Electroflocculation Coagulation Process for Treatment of Heavy Metals Containing Wastewaters Prof' Y - PowerPoint PPT Presentation

1 / 95
About This Presentation
Title:

Electroflocculation Coagulation Process for Treatment of Heavy Metals Containing Wastewaters Prof' Y

Description:

1. Electroflocculation Coagulation Process for Treatment of Heavy Metals Containing Wastewaters ... Antimony (Sb) 0.01 0.005 *The limit shown will apply in 2013. ... – PowerPoint PPT presentation

Number of Views:812
Avg rating:3.0/5.0
Slides: 96
Provided by: CEE01A
Category:

less

Transcript and Presenter's Notes

Title: Electroflocculation Coagulation Process for Treatment of Heavy Metals Containing Wastewaters Prof' Y


1
Electroflocculation Coagulation Process for
Treatment of Heavy Metals Containing
WastewatersProf. Yung-Tse Hung, Ph.D., P.E.,
DEE, F-ASCE, ProfessorDepartment of Civil and
Environmental EngineeringCleveland State
UniversityCleveland, Ohio 44115-2214
USAVisiting ProfessorSchool of Civil and
Environmental EngineeringNanyang Technological
UniversitySingapore 639798
2
OUTLINES
  • Overview
  • Objectives
  • Literature Review
  • Theory
  • Experimental Setup, Math Model
  • Mathematical Model
  • Results Cd, Zn, Cd and Zn Removal
  • Conclusions

3
  • Overview
  • USEPA new Effluent Guidelines became effective in
    December 2000.
  • Applicable to Metal Product Machinery (MPM)
    industries.
  • 200 different types of industries affected by new
    standard.
  • Typical operations include
  • Acid treatment, Adhesive bonding, Anodizing,
    Chemical conversion coating, Abrasive blasting,
    Corrosion preventive coating, Electroplating,
    heat treatment, Solvent degreasing, and Dip
    coating and sputtering.
  • MPM industry regulation include
  • New facilities
  • Existing facilities

4
EU DRINKING WATER DIRECTIVE STANDARDS FOR
HEAVY METALS
  • Heavy Metal  1980 Directive/   1998
    Directive/        
  • 1988 Regulations (a)
    2000 Regulations (b)
  • mg/L
    mg/L
  • Arsenic (As)    0.05    
    0.01      
  • Mercury (Hg)    0.001    
    0.001      
  • Chromium (Cr)    0.05
    0.05  
  • Lead (Pb)  0.05    
    0.01      
  • Nickel (Ni) 0.05      
    0.02      
  • Selenium (Se)    0.01      
    0.01      
  • Antimony  (Sb)   0.01      
    0.005
  • The limit shown will apply in 2013. There is an
    interim limit of 0.025 mg/L
  • In effect to 31 December 2003
  • In effect from 01 January 2004

5
OSHA regulates heavy metals in the work place
through Permissible Exposure Levels (PELs) for
airborne chemicals
  • Metal/Compound PEL
  • Permissible Exposure Level ( mg/m3)
  • Lead, 0.005
  • Metallic Cr, 1.0
  • Insoluble Cr soluble Cr3 salts 0.5
  • Cr6 chromates, chromic acid, 0.1 (This is the
    highest acceptable level)
  • Nickel, nickel compounds, 1.0
  • Cadmium, 0.2

6
  • Objectives
  • To determine the optimal operational parameters
    of the ECF reactor
  • To determine the cadmium, zinc, and organic load
    removal efficiencies of the ECF reactor at
    different applied current levels
  • To observe the influence that organic load
    concentrations may have upon the heavy metal
    removal efficiency
  • To develop a theoretical mathematical model that
    describes the kinetics in the ECF reactor

7
  • To develop an empirical mathematical model that
    correlates the independent variables affecting
    the heavy metal removal rates
  • To make predictions of output concentrations
    using the developed models
  • To present a cost estimate for scaled-up ECF
    reactor.

