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Flory-Huggins isotherm for the reduction of Cr 6+ ions in presence of different organic acid at 25 °C
Source publication
The kinetics of the removal of toxic hexavalent chromium (Cr6+) from acidified potassium dichromate solution using iron cylinder as reducing agent was studied. The effect of the presence of different organic acids (e.g., acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, sulphosalicylic acid, citric acid and phthalic acid) u...
Context in source publication
Context 1
... isotherm: Fig. 5 shows the Flory-Huggins adsorption isotherm plotted as log θ/C vs. log (1-θ) for Cr 6+ reduction in presence of organic acids at 25 °C. Straight lines with slope x and intercept log xK are obtained. The experi- mental data fits the Flory-Huggins adsorption isotherm which represented by: log θ/C = log xK+ x log ...
Citations
... In recent years, there has been a growing interest in the reduction of hexavalent chromium encountered in wastewaters by iron metal (i.e., zero valent). Cr(VI) ions can be reduced to the trivalent chromium, mainly, by reacting with iron metal as well as its aqueous ferrous ions (Eary and Ray, 1988 Ahmed et al., 2015). Several forms of the iron metal have been employed as reductants such as metal wool, chips, shots, etc., which can be contained in packed columns, rotating chambers or tumble barrels. ...
This paper aims at predicting the optimum operational limits for the utilization of an iron rotating disk for the reduction of Cr(VI) ions to settleable trivalent chromium. The kinetics of the reduction of hexavalent chromium using an iron rotating disk were, therefore, investigated under different experimental conditions, including contact time, rotation rate, ion initial concentration and disk surface area. All experiments were conducted at room temperature and initial pH of 1.5. It was found that the reduction of Cr(VI) to Cr(III) can be well-modeled by first order reaction kinetics with deviation tendency at low rotation speeds. The first order kinetics were also well-fitted at varying initial concentrations of Cr(VI). Plotting the reaction rate constant versus the square root of the rotation speed has revealed almost a constant positive slope (i.e., mass transfer controlled) which starts to decrease at higher angular velocities until it almost becomes independent of the rotation speed (i.e., reaction kinetics controlled) as the flow transits to a turbulent state. Accordingly, the achievement of high removal efficiencies in a reasonable contact time requires operating the rotating disk under optimal conditions of Cr(VI) initial concentration, rotation speed and disk area that assure diffusion controlled reduction reaction.
