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METHODS OF PAINT WASTES

SOLIDIFICATION/STABILIZATION

Arce R., Andrs A., Coz A., Irabien A., Viguri J.

Universidad de Cantabria. Dpto. de Ingeniera Qumica y Qumica Inorgnica . ETSIIT.

Avda. Los Castros, s/n 39005 Santander, Espaa. E-mail:arcer@unican.es

Subject : Sustainable development

Summary: The industrial coating of metallic surfaces is found in most of the metal industries in Europe,

compasses a complex range of coatings, coating technologies and products to be coated. Solvent-based wet

paint by spraying is extensively applied for automobile parts finished to supply protective properties of metallic

products. The solvent-based coating application in spray booths is a major volatile organic compounds (VOCs)

source and also a source of significant liquid and solid/sludges wastes. Wastewater from spraying cabins,

boothwater, may be treated by coagulating the overspray and continuously extracting the paint slurry as floating

or settling sludge. These sludge represent an important environmental problem due to their hazardous

characteristics. Therefore it is necessary a previous treatment before final management by landfilling.

Apart from the wastes minimisation options related with the reduction of volume and/or toxicity of paint wastes,

different kinds of paint wastes treatment as Condensation-Incineration, Drying + Incineration, Cured and

simultaneous volatilization, Stripping with steam of the suspension of the waste, Thermal Desorption, Distillation,

Drying and volatilizacin, Encapsulamiento in silica and Solidification /Stabilisation (S/S) are used.

The present work shows the results of characterisation and solidification/stabilisation (S/S) of paint sludges from

paint booths in automotive component factory using an alkyd paint with toluene and xylene as organic solvents.

The environmental impact assessment of the paint sludges and the stabilised products have been performed by

the determination of parameters i) by direct characterisation of solvents contents and flammability, and ii) by

leaching behaviour characterisation of ecotoxicity (EC50), chemical oxygen demand, (COD) and TOC from

leaching standard procedures. The high solvents content (7%-18%) depending on factors as paint process

scheduling, operation conditions and waste removal period and its low flash point (42 C), identify the paint

sludge as hazardous waste, although it is not ecotoxic due to the high value of EC50 (5.515 mg/l) according to the

Spanish legislation which adopt < 3.000 mg/l as legal limit.

The sludge S/S process has been carried out mixing the paint waste with different quantities of lime as binder

(from 42 to 72%), additives (from 6 to 50%) . As additives we use clays (Sepiolite) , and coal combustion fly ash,

fly ash+CO2, cement , in nitrogen atmosphere using a laboratory prototype industrial mixer.

With regard to the characterization of the stabilized one the procedures have been followed following :

S/S characterization :

VOCs : EPA 5091 CG/FID High concentration

Flash Point: ISO 3680

Water: KARL FISHER

Metals : EPA 3052

mailto:arcer@unican.esmailto:arcer@unican.esmailto:arcer@unican.es

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Lecheate characterization :

TCLP lecheate : Bioensayo de luminiscencia EC50

DIN 38414 S-4 lecheate : TOC UNE EN 1484 , COD

The obtained results shows the feasibility of the S/S process, improving the solid manageability, and obtaining

products characterised as non-inflammable ( > 55C), with VOCs contents less than 3%, non-ecotoxic ( EC50 >

6.125 mg/l) and with organic contents in DIN-S4 leachates (1.470 mg/l to 6.510 mg/l) COD values and with (656

to 2.972 mg/l) TOC values .

The best results has been obtained using CaO+Fly ash+CO2 or CaO+Cement .

1,95

2,15

2,23

1,01

1,03

0,66

0,82

0,8

0,4

0,3

0,31

0,23

0,43

0,3

0,29

0,14

38

48

58

68

78

0 0,5 1 1,5 2 2,5

VOC's (%)

%B

INDER(C

0

5

10

15

20

25

30

35

40

%A

DDITIV

SEPIOLITE FLY ASH

FLY ASH+CO2 CEMENT

% VOC's versus % BINDER and % ADDITIVE