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RECYCLING WASTES COMING FROM THE PIGMENT TiO2 INDUSTRY

J.P. Bolívar1), M.J. Gázquez1), M. Contreras1), S. Pérez‐Moreno1), M. Romero2) and R. García‐Tenorio3)

1) Departamento de Física Aplicada, Universidad de Huelva, Spain

2) Grupo de Materiales Vítreos y Cerámicos, Departamento de Construcción, Instituto de Ciencias de la Construcción Eduardo Torroja IETcc‐CSIC 28033 Madrid, Spain.

3) Departmento de Física Aplicada II, Universidad de Sevilla, Escuela Superior de Arquitectura, Av. Reina Mercedes, Sevilla, Spain

E‐mail: bolivar@uhu.es

Radiation Physicsand Environment Group

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NORM = Naturally Occurring Radioactive Material

The valorisation of NORM waste adds a new aspect: theassociated radiological problem.

The present study has been carried out with the aim ofevaluating the radiological problem related to the valorizationof two wastes from the TiO2 NORM industry.

The factory of Tioxide‐Huelva (TiO2) is the only one inSpain devoted to the titanium dioxide production.

The raw material, called Ilmenite (ILM) and composedmainly by FeTiO3, and two residues, Red Gypsum (RG) andun‐attacked ilmenite mud from the mineral digestion (MUD)have been studied.

INTRODUCTION

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LOCATION

TiO2PLANT

HUELVA city

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ILMENITE (FeTiO3)+

H2SO4

TiO2

RED GYPSUM

CRISTALIZATION

CaparrosaFeSO4.7 H2 O

MUD

MonohidrateFeSO4.1 H2 O

CONCENTRATION

EFFLUENTInto to sea

RECYCLEDACID

CLARIFICATION FILTER AND WASH CALCINATION

NEUTRALIZATION(Weak acid stream)

DIGESTION

MAIN STEPS OF THE PROCESS 

Recycling line

Green = Main Line of production

To characterize two waste (RG and MUD), inelemental composition, mineralogy, granulometry andradioactive contents.

To evaluate the use of MUD as additive incommercial ceramics, due to its high contents ofrefractory minerals.

To check the possibility of substituting naturalgypsum (NG) by red gypsum (RG) in cementmanufacturing.

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OBJECTIVES

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MATERIALS

ILM, MUD and RGsamples were collected every5 days for 1 month, in orderto evaluate the possibletemporal variability of thecharacteristics of thesematerials.

OPC (Ordinary PortlandCement, 52.5 N/mm2, 97 %Clinker + 3 % NG), clinkerPortland and Red Stonewere(RSM) were also collected tobe used as raw materials ofthe new materials.

MUD

Red Gypsum

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CHARACTERISATION 

OF RED GYPSUM AND 

MUD

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MAJOR ELEMENTS

The main components in ILM are Ti and Fe given as oxides,around 50 and 44 %, respectively.

RG contains Ca (as CaO 33%) and S (as SO3 with 27 %) withimpurities of Fe (14%) and TiO2(7.6%).

MUD shows high concentration of TiO2 (53 %) + significantconcentrations of Fe (11%) and Si (18%), and ZrO2 (2 %).

Table 1. Concentration (%) of major elements in the materials under study. Thetotal iron content is given as Fe2O3. (*) Continental crust composition

SiO2 Al2O3 Fe2O3 MnO MgO CaO TiO2 SO3 ZrO2

ILM 0.85 ± 0.09 0.71 ± 0.09 44 ± 1 1.3 ± 0.1 0.32 ± 0.07 0.05 ± 0.01 49.6 ± 0.3 <0.01 0.15±0.03

MUD 18 ± 1 2.5 ± 0.2 11 ± 1 0.36 ± 0.01 0.38 ± 0.02 0.75 ± 0.01 53 ± 1 6.1 ± 0.7 2.1 ± 0.4

RG 1.2 ± 0.2 1.4 ± 0.2 14 ± 2 0.35 ± 0.04 1.4 ± 0.2 33 ± 2 7.6 ± 1.2 27 ± 1 < 0.01

Soil (*) 67 15 5 0.1 2.5 3.6 0.64 - 0.02

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XRD (Mud)

Mud contains several mineralogical species : ilmenite, rutile, zircon (ZrSiO4), quartz (SiO2), and Fe and Ti oxides (Fe3Ti3O10).

