Christy Ijagbemi Ph. D  Department of Mechanical Engineering Federal University of Technology, Akure, NIGERIA Adsorption  ...
<ul><li>Escape into the environment pose a serious health hazard –  </li></ul><ul><li>escapes on the increase     </li></u...
<ul><li>Heavy Metals </li></ul><ul><li>Are natural components of the earth’s crust. </li></ul><ul><li>Relatively high dens...
Hg   Al Ba Pb Cd Fe Heavy Metals Toxic Heavy Metals
Heavy metals employed in some major industries (Palmer et al., 1988). Introduction Industries Cd Cr Cu Fe Hg Pb Ni Zn Pulp...
<ul><li>Recent  toxicology studies  </li></ul><ul><li>Stricter regulations with regard to toxic metal ions discharge,  </l...
<ul><li>Why MMT? </li></ul><ul><li>Montmorillonite is a clay silicate formed by crystallization from solution high in solu...
<ul><li>Mg 2+  for Al 3+  leads to permanent  negative  charge </li></ul><ul><li>Mg 2+  move to interlayer space </li></ul...
Research goal :  To develop an effective and regenerative material from  MMT and evaluate its application potentials to re...
To modify MMT surface properties and evaluate the effects of the modifications on adsorptive behavior of MMT for heavy met...
<ul><li>adsorption by (living or dead) microbial biomass, bioremediation  </li></ul><ul><li>systems  </li></ul><ul><li>low...
Researchers have focused on use of other relatively cheaper adsorbents to  replace activated carbon  Adsorption Background
<ul><li>Evaluation studies </li></ul>MMT for heavy metal  pollution remediation Approach Phase 1 Phase 2 Phase 3 <ul><li>A...
Beaker Charge determination  <ul><li>100 mL KCl electrolyte [conc (0.01- 0.001M)] </li></ul><ul><li>20g MMT added and titr...
Sodium montmorillonite (Na-MMT) MMT : 1 M NaCl solution = 1 g : 10 mL Mechanical stirring (24 h), repeated 5 times Centrif...
Acid treated montmorillonite (A-MMT) MMT : 4 N H 2 SO 4  = 1 g : 40 mL Drying at 105  o C for 6 h Sieving to 150  μ m Synt...
<ul><li>Adsorbent (Na-MMT and A-MMT) </li></ul><ul><li>Adsorbate (50 mL of Copper Solution) </li></ul><ul><li>Adsorbent do...
Materials and methods Chemical assay of industrial wastewater . Parameters Quality/ 4 L  of effluent pH 6.1 COD 117.5 (mg)...
Applied isotherm models Results and discussion <ul><li>V ital information in optimizing the use of adsorbents: </li></ul><...
Applied kinetic models Results and discussion Isotherm  Empirical form Linear form Plot Pseudo first-order Pseudo second-o...
Characterization of montmorillonites Results and discussion Adsorbent CEC (meq/100g ) d -spacing (nm) Surface  area (m 2 /...
Effect of pH Results and discussion Effect of pH on the adsorption of Cu 2+  onto Na-MMT and A-MMT (Cu 2+  concentration, ...
Equilibrium sorbed amount of Cu 2+  according to time by (a )Na-MMT  and (b) A-MMT at different initial concentrations (ad...
Equilibrium isotherm model parameters for Cu(II) sorption onto modified montmorillonites. Results and discussion <ul><li>P...
Results and discussion Kinetics Kinetic model parameters for the sorption of Cu(II) onto modified  montmorillonites. Kinet...
Thermodynamic parameters Results and discussion Thermodynamic parameters for the sorption of Cu(II) onto modified montmori...
Results and discussion Application to real industrial wastewater Removal of Cu(II) and Ni(II) from industrial wastewater b...
Conclusion and recommendation The  natural occurrence, availability, adsorption and regeneration capabilities, even cost, ...
 
Sources and Sinks of Heavy Metals Modified – from  http://pubs.usgs.gov/circ/circ1133/images/fig 21.jpeg
Route of Exposure: Absorption, Ingestion, Inhalation http:healtheffects.net/he/images/ToxTri.gif
Maximum contaminant level (MCL) of heavy metals in surface water and their toxicities  (prepared from http://www.epa.gov/s...
