Bioremediation Approaches for Degradation …
123
and undergoes chemical reaction with the dye components (azo dyes) and convert
into amide, subsequently to ammonium salts (Rahman Bhuiyan et al. 2014; Parvin
et al. 2014).
2.9.1 Electrochemical Methods
Electrochemical methods are
1. Electrochemical oxidation
2. Electro coagulation
3. Electro floatation.
Electrochemical oxidation
In this method, pollutants are converted into simple forms like CO 2 and H 2 O by
oxidation. Pollutants are oxidized either direct or indirect.
Direct oxidation (anodic oxidation process)—In this method, pollutants are adsorbed
on the anode surface and oxidized by anodic electron transfer reaction.
Indirect oxidation—Here, electrochemically potent oxidants such as chlorine,
hypochorite, hydrogen peroxide, ozone and hydroxyl ions are produced at the anode
surface. Potent oxidants are formed in two stages.
First stage—Adsorbed hydroxyl radical is produced at the anode by H
+ in acidic
solution or OH
− in alkalin solution.
Second stage—Interaction between the adsorbed hydroxyl radical and metal oxide
leads to produce higher oxide components (Feng et al. 2016; Radjenovic and Sedlak
2015; Martínez-Huitle and Andrade 2011).
Electro Coagulation
In this method, electrostatic charges on pollutants are neutralized and expedite coagulation formation, which will help to purify the water. This technique includes
simultaneous formation electro coagulation followed by electro flocculation.
For electro coagulation aluminium from aluminium electrode or ion from ion
electrodes are used to generate corresponding metal ions. These metal ions can form
multi-charged polynuclear complex, which has an improved adsorption characteristic
property leads to form coagulation of the pollutant. Instantaneously hydrogen gas
is engendered from the cathode; it will help to float the coagulated particles out of
water. For coagulation of chemical method, metal salts such as Al 2 (SO 4 ) 3 , Fe 2 (SO 4 ) 3 ,
Fe(SO 4 ) and FeCl 3 are preferred. Schematic diagram of an electrocoagulation process
(Cañizares et al. 2005) is shown in Fig. 6.
Steps involved in the electrocoagulation process are
1. Electrolytic reactions at the electrode
2. Coagulants formation
123
and undergoes chemical reaction with the dye components (azo dyes) and convert
into amide, subsequently to ammonium salts (Rahman Bhuiyan et al. 2014; Parvin
et al. 2014).
2.9.1 Electrochemical Methods
Electrochemical methods are
1. Electrochemical oxidation
2. Electro coagulation
3. Electro floatation.
Electrochemical oxidation
In this method, pollutants are converted into simple forms like CO 2 and H 2 O by
oxidation. Pollutants are oxidized either direct or indirect.
Direct oxidation (anodic oxidation process)—In this method, pollutants are adsorbed
on the anode surface and oxidized by anodic electron transfer reaction.
Indirect oxidation—Here, electrochemically potent oxidants such as chlorine,
hypochorite, hydrogen peroxide, ozone and hydroxyl ions are produced at the anode
surface. Potent oxidants are formed in two stages.
First stage—Adsorbed hydroxyl radical is produced at the anode by H
+ in acidic
solution or OH
− in alkalin solution.
Second stage—Interaction between the adsorbed hydroxyl radical and metal oxide
leads to produce higher oxide components (Feng et al. 2016; Radjenovic and Sedlak
2015; Martínez-Huitle and Andrade 2011).
Electro Coagulation
In this method, electrostatic charges on pollutants are neutralized and expedite coagulation formation, which will help to purify the water. This technique includes
simultaneous formation electro coagulation followed by electro flocculation.
For electro coagulation aluminium from aluminium electrode or ion from ion
electrodes are used to generate corresponding metal ions. These metal ions can form
multi-charged polynuclear complex, which has an improved adsorption characteristic
property leads to form coagulation of the pollutant. Instantaneously hydrogen gas
is engendered from the cathode; it will help to float the coagulated particles out of
water. For coagulation of chemical method, metal salts such as Al 2 (SO 4 ) 3 , Fe 2 (SO 4 ) 3 ,
Fe(SO 4 ) and FeCl 3 are preferred. Schematic diagram of an electrocoagulation process
(Cañizares et al. 2005) is shown in Fig. 6.
Steps involved in the electrocoagulation process are
1. Electrolytic reactions at the electrode
2. Coagulants formation