Wojciech Hyk, Konrad Kitka Faculty of Chemistry University of - - PowerPoint PPT Presentation

Wojciech Hyk, Konrad Kitka

Faculty of Chemistry University of Warsaw

Naxos 2018

Heavy metals removal from wastewater by ferrogels

Wojciec jciech Hyk Hyk

The aim

• To develop a method for metal removal from

waste water samples using thermoresponsive ferrogel sorbents („magnetic sponge”)

Wojciec jciech Hyk Hyk

Realization – general scheme

• The synthesis procedure of hydrogel matrix for

the implementation of a metal sorbent in aqueous systems with strictly defined composition of the sorption system

• Gel matrix – thermoresponsive

poly(N-isopropylacrylamide) hydrogel

• Metal sorbent – nanosized

magnetite (ferromagnetic properties)

• Examination of the composite material for silver

and copper removal from aqueous media

ΔT

Wojciec jciech Hyk Hyk

Realization - details

• Preparation of pNIPA gel swollen by water – free-radical

polymerization of N-isopropylacrylamide (NIP A) using well documented procedures

• Purification and drying the resulting polymeric material

(pNIPA)

• Grinding the pNIPA material to a fine powder
• Preparation of the ferro-pNIPA system – mixing the pNIP

A powder with known amount of nanosized magnetite

• Formation of the pNIPA ferrogel swollen by the aqueous

solution – transferring the ferro/ pNIP

A mixture into the aqueous solution containing heavy metal cations

• Aqueous solution purification – inducing volume phase

transition of the gel system and removing the collapsed gel by an external magnetic field

Wojciec jciech Hyk Hyk

Realization – the idea

• Water purification using sponge like behaviour of poly(N-

isopropylacrylamide) ferrogels

ΔT B t

solvent molecule metal cation sorbent particle dry polymer fragment

Wojciec jciech Hyk Hyk

Results – silver removal from water samples

• Effect of pNIPA matrix on the silver adsorption

efficiency

1 / m(Fe3O4) [1/g]

50 100 150

Qe [mg/g]

2 4 6 8 10 12 14

magnetite solution pNIP A / magnetite gel

Wojciec jciech Hyk Hyk

Results – silver removal from water samples

• Determination of adsorption isotherm

ce(Ag+) [mg/L]

10 20 30 40 50 60 70

ce(Ag+) / Qe

2 4 6 8 10

log(ce(Ag+))

• 0.8
• 0.4

0.0 0.4 0.8 1.2 1.6 2.0

log(Qe)

0.2 0.4 0.6 0.8

A B

aqueous solution of magnetite – Langmuir isotherm Qmax: 9.1 ± 3.4 mg / g pNIPA / magnetite ferrogel – Freundlich isotherm Qmax: 13.6 ± 3.8 mg / g

Wojciec jciech Hyk Hyk

Results – mechanism of silver adsorption on magnetite

• Chemical reduction of silver (I) cations on the

surface of magnetite (silver chemical deposition)

• Diffusion of silver (I) cations to iron oxide grains
• 2Fe3O4(s) + H2O + 2Ag+ ↔ 3Fe2O3(s) + 2H+ + 2Ag(s)
• Extraction of silver requires concentrated nitric

(V) acid

Wojciec jciech Hyk Hyk

Method validation for real wastewater samples

• Sample prepared to mimic copper ore post -

flotation waste

%(Fe3O4) in pNIPA gel

2 4 6 8 10 12 14 16

%R

20 40 60 80 100

Ag(I) Cu(II)

cAg: 100 mg / L cCu: 664 mg / L

Wojciec jciech Hyk Hyk

Conclusions

• Synthesis procedure of universal hydrogel matrix

for controlled implementation of metal sorbents

• Highly efficient silver removal by a “magnetic

sponge” (pNIPA / magnetite thermoresponsive ferrogel)

• Silver adsorption on magnetite in pNIPA ferrogel

is described by the Freundlich model

• The presence of gel matrix increases efficiency
• f silver sorption on magnetite