1035-B4

ENVIRONMENTAL BEHAVIOR OF SOILS AND MIXTURES OF SOIL-WHITEWASH MUD

Carlos Cardoso Machado; José Maurício Machado Pires; Maurício Paulo F. Fontes; Reginaldo Sérgio Pereira; Dalila Campos de Medeiros Fernandes ¹ .

SUMMARY

The present study sought to observe the behavior of soils in natural state and in mixtures, in different ratios, with the industrial solid residue called whitewash mud. The work was conducted with samples of typical soils of the area of Alagoinhas, Bahia-Brazil. Wet chemical analysis and atomic absorption spectrophotometry were used in order to obtain the classification of the industrial solid residue. Solubilization and leaching essays were performed and X-ray diffraction and electron microscopy techniques were conducted. The results showed that the whitewash mud was classified as not inert, but with great capacity of retention of heavy metals largely owed to the kaolinite presence and goethite in the fraction clay of the soils, what makes it difficult to have the heavy metals readily available for exchange.

1. INTRODUCTION

The terms pollution and contamination are being heavily used in the current days. For CRATHORNE (1996), they are mistakenly taken as synonymous in the everyday common language usage. In the scientific field they have different meanings. The term contamination is used to designate a chemical substance in a sample without evidence that it causes problems. The term pollution is used in cases where the presence of the substance is harmful. Pollutants are, therefore, chemical substances that cause damage to the environment. There are several pollution types, going from the simple thermal pollution to the input of heavy metals in the environment.

The industrial residues are one of the main responsible for the environmental pollution, being originated from cooling processes, washes, discharges, extractions, impregnations, chemical treatments, among others. They are one of the great concerns nationally and worldwide (ROCCA et al., 1993).

The reuse of industrial by-products represents one of the technological alternatives for application for those residues. Works with that focus are being developed in laboratories of the Federal University of Viçosa, MG, (UFV), where the utilization of some of these residues is sought in pavements of forest highways. Particularly one residue with great potential for reutilization is the whitewash mud, which comes from the cellulose and paper industry. However, the environmental aspect of this utilization becomes of fundamental relevance.

Therefore, the present study has the following objectives: (a) to characterize chemically and mineralogically the industrial solid residue called whitewash mud; (b) to carry through the classification of this material as related to its environmental potential danger when used together with soil samples.

2. MATERIAL AND METHODS

2.1. Samples of soils

Two samples of soils, coming from the company Klabin-Bacell, located in Alagoinhas, Bahia - Brazil, were used in the study. The samples were identified as:

• Farm Klabin Bacell - Sand Soil (SS);
• Farm Klabin Bacell - Gravel Soil (GS);

2.2. Industrial solid residue or whitewash mud

The solid residue whitewash mud which comes from the process of paper and cellulose production was used in this study. The portion of the residue that passes in the sieve of 0.25 mm was used.

2.3. Dosage of the mixtures soil + whitewash mud

The amount of whitewash mud was: 5, 10, 15, 20 and 25% of the dry weight of the soil.

2.4. Laboratory Essays

The laboratory essays with the soil samples in natural state and in mixtures with the whitewash mud consisted of the following: determination of the trace elements Cu, Cd, Cr, Fe, Pb, Zn and Mn by atomic absorption spectrophotometry (ABNT, 1987a - NBR 10004); (b) soils classification of: leaching essay by determination of Cd, Cr and Pb (ABNT, 1987b-NBR 10005), solubilization essay by determining the contents of Cr, Pb, Cd, Fe, Mn and Na (ABNT, 1987c-NBR 10006); (c) textural analysis and cation exchange capacity (EMBRAPA, 1990); (d) determination of the organic carbon content (WALKLEY, 1947); and (e) X-ray diffraction for determination of the clay fraction minerals (FORMOSO, 1984).

3. RESULTS AND DISCUSSION

3.1 - Determination of trace elements

The determinations of trace elements present in the soils and in the mixtures soil- whitewash mud was performed according to Norm 10004 of ABNT (ABNT, 1987a). The results of the soil samples and the mixtures soil- whitewash mud are shown in Tables 1 and 2.

Table 1 - Amount of several trace elements of natural soil samples (_g/g)

By analyzing Table 1 it can be observed the presence of iron, zinc and manganese in the samples of Sand Soil and Gravel Soil. In the sand soil samples it was observed a larger concentration of iron, zinc and manganese.

In Table 2 it can be seen that the concentration of the elements copper, iron, zinc and manganese decreased with the increase of the concentration of the mud-of-whitewash.

Table 2- Amount of trace elements in the mixtures of soil-mud of whitewash (_g/g)

For both situations it was observed that some elements were below the detection limit (ND).

3.2 - Soils classification with relationship to the pollution degree

The classification of soils with relationship at the pollution level was accomplished according to the Norms 10005 and 10006 of ABNT (ABNT, 1987b,c) .

3.2.1-Results of the leaching essay

Table 3 shows the results of the leaching essays with soil samples and mixtures of soil- whitewash mud.

Table 3 - Contents of Cd, Cr and Pb in _g/mL in the leaching essay of soils and mixtures

3.2.2-Results of the Solubilization essays

Table 4 shows the results of the Solubilization essays with soil samples and soil- whitewash mud.

