PSU-UNS International Conference on Engineering and Environment - ICEE-2007, Phuket May10-11, 2007

Prince of Songkla University, Faculty of Engineering Hat Yai, Songkhla, Thailand 90112

Abstract: Chromium electorplating wastewater which

mainly contain Chromate ion (CrO4- ) nomally is treated

with reduction and precipitation process to precipitate

chromium as chromium hydroxide (Cr(OH)3) and

disposal by engineering construction landfill. However,

partial soluble chromium hydroxide could occur at some

range of pH. Alternatively, the chromate wastewater is

treated with Lead nitrate from Battery manufacturer

waste to precipitate as lead chromate (PbCrO4). Lead

Chromate is more stable than chromium hydroxide.

Experimental results show that leachate test of lead

chromate and chromium hydroxide contain slightly

dissolved chromium (pH 6) as 0.02 mg./l and 0.39 mg./l

respectively. Eventually lead chromate precipitate is

more stable than chromium hydroxide. Lead chromate

precipitate could be produced yellow chrome pigment

which prices about 200 Baht/Kg of pigment.Study on

chrome pigment production from chrome electroplating

wastewater to gain more stable form of PbCrO4 not only

capable to manage or utilize hazardous heavy metal but

also to refund as value added by product.

Key Words: Chromium/ Electroplating/ Yellow/

Chrome / Pigment/ Wastewater / Industrial waste

1. INTRODUCTION

The name “Chrome yellow” comes from Greek. The

definitions of Chrom yellow are the first, any of several

yellow pigments consisting of normal lead chromate and

other lead compounds, second, yellow pigment

consisting of neutral lead chromate, third, chrom yellow

is a natural yellow pigment made of lead(II) chromate

(PbCrO4). It was first extracted from the mineral crocoite

by the french chemist. Because the pigment tends to

oxidize and darken on exposure to air over time, and it

contains lead, a toxic, heavy metal, it has been largely

replaced by another pigment, Cadmium Yellow [1]. It is

commonly produced by mixing solutions of lead nitrate

and potassium chromate and filtering off the lead

chromate precipitate. In 1797 a Parisian chemist, Louis

Nicholas Vauquelin isolated natural lead Chomate

(chrocoite) and called it chrome because of the range of

hues that could be derived from it. He named it after the

Greek word xpwua, meaning color. The preparation of

chromates of lead, specifically chrome yellow was

published by Vauquelin in the Annaleds de Chimie IXX

in 1809. The Chrome colors were in use by 1816 but on a

limited basis. In 1820, a substantial source of chrome ore

was found in North America and large scale production

began, j. J. White of Rutherglen, Scotland is known to

have produced chrome colors that year. Their excellent

hiding power and low cost made them a welcomed

alternative to Turner’s Patent yellow and orpiment.

Chrome yellow cost one shilling per watercolor cake in

1835. Chrome pigments were fast drying in oil and more

permanent in oil than in watercolor. The darker shades

were more permanent than the lighter ones that tended to

fade when exposed to sunlight. The darker shades were

known to brorn over time. All chrome colors were

blackened by sulfur-bearing air and the yellow variety

sometimes would turn green when mixed with organic

pigments [2]. It is chemical identification chrome yellow.

The pigments are microscopically identified by their

crystalline particle, the deeper shade having a more

rectangular shape. The lighter, more yellow shades have

finer particles. They are identified chemically by a

change to black in sodium sulfide. In nitric acid, The

orange turn’s bright yellow and the yellow is only

slightly affected. In other acids, the yellow turns red [3].

Yellow line is painted on the road to set for road traffic.

It show that Fig.1. This Yellow pigment is a chemical

compound of hazard heavy metal, Chromium Cr and

Lead Pb as chemical compounds are Lead Chromate

(PbCrO4) or ''Yellow Chrome pigment''. These are very

stable and a little dissolve in water. That is to say in the

water 100 cm3 can dissolved 0.0058 mg of PbCrO4 or

concentration of 0.058 mg/l PbCrO4 (Thailand effluent

standard for industrial wastewater are contaminated

Chromium hexavalence Cr+6

not excess 0.25 mg/l).

Commercial yellow Chrome pigments are produced from

natural mineral is called Crociote. These showed that in

THE YELLOW CHROME PIGMENT

FROM ELECTROPLATING

WASTEWATER

Sawaeng Gerdpratoom1*, Athitan Timyamprasert

2, Chanakan Asasutjarit

3

1, 2, 3Thailand Institute of Scientific and Technological Research (TISTR), Department of Engineering

*Authors to correspondence should be addressed via email: water108water@yahoo.com

ICEE2007176-530

Fig.2. This pigment is imported from oversee. At the

present moment, this price of pigment is 200 Baht/Kg.