Numbers of tested adults reported to the NYS Department of health for  (A) Arsenic and (B) Lead by level (A) (B) USDA Repo...
Hg   Al Pb Heavy Metals Toxic Heavy Metals Cu Cd Ni
Theory   -  ideal  MMT
The amount of metal ion   adsorbed per unit mass of adsorbent  q t  (mg/g) at each time t , by adsorbents was calculated f...
The net surface charge density,  S o , was calculated using the equation above.  S o  = surface charge (C cm −2 )   n =  n...
<ul><li>Large surface area </li></ul><ul><li>Relative abundance of reactive surface groups on its surface </li></ul><ul><l...
Adsorption capacities (mg/g) of adsorbent for different heavy metals Babel, 2002 Adsorbent Cd 2+ Hg 2+ Cu 2+ Ni 2+ Zn 2+ P...
Montmorillonite  Van Olphen, 1979
Schematic picture of the montmorillonite particle (A), the top plane (basal plane) possesses exchangeable sites, whereas t...
Mineral surface properties Surface charge of an oxide mineral surface in aqueous systems will change with changing pH as a...
Surface Charge Development   Theory <ul><li>Three parameters contribute on surface charge of clay minerals: </li></ul><ul>...
Definitions of the surface charges of clays and relevant characteristic points determined from potentiometric titrations o...
 
Surface Charge Development   -  Theory In environmental chemistry  and several industrial processes -  PZC is a very impor...
Metal Ionic radius Atomic radius Na  + 116 168 H + - 25 Zr 3+ 88.5 160 Ni 2+ 83 135 Cu 2+ 87 135 Al 3+ 53.5 125 Mg 2+ 86 1...
Upcoming SlideShare
Loading in …5
×

ICWES15 -Comparative Absorption of Copper from Synthetic and Real Wastewater by Uncalcined Sodium Exchanged and Acid Modified Montmorillonite. Presented by Dr christianah Olakitan Ijagbemi, Akure, Nigeria

1,405 views

Published on

Published in: Technology, Business
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
1,405
On SlideShare
0
From Embeds
0
Number of Embeds
5
Actions
Shares
0
Downloads
123
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide
  • In the right concentrations, many metals are essential to life. In excess, these same chemicals can be poisonous. Similarly, chronic low exposures to heavy metals can have serious health effects in the long run. The main threats to human well-being are associated with lead, arsenic, cadmium and mercury, and it is these substances that are targeted by international legislative bodies.
  • Transition metal is &amp;quot;an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell.&amp;quot; An ion is an atom or molecule which has lost or gained one or more valence electrons , giving it a positive or negative electrical charge. A negatively charged ion , which has more electrons in its electron shells than it has protons in its nuclei , and is known as an anion A positively-charged ion , which has fewer electrons than protons, is known as a cation Metallic bonding is the electrostatic attraction between delocalized electrons , and the metallic nuclei within metals . It involves the sharing of free electrons among a lattice of positively-charged metal ions. Chelation therapy is a series of intravenous infusions containing EDTA and various other substances. EDTA is a polyamino carboxylic acid The first widely used chelating agent, the organic dithiol compound dimercaprol (also named British Anti-Lewisite or BAL), was used as an antidote to the arsenic-based poison gas,
  • Distill water – for proton adsorption Charge determination (KCl solution) Initial pH values (pH i ) of 20 mL of KCl solutions (concentrations 10 −3 and 10 −2 M) were adjusted in pH range of 3.1–10 using 0.01 M of HCl or NaOH. Then, 0.05 g of MMT was added to each sample. Equilibration was carried out by shaking, in a rotary incubator at 200 rpm for 2 h at 25±1 ◦ C. The dispersions were then filtered and the final pH of the solutions (pH f ) was determined, point of zero charge was found from a plot of pH f vs. pH i . Each addition of 0.05 g of dry MMT sample were added to 30mL of KCl solution at a given ionic strength, I = 0.01M, having a pH between 2.4 and 5.1. After each addition, the pH was recorded after an equilibrium time. It was verified that the pH reached a constant value for exactly 10min after each addition of the mineral. Then, a new amount of sample was introduced to change the pH; this procedure was repeated until a pH was found where no pH change occurs with further addition of the sample. For a clay or oxide free of contamination (Zalac and Kallay, 1992), this pH value has been shown to be a good approximation to the PZNC of oxide or clay surfaces.
