The study of Effective Factors in Mercury Removed from Aqueous Solutions Using Granular Activated Carbon

Introduction:Wastewaters of chemical, petrochemical, electrical, pharmaceutical and paper industries are the main sources of mercury and its compounds. Mercury is one of the toxic elements, so its removal from water and industrial wastewaters seems to be important and essential. The objective of this study was to investigate effective factors such as PH, contact time, absorbent dose, mixing rate and initial concentration in mercury removed by employing Granular Activated Carbon (GAC).

Materials and Methods: In this study GAC was used as absorbent of the mercury. Mercury solution was prepared by mercury chloride. 136 samples were analyzed and the mixture of samples and activated carbon in 100^cc flasks were shaked. Then the samples filtered and the filtrates were tested to determine the mercury concentration by employing Cold Vapor Atomic Absorption Method at the wavelength of 253.7 nm.

Results: Mercury removal increased at pH from 2 to 4 and optimum pH occurred in the range of 4-8. Increasing processing time to more than 10 min, had no significant effect on the absorption rate of mercury. Removal percentage increased with increasing weight of GAC but the amount of absorbed mercury ion per unit weight decreased from 2.216 mg to 0.0806 mg.

conclusion: Increasing the amount of mercury at pH>4 was due to formation of predominant species of Hg(OH)₂ which retained in micro pores of GAC particles. The kinetic of mercury absorption by GAC was remarkably fast and increasing processing time to more than 10 min up to equilibrium absorption had no significant effect.
The results showed that the mercury removal had increased with increasing weight of GAC. This phenomenon happened as the result of increasing absorbent surface