Temperature, pH and Particle Size Effect in the Thermodynamic of Biosorption of Mercury in Waste Water

In the present investigation, the temperature effect over the capacity of adsorption of mercury (II) was studied from corn husk biomass (Zea mays), determining the functional groups on the surface of the biomass, by means of FTIR analysis; it was found that the hydroxyl, carboxylic and aliphatic groups are those of greatest contribution to the process of removal. Then, batch adsorption tests were carried out, varying parameters such as pH (2, 4 and 6), temperature (25, 50 and 75 °C) and particle size (0.355, 0.5 and 1 mm); where pH was found to be the most influential factor, the highest adsorption capacity was given at pH = 6 for mercury, T = 25 °C and size of 0.355 mm. The kinetic model that best fitted the experimental data was Elovich with a statistical error of SS = 3.42 for Hg (II). The isotherm that best described the adsorption was Freundlich with an SS = 2.55 for Hg (II). Regarding the thermodynamic parameters, free energy of Gibbs (ΔG⁰), enthalpy free of adsorption (ΔH⁰) and entropy of adsorption (ΔS⁰) for mercury indicated that the adsorption process for the metal is favorable, spontaneous, endothermic, chemical and reversible in nature. All this shows the corn husk is a good alternative as an adsorbent of mercury.