  • silver nitrate + dilute nitric acid.) Cl ions give a white precipitate with silver nitrate.
  • barium chloride + zinc sulfate , in the presence of HCl - zinc chloride + barium sulfate. (white precipitate) BaCl 2(aq)       +      ZnSO 4(aq)                    ZnCl 2(aq)      +     BaSO 4(s)
  • CEC : The pH 7.0 ammonium acetate procedure of Chapman (1965) is recommended. NH 4 + saturation: the soil is saturated with NH 4 +, then the NH 4 + is replaced by Ca++, and lastly the NH 4 + removed is measured to determine the number of exchange sites that were occupied by ammonium. To estimate the actual CEC (at the pH of the soil), the sum of cations extracted by a routine Soil test (CECe) should suffice. For a very precise measure of CEC, the BaCl 2 -compulsive exchange procedure is suggested (Gillman, 1979, Gillman and Sumpter, 1986; Rhoades, 1982). EGME : placed in vacuum desicator containing diphosphorus pentaoxide for 4hrs to remove moisture from the surface. Dried adsorbent is weighed. Excess amt of ethlene glycol monoethyl ether (EGME) was applied to wet adsorbent surface. And then placed in a vacuum again containing calcium chloride. Weight of EGME remaining as a function of time was ploted. Equilibrium weight of EGME for monolayer coverage was obtained.
  • With Mg 2+ substituting for Al 3+ there are fewer positive charges to neutralize the negative charges and a large permanent (negative) charge results (it is called permanent charge since it takes place during crystallization and it is not a subject to changes). In contrast, there are also variable or pH-dependent charges that are formed by protonation and deprotonation of functional groups like -OH.
  • &amp;quot; charge density &amp;quot; defined as: the number of charges on the cation divided by it’s surface area
  • ICWES15 -Comparative Absorption of Copper from Synthetic and Real Wastewater by Uncalcined Sodium Exchanged and Acid Modified Montmorillonite. Presented by Dr christianah Olakitan Ijagbemi, Akure, Nigeria

    1. 1. Christy Ijagbemi Ph. D Department of Mechanical Engineering Federal University of Technology, Akure, NIGERIA Adsorption of Copper from Synthetic and Real Wastewater by Un-calcined Sodium Exchanged and Acid Modified Montmorillonite
    2. 2. <ul><li>Escape into the environment pose a serious health hazard – </li></ul><ul><li>escapes on the increase </li></ul><ul><li>Accumulate in living tissues throughout the food chain </li></ul><ul><li>At higher concentrations they can lead to poisoning </li></ul>The Problem - threat to the Environment Health and environmental concerns about heavy metal ions - Why ? Introduction
    3. 3. <ul><li>Heavy Metals </li></ul><ul><li>Are natural components of the earth’s crust. </li></ul><ul><li>Relatively high density - > 5 g/cm 3 </li></ul><ul><li>May exist as o xides, hydroxide, sulfide and carbonate salts – soluble, sparing soluble or insoluble in </li></ul><ul><li>water . </li></ul><ul><li>Possess a cationic nature (monovalent, divalent or trivalent) e.g Ag + , Cd 2+ , Hg 2+ , Ni 2+ , Cu 2+ , Pb 2+ , Fe 2+ </li></ul><ul><li>or Fe 3+ , Zr 4+ has multiple oxidation states. </li></ul><ul><li>Cannot be degraded or destroyed - can only be changed in valence or by chelation. </li></ul><ul><li>Toxic or poisonous at low concentrations, some are carcinogenic. </li></ul><ul><li>Greater solubility = Greater toxicity </li></ul><ul><li>C onstitute the Group III transition metals, the actinides series, the lanthanide series, and three of the </li></ul><ul><li>Group IV metalloids </li></ul><ul><li>Readily loses electrons to form positive ions (cations) </li></ul><ul><li>Have metallic bonds </li></ul>Metals Background
    4. 4. Hg Al Ba Pb Cd Fe Heavy Metals Toxic Heavy Metals
