Preparo, caracterização e aplicação de ferro valência zero imobilizado em esferas de alginato em processos de oxidação avançada

Abstract

The low efficiency of conventional treatments for textile effluents makes it necessary to continue studies that develop technologies capable of degrading these pollutants. An alternative to this would be the use of immobilized nFVZ in polymer matrix of alginate since these can act like catalytic material to induce the reactions of Fenton or to participate in the reactions of catalytic ozonation, emergent technologies belonging to the AOP's. Thus, the present work aimed to synthesize nFZV and immobilize it in a calcium and zinc cross-linked alginate polymer matrix, to characterize and evaluate the catalytic efficiency by means of Fenton reactions and catalytic ozonation using the oxidizing agents H2O2 and O3, respectively, in catalytic tests applicable to the degradation study of the reactive red dye 195, and, finally, to evaluate the effluent toxicity before and after the treatments. The results indicated that the procedure chosen for synthesis allowed to obtain crystalline nanoparticles with low concentration of oxides, proving the efficiency of the synthesis in oxidizing atmosphere. Instrumental techniques revealed that the particles were efficiently incorporated into the polymer matrix using calcium and zinc alone and in the ratio of 4:1 (Ca2+/Zn2+) as a crosslinker. In the redox tests, it was possible to prove the interaction of the nanoparticles with the synthetic effluent. A factorial design showed that larger masses of catalytic spheres (7.0 g) at acid pH (3.0) favored the discoloration mechanism. Among the catalytic spheres, CaZn-Alg-nFVZ promoted a better discoloration result, suggesting a synergism between the two cations used in the crosslinking. In the Fenton reaction, the H2O2 attacked the polymer matrix causing an uncontrolled release of the ferrous ions. Therefore, it was chosen to work with the ozone oxidizing agent, which was significantly more effective in the catalytic ozonation tests with discoloration of 88.23%, 78.45% and 55.27% for the CaZn-Alg-nFVZ beads, Ca-Alg-nFVZ and Zn-Alg-nFVZ, respectively, with only one minute of reaction. Already in 73 minutes, 99% discoloration was obtained for Zn-Alg-nFVZ, Ca-Alg-nFVZ and 94% for Zn-Alg-nFVZ beads. Ecotoxicity tests showed that Artemia saline was sensitive to the element Zinc. The tests performed with Lemna showed no toxicity. In view of this, it is believed that the CaZn-Alg-nFVZ beads would be the best option to be used in the polishing of the effluent containing the reactive red dye 195.