8
  • Literature review
  • Electroflotation Performance Studies
  • Ketkar, Mallikarjunan, and Venkatachalam, 1991
  • Alexandrova, Nedialkova, and Nishkov, 1994
  • Hosny, 1996
  • Llerena, Ho, and Piron, 1996
  • Poon, 1997
  • Venkatachalam, and Setty, 1997
  • Kolesnikov, and Varaxin, 1998

9
  • Electrode Materials
  • Kamenev, Bibikova, Simonova, and Rusin, 1983
  • Ho and Chan, 1986
  • Mraz and Kryza, 1993
  • Mraz and Kryza, 1994
  • Zubareva, 1997
  • Poon, 1997
  • Romanov, 1998

10
  • Separating oil from oil-water emulsion by
    electroflotation technique
  • by Ashraf Y. Hosny, 1996
  • Studied oil removal by continuous flow
    electroflotation reactor.
  • (8 x 9 x 30 cm) plexiglass electroflotation cell.
  • Volume 1.5 to 2.5 liters.
  • Stainless steel cathode and lead anode
  • Oil droplet distribution
  • (1 ?m 38, 2 ?m 25, 3 ?m 20, 4 ?m 10
    and 5 ?m 7)
  • pH range was 4.5
  • Flocculant (Nalco 7720) 4 to 32 mg/l

11
  • 3.5 wt salt to simulate seawater
  • Presence of salt decreases the size of oil
    droplets.
  • Flow rate from 10 to 50 ml/min
  • Maximum oil removal efficiency 92
  • Optimal operating conditions
  • 1.2 amp, 40 min, 3.5 salt conc., 16 mg/L
    flocculant conc.
  • Linear Regression
  • oil removal -22.3 9.18x10-3 (C) 1.09
    (t) 27.13 (I)
  • valid for C (500 2000 mg/l), I (0.3
    -1.2 amp), t (10 -40 min)

12
  • Electroflotation for groundwater
    decontamination
  • by Calvin P.C.Poon, 1997
  • Removal of Ni, Zn, Pb, Cu, CN by
    electroflotation.
  • Studied relation between depth (D), power input
    (P), HDT
  • (40 x 15 x 30 cm) plexiglass electroflotation
    cell.
  • Volume 5.25 to 10.67 liters
  • Stainless steel cathode and platinum-clad
    columbium anode
  • pH range 7.86 to 10.58
  • 3.0 wt rock salt to simulate seawater
  • Batch and continuous studies (4.8 75 min HDT)
  • Samples taken at three depths (10.3, 15.45, 20.6
    cm)

13
  • Optimal conditions
  • treatment effectiveness increased with depth
  • 75 min detention time
  • Effluent Conditions
  • 0.02 - 0.08 mg/l Cu
  • 0.02 - 0.16 mg/l CN
  • 0.04 - 0.52 mg/l Zn
  • 0.10 - 0.34 mg/l Pb

14
  • Multiple Linear Regression
  • Cu removal 7669 - 226 (P) 593 (D)
  • r2 0.896
  • CN removal 30108 - 829 (P) 2138 (D)
  • r2 0.726
  • Zn removal 2422 - 55 (P) 243 (D)
  • r2 0.91
  • Pb removal 10375 - 300 (P) 368 (D)
  • r2 0.819

15
  • Theoretical Background
  • Electrolytic reactions
  • 3.2(a) 2 e- 2 H2O ?
    H2 (g) 2 OH-
  • (0.83 volts)
  • 3.2(b) 2 H2O ?
    O2 (g) 4 H 4e-
  • (1.23 volts)
  • Product of reduction at the cathode
  • 3.3 NaCl ? Na Cl-
  • 3.4 Na e- ? Na
    (2.71 volts)
  • 3.5 2 H2O 2 e- ? H2 2 OH-
    (1.23 volts)