    5. 5. Heavy metals employed in some major industries (Palmer et al., 1988). Introduction Industries Cd Cr Cu Fe Hg Pb Ni Zn Pulp, paper mills, board mills x x x x x x Organic chemical, petrolchemicals x x x x x x Alkalis, inorganic chemicals x x x x x x Fertilizers x x x x x x x x Petroleum refining x x x x x x x x Basic steel work foundries x x x x x x x Motor vehicles, aircraft plating and finishing x x x x x x Steam generation power plats x x
    6. 6. <ul><li>Recent toxicology studies </li></ul><ul><li>Stricter regulations with regard to toxic metal ions discharge, </li></ul><ul><li>particularly in industrialized countries. </li></ul><ul><li>Conventional materials and techniques: </li></ul><ul><li>- secondary problems of metal-bearing sludge. </li></ul><ul><li>- ineffective at low metal ion concentrations </li></ul><ul><li>- expensive and non-regeneration of adsorbent (activated carbon) </li></ul><ul><li>Developing an alternative material to the conventional adsorbent – </li></ul><ul><li>activated carbon, normally used in adsorption processes of removing </li></ul><ul><li>heavy metal ions in water and wastewater treatment facilities would </li></ul><ul><li>result in a more cost-effective way of treating heavy metal. </li></ul>Current Situations and Arising Needs Introduction
    7. 7. <ul><li>Why MMT? </li></ul><ul><li>Montmorillonite is a clay silicate formed by crystallization from solution high in soluble silica and magnesium. </li></ul><ul><li>MMT is a member of the smectite family, a 2:1 clay, has 2 tetrahedral sheets sandwiching a central octahedral sheet. </li></ul><ul><li>The particles are plate-shaped with an average diameter of approximately 1 micrometer. </li></ul><ul><li>Increases greatly in volume when it absorbs water. </li></ul><ul><li>Chemically, it is hydrated sodium calcium aluminium magnesium silicate hydroxide (Na,Ca) 0.33 (Al,Mg) 2 (Si 4 O 10 )(OH) 2 · n H 2 O. Potassium, iron, and other cations are common substitutes. </li></ul>Montmorillonite Background
    8. 8. <ul><li>Mg 2+ for Al 3+ leads to permanent negative charge </li></ul><ul><li>Mg 2+ move to interlayer space </li></ul><ul><li>At the interlayer Mg 2+ , Ca 2+ or Na + can react with water – Free expansion </li></ul><ul><li>Large internal surface </li></ul><ul><li>Poorly crystallize </li></ul><ul><li>- difference in sizes </li></ul><ul><li>- isomorphous substitution </li></ul><ul><li>- large cation adsorption </li></ul>MMT as metal ion adsorbent Background Adapted from Olphen and Fripiat, 1979 O T Mg 2+ for Al 3+ Al 3+ or Fe 3+ for Si 4+ T T T O Interlayer
    9. 9. Research goal : To develop an effective and regenerative material from MMT and evaluate its application potentials to replace activated carbon for the treatment of heavy metal- loaded industrial effluents Research idea To provide explicit information on how the physicochemical nature and behavior of a natural clay (montmorillonite - MMT) surface can be articulated for designing effective heavy metal ion treatment strategies in water and wastewater systems. Research idea and goal
    10. 10. To modify MMT surface properties and evaluate the effects of the modifications on adsorptive behavior of MMT for heavy metal ions removal in aqueous solutions. Research Objective
    11. 11. <ul><li>adsorption by (living or dead) microbial biomass, bioremediation </li></ul><ul><li>systems </li></ul><ul><li>low operating cost, eco-friendly </li></ul><ul><li>most economical alternative compared with other processes </li></ul><ul><li>technical constraints – large land area, less flexibility in design and </li></ul><ul><li>operation </li></ul><ul><li>ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, ion </li></ul><ul><li>exchange, adsorption </li></ul><ul><li>membrane fouling occurs often  not cost-effective </li></ul><ul><li>precipitation, coagulation-flocculation, flotation, electrochemical </li></ul><ul><li>processes </li></ul><ul><li>although metal ions are removed, accumulation of concentrated </li></ul><ul><li>sludge creates a disposal problem </li></ul><ul><li>a secondary pollution problem  excessive chemical use </li></ul>Treatment processes for industrial wastewater laden with toxic heavy metal ions Background Biological treatment process Physical treatment process Chemical treatment process