Table 4 - Contents of Cd, Cr, Pb, Mn, Fe and Na in, _g/mL, in the solubilization essay

Tables 3 and 4 present the contents of several trace elements, including sodium, obtained in the leaching and solubilization essays. The simple inspection and comparison of the values obtained in relation to the values controlled by Norm 10004 of ABNT (Tables 5 and 6) suggest that the whitewash mud can be classed as a non inert material because of the high concentration of sodium found in these essays.

Table 5 - Maximum allowable values in the extract from the leaching essay

Table 6 - Maximum allowable values in the extract from the solubilization essay

3.3 - Results of the textural analysis of soils and mixtures of soil-mud of whitewash

Table 7 presents a synthesis of the main results of the textural analysis of the samples of natural soil and of the mixtures soil- whitewash mud in different concentrations.

Table 7 - Results from the textural analysis of soils and mixtures of soil-mud of whitewash

3.4 - Analysis of X-Ray diffraction

Table 8 exhibits the main results of the X-Ray analysis of the soil samples and of mixtures of soil- whitewash mud. In general, kaolinite, goethite and quartz were the main minerals found.

Table 8 - Results of X-ray diffraction analysis

3.5 - Results of Cation Exchange Capacity (CEC)

Table 9 presents the results of cation exchange capacity (CEC) of the samples of natural soil and of the mixtures soil- whitewash mud. The importance of this analysis is that it gives a pretty good idea of the capacity for adsorption on the surface of the minerals components of these soils and the soil mixtures. It can be observed that the whitewash mud increases a lot the CEC of the soil samples making the mixtures a lot better adsorbents of cations.

Table 9 - Cation exchange capacity of soil and soil mixtures

3.6. Results of the analyses of organic carbon

By analyzing Table 10 it can be observed that the contents of organic carbon are very low, showing a very poor relationship between these sandy soils and mixtures soil- whitewash mud and organic carbon. Sand and organic carbon can not form stable complexes as compared to soils with larger contents of clay fraction.

Table 10 - Results of organic carbon contents in %

4-CONCLUSIONS

a) The mixture soil- whitewash mud was not a dangerous material as far as the pollution point of view is concerned;

b) The contents of Cadmium, Chromium and Lead in the mixture soil-whitewash mud were below the limits recommended by the norms of Brazilian Association of Technical Norms (ABNT);

c) The whitewash mud belongs the Class 2 of ABNT, therefore the material is not inert, due to the contents of Sodium obtained in the Solubilization essays, which are above the limit recommended by the norms of ABNT;

d) The contents of kaolinite and goethite ranged from 20 to 50%, imparting to these natural soils and the mixtures soil-whitewash mud a good capacity to retain heavy metals, making them less available to exchange and percolation to the water system;

e) Natural soils and the mixtures soil-whitewash mud presented low contents of organic carbon showing that their sandier nature does not allow for holding higher amounts of Organic Carbon.

5. BIBLIOGRAPHY

ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS (ABNT), 1987a. NBR 10004. Classificação de resíduos sólidos. [BRAZILIAN ASSOCIATION OF TECHNICAL NORMS-NBR 10004. Classification of solid residues]. Rio de Janeiro, 63p.

ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, 1987b. - NBR 10005. Lixiviação de resíduos sólidos. [ BRAZILIAN ASSOCIATION OF TECHNICAL NORMS-NBR 10005. Leaching of solid residues ]. Rio de Janeiro, 7p.

ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, 1987c.- NBR 10006. Solubilização de resíduos sólidos. [ BRAZILIAN ASSOCIATION OF TECHNICAL NORMS-NBR 10006. Solubilization of solid residues ]. Rio de Janeiro, 2p.

ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, 1987d. - NBR 10007. Amostragem de resíduos sólidos.[ BRAZILIAN ASSOCIATION OF TECHNICAL NORMS-NBR 10007. Sampling of solid residues]. Rio de Janeiro, 25p.

CRATHORNE, B.; DOBBS, A. J.; REES, Y., 1996. Chemical pollution of aquatic environment by priority pollutants and its control. IN: pollution causes, effects and control Harrison R. M. ed. The Royal Society of Chemistry, 3 ed. p.1, England.

FORMOSO, M. L. L. 1984. Difratometria de raios-X. IN: Técnicas Analíticas Instrumentais Aplicadas à Geologia. Santos, P. S. (coord.). Edgard Blücher, São Paulo, 218p.

MANUAL DA EMBRAPA, 1990, Rio de Janeiro. 470p.

ROCCA, A. A. C.; et al. , 1993. Resíduos sólidos industriais. CETESB, São Paulo, 2 ^o ed., 1993. 233p.

WALKLEY, A., 1947. A critical examination of a rapid method for determining organic carbon in soils: effect of variations in digestion conditions and of inorganic soils constituents. Soil Science, n. 63, p.251-263.

¹ Federal University of Viçosa, Professor-Viçosa, MG, Brazil- [email protected]; [email protected]
Federal University of Viçosa, Graduate Student-Viçosa, MG, Brazil- [email protected]
Federal University of Viçosa, Graduate Student- Viçosa, MG, Brazil- [email protected]
Federal University of Viçosa, Researcher- Viçosa, MG, Brazil- [email protected]