15 min for Ni(II), Co(II) and Cu(II), respectively, with maximum adsorptions at pH 4.8. In order to evaluate the Ponkan mandarin peel a biosorbent in dynamic system, a glass column was fulfilled with 1.00 g of this natural adsorbent, and it was fed with 5.00 x 10(-4)mol l(-1) of Ni(II) or Co(II) or Cu(II) at pH 4.8 and 3.5 ml min(-1). The lower breakpoints (BP(1)) were attained at concentrations of effluent of the column attained the maximum limit allowed of these elements in waters (>0.1 mg l(-1)) which were: 110, 100 and 130 bed volumes (V(effluent)/V(adsorbent)), for Ni(II), Co(II) and Cu(II), respectively. The higher breakpoints (BP(2)) were attained when the complete saturation of the natural adsorbent occurred, and the values obtained were: 740, 540 and 520 bed volumes for Ni(II), Co(II) and Cu(II), respectively.

Favorable chitosan/cellulose film combinations for copper removal from aqueous solutions.

Three well-formed film combinations of chitosan, in the beta form and cellulose acetate biopolymer, having different proportions, have been synthesized and characterized by X-ray diffraction and infrared spectroscopy. The film having a 1.0/0.50 proportion presented 6.87 mmol of nitrogen atoms per gram of synthesized hybrid, with the highest affinity for adsorbing copper from aqueous solutions at 298+/-1K. The isotherm obtained in this adsorption showed a saturation plateau that corresponds to 1.92 mmol of copper per gram of hybrid. The energetic effects caused by copper ion interaction were determined through calorimetric titration at the solid-liquid interface in aqueous solution and gave a net thermal effect that enabled the calculation of the exothermic enthalpic values and the equilibrium constant. The complete thermodynamic data showed that the system is favored by exothermic enthalpies, negative Gibbs free energies and positive entropies.