    12. 12. Researchers have focused on use of other relatively cheaper adsorbents to replace activated carbon Adsorption Background
    13. 13. <ul><li>Evaluation studies </li></ul>MMT for heavy metal pollution remediation Approach Phase 1 Phase 2 Phase 3 <ul><li>Adsorption and </li></ul><ul><li>Field application </li></ul><ul><li>MMT surface properties determination </li></ul><ul><li>CEC </li></ul><ul><li>d-spacing </li></ul><ul><li>Surface area </li></ul><ul><li>MMT surface properties modification </li></ul><ul><li>Salt treatment </li></ul><ul><li>Acid treatment </li></ul>
    14. 14. Beaker Charge determination <ul><li>100 mL KCl electrolyte [conc (0.01- 0.001M)] </li></ul><ul><li>20g MMT added and titrated with </li></ul><ul><li>0.01M NaOH till pH 10. </li></ul><ul><li>Reversibility </li></ul><ul><li>Same suspension titrated with 0.01 M HCl </li></ul><ul><li>till pH 2.5 </li></ul><ul><li>pH measurement after stirring and </li></ul><ul><li>equilibration for 1hr </li></ul>Materials and methods
    15. 15. Sodium montmorillonite (Na-MMT) MMT : 1 M NaCl solution = 1 g : 10 mL Mechanical stirring (24 h), repeated 5 times Centrifugation and AgNO 3 test for Cl - Drying at 105 o C for 6 h Sieving to 150 μ m Synthesis( Na-MMT) Materials and methods
    16. 16. Acid treated montmorillonite (A-MMT) MMT : 4 N H 2 SO 4 = 1 g : 40 mL Drying at 105 o C for 6 h Sieving to 150 μ m Synthesis (A-MMT) Materials and methods Refluxing in a shaking water bath (3 h) at 90 o C Centrifugation and BaCl 2 test for SO 4 2-
    17. 17. <ul><li>Adsorbent (Na-MMT and A-MMT) </li></ul><ul><li>Adsorbate (50 mL of Copper Solution) </li></ul><ul><li>Adsorbent dosage (0.3 g) </li></ul>Shaking(200 rpm) Filtration Analysis AAS 100mL Erlenmeryer flask <ul><li>Parameters </li></ul><ul><li>Initial concentration of copper solution : 50 - 100 mg/L </li></ul><ul><li>Temperature : 15 - 45℃ </li></ul><ul><li>pH: 2.3-10 </li></ul>Sorption Materials and methods
    18. 18. Materials and methods Chemical assay of industrial wastewater . Parameters Quality/ 4 L of effluent pH 6.1 COD 117.5 (mg) Suspended solids 57.4 (mg) Normal hexane 1.0 Total Nitrogen 57.78 Total Phosphorus 10.08 Cyanide 0.348 (mg) Copper 124.37 (mg) Nickel 60.19 (mg) Chromium 0.317 (mg)
    19. 19. Applied isotherm models Results and discussion <ul><li>V ital information in optimizing the use of adsorbents: </li></ul><ul><li>affinity between sorbates and sorbents </li></ul><ul><li>bond energy and adsorption capacity </li></ul>Isotherm Empirical form Linear form Plot Freundlich Langmuir Tempkin Dubinin-Radushkevich Redlich-Peterson
    20. 20. Applied kinetic models Results and discussion Isotherm Empirical form Linear form Plot Pseudo first-order Pseudo second-order Elovich Intra-particle
    21. 21. Characterization of montmorillonites Results and discussion Adsorbent CEC (meq/100g ) d -spacing (nm) Surface area (m 2 /g) MMT 89.24 0.126 267 Na-MMT 94.18 0.128 286 A-MMT 57.69 0.098 190
    22. 22. Effect of pH Results and discussion Effect of pH on the adsorption of Cu 2+ onto Na-MMT and A-MMT (Cu 2+ concentration, 100 mg/L; adsorbent dose, 6 g/L; equilibrium time, 250 min; temperature 25 ± 0.1 °C; 200 rpm) Adsorption was highly pH dependent: imply that surface complexation contributes to Cu(II) adsorption. Na-MMT displayed a higher adsorption capability.
