Dr. Salah El Mofty - Use of Electrophoresis Technique to Study Removal of Toxic Metal Ions from Waste Water by Mineral Absorption on SurfacePresentation Transcript
Prof. Dr. Salah Eldin EIMofty Prof. of Mining & Environmental Engineering, Faculty of Engineering, Cairo University, Egypt October/2011 4 th Kuwait Waste Management Conference 2011 USE OF ELECTROPHORESIS TECHNIQUE TO STUDY REMOVAL OF TOXIC METAL IONS FROM WASTE WATER BY ADSORPTION ON MINERAL SURFACE
Large quantities of toxic metals and pollutants
Entering the Environment
Different Areas of Research
Adsorption on Mineral Surfaces such as Clay
The Clay Sample from Alex, Egypt
The surface area of Clay was found to be 155m 2 /g
% by weight Compound 55.5 19.4 1.34 11.2 SiO 2 Al 2 O 3 MgO L.O.I
Electro Kinetic Characterization
Double-layer showing the surface of clays particles (left side), and the distribution of the adsorbed cations and anions within the double layer (right side) .
Surface Charge Results
The surface charge patterns of Clay mineral particles in the absence and presence of the chloride salts of the heavy metals
Zeta potential of clay particles in absence and presence of different heavy metal cations
Effect of equilibrium time on adsorption density of M 2+ onto Clay. (S/L 50g/L, C i =10 -3 M/L, temperature 20 0 C).
The adsorption density at equilibrium q e (g/m 2 ) was calculated according to eq. (1)
The pseudo first-order and pseudo second-order models were used. The first-order model is generally expressed as follows :
Integrating eq.(2), at the following boundary conditions, t = 0 and qt =0 to t = t and q e = qt eq. (2) becomes:
On the other hand, the second-order equation was used to predict the behavior over the whole range of adsorption. The second-order rate equation is described by:
Where K2 is the rate constant of pseudo-second-order sorption (g/mg min). Integrating eqn (4) at the boundary conditions t =0 and qt =0 to t = t and q e = qt eq. (4) becomes:
The constants q e and k 2 can be determined using Excel Solver. The values of constants q e and k 2 for second-order sorption.
Kinetic Models Constants For Heavy Metals Adsorption On Clay
Heavy metals Model constants Model type Ni Co Cd Pb 0.006 18.196 0.006 18.196 0.01 18.196 0.02 18.196 q e k 1 First order 0.008 200 0.008 200 0.0124 200 0.0228 200 q e k 2 Second order
Effect of solid to liquid ratio on the adsorption of M 2+ onto Clay (Conditioning time of 15 min, C i = 10 -3 M/L, Temperature 20 o C, and pH 5-8)
Effect of pH on adsorption density of M 2+ , onto Clay (S/L ratio 50g/L, C i = 2x10 -3 M/L, T= 20 o C, and conditioning time 2 h)
Effect of heavy metal concentration on adsorption density of M 2+ onto clay. (S/L ratio 50g/L, T= 20C o , and conditioning time 2 h, and pH 4.8-7.6)
Schematic of treatment plane for waste water with dissolved heavy metal ions, including adsorption of heavy metal using clay particles.
Electrophoresis measurements (Zeta potential) of these studies indicated the adsorption of the hydrolysable metal toxic ions on the Clay surfaces.
The sorption study indicated that the heavy and toxic metals Pb (II), Ni (II), Co (VI) and Cd (II) could be adsorbed and thus removed significantly by Clay from aqueous solutions.
The batch adsorption tests showed that the removal of metal ion by Clay is a fast process which can reach the equilibrium after 30 seconds.
The adsorption increases with increasing the initial ions concentration and pH. Kinetic modeling showed that the first-order model was appropriate for the description of this type of adsorption.
The experiment of heavy metal ion uptake by adsorbents showed a marked trend as follows: Pb 2+ < Cd 2+ < Co 2+ ≥ Ni 2+ .