Benign by design: Development and

applications of new Fenton-like catalysts

Raffaele Cucciniello rcucciniello@unisa.it

Post-Doc Researcher

University of Salerno, ITALY

Dep. Chemistry and Biology

Environmental Chemistry and Complex System Research group directed by Prof. Antonio Proto

The research group is active in the field of environmental chemistry. The main focus is the

design and development of sustainable process for green-chemicals production and pollutants

removal through catalysis, following the twelve principles of Green Chemistry.

Advanced oxidation processes (AOP): Fenton process

The history of Fenton chemistry dates to 1894, when Henry J. Fenton reported that H2O2

could be activated by Fe(II) salts to oxidize tartaric acid (Fenton, 1894).

About 1000 papers in 2016! (Scopus 3/9/2017)

In 1934 Haber and Weiss proposed that the active

oxidant generated by the Fenton reaction is the

hydroxyl radical (HO· ), one of the most

powerful oxidants known (E ◦ = 2.73 V).

The Fenton and related reactions are viewed as

potentially convenient and economical ways to

generate oxidizing species for treating chemical

wastes.

Fenton process: an overview

J. J. Pignatello et al., Critical Reviews in Environmental Science and Technology (2006) 36:1, 1-84

H2O2 and Fe(II) salts are both environmental friendly compounds.

Oxidant for degrading the target pollutant

The neat reaction is the iron catalyzed conversion of H2O2

The hydroxyl radical may be generated stoichiometrically simply by combining an Fe(II) salt with H2O2.

This produces stoichiometric amount of Fe(III) which later precipitates to amorphous ferric

oxyhydroxides as the pH is increased from strongly acidic to neutral.

Generation of HO· is catalytic in iron, which can therefore be used in relatively low concentration.

Peroxide-to-iron molar ratios employed in water treatment typically lie in the range 100 to 1000.

The use of iron catalytically helps to minimize scavenging of HO· by Fe(II) and also minimizes ferric oxyhydroxides production.

Mechanicistic aspects

Organic molecules degradation

In the presence of air, radicals may react with O2 to give HO·2 (O2 ·−),

peroxyl radicals R–OO·, or oxyl radicals R–O·

Stable molecules

Fenton and Fenton like catalysts

Generally, Fenton catalyst consists of Fe(II) salts (mainly FeSO4).

How to improve the catalyst activity? Use of ligands 1. Chelation extends the pH range over which iron is

soluble because the chelating ligand competes

favorably with hydroxide ion for coordination, and

chelated complexes typically are soluble.

2. Chelation may also accelerate the production of

OH radicals but may scavenge it.

Acc. Chem. Res. (2002) 35, 782-790

NTA = Nitriloacetic acid

Recently published applications of iron complexes for Fenton process

EDDS = ethylendiamine-N,N’-disuccinic acid

Iron free Fenton like catalytic systems

J. Hazardous Materials (2014) 275, 121-135.

Application of the Fenton reactions

Limitations of Fenton-based AOPs for wastewater treatment stem mainly from the need for

pH control and the problem of sludge generation.

Dye wastes

Pulp bleaching wastes

Agricultural effluents

Landfill leachates

Surfactants

Industrial wastewater

Water treatment

New research perspecitives: Development of

Bio-degradable ligands

11

n

(PASP)

(IDS)

(EDDS) -Kołodynska et al, Expanding Issues in Desalination, (2011) 17, 339-370.

1. Inherent rather than circumstantial;

2. Prevention instead treatment ;

3. Design for separation - Minimize energy

consumption and material use during separation

and purification procedures;

4. Maximize efficiency - Design products, processes

and systems in order to maximize mass, energy,

space and time efficiency,

5. Out-put versus Input-pushed;

6. Conserve complexity;

7. Durability rather than immortality;

8. Meet need, minimize excess;

9. Minimize material diversity;

10. Integrate material and energy flow ;

11. Design for commercial “afterlife” ;

12. Renewable rather than depleting.

1. Waste prevention and reduction;

2. Atom economy;

3. Generate substances with little or no toxicity to

human health;

4. Chemical products should be designed reducing

toxicity;

5. Use of auxuliary should be made unnecessary;

6. Energy requirements should be minimized;

7. Use renewables raw-materials as feedstocks;

8. Avoid unnecessary derivatization;

9. Use catalytic reagents instead stoichiometric;

10 . Less persistence in the environmental ;

11. Avoid the formation of hazardous substance;

12. Minimize chemical accidents (e.g. explosions).

P.T. Anastas, J. B. Zimmerman, Env. Sci. Tech., 2003, 37, 94-101. P. T. Anastas, J. C. Warner, Green Chemistry: Theory and Practice, Oxford, 1998

Green Chemistry Green Engineering

13

1. NaOH 2. NH3, ∆

Baypure CX 100 Tetrasodium

Iminodisuccinate (Purity of 65%)

-Bayer, Baypure General product information

IDS industrial preparation, developd by BASF

14

Reaction mechanism: what happen?

Process intensification…

IDS isomers biodegradability

15

-Hyvönen, Green Chemistry, (2003) 5, 410-414

-Kołodynska et all, Expanding Issues in Desalination, (2011)

17, 339-370.

-Schowanek et all, Chemosphere, (1997) 34, N° 11, 2375-

2391

All the IDS isomers are fully biodegradable!

(EDDS)

[S,S] ≥ 90% [R,R] 0% Mix ≤ 35%

EDDS isomers show very different biodegradability

IDS stability and biodegradability

16

0

20

40

60

80

100

1,5 4,0 7,0 11,0 13,5

Stab

ility

(%

)

pH

Stability of iminodisuccinic acid sodium salt (11% by wt.) in water solution at 100°C

Tempo: 5h

Tempo: 20h

0

20

40

60

80

100

0 5 10 15 20 25 30

Bio

deg

rad

atio

n (

%)

Time (days)

Biodegradation of Baypure® CX100

Test design OECD 302 B as a …

-Bayer, Baypure General product information -Cokesa et all, Biodegradation (2004) 15, 229-239

IDS is fully converted in NH3 and fumaric acid.

17

13C-NMR characterization of the reaction products

Spectra are acquired using an NMR instrument 400 MHz, samples are prepared in D2O

UV-VIS spectrophotometry analysis

18 -

-Hyvönen, Green Chemistry, (2003) 5, 410-414

Cu-IDS complex purification

19

1. Cu (II) Cu-IDS complex 2. Chromatographic

separation

20

Experimental conditions:

[Cu-IDS] = 6.2 mM

1.5<pH<8

T= 20°C

Experimental conditions:

[Cu-IDS] = 6.2 mM

pH=7

20°C<T<85°C

pH and T influences on Cu-IDS complex stability

Conclusions and future perspectives

• A new Cu-based catalyst has been synthesized and tested in AOPs

• Cu-IDS catalyst shows an activity higher than classic Fenton catalysts (based on iron)

• New bio-degradable ligands for Fenton-based processes

• Design of Fe-based biodegradable catalysts

“We have no desire to do Green Chemistry. We desire to do the best Chemistry, and it happens to be green.” P. T. Anastas, The father of Green Chemistry

Invited to held a plenary lecture at XXVI Congress of the Italian Chemical Society

14th September 2017 Hotel Ariston (Paestum, Salerno)

Acknowledgements

Department of Chemistry and Biology - UNISA Environmental Chemistry and Complex System Group

Prof. Antonio Proto

Dr. Prisco Prete

Department of Civil Engineering – UNISA

Prof. Luigi Rizzo

Dr. Antonino Fiorentino