Environmental Engineering Reference
In-Depth Information
Sorption
Contaminated
groundwater
chlorinated solvents,
PAH, BTEX,
heavy metals, etc.
Oxidation-
reduction
Decay
reactions
precipitation,
etc.
Pure
groundwater
Permeable
reactive
barrier
Bedrock
Bedrock
FIGURE 37.1
Schematic diagram of a PRB. Source of a contaminant plume lows through PRB; sorption, oxidation-reduction,
and precipitation occurs while treating contaminant plume.
in leachate treatment, but restricted to developed and temperate countries [46]. In addition to
NZVI, iron oxide nanoparticles (IONPs), silver nanoparticle (AgNPs), and gibbsite nanopar-
ticles (GNPs) have been applied for removal of heavy metals, organic dyes, and wastewater
treatment [40,46,50,51]. Therefore, a case study is described here, focusing on synthesizing
and characterizing nanoparticles (NZVI, iron oxide, gibbsite, silver) to investigate their efi-
ciency for the treatment of landill leachate in the tropics, with a focus on Sri Lanka.
37.2 Materials and Methods
37.2.1 Synthesis of Nanoparticles
37.2.1.1 Synthesizing NZVI
The NZVI was prepared by modifying a borohydride reduction method, dropping an
aqueous borohydride solution into an aqueous ferrous solution [52]. We used FeSO
4
·7 H
2
O
because of its high reactivity with borohydride, less oxidation after synthesis, and require-
ment for signiicantly less amount of borohydride; hence, the cost involved is low for large-
scale applications [53].
In brief, the starch-stabilized NZVI (hereafter referred as S-NZVI) was synthesized by
adding 100 ml of 0.5 M sodium borohydride solution into a lask containing 100 ml of
0.14 M FeSO
4
·7 H
2
O solution with 5% (w/w) starch. The dropwise borohydride addition was
approximately completed in 2 h to control the particle size. An additional 10 ml sodium
borohydride was added to the solution, and the mixture was stirred under nitrogen gas
bubbling for a further 15 min to complete the reaction. The precipitated NZVI particles
were separated by centrifugation (Beckman GP Centrifuge) at 3000 rpm for 10 min, and