    23. 23. Equilibrium sorbed amount of Cu 2+ according to time by (a )Na-MMT and (b) A-MMT at different initial concentrations (adsorbent dose, 6 g/L; reaction time, 250 min; pH, 5.8 ± 0.1; temperature 25 ± 0.1 °C; 200 rpm). (a) (b) Effect of initial concentration and time Results and discussion <ul><li>M aximum adsorbed amount for Cu(II) with Na-MMT </li></ul><ul><li>and A-MMT was achieved within 180 min. </li></ul><ul><li>Increase in initial concentration α increase adsorption . </li></ul>
    24. 24. Equilibrium isotherm model parameters for Cu(II) sorption onto modified montmorillonites. Results and discussion <ul><li>Process of adsorption of metal ions occurred on </li></ul><ul><li>the homogeneous surface of MMT (a chemically </li></ul><ul><li>equilibrated phenomenon). </li></ul>Equilibrium models Parameters Na-MMT A-MMT Freundlich K F ((mg/g)(L/mg) 1/n ) 7.281 1.050 n F 9.373 1.986 q e Cal.(mg/g) 10.67 7.85 R 2 0.998 0.971 Langmuir Q m (mg/g) 10.89 12.14 B (L/mg) 0.867 0.032 q e Cal.(mg/g) 10.57 7.71 R 2 0.999 0.986 Tempkin A T 148.9 0.011 b T (kJ/mol) 2.495 0.798 q e Cal.(mg/g) 10.64 7.75 R 2 0.999 0.982 Dubinin-Radushkevich Q DR (mg/g) 10.28 8.25 E (kJ/mol) 1.227 0.108 q e Cal.(mg/g) 10.23 7.59 R 2 0.975 0.999 Redlich-Peterson B 9.85 4.82 A 0.059 0.038 ζ 0.977 0.546 q e Cal. (mg/g) 10.61 7.79 R 2 1.00 0.973 Experimental q e Exp.(mg/g) 10.61 7.59
    25. 25. Results and discussion Kinetics Kinetic model parameters for the sorption of Cu(II) onto modified montmorillonites. Kinetic models Parameters Na-MMT A-MMT Concentration of Cu(II) solution (mg/L) 50 75 100 50 75 100 Pseudo first-order k 1 0.013 0.027 0.024 0.016 0.022 0.024 q e Cal.(mg/g) 3.87 4.16 9.98 3.17 5.13 5.91 R 2 0.968 0.976 0.944 0.989 0.964 0.995 Pseudo second-order k 2 (g/mg min) 0.011 0.032 0.004 0.007 0.007 0.001 q e Cal.(mg/g) 8.22 10.07 10.86 5.06 7.03 8.00 R 2 0.999 0.999 0.998 0.999 0.999 0.999 Elovich α (g/(mg min)) 1.90 1.67 2.50 1.09 4.35 3.26 τ (mg/g) 1.11 1.33 0.57 1.21 1.06 0.86 q e Cal. (mg/g) 8.69 7.78 11.26 3.64 7.02 6.14 R 2 0.995 0.962 0.988 0.983 0.988 0.976 Intraparticle k id (mg/g min 1/2 ) 0.138 0.085 0.222 0.242 0.179 0.199 q e Cal. (mg/g) 8.41 8.23 10.74 5.11 7.29 8.09 R 2 0.995 0.968 0.998 0.978 0.988 0.987 Experimental q e Exp.(mg/g) 7.94 9.89 10.61 4.76 6.71 7.59 <ul><li>Chemisorption through sharing or exchange of electrons </li></ul><ul><li>between sorbent and adsorbate . </li></ul><ul><li>Rate constant decreases with increasing initial metal ion </li></ul><ul><li>concentrations i.e. time required for the adsorption may </li></ul><ul><li>monotonically increase with increase in initial metal ions </li></ul><ul><li>concentration in practical applications. </li></ul>
    26. 26. Thermodynamic parameters Results and discussion Thermodynamic parameters for the sorption of Cu(II) onto modified montmorillonites. <ul><li>Adsorption increased with increase in temperature </li></ul><ul><li>… Endothermic process </li></ul><ul><li>Adsorption is thermodynamically spontaneous and feasible </li></ul><ul><li>+ve entropy supports complexation and stability of sorption </li></ul><ul><li>(irreversibility) </li></ul>Adsorbent Temp (K) ∆ G o (kJ/mol) ∆ H o (kJ/mol) ∆ S o (J/mol K) Na-MMT 288 -13.00 11.56 85.30 298 -13.86 303 -14.70 318 -15.56 A-MMT 288 -11.55 8.61 70.00 298 -12.25 303 -12.95 318 -13.65
