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
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ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
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Chapter1: Chemical Foundations
Section: Chapter Questions
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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)?](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F6e532244-1a69-487f-88f4-10ae0a919295%2Fb282eca3-f4f7-4953-be70-77c4005da72b%2F0dgk3i_processed.png&w=3840&q=75)
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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