International Symposium EU‐NORM1. Tallin 2012

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XRD (Red Gypsum)

RG is mainly formed by CaSO4∙2H2O (gypsum), similar tonatural gypsum.

Fe is in amorphous form as sulphates and hydroxides.

RADIOACTIVE CHARACTERIZATION

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Table 2. Activity concentration (Bq/kg) of ILM, MUD and RG samples.

TITANIUM DIOXIDE: 1 g of Raw Material0.10 g MUD (dry)

0.60 g RG (dry)

238 U 226 Ra 232 Th 228 Ra 40 KILM 95 ± 10 86 ± 5 315 ± 20 301 ± 20 30 ± 5MUD 91 ± 5 457 ± 19 78 ± 3 1958 ± 68 477 ± 30RG 20 ± 1 14 ± 1 127 ± 3 91 ± 3 12 ± 2

Soil: 30 Bq/kg (238U‐, and 232Th‐series); 500 Bq/kg (40K)

ILM is a NORM mineral due to is enriched in the naturalradionuclides from the Th and U series in relation to soils.

The radioactive content for RG is similar to unperturbed soil

MUD contains high levels of radioactivity (greater than 1 Bq/g),especially for Ra‐isotopes.

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VALORISATION OF RED 

GYPSUM AND MUD

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SAMPLES PREPARATION

The mixtures studied were: YC (90% CLINKER‐10%RG), YB (95% CLINKER‐5% RG) and YA (97.5%CLINKER‐2.5 %RG).

The technological properties of these RG‐cements(water/cement ratio EN 196‐3, setting times in mortars(mixture of sand to cement in proportion 3:1), andmechanical properties, EN 196‐1), were compared witha standard commercial cement CEM (type I 52.5 N/SR).

RED GYPSUM IN COMMERCIAL CEMENTS

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PROPERTIES

Table 3. W/C ratios, setting times and expansion were determined following anormalized protocol using different proportions of red gypsum. For comparison,the commercial cements (CEM) taken as reference in this work are shown.

SampleOptimum 

W/CInitial setting times (min)

Final setting times (min)

∆t(min)

Expansion (mm)

REF. CEM. 0.27 139 224 85 2YC (10% RG) 0.29 216 351 135 1YB (5% RG) 0.27 108 298 190 1YA (2.5% RG) 0.29 82 129 47 1

All W/C ratios are similar to CEM.

The values of expansion are less than 10 mm.

Adding higher percentages of RG extends the initial and finalsetting times but always complying with Spanish regulation.

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MECHANICAL BEHAVIOUR

010203040506070

2 days 28 days 2 days 28 days

MPa

BENDING         COMPRESSION

CEM RG1 RG2 RG3YC YB YA

The mechanical behavior of the new cements improves whenmore RG is added.

In the YC sample the mechanical resistance is similar to CEM.

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ENVIRONMENTAL IMPLICATIONS

RG metal concentrations are lower than the ecotoxicity limits.Only Cr concentration is slightly higher than this threshold.

The lixiviation results carried out to the sample YC (10% RG) issimilar to the reference cement CEM.

Concentration in solid samples (mg kg-1) Leaching TCLP test (µg L-1)

Element Critical concentration RG RG YC CEM

As 20-50 10 1.8 1.9 1.1Cd 3-8 1 <0.1 <0.1 <0.1Co 25-50 16 65 <0.1 <0.1Cr 75-100 109 103 82 89Ni 100 30 176 4.1 3.3Pb 100-400 19 8.0 8.3 2.9Zn 70-400 212 - - -

Table 4. Critical concentration values (*) and leachability of metals fromthe RG cements YC, RG sample and reference cement (CEM).

(*) A. Kabata-Pendias, and H. Pendias. Trace elements in soils and plants. CRC Press. 413 pp, 2001

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Red stoneware (RSM) and ilmenite mud (3, 5, 7, 10, 30 and50%, with code samples 97/3, 95/5, 93/7, 90/10, 70/30 and 50/50respectively) were prepared in different concentrations.