    27. 27. Results and discussion Application to real industrial wastewater Removal of Cu(II) and Ni(II) from industrial wastewater by modified montmorillonites . N.D : Not Dedectable Metals Effluent concentration/50 mL (mg/L) Remaining concentration in mg/L (% removal) Na-MMT A-MMT Zr-MMT AC Cu(II) 69.67 10.01 (85.6) 28.43 (59.2) 19.47 (72.1) 3.68 (94.7) Ni(II) 10.27 N.D N.D N.D N.D Cr(VI) 0.049 N.D N.D N.D N.D
    28. 28. Conclusion and recommendation The natural occurrence, availability, adsorption and regeneration capabilities, even cost, pose MMT as a substitute for activated carbon in toxic heavy metal ions treatment of industrial wastewater. The application of these modified-MMTs by industrial units using a batch stirred-tank flow reactor is hereby recommended for direct solution to problems of heavy metal-loaded wastewater discharge. The loaded MMT after several use, can be disposed off for brick making in the building industry. Conclusions
    29. 30. Sources and Sinks of Heavy Metals Modified – from http://pubs.usgs.gov/circ/circ1133/images/fig 21.jpeg
    30. 31. Route of Exposure: Absorption, Ingestion, Inhalation http:healtheffects.net/he/images/ToxTri.gif
    31. 32. Maximum contaminant level (MCL) of heavy metals in surface water and their toxicities (prepared from http://www.epa.gov/safewater/mcl). Heavy metal Rank Toxicities Maximum effluent discharge standards (mg/L) EPA (CERCLA, 2005) USA Cr(VI) 18 Headache, nausea, diarrhea, vomiting 0.01 Pb(II) 02 Kidney damage, renal disorder, cancer 0.015 Zn(II) 74 Depression, lethargy, neurologic signs such as seizures and ataxia, and increased thirst 5.0 Cu(II) 133 Liver damage, Wilson disease, insomnia 1.3 Cd(II) 08 Kidney damage, renal disorder 0.005 Ni(II) - Dermatitis, nausea, chronic asthma, coughing 0.20
    32. 33. Numbers of tested adults reported to the NYS Department of health for (A) Arsenic and (B) Lead by level (A) (B) USDA Report, 2005
    33. 34. Hg Al Pb Heavy Metals Toxic Heavy Metals Cu Cd Ni
    34. 35. Theory - ideal MMT
    35. 36. The amount of metal ion adsorbed per unit mass of adsorbent q t (mg/g) at each time t , by adsorbents was calculated from the mass balance expression: and the percentage removal of metal ions was obtained using: Removal (%) V = volume of metal ion solution (mL) C 0 = initial concentration of the metal ion solution (mg/L) C t = liquid-phase concentrations of the metal ion solution at any time t (mg/L) m = amount of adsorbent used (g) Adsorption Calculation
    36. 37. The net surface charge density, S o , was calculated using the equation above. S o = surface charge (C cm −2 ) n = numbers of moles of ions F = Faraday constant. Г H + and Г OH - = adsorbed amounts of H + and OH − ions (mol cm −2 ) during the titration process In this manner, the dependence of the surface charge density on pH and the electrolyte concentration were obtained. Calculation Surface charge density
    37. 38. <ul><li>Large surface area </li></ul><ul><li>Relative abundance of reactive surface groups on its surface </li></ul><ul><li>Predominance in sub-surface </li></ul><ul><li>- Predominance as particles in suspensions in surface water </li></ul><ul><li>- Abundant natural mineral in many regions </li></ul>
    38. 39. Adsorption capacities (mg/g) of adsorbent for different heavy metals Babel, 2002 Adsorbent Cd 2+ Hg 2+ Cu 2+ Ni 2+ Zn 2+ Pb 2+ Cr 2+ Cost (kg/USD) Chistosan 815 222 164 75 273 15.43 Zeolite 2.2 1.6 0.48 0.5 1.4 3.3 0.03-0.12 Clay (smectite ) 0.04-0.12 Montmorillonite 4.72 4.98 0.68 Kaolinite 0.32 1.25 0.12 Illite 4.29 Peat 22.48 12.07 11.74 13.08 43.9 0.023 Fly ash 2.82 2.92 Activated carbon (GAC) 44.44 0.87 Cellulose 73.46 1.07 Natural oxides Aluminium oxides 31 33 11.7 Ferric oxide 72 230 Industrial waste Lignin (Black Liquor) 1865 1USD/ton Sawdust 13.80
