Environmentally-friendly produced dyestuffs and optical brighteners

Dr. Harald Schönberger

Optical brighteners

Dyestuffs for textiles

High fastnesses: light, washing, perspir. very stable substances (non-biodegr.)

Outline Environmental hotspots of the textile value chain Production of dyestuffs and optical brighteners for

textiles (example reactive black 5 and stilbene-based optical brighteners)

Conclusions

Issues concerning the responsible management of the supply chain in the garment sector • Environmental issues (hotspots) • social and governance issues, e.g. establishing fair

working conditions, setting social standards, establishing minimum wages, ensuring occupational safety, imposing a ban on child and forced labour,

Textile value chain – simplified scheme

Fibre production

Yarn production

Weaving or knitting

Textile finishing

Confection and retail

Use phase

Disposal/recycling

rawmaterials

seeds

end-of-life

Raw materials

e.g. reactive black 5 e.g. H acid

Raw materials

e.g. Naphthalene, H2SO4, HNO3, NaOH

brand

disposal

re-use, recycling

AccessoiresRaw materials

rawmater.

Raw materials

Rawmater.

.

.

Synt. fibre prod.

Natur. fibre prod.

Fibre production

Weaving/knitting

Sizing agents

Preparations

Textile auxiliaries

Dyestuff manuf. Dyestuff intermed.

Washing agents

Textile finishing

en

erg

y

wat

er

che

mic

als

was

tew

ate

r

was

tega

s

solid

was

te

Garment manuf.

Use phase

Optical brightenersDiamino stilbene-disulphonic acid

Raw materials

e.g. softeners

Raw materialsPreparations

The textile value chain and mass stream thinking

plus transport activities at all stages

rawmaterials

seeds

end-of-life

Raw materials

e.g. reactive black 5 e.g. H acid

Raw materials

e.g. Naphthalene, H2SO4, HNO3, NaOH

brand

disposal

re-use, recycling

AccessoiresRaw materials

rawmater.

Raw materials

Rawmater.

.

.

Synt. fibre prod.

Natur. fibre prod.

Fibre production

Weaving/knitting

Sizing agents

PreparationsTextile auxiliaries

Dyestuff manuf. Dyestuff intermed.

Washing agents

Textile finishing

en

erg

y

wat

er

che

mic

als

was

tew

ate

r

was

tega

s

solid

was

te

Garment manuf.

Use phase

Hot spot: cotton production

Hot spot: Dyestuff production

Hot spot: Textile finishing

The textile value chain – environmental hotspots

plus transport activities at all stages

The textile chain – actors- and framework-oriented

• the cultivation of cotton due to the high water demand and the high fertiliser and pesticide consumption

• textile finishing (pre-treatment, dyeing/printing, final finishing) causes large quantities of waste water containing high concentration of inorganic and organic compounds

• the production of dyestuffs, pigments and optical brighteners including the intermediates is associated with high amounts of solid wastes and waste water containing non-biodegradable and ecotoxic organic compounds

The textile value chain – environmental hotspots

Production of dyestuffs and optical brighteners needs to be taken into account

Production of dyestuffs and the related intermediates Example: reactice black 5 with intermediate: H acid (globally the most important dyestuff and intermediate)

Production of H acid - 4 production stages - yield referred to naphthalene: ca. 42 %, best ever: 51 %

Production of H acid – Sankey diagram (16 t of raw materials for 1 tonne of product, 1.5 tonnes of organic by-products)

reactive black five 5 – the most important dyestuff in the world ….and H Acid is the most important dyestuff intermediate

Filling bags with reactive black five 5

Inadequate unloading of acids (HCl, H2SO4, NO3)

Inadequate unloading of naphthalene

Single wall HCl and NO3 tanks

Manual removal of a filter sludge

Manual removal of a powder (intermediate)

Inadequate waste water discharge - many severe cases

Inadequate dumping of solid waste

Process- and production-integrated measures to improve the production process – example for J Acid

Improvement of the H Acid production process

Process optimisation (process- and production-integrated)

Neutralisation after sulfonation and nitration

High quantities of solid residues per ton of H acid:

• about 5.6 t gypsum (chalk consumption: about 3 t)

Disadvantage:

reactive extraction as the alternative

Reactive extraction

nitro T acid in sulfuric

acid solution

+ tert. Amine

3 NR3

+ solvent

Ion pair comlex solved

in the solvent

Sulfuric acid (about

30%) for H acid

precipitation extraction

Na –salt solution to reduction

recycling of

amine and

solvent

H acid manufacture –

ion pair extraction after sulfonation and nitration and catalytic

reduction of the nitro group with hydrogen (no iron sludge)

sulfonation

nitration

extraction/

reextraction

cat. hydro-

genation

naphthalene

H2SO4

oleum 65%

T acid

SO2-scrubber NOx to TCR H2 to TCR

HNO3 H2SO4

30%

tert. amine/

solvent H2 Ni catal.