Fig. 1. Yellow line is painted on the road

A B

Fig. 2. Commercial yellow chrome pigment (A) and

Crociote mineral (B )

Another, Chrome Yellow pigments are mainly used for

paints, coil coatings, and plastics. They have low binder

demand and good dispersibility, hidin power, tinting

strength, gloss and gloss stability. Chrome yellows are

used in a wide range of applications not only for

economic reasons, but also on account of their valuable

pigment properties. They are important base pigment for

yellow colours in the production of automotive and

industrial paints [4].

1.1 Physical and chemical properties [5 ]

Substance name is Chromium (VI) compounds.

CASR number is 7440-47-3 (Cr metal),18540-29-9 (Cr

(VI)). Molecular formula is Cr 6+

. Chromium (VI) is

oxidation state of the element chromium. Other common

oxidation states of chromium include O (the metallic

element chromium), and III (the state in which chromium

is found in nature. Chromium (III) counds are dealt with

elsewhere in the NPI). Hexavalent chromium compounds

(VI) include ammonium dichromate, barium chromate,

calcium chromate, chromium trioxide, lead chromate,

sodium dichromate, strontium chromate, potassium

chromate, potassium dichromate, sodium chromate, and

zinc chromate. Physical Properties : Vary widely

depending on the paticular compound, for example: Most

Cr (VI) compounds are soluble inwater, however, barium

chromate (a yellow powder with specific gravity is equal

to 4.49) and lead chromate (an orange yellow powder

with specific gravity

is equal to 6.3 ) are insoluble in water, and calcium

chromate (a yellow powder) is slightly soluble in water.

Sodium dichromate is in the form or red to orange

crystals, with specific gravity is equal to 2.35,and

soluble in water. Chromic acid (H2CrO4) exists only as

salts (e.g. lead chromate, barium chromate) or in

solution.

Chemical Properties : Chromic acid is very reactive.

Most Cr (VI) solutions are powerful oxidising agent in

acidic conditions, but much less oxidising under alkaline

conditons, but much less oxidising under alkaline

conditions. Chromium trioxides are soluble in alcohol,

ethanol, sulfulic acid, and nitric acid; when heated to

decomposition chromium trioxides emit smoke and

irritating fumes. Lead Chromate is insoluble in water,

acetic acid, and ammonia, but is soluble in acid and

alkalies; when heated to decomposition emits toxic

fumes of lead. Potassium chromate and potassium

dichromate are soluble in cold and hot water and

insoluble in alcohol. Sodium dichromate is soluble in

cold and hot water and insoluble in alcohol; toxic fumes

of sodium monoxide are emitted when this compound is

heated to decomposition. Strontium chromate is soluble

in cold and hot water, hydrochloric acid, nitric acid,

acetic acid, and ammonium salts. Zinc chromate is

insoluble in cold water and acetone, dissolves in hot

water, and is soluble in acid and liquid ammonia.

2. METHODOLOGY

In this study to recover chromic acid from rinse

wastewater of electroplating process. it use solution from

electroplating bath to purified, reuse and reclaim in Lead

chromate chrome pigment by precipitate with Lead

nitrate (PbNO3). They were from battery manufactory

waste. It was showed that in Fig. 4. Lead chromate

chrome pigment was yellow. Normally, it mixes with

binder as point painting the traffic line on the road.

2.1 Synthesis of chrome pigment

The Chrome Pigment was produced from industrial

waste. This experiment use wastewater from Chromium

Industry and lead powder from Battery Industry. Then

the lead powder from battery industry was reacted on

Nitric acid (HNO3). After them get the Lead Nitrate

(Pb(NO3)2), Thus, the reaction was below.

PbS + H2SO4 PbSO4 + H2S (1)

PbSO4 + Na2CO3 PbCO3 + NaSO4 (2)

PbCO3 + 2HNO3 Pb(NO3)2 + H2O + CO2 (3)

Lead Nitrate from this reaction mix with wastewater

from Chromium Plating Industry which has Chromic

acid (H2CrO4). Therefore, from the reaction was lead

chromate (Pb(CrO4). The reaction was below.

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CHROMIUM ELECTROPLATING BATH

SOLAR

EVAPORATOR

Ca

IX

IX

IX

PURE WATER RINSE

DILUTE WATER RINSE

CONCENTRATE RINSE

An

Ca

5% H2CrO4

20% H2CrO4 reuse

CONCENTRATE RINSE

~20 ppm. H2Cr2O4

5%NaOH

5%H2SO4

REDUCTION AND PRECIPITATION

PROCESS FLOW

5%H2SO4

Reproduce as yellow chrome pigment

Expire drain

H2CrO4 + KOH K2CrO4 + H2O (4)

K2CrO4+ Pb(NO3)2 PbCrO4 + 2KNO3 (5)

After, the lead chromate was precipitated and dried at

ambient temperature. The lead chromate sediment was

called “Chrome Pigment”.

