The efficiency of date tree leaves as a low cost adsorbent for removing lead ions from aqueous solution has been investigated in this paper. Batch experiments were conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), adsorbent dose, solution pH, agitation speed, ionic strength, and temperature on the adsorption of Pb(II) by date tree leaves. The maximum removal of lead(II) is found to be 94 % at pH 5.8, initial Pb(II) concentration of 10 mg 3 L -1 , adsorbent dose of 1 g 3 L -1 , agitation speed of 200 rpm, ionic strength of 0.005 M, and temperature of 25 °C. Dynamics of the adsorption process were studied, and the values of rate constants of pseudofirst-order and pseudosecond-order were calculated. Equilibrium isotherms for the adsorption of Pb(II) were analyzed by the Langmuir, Freundlich, and Temkin isotherm models. The Temkin isotherm model was found to represent better the data of Pb(II) sorption onto date tree leaves. Different thermodynamic parameters, namely, changes in standard Gibbs energy, enthalpy, and entropy, were also evaluated from the temperature dependence, and the results suggest that the adsorption reaction is spontaneous and endothermic in nature.
Coffee residue, a low-cost agricultural byproduct, was tested as a precursor for the production of porous carbons in a chemical scheme using phosphoric acid and zinc chloride. The raw material was impregnated with increasing impregnation ratio (mass of ZnCl2 or H3PO4/mass of coffee residue) from (0 to 100) % followed by pyrolysis at 600 °C for 1 h. The products were characterized by adsorption of N2 at 77 K and proved to be highly microporous with high surface area. The impregnation ratio had a strong influence on the pore structure of these activated carbons, which could be easily controlled by simply varying the proportion of activating agents used in the activation. Thus, a low impregnation ratio led to essentially microporous activated carbons. At intermediate and high impregnation ratios, activated carbons with a wider pore size distribution (from micropores to mesopores) were obtained with high surface area. These low-cost adsorbents developed with ZnCl2 and H3PO4 were used for the removal of lead(II) and cadmium(II), and they showed a substantial capability to adsorb lead(II) and cadmium(II) ions from aqueous solution. The kinetics of adsorption and extent of adsorption at equilibrium were dependent on the physical and chemical characteristics of the adsorbent, adsorbate, and experimental parameters. The effect of contact time and initial concentrations of adsorbate on the uptake of lead and cadmium was studied in batch experiments. The kinetic data were fitted to pseudofirst-order and pseudosecond-order models and follow closely the pseudosecond-order model. Equilibrium adsorption isotherms of Pb(II) and Cd(II) were analyzed by the Langmuir and Freundlich isotherm models. The Langmuir model gives a better fit than the Freundlich model.
A B S T R A C TThis work investigates the possibility to use the reed as an adsorbent for removal of basic yellow 28 (BY28), an industrial textile dye from aqueous solution. Batch adsorption experiments at 25˚C and agitation speed of 400 rpm were carried out and the effects of operational parameters including contact time, initial dye concentration, adsorbent dose, as well as solution pH on sorbed amount were investigated and discussed. The maximum uptake of BY28 was about 140 mg/g of adsorbent and it was obtained at pH6, initial dye concentration of 100 mg/L, and adsorbent dose of 0.5 g/L. It was also established that almost 15 min are sufficient to attain equilibrium sorption. Results of batch experiments showed that this adsorbent exhibited high sorption capacities toward BY28. Experimental data were analyzed using pseudo-first-order and pseudo-second-order kinetics and it was found that kinetic followed a pseudo-second-order equation. The equilibrium results have been modeled and evaluated using Langmuir, Freundlich, Sips, and Generalized model isotherms. The Langmuir model provides the best fit of equilibrium data of BY28 and according to this model, the maximum sorption capacity was estimated to181 mg/g of reed. FTIR spectrum of reed confirms the existence of various functional groups such as carboxyl, phenolic, hydroxyl, and amine groups on their surface and these functional groups have always been considered to effectively form some physicochemical interactions, e.g. ion exchange or inner-sphere complex formation, with BY28. Results from this study suggest that reed is an effective adsorbent for the removal of BY28 from aqueous solutions.
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