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2. Ferrous iron (Fe2+) must be removed from a steel plant wastewater to meet a pretreatment standard of 106 M. The proposed treatment scheme involves oxidizing the ferrous iron to ferric iron (Fe³+) in a CMFR. The ferric hydroxide precipitate (Fe(OH)3(s)) will be continuously removed from the bottom of the reactor to maintain steady state conditions. Dissolved oxygen will be added to the reactor by bubbling air through the solution. The pH in the reactor will be kept constant by the addition of a well-buffered caustic waste stream from another part of the plant. You are given the following information: Temperature=20 °C Waste stream flow rate Caustic stream flow rate = 1000 L/min = 100 L/min Concentration of Fe²+ in the waste stream=5x10-3 M Volume of reactor-72,500 L Saturation concentration of oxygen at 20 °C = 9.08 mg/L = 2.84x104 M Constant pH in the reactor = 9 Assume that there is no dissolved oxygen in either the waste stream or the caustic stream. The reaction occurs in two steps, with the first step rate limiting: (1) (2) Fe2+1/4 02 + H+ <——> Fe³+ + 1/2 H₂O Fe3+ 30H -> Fe(OH)3(s) The kinetics of reaction (1) are described as follows: d[Fe²+]/dt = k[Fe²*][O₂][OH¯]² The reaction rate constant is k = 6.9 x 10¹6 min-¹M-3 All concentrations are expressed in moles/liter (M). (a) Calculate the dissolved oxygen concentration required in the reactor to meet the effluent standard for Fe²+. (b) What must be the value of the overall oxygen mass transfer coefficient (KLa) in the reactor to produce the dissolved oxygen concentration calculated in (a)?

2. Ferrous iron (Fe2+) must be removed from a steel plant wastewater to meet a pretreatment standard of 106 M. The proposed treatment scheme involves oxidizing the ferrous iron to ferric iron (Fe³+) in a CMFR. The ferric hydroxide precipitate (Fe(OH)3(s)) will be continuously removed from the bottom of the reactor to maintain steady state conditions. Dissolved oxygen will be added to the reactor by bubbling air through the solution. The pH in the reactor will be kept constant by the addition of a well-buffered caustic waste stream from another part of the plant. You are given the following information: Temperature=20 °C Waste stream flow rate Caustic stream flow rate = 1000 L/min = 100 L/min Concentration of Fe²+ in the waste stream=5x10-3 M Volume of reactor-72,500 L Saturation concentration of oxygen at 20 °C = 9.08 mg/L = 2.84x104 M Constant pH in the reactor = 9 Assume that there is no dissolved oxygen in either the waste stream or the caustic stream. The reaction occurs in two steps, with the first step rate limiting: (1) (2) Fe2+1/4 02 + H+ <——> Fe³+ + 1/2 H₂O Fe3+ 30H -> Fe(OH)3(s) The kinetics of reaction (1) are described as follows: d[Fe²+]/dt = k[Fe²*][O₂][OH¯]² The reaction rate constant is k = 6.9 x 10¹6 min-¹M-3 All concentrations are expressed in moles/liter (M). (a) Calculate the dissolved oxygen concentration required in the reactor to meet the effluent standard for Fe²+. (b) What must be the value of the overall oxygen mass transfer coefficient (KLa) in the reactor to produce the dissolved oxygen concentration calculated in (a)?

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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2. Ferrous iron (Fe2+) must be removed from a steel plant wastewater to meet a pretreatment standard of 106 M. The proposed treatment scheme involves oxidizing the ferrous iron to ferric iron (Fe³+) in a CMFR. The ferric hydroxide precipitate (Fe(OH)3(s)) will be continuously removed from the bottom of the reactor to maintain steady state conditions. Dissolved oxygen will be added to the reactor by bubbling air through the solution. The pH in the reactor will be kept constant by the addition of a well-buffered caustic waste stream from another part of the plant. You are given the following information: Temperature=20 °C Waste stream flow rate Caustic stream flow rate = 1000 L/min = 100 L/min Concentration of Fe²+ in the waste stream=5x10-3 M Volume of reactor-72,500 L Saturation concentration of oxygen at 20 °C = 9.08 mg/L = 2.84x104 M Constant pH in the reactor = 9 Assume that there is no dissolved oxygen in either the waste stream or the caustic stream. The reaction occurs in two steps, with the first step rate limiting: (1) (2) Fe2+1/4 02 + H+ <——> Fe³+ + 1/2 H₂O Fe3+ 30H -> Fe(OH)3(s) The kinetics of reaction (1) are described as follows: d[Fe²+]/dt = k[Fe²*][O₂][OH¯]² The reaction rate constant is k = 6.9 x 10¹6 min-¹M-3 All concentrations are expressed in moles/liter (M). (a) Calculate the dissolved oxygen concentration required in the reactor to meet the effluent standard for Fe²+. (b) What must be the value of the overall oxygen mass transfer coefficient (KLa) in the reactor to produce the dissolved oxygen concentration calculated in (a)?
Transcribed Image Text:2. Ferrous iron (Fe2+) must be removed from a steel plant wastewater to meet a pretreatment standard of 106 M. The proposed treatment scheme involves oxidizing the ferrous iron to ferric iron (Fe³+) in a CMFR. The ferric hydroxide precipitate (Fe(OH)3(s)) will be continuously removed from the bottom of the reactor to maintain steady state conditions. Dissolved oxygen will be added to the reactor by bubbling air through the solution. The pH in the reactor will be kept constant by the addition of a well-buffered caustic waste stream from another part of the plant. You are given the following information: Temperature=20 °C Waste stream flow rate Caustic stream flow rate = 1000 L/min = 100 L/min Concentration of Fe²+ in the waste stream=5x10-3 M Volume of reactor-72,500 L Saturation concentration of oxygen at 20 °C = 9.08 mg/L = 2.84x104 M Constant pH in the reactor = 9 Assume that there is no dissolved oxygen in either the waste stream or the caustic stream. The reaction occurs in two steps, with the first step rate limiting: (1) (2) Fe2+1/4 02 + H+ <——> Fe³+ + 1/2 H₂O Fe3+ 30H -> Fe(OH)3(s) The kinetics of reaction (1) are described as follows: d[Fe²+]/dt = k[Fe²*][O₂][OH¯]² The reaction rate constant is k = 6.9 x 10¹6 min-¹M-3 All concentrations are expressed in moles/liter (M). (a) Calculate the dissolved oxygen concentration required in the reactor to meet the effluent standard for Fe²+. (b) What must be the value of the overall oxygen mass transfer coefficient (KLa) in the reactor to produce the dissolved oxygen concentration calculated in (a)?
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