Remoção de metais em água utilizando Eichhornia crassipes na forma in natura, biocarvão e híbrido magnético

• Ano de defesa: 2018
• Autor(a) principal: Lima, Jôse Raymara Alves
• Orientador(a): Romão, Luciane Pimenta Cruz
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Programa de Pós-Graduação: Pós-Graduação em Química
• Palavras-chave em Português: Biorremediação; Adsorção; Metais; Aguapé (Eichhornia crassipes); Híbrido magnético; Remediação ambiental
• Palavras-chave em Inglês: Water hyacinth (Eichhornia crassipes); Magnetic hybrid; Adsorption; Metals; Environmental remediation
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: http://ri.ufs.br/jspui/handle/riufs/8246

Water hyacinth (Eichhornia crassipes) is an invasive aquatic weed whose main characteristic is its high growth rate. The methods applied to control this plant have high cost and waste generation. Using the water hyacinth as an adsorbent for remediation of metals is a viable and eco-friendly application. In this work, a magnetic hybrid adsorbent matrix (AGMG) was synthesized utilizing water hyacinth (Eichhornia crassipes) biomass to compose an organic phase, and its adsorption efficiency was compared to the adsorption efficiency of in natura (AGIN) water hyacinth and its biochar (BIO) in the remediation of metals in water. The adsorbents were characterized by infrared spectroscopy, confirming the presence of hydroxyl groups and carboxylates, with bands that are typical of cellulose, hemicellulose and lignin, structures found in AGIN and BIO. The AGMG spectrum presented the bands previously described and new bands in the region of 513 cm-1, characteristic of the Fe-O bond of CoFeO4, confirming the formation of a magnetic hybrid. The essays on the influence of pH on the remediation of copper, zinc, nickel and cobalt presented higher percentages of removal in the range of pH 4-5 for all adsorbents, and the following crescent order of removal efficiency AGIN<AGMG<BIO for all metals. The kinetic studies showed fast kinetics for the three adsorbents and the metals under study with a removal rate of more than 50% in the first 5 minutes. The kinetic data were adjusted to the pseudo-second order model, with correlation coefficients higher than 0,99 for the three materials. The AGMG was prominent among the other adsorbents because its adsorption capacity is high and its separation from the aqueous medium is more feasible. The isotherm data for the AGMG were adjusted to the Langmuir model, showing a good linear correlation in the concentration range studied (5-250 mg g-1), with correlation coefficient r2 between 0,9973-0,9999. The values of the calculated maximum capacity of AGMG (qmax) were 18,3 mg g-1 Cu (II), 10,1 mg g-1 Zn (II) and 7,33 mg-1 Ni (II). The percentage of removal in the different mixed solutions by the adsorbent AGMG followed this order of selectivity, Cu>Zn>Ni, copper as a highlight, > 84% removal in all evaluated mixed solutions. The AGMG was reused in four cycles of adsorption in mixed solution, without using a desorption process, and the efficiency varied according to the metal. The adsorption of copper remained high in all cycles, with 77% removal in the first cycle and 72% in the fourth cycle. For zinc and nickel, the removal decreased with each cycle, and in the third cycle there was no more nickel removal. The saturated with metals AGMG residues (AGMG-sat) showed high catalytic activities in the reduction of 4- nitrophenol to 4-aminophenol. The residues were reused in ten reduction cycles and the conversion rate in the cycles ranged from 88,9 to 100%, with short periods of time (21-26 s).