Search

Rare earth elements such as neodymium (Nd) are important elements used mainly in developing new technologies. Although they are found in low concentrations in nature, they can be obtained by extracting solid samples such as phosphogypsum. Among the techniques, adsorption has been used successfully with several adsorbent materials. In this work, two strains of Spirulina platensis (LEB-18 and LEB-52) were employed as biosorbents for efficiently removing the Nd element from the aqueous media. Biosorption tests were carried out in a batch system, and the results of the biosorption kinetics showed that for both materials, the biosorption of Nd was better described by the Avrami model. Moreover, it could be considered that 80 min would be necessary to attain the equilibrium of Nd(III) using both biosorbents. The result of the biosorption isotherms showed that for both strains, the best-fitted model was the Liu model, having a maximum biosorption capacity of 72.5 mg g(-1) for LEB-18 and 48.2 mg g(-1) for LEB-52 at a temperature of 298 K. Thermodynamics of adsorption showed that for both LEB-18 and LEB-52 the process was favorable ( increment G degrees < 0) and exothermic ( increment H degrees -23.2 for LEB-18 and increment H degrees -19.9 for LEB-52). Finally, both strains were suitable to uptake Nd, and the better result of LEB-18 could be attributed to the high amount of P and S groups in this biomass. Based on the results, a mechanism of electrostatic attraction of Nd3+ and phosphate and sulfate groups of both strains of Spirulina platensis was proposed.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES In this work the synthesis of a magnetic geopolymer from silica, metakaolin, iron zero-valent, soybean oil, sodium hydroxide and hydrogen peroxide was proposed. The magnetic geopolymer was characterized by X-ray diffraction, Fourier transform infrared spectrometry, surface area, mean pore diameter and pore volume by BET and BJH methods, scanning electron microscopy and vibrating sample magnetometer. The synthesized material was tested as an adsorbent of the anionic dye Acid Red 97 (AR97). The results showed that the magnetic geopolymer is mesoporous, has sufficient magnetization to be removed by action of a magnetic field of the aqueous solution, removes more than 94% of dye in only 20 minutes, and has a high adsorptive capacity of 1814.27 mg g-1 of AR97 at a temperature of 318 K. The magnetic geopolymer presented adsorption capacity very close to the initial one for up to five cycles of use. This adsorbent was synthesized from low cost materials with extremely high adsorption capacity and could be easily separated from the treated liquid effluent. Neste trabalho foi proposto a síntese de um geopolímero magnético a partir de sílica, metacaulim, ferro zero valente, óleo de soja, hidróxido de sódio e peróxido de hidrogênio. O geopolímero magnético foi caracterizado por difração de raios-X, espectrometria de infravermelho com transformada de Fourier, área superficial, diâmetro médio de poro e volume de poro pelos métodos BET e BJH, microscopia eletrônica de varredura e magnetômetro de amostra vibrante. O material sintetizado foi testado como adsorvente do corante aniônico Acid Red 97 (AR97). Os resultados mostraram que o geopolímero magnético é mesoporoso, possui magnetização suficiente para ser removido por ação de um campo magnético da solução aquosa, remove mais de 94% de corante em apenas 20 minutos, e possui alta capacidade adsortiva, de 1814,27 mg g-1 de AR97 na temperatura de 318 K. O geopolímero magnético apresentou capacidade de adsorção muito próxima da inicial por até cinco ciclos de utilização. Este adsorvente foi sintetizado a partir de materiais de baixo custo, apresentando capacidade de adsorção extremamente alta, podendo ser facilmente separado do efluente líquido tratado.