The properties of these mixtures (water absorption EN ISO10545‐3, apparent porosity ASTM C373‐88, bulk density, linearshrinkage and Bending strength, EN 843‐1), were comparedwith a commercial ceramics (RSM 100%).

MUD AS ADDITIVE IN CERAMICS

SAMPLES PREPARATION

APR: 100%TLI: 0%

APR: 70%TLI: 30%

APR: 90%TLI: 10%

APR: 93%TLI: 7%

APR: 97%TLI: 3%

APR: 95%TLI: 5%

APR: 50%TLI: 50%

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PROPERTIESFigure. Technological properties of fired tiles.

LS increases with the content of MUD, while P generally increases with theconcentration of ilmenite mud.

E also follows this trend, decreasing in range 3 and 5% of ilmenite mud (2.82 and 2.48wt% respectively).

B increases with the concentration of mud until 10%. Concentrations higher than 30%,decreases the B due to the increase of P.

BS are upper than 30 MPa, minimum value in EN 14411.

0

10

20

30

40

50

0

5

10

15

20

25

100/0 97/3 95/5 93/7 90/10 70/30 50/50

Mpa

(%)

RSM/MUD

Linear shrinkage LS Apparent porosity P Water absorption E Bending strength BS

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RADIOLOGICAL EVALUATION

The EU has established criteria that define the external risk rate “I” inbuilding material.

In new ceramics samples, Index I are below the EU reference value (I< 1) for bulk building materials. I < 6 for thin elements (several mm).

238U 226Ra 232Th 228Ra 40K “I”100/0 35 ± 2 50 ± 1 60 ± 2 61 ± 2 1104 ± 16 0.8497-3 37 ± 2 55 ± 1 62 ± 2 97 ± 3 1154 ± 15 1.0595-5 44 ± 2 72 ± 2 59 ± 2 127 ± 4 1182 ± 18 1.2793-7 40 ± 2 79 ± 2 59 ± 4 141 ± 5 1158 ± 23 1.3590-10 37 ± 2 75 ± 2 63 ± 5 139 ± 5 1124 ± 24 1.32MUD 91 ± 6 457 ± 19 78 ± 3 1158 ± 48 477 ± 30 7.47

Table 6. Concentration in Bq kg‐1 of each sample analyzed by alpha andgamma spectrometry. External risk rate “I” in samples and raw material.

kC

ThC

RaC

I3000 Bq/kg

40

200 Bq/kg

232

300 Bq/kg

226 ++=

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ENVIRONMENTAL IMPLICATIONS

RSM 97/3 95/5 93/7 90/10 MUD U.S.EPAAs 110 40 40 60 60 < 30 5000Cd 22 24 24 23 23 < 2 1000Cr 200 200 200 240 220 < 20 5000Fe 2100 3220 3200 3040 3000 40 -Pb 100 300 20 150 110 < 10 5000Sr 60 60 50 40 40 < 10 -Ti < 10 < 10 20 < 10 < 10 10 -Zn 41 138 103 122 101 6 25000

Table 7. Leachability concentrations of metals (μg L‐1) obtained by TCLPtest from the raw materials and tile. Limit values given in the U.S. EPAstandard.

The amount of leached metals increases with the proportion ofmud, but generally is similar to the reference ceramic (RSM).

The leached metals values are clearly lower than the limitsimposed by US EPA for waste.

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CONCLUSIONS

Detailed information on the wastes composition generated inthe titanium dioxide pigment industry have been obtained.

RG can be used safely in the manufacturing of cement assubstitute on Natural Gypsum without decreasing thetechnological properties of the produced cements.

The radiological and environmental impacts, given by theradioactive index I and the TCLP tests, are lower than thereferences values established by the internationals regulations forthese two applications.

The study carried out to evaluate the possible use of MUD asadditive in the manufacture of ceramics tiles showed a similarbehavior that reference ones, improving in some case the technicalproperties of the commercial ceramics taken as a reference.

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Thank you for your attention

International Symposium EU‐NORM1. Tallin 2012

Radiation Physicsand Environment Group

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RECYCLING WASTES COMING FROM THE PIGMENT TiO2 INDUSTRY

Juan Pedro Bolívar Raya

University of Huelva (Spain)

E‐mail: bolivar@uhu.es

Radiation Physicsand Environment Group