    39. 40. Montmorillonite Van Olphen, 1979
    40. 41. Schematic picture of the montmorillonite particle (A), the top plane (basal plane) possesses exchangeable sites, whereas the edge surface dissociable ones. Parts (B) and (C) show the electrical double layer model for both kinds of planes. Duc et al., 2005
    41. 42. Mineral surface properties Surface charge of an oxide mineral surface in aqueous systems will change with changing pH as a function of the PZC of that mineral. Surface charge creates a surface condition in which there is an uneven charge distribution. The consumption and release of protons during an acid/base titration can be due to: – proton adsorption/desorption on the edge sites (i.e.aluminols and silanols) – exchange reactions on basal planes to compensate the negative structural charge – hydrolysis of aqueous cations released during mineral dissolution. Surface Charge Theory
    42. 43. Surface Charge Development Theory <ul><li>Three parameters contribute on surface charge of clay minerals: </li></ul><ul><li>σ O : the permanent structural charge density created by isomorphic substitutions in a mineral structure, </li></ul><ul><li>σ H : the net proton surface charge density created only by proton adsorption and desorption reactions at the interface clay-aqueous solution and, </li></ul><ul><li>Δ q : the net adsorbed ion surface charge density from background electrolyte, exclusive of that contributed by adsorbed protons and hydroxide ions. </li></ul><ul><li>These components are related by the law of surface charge balance: </li></ul><ul><li>σ O + σ H + Δ q = 0 </li></ul><ul><li>The sign of σ H varies with aqueous solution pH, taking on zero at the point of zero net proton charge ( PZNPC ) and becoming negative at higher pH values. </li></ul>
    43. 44. Definitions of the surface charges of clays and relevant characteristic points determined from potentiometric titrations or electrokinectic measurements Acronym Name Definition Proton charge Surface charge developed by protonation- deprotonation of surface groups. Lattice charge Charge originating from lattice substitutions by lower-charge metals and giving rise to the cation exchange capacity. PZNPC Point of zero net Intersection between raw titration curve for the proton charge blank and for the suspension. PZSE Point of zero salt Intersection between charge curves at different effect electrolyte concentrations PZC Point of zero Common intersection point where both PZNPC charge and PZSE coincide. IEP Isoelectric point pH of zero ζ potential on eletrokinectic curves
    44. 46. Surface Charge Development - Theory In environmental chemistry and several industrial processes - PZC is a very important parameter playing a crucial role in many chemical phenomena , such as adsorption, interaction between particles in colloidal suspensions, coagulation, dissolution of mineral hydroxides and electrochemical phenomena. The principal mechanism of the development of surface charge is the adsorption of protons, hydroxyls, metallic cations, anions and organics species. a) Lattice imperfection b) Adsorption of ions <ul><li>Chemical reactions on the surface </li></ul><ul><li>(dissociation of functional surface groups) </li></ul>d) Adsorption or dissociation of charge-bearing molecules
    45. 47. Metal Ionic radius Atomic radius Na + 116 168 H + - 25 Zr 3+ 88.5 160 Ni 2+ 83 135 Cu 2+ 87 135 Al 3+ 53.5 125 Mg 2+ 86 150 Si 3+ - 110 Fe 3+ 63 140

    ×