M.Sc. Tezi Görüntüleme

      Cyanide is currently used in the recovery of gold and silver and more extensively in electro plating, chemical and aluminium industries. Because of the slow degradation kinetics and dependency of natural degradation on seasonal changes the use of chemical destruction processes becomes increasingly important. Development of novel processes and/or refining the existing ones to improve their efficiency are also of prime importance for fullfilling the stringent environmental regulations.

      In this study the removal of cyanide from synthetic waste waters using hydrogen peroxide, activated carbon adsorption and ultrasonic waves was investigated. The decomposition kinetics of cyanide by hydrogen peroxide were found to be consistent with first order reaction model. With increasing the initial cyanide, hydrogen peroxide and copper sulphate concentration, the decomposition rate of cyanide was observed to increase.

      It was shown that activated carbons, rice husks and hazelnut shells could be used for the removal of cyanide from waste waters. The impregnation of activated carbon (AK) with silver (AK-Ag10) and copper (AK-Cu) were found to significantly increase the capacity for the removal of cyanide (e.g. 19,7 mg CN^-/gr for AK c.f. 29,6 mg CN^-/gr for AK-Ag10). The aeration of the solution was noted to exert a positive effect on the adsorption of cyanide on activated carbon. Kinetics of adsorption process were consistent with the pseudo-second order reaction model while Langmuir adsorption model was used to describe appropriately the adsorption isotherm. In accordance with the data of adsorption isotherm and kinetics, the breakthrough capacity of adsorbents was found to be in an increasing order of AK<AK-Cu<<AK-Ag10 (~500 ml for AK-Ag10, 50 bed volume).

      The production of hydrogen peroxide by ultrasonic waves in water and the potential use of ultrasound for the destruction of free cyanide were studied. The increase in the intensity of ultrasound and the addition/increase in concentration.of CCl_4 and/or NaCl were shown to markedly improve the rate and extent of cyanide removal (e.g. 100% cyanide removal over 90 min. at 24 gr/lt CCl_4). It may be inferred from these findings that ultrasonic treatment could be used more suitably for the waste waters with low cyanide content or as a polishing stage following the main treatment process.

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