8/10/2019 Heavy metal removal by novel hybrid material

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Mesoporous graphene/IL Hybrid material coated

sand: an efficient mode for heavy metal detoxification

Varsha Khare Shiva Raj Poudel Dae Seob Song Sung Hoon Ahn

Mechanical Aerospace Engineering, Seoul National University

Institute of Advanced Machinery and Design

The control of heavy metal pollutants and their associated toxicities remain a key environmental concern. Reduced Graphene oxide has been pursued in recent years as a leadingcandidate

for heavy metal remediation primarily due to its highsurface area and modifiableproperties. In the present work, the formation of mesoporous graphene and its applicability forheavy metal detoxification is discussed. Here, we demonstrate the flexible tunability of porous reduced graphene oxide (rGO) with sulfonium based ionic liquids (SIL) to generate porous rGO-SIL hybrid

nanomaterials derived from GO using glycerol as a reductant. The genesis of mesoporous graphene can be explained on the basis of opening of edges via stress strain generated by surface

and interlayer interaction of ions from ionic liquid with sp2 andsp3 bonded carbon atoms (Fig.1).The application of a facile and mild reduction process assisted by the IL environment is further

advantaged by its simplicity as a single-step chemical process that is essentially green. The complete reaction wasperformed in presence of sand to coat the hybrid material onto the sand.

Background

Objective

Separation / Filtration technologyFractionation distillation

Coated bulk materials

Crystallization

LimitationsHigh energy consumption

Complex and expensive setups

Material wastage

Methods

SILMG

Sulfer doped ionic liquid

mesoporous graphene (SILMG)

coated sand TechnologyEnvironmentally friendly materials

Simple economic low cost process

High surface area and permeability

Material recyclability

Cost effective hybrid nanomaterial for water detoxification Develop an environmentally friendly and cost effective stable hybrid

nanomaterial with high filtration properties

Hybrid nanomaterial will combine the high surface of graphene with the

electrostatic properties of ionic liquids

Synthesize graphene-ionic liquid hybrid materials and characterize the

hybrid properties using X-ray diffraction, electron microscopy, X-ray

photoelectron spectroscopy, batch test.

Develop stable graphene coated sand filtration technique for heavy metal

removal

Concept

Graphene coated sand technology

Experimental

Discussion and Conclusions

Synthesis of Ferric Green Rust

Simple one pot synthesis

Structure-Microstructure : Presence of Mesoporous Graphene

Heavy Metal Toxic Water PollutionIncreasing global environmental concern

Toxic bioaccumulation in humans through food consumption

Need for effective heavy metal detoxification technology

Applicability The Concept

Green Rust LDH

~ 7.6

A

B

B

C

C

A

A

B

A

B

A

B

~ 11

GR1GR2

Anions are planar

No long range ordering betwee

n Fe(III) and anions

OH--Hexagonal Layer

Fe (II) ionLocated at centerof t

he octahedron

intercalated anion and water m

olecule should be counterbala

nced by Fe(II I) in brucite like layer

AcBiBaCjCbAkA. . .AcBijA. . .. . .

Anions 3-D

long range ordering betw

een Fe(III) and anions

Two anion layer at betwe

en the Hexagonal Layer

of Fe (OH)2

SIL Mesoporous

Graphene/Fe HM

Coated Sand

N2 N2

4FeIISO 4 +

Fe III 2(SO 4)3

pH

Eh

Reagents

Fe II-Fe III mixed solution of 0.4M

Na2CO

3-NaOH

Stoicheometric GR

controlled oxidation via H 2O2

Synthesis of green rust

N2 N2

4FeIISO 4 +

Fe III 2(SO 4)3

pH

Eh

ReagentsN2 N2

4FeIISO 4 +

Fe III 2(SO 4)3

pH

Eh

Reagents

Fe II-Fe III mixed solution of 0.4M

Na2CO

3-NaOH

Stoicheometric GR

controlled oxidation via H 2O2

SIL Mesoporous Graphene

SIL/MPrGO/FGR SIL/MPrGO/Fe0SIL/MPrGO

SIL/MPrGO Hybrid materials

2

Intensity

(a.u.)

Functionalization chemistry: Sulfur doped MPrGO

FTIR XPS

Absorption Analysis on HM Coated sand

ICPMS: Heavy Metal Absorption Efficiency: pH Effect

SEM and EDS: Surface Morphological and Elemental changesSEM

EDAX

XPS on coated sand after absorption of Hg and Cr

Sulfur doped Mesoporous rGO, rGO/Fe HM were synthesized as evidenced by FTIR and XPS.

Sulfur atom occupies more space within the lattice than carbon and leads to the formation of

MPrGO due to the occurrence of lattice stress and strain events

HM combined with iron species are promising materials for coated sand and demonstrate

enhanced absorption of heavy metals

Sand coated with FGR with HM was investigated for heavy metal absorption as a function of pH

and showed Hg absorption to be independent of pH. Cr absorption however improves under both

acidic and basic conditions indicating the presence of more than one of reactive species

Formation of organometallic of Hg and Cr after absorption are good for recyclability

Present work shows almost 95% absorption of Pb

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government (MEST) (No. NRF-2012R1A1A2008196, NRF-2010-0029227 and NRF-2012R1A2A2A01047189)

Innovative Design and Integrated Manufacturing Laboratory

0 200 400 600 800 1000 1200

0

40000

80000

120000

160000

S2p

CPS

Binding Energy

SIL/MPrGO

S2s

Bondvibrationsare

consistentwith theC-S

bondsindicatingthe C

atomreplacingby S.

Binding Energies in survey

spectrum of SIL/MPrGO are

consistent with S2p and S2s

core level excitations.

Results

General Formula

[Fe(1-x)2+ Fex

3+(OH)2]x+ [(x/n)An (mx/n)H2O]x

(withx being the Fe3+ molar fractio

n Fe3+

/Fetotal)

(CO32-), (Cl)-

GR(SO42-)

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