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Competitive adsorption between Cu<sup>2+</sup>and Ni<sup>2+</sup>on corn cob activated carbon and the difference of thermal effects on mono and bicomponent systems

Abstract:

Generally, a single heavy metal is not discarded into natural waters and wastewaters, but a mixture of at least two components. When adsorption is the treatment used, the competition for active sites on surface of adsorbents determines the removal efficiency. In this work, the adsorption of Cu2+ and Ni2+ considering mono and bicomponent systems was evaluated using corn cob activated carbon as an adsorbent. Effects of pH, initial concentration and temperature were investigated. Kinetics and equilibrium of adsorption studies were performed. The equilibrium was established after 240 min and 100 min for Cu2+ and Ni2+, respectively. The adsorption capacities were 0.39 mmol g-1 and 0.28 mmol g-1 for Cu2+ and Ni2+, respectively. High values of pH and initial concentration favors the adsorption, although Cu2+ adsorption was not affected by Ni2+ presence. Thermal effects on the amount adsorbed were not statistically significant on monocomponent system. For bicomponent system, the temperature was statistically significant only on Cu2+ adsorption. The work clearly shows that under the investigated conditions, for monocomponent systems, only aspects related to concentration in solution and characteristics of the adsorbent influence the mass transfer and removal of metal. In this case, the adsorption process must be designed as isothermal. On the other hand, for multicomponent systems, the temperature also affects the process, being one more parameter that need be optimized. This behavior has not been previously reported in the literature about the adsorption of heavy metals.