(recycling)

evaporation

fusion

H acid

precipitation

isolation/

drying H acid

NaOH H2SO4 from

extraction

water (reuse) SO2 (sale)

wastewater to treatment

(wet oxidation)

T acid

H2O NaOH 50%

Reduction of raw material

consumption/avoidance of residues

in [ about t/t H acid]

• natural chalk: 3

• soda: 0.25

• sulfuric acid (96%): 3

Reduction of raw material consumption

• gypsum sludge: 5.6

• waste chalk: 0.3

Reduction of residues to be disposed

• CO2: 1.3

Avoidance of CO2-emissions

• Avoidance of iron sludge: 2.4 t

No dumping of gypsum and iron sludge

Improvement of the H Acid production process

Mother liquor

Catalytic wet oxidation process Chemistry and process engineering

Basic chemical reaction

wastewater compounds + O2 + H2O2 CO2 + H2O + biodegr. org. compounds cat.

pH

air

catalyst

hydrogen peroxide

Off-gas

wastewater acid

pre-treated wastewater

temperature

pressure

reactor nozzle

Process parameter

reaction accelaration

higher O2-solubility

increased phases interface

=

=

= pH

Oxidation reactor

Reaction cycles in the cat. oxid. process

Starting and

catalyst cycle

Propagation steps

of Fenton's cycle

Propagation steps

of oxygen cycle

RH = Substrate

Me3+

Me2+

Me3+ + H2O2 O2 + Me2+

R*

H2O2

HO*

HO* + RH

R* + O2

ROO* + RH

R*

HOO*

ROOH

O2

H2O2

HOO* + RH

product

R* R*

Termination:

R* + R*

ROO* + R*

HOO* + Me2+

HOO* + Me3+

Flow chart of a cat. oxidation plant

circulation catalyst H2O2

off-gas

Wastewater

pre-treated

wastewater

acid

Alkali/alkaline

wastew.

air

demister

steam

neutralization

separator

compressor

sludge

storage tank for

wastewaterr

reactor

he

at

exch

an

ge

r

pH

F

F F

T

p

pH

option

F filter

Cat. oxidation plant for contin. operation Technical data

temperature

pressure

hydraulic

load

energy demand

100 – 140 °C

3 – 5 bar

1 – 20 m3/h

Autothermic

(COD>4000 mg/l)

air demand

hydrogen peroxide

(35 %)

catalyst

acid

ca. 10 Nm3/m3

per COD of 1000 mg O2/l

1.5 - 1.8 l/m3

per COD of 1000 mg O2/l

0.3 – 0.8 kg/m3

depends on wastewater-pH

Spec. consumption [/m3 wastewater]

COD: 6- 8 g O2/l

3 - 4.5 m3/h

Catalytic oxidative degradation of H acid and by-productsfrom ist production

LegendTemperature 120°CPressure 3 barEnergy consum.: autotherm.

oxi

dat

ive

deg

rad

atio

nin

%

per

oxi

de

oxi

d.

air

oxi

dat

ion

time in min

Summary of the results of the catalytic oxidation process

reactor feed:

- BOD5/COD (toxic)

- COD reactor feed

< 0.1

5.1 bis 8.0 g O2/l

reactor after oxidation:

- BOD5/COD (biodegradable)

- COD reactor after oxidation

0.7

1.1 bis 2.1 g O2/l

COD removal 74 - 85 %

Comparison of biodegradability:

- BOD5/COD reactor after oxid.

- BOD5/COD of glucose 0.7

0.8

Catalytix oxidation process: operating costs

Operational costs of batch and continuous reactors

Treatment capacity for organic compounds 5 – 8 kg O2 m-3 h-1

Hydraulic load : batch m3/d 1 – 2

continuous m3/d 5 – 300

Cost parameter dimens. consumption EUR/kg O2

batch contin. batch contin.

Energy without air

Hydrogen peroxide

Iron(II)-sulfate

Air oxygen

Sulfuric acid

kWh/kg

l/kg O2

kg/kg O2

m3/kg O2

l/m3

1.00

2.20

0.15

10

?

1.20

1.8

0.13

13

?

0.08

0.59

0.07

0.11

?

0.095

0.48

0.06

0.14

?

Total cost -- -- -- 0.85 0.78

Basic prices:

1 kWh

1 l H2O2

1 kg cat.

1 Nm3 air

1 l H2SO4

0.08 EUR

0.268 EUR

0.462 EUR

0.0108 EUR

0.47 EUR

Raw optical brightener – DNS-based

Stilbene-based optical brighteners

SO3Na

NaO3S

NH2

NH2 + N

N

N

Cl

ClCl

2

0-5°C

pH 4.5-5

SO3Na

NaO3S

NH

NH

N

N

N

Cl

Cl

N

N

N

Cl

Cl

+

NH2

SO3H

SO3H

SO3Na

NaO3S

NH

N

N

N

NH

N

N

N

NH

Cl

Cl

NH

SO3H

HO3S

SO3H

SO3H

2

+ 2 HNRR'

SO3Na

NaO3S

NH

N

N

N

NH

N

N

N

NH

NRR'

R'RN

NH

SO3H

HO3S

SO3H

SO3H

cyanuric chloride

Di-, Tetra-, Hexasulfo Stilbene Brighteners

1. Condensation step

2. Condensation step

3. Condensation step

Synthesis of stilbene-based optical brighteners

Di-Sulpho MEK process

DAS Solution

Synthesis

Crystallization

Filtration

Slurry

MEK distillation

Paddle drier Pretreatment ML

ETP

mother liquor

Mother liquor from optical brightener isolation

Mother liquor: e.g. COD about 12000 mg/l, BOD5 about 200 mg/l very low biodegradability

special treatment required (e.g. wet oxidation)

Hotspot: textile finishing In the focus again (due to Greenpeace activities)

Textile Finishing

Impact of textile finishing on natural water

Impact of textile finishing on natural water

Conclusions and message of this presentation

- Mass stream and LCA thinking required - basis for solutions

- Synchronisation of mass (energy and chemicals) and information flow required (traceability)

- Qualify and quantify the environmental hotspots - Take production of dyestuffs, pigments and optical

brighteners also into account develop appropriate environmental indicators

…. and have a dream

….to convert rivers like this

... into to clear, natural rivers ...

Dr. Harald Schönberger Independent International Consultant on Industrial Integrated Pollution Prevention and Control Carl-Frey-Str. 3, 79288 Gottenheim/Germany e-mail: hgschoe@t-online.de mobile: +49-1795142415