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8/8/2019 Darshit Final Presentation
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Metal removal byelectro-coagulation
Guided by:Prof. Nikita Chokshi
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Need for the removal of metal
y Nowdays in this era of industrialisation large amount amount of toxic metals copper,
sulphate, arsenic etc. are released from industrial activites which can lead to
contamination of ground water as well as surface water if released without any
treatment because of it there is always a need to treat this effluents of industries before
releasing them to the environment.
y Also many trace element like arsenic present in ground as well as surface water has
became a major unavoidable threat for the life of human beings and useful
microorganisms.
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Methods available for metal removal
y Chemical coagulation
y Adsorption
y
Electrocoagulation
y Reverse osmosis
y Nano filtration
y electrodialysis
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Electrocoagulation process
y In the electrocoagulation process, the coagulant is generated in situ by the electrolytic
oxidation of an appropriate anode material.
y In this process charge ionic species like metals or otherwise are removed from
wastewater by allowing it to react with an ion having opposite charge or with floc of
metallic hydroxides generated within the effluent.
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Comparison of chemical coagulation
y Main advantages of EC over conventional coagulation are as follows:
No alkalinity consumption
No change in bulk pH
Direct handling of corrosive chemical is eliminated
Can be easily adapted for use in portable water treatment unit especially
during emergencies
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Metal removal using organic adsorbents
y We have to find a suitable a adsorbent for each and every specific metal to be removed
from waste water while we can use any of the iron, aluminium or steel elctrode in
general to remove metal from water.
y Also the adsorbent used for process should be recovered because of the cost of
adsorbent used and so the total cost including the recovery cost makes it an ineffective
option.
y For example for arsenic removal activated carbon specifically named As-GAC
(granular activated carbon) that contained iron by Gu et al has a working range of 5-
20 mg/l at pH 7 and can remove only As (III) and not As (V) only upto 1.393 mg/g
y For the regeneration of sorbents used sorbing arsenic they need to wash with alkali
such as casutic soda and neutralising using HCl or H2SO4 and thus results in alkaline
waste sludge due to alkali to acid ratio
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EC process setup
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Factors affecting electrocaogulation
y Major factors affecting the electrocogulation seperation are :
Area of the metal plate used as electrode
pH of the medium
Current density
Concentration of the metal in the inlet water/wastewater
total time of the process
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Overview of arsenic removal from water
y Sources of arsenic in water are :
natural occurrence in ground as well as surface water
copper smelting industrial effluent
metal plating effluent
other types of industrial effluents
y Because of high toxicity of arsenic its standard has been set to 2-20 g/l for drinking
purpose.
y Arsenic may present in two states in water i.e. arsenite or arenate depending on th pH
of the medium.
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Reaction mechanism of arsenic removal by EC
y Consider aluminium electrodes :
Al Al3+ + 3e-
Al3+ + 3H2O Al(OH)3 + 3H+
Al(OH)3 + AsO43- Al(OH)3 *AsO4
3-
y Finally the compund formed in the last reaction produced gets aggregate and can be
removed with suitable method.
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Results of arsenic remval using aluminium electrode
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List of analytical methods
y Mass spectrometry
y Powered x-ray diffraction
y
X-ray photoelectron spectroscopy
y Scanning electron microscope and energy dispersive x-ray analyzer
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Disposal methods for arsenic containing treated water
y Landfill
y Mixing with livestock waste
y Incorporating within construction material
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Future goal
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References
y M.Yousuf A. Mollah , Robert Schennach, Jose R. Parga, David L. Cocke,
Electrocoagulation (EC) Science and applications, journal of Hazardous Material B84
(2001) 29-41
y Dinesh Mohan, charles U. Pittman Jr., Arsenic removal from water/wastewater using
adsorbents A critical review, journal of Hazardous Materials 142 (2007) 1-53
y Jochen Bundschuh, Marta Litter, Virginia S.T. Ciminelli, Maria Eugenia Morgada,
Lorena Cornejo, Sofia Garrido Hoyos, Jan Hoinkis, Ma. Teresa Alarcon-Herrera, Maria
Aurora Armienta, prosun Bhattacharya, Emerging mitigation needs and sustainable
options for solving the arsenic problems of rural and isolated urban areas inL
atinAmerica- A critical analysis, Water research (2010) 1-18
y Jewel A.G. Gomes, Praveen Daida, Mehmet Kesmez, Michael Weir, Hector Moreno,
Jose R. Parga, George Irwin, Hylton McWhinney, Tony Grady, Eric Peterson, David L.
Cocke, Arsenic removal by electrocoagulation using combined Al-Fe electrode system
and characterization of products, Journal of Hazardous Materials B139 (2007) 220-231
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Continued
y Ashima Baggaa, Shankararaman Chellam , Dennis A. Clifford, Evaluation of iron
chemical coagulation and electrocoagulation pretreatment for surface water
microfiltration, Journal of Membrane Science 309 (2008) 8293.
y Ilona Heidmann, Wolfgang Calmano, Removal of Zn(II), Cu(II), Ni(II), Ag(I) and
Cr(VI) present in aqueous solutions by aluminium electrocoagulation, Journal of
Hazardous Materials 152 (2008) 934-941.
y Isik Kabdasah, Tulin Arslan, Tugba Olmez-Hanci, Idli Arslan-Alaton, Olcay Tunnay,
Complexing agent and heavy metal removals from metal plating effluent by
electrocoagulation with stainless steel electrodes, Journal of Hazardous Materials, 165(2009) 838-845.
y Colin Sullivan, Mark Tyrer, Christopher R. Cheeseman, Nigel J.D. Graham, Disposal
of water treatment wastes containing arsenic- A review, Science of the total
environment 408 (2010) 1770-1778.