darshit final presentation

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.

darshit final presentation

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