16
  • Product of oxidation at the anode
  • 3.6 2 Cl- ? Cl2 2e-
    (1.36 volts)
  • 3.7 2 H2O ? O2 4H 4e-
    (1.23 volts)
  • Hypo-chlorite formation
  • 3.8 Cl2 (g) 2 OH- (aq) ? Cl- (aq)
    OCl- (aq) H2O (l)
  • Overall product in the electrolysis of aqueous
    NaCl solutions
  • 3.9 2 NaCl(aq) 2 H2O(l) ? 2 Na (aq) 2 OH-
    (aq) H2 (g) Cl2 (g)

17
  • Chemistry of Cadmium and Zinc
  • Cadmium Reactions
  • 3.11 CdCl2? Cd2
    2 Cl-
  • 3.12 Cd2 H2O ? Cd(OH)
    H-
  • 3.13 Cd(OH) OH- ? Cd(OH)2
  • 3.14 Cd(OH) 2Cl- ? CdCl2
    2Cl-
  • 3.15 Cd(OH) 2Cl- ? CdCl(OH)

18
  • Zinc Reactions
  • 3.16 ZnCl2 ? Zn2 2Cl-
  • 3.17 Zn2 H2O ? Zn(OH) H-
  • 3.18 Zn(OH) OH- ? Zn(OH) 2

19
  • Primary reaction products involving the iron
    metal
  • 3.20(a) Fe(s) ? Fe2 2 e- ? Fe3 e-
  • 3.20(b) 4 Fe(s) 3 O2 (g) ? 2 Fe2O3
  • 3.20(c) 2 Fe2 Cl2 (g) ? FeCl2
  • 3.20(d) Fe2 2 OH- ? Fe(OH) 2
  • 3.20(e) Fe3 3 OH- ? Fe(OH)3

20
Chemistry of Iron Corrosion MechanismFig. 3.2
Two Major Pathways Involving Production and
Depletion of Fe2
21
Fig. 3.3 Electrode Corrosion and Dilution
Mechanisms
22
Experimental Setup
23
Experimental Procedures
  • (A) Preparation of synthetic wastewater
  • cadmium chloride, CdCl2
  • zinc chloride, ZnCl2
  • pH adjustment by addition of lime, Ca(OH) 2
  • adjustment by NaCl to facilitate conductivity
  • evaporated milk (D-lactose) as organic load.
  • (B) Experimental Conditions
  • treatment time 5, 10, 15, 30, 45 min
  • pH range 8.0, 9.5, and 10.5
  • applied current 1, 3, and 6 amp
  • NaCl 0.2 2.0

24
  • TOC 0, 100, 500, 1000 mg/l.
  • (C) Measured initial final pH, temperature,
    conductivity, and turbidity.
  • Initial and final samples prepared for TOC
    and AA analysis.
  • Data gathered and analyzed
  • (D) Instrument
  • 3100 Perkins Elmer Atomic Adsorption unit
  • 5050A Shimadzu TOC analyzer with ASI 5000A
    autosampler
  • Orion, Inc. Model 116 Quickchek portable pH meter
  • YSI, Inc. Model 30/40 FT conductivity,
    temperature and salinity meter.
  • Hach Model 2100A turbidity meter.

25
Mathematical Model and Manipulation
  • Primary processes responsible for the cadmium
    removal efficiency
  • cadmium hydrolysis
  • coagulation-flotation.

26
Figure 4.1 Generalized schematic of the
electrocoagulation/flotation process
27
  • Mathematical expression of the process may be
    written as
  • Koverall Khydrolysis Kcoag-flot
  • Previous studies showed first order behavior
    (i.e., Kolesnikov, Kokarev, Shalyt, Varaksin, and
    Kodintsev (1989).
  • Kolesnikov (1989)
  • kinetic study of cadmium hydroxide
    electroflotation
  • rectangular (50 x 40mm) 0.5 liters
    electroflotation reactor
  • steel screen as the cathode
  • titanium sheet with a metal oxide coating served
    as the anode
  • experiments at pH 9.5
  • cadmium hydroxide initial concentration of 0.2
    g/L
  • current density varied between 50 to 150 A/m2

