Pd nanoparticles have also shown their efficiency in integrated system.
Chidambaram et al. (2010) reported in situ synthesis of Pd nanoparticles using
C. pasteurianum BC1 cells, wherein C. pasteurianum reduced the Pd (II) ions to
Pd nanoparticles which were retained in the cell wall and cytoplasm of the cells in
the form of bio-Pd. This bio-Pd system successfully catalyzed the reduction process
of Cr (VI) to insoluble Cr (III) species. One added benefit of bio-Pd system mediated
reduction was the production of hydrogen gas which provides an alternative to the
costly addition of molecular hydrogen to above ground pump and treat systems.
MgO nanoparticles in combination with yeast Candida sp. SMN04 have been
studied for treating Cefdinir in aqueous medium (Adikesavan and Nilanjana
2016). The half-life of Cefdinir in nano-bio system was observed to reach less
than half of the time taken by the individual yeast cell. Incorporation of MgO
nanoparticles in the system was reported to increase the permeability of cell membrane allowing more amount of contaminant to get access to the cells, thereby
accelerating degradation rate in comparison to individual system. Table 7.2 presents
nano-bioremediation methods reported for a variety of environmental contaminants.
4 Application Methods and Process
There are two ways which have been reported for application of integrated nano-bio
process in treatment system. First is sequential method wherein the contaminant is
subjected to nanoparticles first and later on bioagent is added to carry out further
process. The second method is concurrent or combined method where both nanoparticle and biological agent are added to the system simultaneously. The examples
of both methods along with their process are given below:
4.1 Sequential Method
Bokare et al. (2010) developed a sequential hybrid treatment system with bimetallic
nanoparticle (Pd/nFe) and an enzyme for studying degradation of triclosan (TCS)
which is an antimicrobial agent used widely in personal care products. In the first
step, triclosan (5 mg/L) was reduced with Pd/nFe nanoparticles (1 g/L) under
anaerobic conditions which resulted in dechlorination of TCS to 2-phenoxyphenol.
In the next step, nanoparticles were separated from the system, and the dechlorinated
product was subjected to oxidation by laccase enzyme isolated from Trametes
versicolor in presence of syringaldehyde (a natural redox mediator). The study
reported complete transformation of TCS through redox process to nontoxic oligomers. Similar kind of reductive-oxidative hybrid strategy was successfully employed
to demonstrate degradation of polybrominated diphenyl ethers (PBDEs) in aqueous
solution using nZVI along with diphenyl ether-degrading bacteria Sphingomonas
sp. PH-07 (Kim et al. 2012). Debromination of deca-BDE (5 g/L) was carried out
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R. Singh et al.
Chidambaram et al. (2010) reported in situ synthesis of Pd nanoparticles using
C. pasteurianum BC1 cells, wherein C. pasteurianum reduced the Pd (II) ions to
Pd nanoparticles which were retained in the cell wall and cytoplasm of the cells in
the form of bio-Pd. This bio-Pd system successfully catalyzed the reduction process
of Cr (VI) to insoluble Cr (III) species. One added benefit of bio-Pd system mediated
reduction was the production of hydrogen gas which provides an alternative to the
costly addition of molecular hydrogen to above ground pump and treat systems.
MgO nanoparticles in combination with yeast Candida sp. SMN04 have been
studied for treating Cefdinir in aqueous medium (Adikesavan and Nilanjana
2016). The half-life of Cefdinir in nano-bio system was observed to reach less
than half of the time taken by the individual yeast cell. Incorporation of MgO
nanoparticles in the system was reported to increase the permeability of cell membrane allowing more amount of contaminant to get access to the cells, thereby
accelerating degradation rate in comparison to individual system. Table 7.2 presents
nano-bioremediation methods reported for a variety of environmental contaminants.
4 Application Methods and Process
There are two ways which have been reported for application of integrated nano-bio
process in treatment system. First is sequential method wherein the contaminant is
subjected to nanoparticles first and later on bioagent is added to carry out further
process. The second method is concurrent or combined method where both nanoparticle and biological agent are added to the system simultaneously. The examples
of both methods along with their process are given below:
4.1 Sequential Method
Bokare et al. (2010) developed a sequential hybrid treatment system with bimetallic
nanoparticle (Pd/nFe) and an enzyme for studying degradation of triclosan (TCS)
which is an antimicrobial agent used widely in personal care products. In the first
step, triclosan (5 mg/L) was reduced with Pd/nFe nanoparticles (1 g/L) under
anaerobic conditions which resulted in dechlorination of TCS to 2-phenoxyphenol.
In the next step, nanoparticles were separated from the system, and the dechlorinated
product was subjected to oxidation by laccase enzyme isolated from Trametes
versicolor in presence of syringaldehyde (a natural redox mediator). The study
reported complete transformation of TCS through redox process to nontoxic oligomers. Similar kind of reductive-oxidative hybrid strategy was successfully employed
to demonstrate degradation of polybrominated diphenyl ethers (PBDEs) in aqueous
solution using nZVI along with diphenyl ether-degrading bacteria Sphingomonas
sp. PH-07 (Kim et al. 2012). Debromination of deca-BDE (5 g/L) was carried out
174
R. Singh et al.