The standard synthesis was showed in Fig.3 [6].,

Lead nitrate (Pb(NO3)2) and Potassium dichromate

(K2(CrO4) were prepared, 5.1 g. and 3 g. Each one was

water dissolved. After, Lead nitrate (Pb(NO3)2) and

Potassium dichromate (K2(CrO4) were mixed. Then the

solution was precipitated. The Chrome Pigment sediment

was dried by ambient air. Therefore Chrome pigments

from synthesis were like the Crocoite Mineral.

Fig. 3 Standard synthesis of Chrome Pigment

Fig. 4. Yellow chrome pigments from Chromium

electroplating wastewater

Fig. 5. Chromium electroplating recycle rinse water

treatment flow diagram

From the Fig. 5. the industrial wastewater treatment

point of view, there has been a study on the application

of the reused materials from industrial waste to substitute

the imported mineral chrome pigment.

3. RESULTS

The result to analyze by X-ray Fluorescent was found

that the sample of yellow pigment are kept from painted

yellow line painted on the road compared with

commercial yellow chrome pigment, and yellow chrome

pigment from wastewater found that they are that

contained similar elements, chromium and lead. That

was showed in Fig.6.

The product was lead chromate compounds. This

yellow chrome pigment was tested for the stability and

solubility (leachate test) in various pH conditions. Fig. 7.

illustrated the comparison of synthetic yellow chrome

pigment from electroplating wastewater and commercial

yellow chrome pigment in difference pH condition. The

results showed a good correlation and compatibility

betweeen two sources of yellow chrome pigments.

Fig. 6. X-ray fluorescent spectrometer analysis spectra of

chrome pigment

Lead chromate chrome pigment from wastewater

Lead Nitrate from battery manufactory waste

(Pb(NO3)2)

5.1 g

K2CrO4

3 g

Solution Solution

(Pb(NO3)2)

Solution

K2CrO4

Solution

Mixture

Precipitation

Drying at ambient air

Chrome Pigment

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0

0.05

0.1

0.15

0.2

0.25

0.3

0 2 4 6 8 10 12 14

pH of Leaching solution

Hexavale

nce c

hro

miu

m C

r+6 in leachate

(mg/l)

Cr(OH)3

PbCrO4

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0 2 4 6 8 10 12 14

pH of Leaching Solution

Hexavalence chromium Cr+6 in

leachate (mg/l)

Yellow Chrome pigment from

wastewater

Comercial yellow chrome pigment

Fig. 7. Result of leachate test for Yellow Chrome

pigment from wastewater and Commercial yellow

chrome pigment

Many chromium electroplating fatories which to use

chemical reduction and precipitation wastewater

pretreatment process. Chromium was precipitated as

Cr(OH) 3 by sodium hydroxide at pH 8.5-9.0. These were

showed in Fig. 8,9. The precipitated sludge was then

discarded in the engineering construction landfil by

hazard waste management License Company. It showed

that in Fig. 10. This process for waste management

including transportation would cost 1,500-2,000 Baht per

ton

Fig. 8. Chromium Hyroxide sludge from conventional

electroplating wastewater plant

A

B

Fig.9. A and B, Transportation to engineering

construction landfill

Fig.10. Engineering construction landfill section

Fig. 11. The leachate test result

of CrOH3 and PbCrO4 precipitate

However, conventional chromium electroplating

wastewater treatment precipitation chromium as

chromium hydroxide (CrOH3) . It stability is lower than

Lead Chromate (PbCrO4). In this study showed that a

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solubility of leachate test of them. The result showed that

Fig. 11.

4. CONCLUSION

This study was an example of hazardous waste

utilization. The utilization of such waste will bring the

benefit for both the environment management. In case

stabilize hazardous hevy metal waste in more stable form

and economic concern. The synthetic yellow chrome

pigment can be used to substitute the imported yellow

chrome pigment from oversea. However, the application

of chrome pigment should be limited in the general areas

paritculates and also prohibit in any food contacted

material because of the health impact of chromium and

lead.

5. REFERENCES

[1] http://en.wikipedia.org/wiki/chrom_yellow

[2] http://webexhibits.org/pigments/indiv/overview/

cryellow.html

[3] http://webexhibits.org/pigment/imdiv/technical/

cryellow.html

[4] www.pigment.com.tr/chrome.htm

[5] http://www.npi.gov.au/database/substance-

info/profiles/25.html

[6]http://webexhibits.org/pigment/indiv/recipe/cryellow.

html

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