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| Author(s): |
Josiane Aparecida Gaspar
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Araraquara. 2016-04-28. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara |
| Defense date: | 2016-04-18 |
| Advisor: | Denise Bevilaqua; Ana Teresa Lombardi |
| Abstract | |
Currently, the sugar industry is considered one of the most important industries of the Brazilian socioeconomic scenario. However, this sector generates large amount of waste products, among which the filter cake (FC) is a representative solid waste. Agricultural recycling can be considered as an alternative to the final disposal of such solid waste. However, one of the main concerns regarding its application in the soil is the presence of contaminants such as trace elements. Studies have shown that bioleaching is a promising alternative for the treatment of various wastes. Bioleaching is efficient for the removal of potentially toxic elements (PTE), allowing the compost to be used as soil conditioner, without causing additional problems. The objectives of the present work were to evaluate the removal of potentially toxic elements present in the filter cake produced by a sugar and alcohol industry, through bioleaching. To accomplish this objective, we used bioleaching tests performed initially with the bacteria Acidithiobacillus ferrooxidans - LR and Acidithiobacillus thiooxidans - FG01. Initially two samples of the filter cake of different harvests in 2014 and 2015 were used. The samples were characterized for their agronomic potential and presence of potentially toxic elements. Bioleaching experiments were carried out in flasks shaked (150 rpm at 30 °C) supplemented with FeSO4 or So depending on the bacteria, as well as their corresponding abiotic controls. An initial concentration of 2% pulp density (w/v) followed by 10% (w/v) concentration of the filter cake along with T&K and 9K media were used. The results showed that samples from the 2014 crop inhibited the growth of microorganisms in comparison with the 2015 one. All subsequent tests were performed with samples from 2015 crop. The potentially toxic elements solubilization in the filter cake was, in descending order using At. ferrooxidans – LR, 91%, Mn; 65%, Zn; 43%, Pb; 34%, Al; 32%, Cr and 22% of the Cu, and with At. thiooxidans - FG01 93%, Mn; 62%, Zn; 38%, Cr; 35%, Al; 35%, Pb and 24% of the Cu. The solubilization of potentially toxic elements in the inoculated experimental groups did not show significant difference except for Cr and Pb. Potentially toxic elements were negatively correlated with pH and positively correlated with redox potential. The Logistic model was shown to accompany the study of the bioleaching process. The sequential extraction of potential toxic elements showed that most of the elements were connected to fractions considered available to organisms, and after the microbial treatment, most of the remaining potential toxic elements of the filter cake were present as more stable fractions. Therefore, we suggest that the bioleached residue can be applied to the soil. Nitrogen and phosphorus leaching were observed, and this is related to the acidic condition of the system. Finally, we tested the bioleached filter cake in lettuce through acute phytotoxicity tests that showed lower toxicity when compared with untreated filter cake. For these tests, we used elutriates obtained from the bioleached filter cake and the untreated filter cake. The Lactuca sativa germination and rootlests were evaluated. In general, we demonstrated that the bioleaching with At. ferrooxidans and At. thiooxidans have attenuated the potentially toxic elements concentrations in the filter cake, so presenting no final toxicity to lettuce. This has important environmental implications, since a residue can be treated and safely used as soil conditioner in agriculture. (AU) | |
| FAPESP's process: | 12/19115-0 - Removal of trace metal elements in waste of the sugar industry for use as substrate |
| Grantee: | Josiane Aparecida Gaspar |
| Support Opportunities: | Scholarships in Brazil - Doctorate |