28
  • Model based on observations of plotted data (i.e.
    Reff vs applied current)
  • Determination rate constant from plotted
    experimental data
  • Adjusted rate constant as a function of applied
    current.
  • Representative Equations for Model Development
  • Based on the concepts of kinetics for
    conservative substances
  • Operating conditions (constant volume,
    temperature, and pressure)
  • Generalized Mass balance equation
  • Min Mout dM/dt (Accumulated Mass)

29
  • Substance A as cadmium ion (Cd2) the total net
    mass going out is zero for a batch reactor, the
    previous equation may be rewritten as
  • Min dM/dt
  • Generalized mass equation for batch reactor
  • N NA NA,o X
  • Mass balance equation with the rate expression
  • dNA/dt rAV
  • Rearranging in terms of concentration values and
    dividing both sides by the total volume (V), the
    resultant expression is shown below
  • (-1/V)(dNA/dt) -d(NA/V)/dt
  • -dCA/dt -rA

30
  • Rate expression of cadmium ion removal can be
    written as
  • -rA -KCA
  • If equation 4.10 is substituted in 4.9, the
    following expression may be written
  • -dCA /dt -K CA
  • Integrating the last equation between the initial
    and final concentrations and treatment time
  • ln CA/CAo
    -K t.
  • Mathematical manipulations lead to
  • CA CAoe
    - Kt

31
  • Initial solution procedure based on showing how
    last equation fit the gathered experimental data
  • CA CAoe
    - Kt
  • Plot ln CA/CAo versus treatment time
  • Linear regression with slope calculation
  • Linear regression evidences a first order
    behavior for the entire process.
  • A linear correlation representative of an
    experimentally determined rate constant, K for
    applied current values.
  • Relationships for applied current and pH were not
    determined due to the fact that these variables
    changed during experimentation.

32
CHAPTER 6Determinations of Optimal Operational
Parameters of Electrocoagulation/Flotation (ECF)
Batch ReactorFig. 6-7

33
Fig 6-13
34
Fig. 6-19
35
Fig. 6-23
36
Fig. 6-24
37
Fig. 6-25
38
Fig. 6-29
39
Fig. 6-30 (Combine Fig. 6-13, 6-25)
40
Fig. 6-31 (Combine Fig. 6-19, 6-24)
41
Fig. 6-33
42
Fig. 6-35
43
Summary of Results
  • Chapter 6
  • Cadmium removal efficiency ranged between 90 to
    99 for treatment times of 30 and 45 minutes,
    respectively at all applied current levels
  • Cadmium concentrations of 30 mg/l were reduced to
    0.03 mg/l under the influence of lime and to 0.01
    mg/l under the influence of alum.
  • Optimal operational parameters were obtained
  • pH 9.5
  • current (I) 3 amp
  • Time (t) 30 min
  • A directed relationship was observed between the
    final wastewater temperature and the applied
    current.

44
CHAPTER 7Determining the Effects of Organic
Loadings upon the Cadmium Removal EfficiencyFig.
7-5
45
Fig. 7-10
46
Fig. 7-15
47
Fig. 7-20
48
Fig. 7-21
49
Fig. 7-22
50
Fig. 7-23
51
Fig. 7-24
52
Fig. 7-25
53
Fig. 7-26
54
Fig. 7-27
55
Fig. 7-28
56
Fig. 7-29
57
Fig. 7-30
58
Fig. 7-31
59
Fig. 7-32
60
Fig. 7-33
61
Fig. 7-34
62
Fig. 7-38
63
Fig. 7-40
64
  • Chapter 7
  • The ECF reactor was able to simultaneously remove
    cadmium metal and organic matter.
  • Cadmium removal efficiency ranged between 68.02
    and 99.47 for treatment times between 15 and 30
    min, respectively for all applied current levels.
  • Cadmium concentrations of 30 mg/l were reduced to
    0.0 mg/l under the influence of organic loads and
    lime as the coagulant, and to 0.08 mg/l under
    influence of alum.
  • Organic load removal efficiencies ranged between
    44.05 to 48.29 for treatment times of 15 and 30
    min for all applied current levels with the
    addition of lime as the coagulant.
  • Organic loads were reduced by a factor of 50
    with the addition of lime as the coagulant, and
    by 30.37 under the influence of alum. The
    organic material caused a detrimental effect on
    the bubble formation in the ECF reactor.
  • Considerable higher volumes of sludge were
    collected for studies conducted under the
    influence of organic loads.

65
CHAPTER 8Determination of Zinc Removal
Efficiency with and without Effects of Organic
LoadsFig. 8-22
66
Fig. 8-27
67
Fig. 8-28
68
Fig. 8-29
69
Fig. 8-30
70
Fig. 8-31
71
Fig. 8-38
72
Fig. 8-39
73
Fig. 8-40
74
Fig. 8-41
75
Fig. 8-42
76
Fig. 8-43
77
Fig. 8-44
78
Fig. 8-45
79
Fig. 8-46
80
Fig. 8-48
81
  • Chapter 8
  • Zinc removal efficiencies ranged from 99.01 to
    99.0 for treatment times between 15 and 30
    minutes, respectively for all applied current
    levels.
  • Initial zinc concentrations from 30 mg/l to 0.04
    mg/l under the influence of lime as the
    coagulant and to 0.01 mg/l under the influence
    of alum as the coagulant.
  • Zinc removal efficiencies ranged between 99.01 to
    99.0 for treatment times of 15 and 30 minutes,
    respectively for all applied current levels.
  • TOC removal efficiencies ranged around 56.99 for
    applied current values of 3 amperes.
  • It was found a direct relationship between the
    organic load removal efficiency and the initial
    organic load concentration.

82
CHAPTER 9DETERMINATION OF COMBINED REMOVAL
EFFICIENCIES FOR ZINC AND CADMIUM METAL USING
ELECTROCOAGULATION/FLOTATION TECHNOLOGY
83
Fig. 9-2
84
Fig. 9-3
85
Fig. 9-4
86
  • Chapter 9
  • Heavy metal removal efficiencies ranged between
    90.84 to 92.11 for cadmium and 97.74 to 98.30
    for zinc.
  • Organic load removal efficiencies ranged between
    4 to 9 and 47.7 to 48 after 5 and 30 minutes of
    treatment time, respectively for all applied
    current levels.
  • Organic loads had some negative effect upon the
    heavy metal removal efficiencies.

87
CHAPTER 10Determination of Heavy Metal Removal
Efficiencies for ECF BatchReactor Using
Steady-State Theoretical and Empirical
ModelsFig. 10-3
88
Fig. 10-4
89
Fig. 10-5
90
Fig. 10-10
91
Fig. 10-11
92
Fig. 10-17
93
Fig. 10-20
94
  • Chapter 10
  • Theoretical Model
  • A theoretical model was developed based on the
    concepts of first order chemical kinetics.
  • At low treatment times (i.e., 5, and 10 minutes)
    the model predicted lower final concentrations
    when compared to actual concentrations.
  • Empirical Model
  • A completely empirical model was developed using
    an SPSS computer package.
  • Empirical mathematical relation is shown below
  • Y() 55.079 5.101 (I) 0.08567 (C)
    1.741 (T) - 4.688 (A)
  • valid for I (1- 3 amp) C
    (10-30 mg/l) T (5-45 min) A(8,9.5,10.5)
  • where,
  • Y predicted heavy metal removal
    efficiency, percentage ()
  • I measured applied current, amperes
  • C initial measured heavy metal
    concentration, (mg/l)
  • T treatment time, minutes
  • A acidity of solution, as measured in pH
    units.

95
  • Applied current and treatment time appeared to be
    the strongest variables influencing the predicted
    removal efficiencies.
  • The empirical model tend to under and
    overestimate the values for removal efficiency
    when compared to the measured concentrations.
  • The model predicted values over 100 percent after
    30 and 45 minutes of treatment time and at high
    applied current levels.
  • The great variability between the calculated and
    predicted values may be attributed to the
    variation in the instrument readings
Write a Comment
User Comments (0)
About PowerShow.com