Remoção de fósforo de efluente utilizando biocarvão de casca de café modificada com magnésio e ferro
Data
2023-04-18
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Universidade Federal de Lavras
Resumo
O fósforo (P), apesar de ser um nutriente essencial para o crescimento das plantas, quando em excesso em ambientes aquáticos pode acarretar a eutrofização. Assim, a sua remoção de efluentes líquidos é fundamental para prevenir a contaminação de corpos hídricos. Enquanto os processos convencionais de tratamento de efluentes, normalmente, são pouco eficientes na remoção de fósforo, os biocarvões têm se mostrado muito promissores na remoção deste poluente, especialmente quando modificado quimicamente para aumentar a performance de adsorção. Deste modo, este trabalho teve como objetivo a produção de um compósito de biocarvão a partir de casca de café, modificada com compostos de magnésio e ferro, e sua aplicação no pós-tratamento de efluentes de abatedouro de suínos para remoção de fósforo. A performance do compósito foi comparada com o biocarvão não modificado (BC) e com a mistura de compostos de Mg e Fe (M-Mg/Fe). As condições de pirólise para o preparo dos materiais foram tempo de residência de 2 horas a 480ºC, com taxa de aquecimento inicial de 22,8ºC min-1 . Para caracterização dos materiais foram realizadas análises de rendimento, pH, ponto de carga zero (PCZ), espectroscopia de infravermelho com transformada de Fourier (FTIR), difração de raios-X (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva (EDS). Foram realizados estudos de adsorção de fósforo pelos materiais utilizando solução sintética, avaliando-se o efeito do pH, força iônica, bem como aspectos cinéticos e de equilíbrio de adsorção. A adsorção de fosfato em efluente de abatedouro foi avaliada pelo teste de dosagem do adsorvente e ensaios de cinética de adsorção. Pela análise morfológica, o BC apresentou superfície muito irregular e com esfoliações e poros, enquanto BC-Mg/Fe apresentou uma estrutura rugosa, com a presença de canaletas e depósitos superficiais amorfos. A M-Mg/Fe mostrou a formação de fases cúbicas e camadas sobrepostas. O teste de efeito de pH evidenciou que o BC tem baixa capacidade de adsorção de fosfato, com a maior eficiência observada de 15,7% (pH 12,0), enquanto para BC-Mg/Fe e M-Mg/Fe obtiveram-se 99,3 e 98,8% de eficiência de adsorção, respectivamente, em pH 2,0 e 7,0. A presença de íons cloreto, no teste de força iônica, não influenciou a adsorção de fosfato pelo BC-Mg/Fe e M-Mg/Fe. O modelo de Elovich foi o que melhor se ajustou aos dados experimentais de cinética para o BC-Mg/Fe e M-Mg/Fe, indicando que a quimissorção pode ser um importante mecanismo na remoção de fosfato por esses adsorventes. O equilíbrio de adsorção para esses materiais foi atingido, respectivamente, após 360 e 600 minutos. A isoterma de Sips foi a que melhor se ajustou aos dados experimentais de BC-Mg/Fe, com capacidade máxima de adsorção (qmáx) estimada de 216,47 mg g-1 . Para a MMg/Fe, foi a isoterma de Redlich-Peterson, com qmáx de 133,52 mg g-1 . Para os ensaios com efluente de abatedouro suíno, a dose de 4 g L-1 de BC-Mg/Fe foi suficiente para remover 97,0% de fosfato presente no efluente, enquanto foram necessárias 6 g L-1 de M-Mg/Fe para remover 96,7% do fosfato. O modelo de pseudo-segunda ordem apresentou um bom ajuste aos dados experimentais de BC-Mg/Fe no estudo com o efluente, enquanto para M-Mg/Fe foi o modelo de Elovich, corroborando que os mecanismos químicos podem ter sido importantes na adsorção de fosfato, sendo alcançado o equilíbrio de adsorção, respectivamente, em 240 e 600 minutos. Assim, a elevada capacidade adsortiva de BC-Mg/Fe e eficiência de remoção de fosfato em efluentes, evidenciaram o potencial deste material para o pós-tratamento de efluentes.
Phosphorus (P), despite being an essential nutrient for plant growth, when in excess in aquatic environments can lead to eutrophication. Thus, its removal from wastewater is essential to prevent contamination of water bodies. While conventional wastewater treatment processes are usually inefficient in removing phosphorus, biochars have shown to be very promising in removing this pollutant, especially when chemically modified to increase adsorption performance. Thus, this work aimed to produce a biochar composite from coffee husks, modified with magnesium and iron compounds, and its application in the post-treatment of swine slaughterhouse wastewater to remove phosphorus. The performance of the composite was compared with unmodified biochar (BC) and with a mixture of Mg and Fe compounds (M-Mg/Fe). The pyrolysis conditions for preparing the materials were a residence time of 2 hours at 480ºC, with an initial heating rate of 22.8ºC min-1 . For the characterization of the materials, analysis of yield, pH, point of zero charge (PCZ), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (DRX), scanning electron microscopy (SEM) and dispersive energy (EDS). Adsorption studies of the materials with synthetic phosphorus solution were carried out, evaluating the effect of pH, ionic strength, as well as adsorption kinetics and equilibrium studies. Phosphate adsorption in slaughterhouse wastewater was evaluated by adsorbent dosage test and adsorption kinetics assays. By morphological analysis, BC had a very irregular surface with exfoliation and pores, while BC-Mg/Fe had a rough structure, with the presence of channels and amorphous surface deposits. M-Mg/Fe showed the formation of cubic phases and overlapping layers. The pH effect test showed that BC has a low phosphate adsorption capacity, with the highest observed efficiency of 15.7% (pH 12.0), while BC-Mg/Fe and M-Mg/Fe obtained 99, 3 and 98.8% adsorption efficiency, respectively, at pH 2.0 and 7.0). The presence of chloride ions, in the ionic strength test, did not influence the phosphate adsorption by BC-Mg/Fe and M-Mg/Fe (removals ≥ 99.0%). The Elovich model best fitted the experimental data for BC-Mg/Fe and M-Mg/Fe, indicating that chemisorption may be an important mechanism in the removal of phosphate by these adsorbents. The adsorption equilibrium for these materials was reached, respectively, after 360 and 600 minutes. The Sips isotherm best fitted the experimental BC-Mg/Fe data, with an estimated maximum adsorption capacity (qmax) of 216.47 mg g-1 . For M-Mg/Fe, it was the Redlich-Peterson isotherm, with qmax of 133.52 mg g-1 . For the tests with swine slaughterhouse wastewater, the dose of 4 g L-1 of BC-Mg/Fe was enough to remove 97.0% of phosphate present in the effluent, while 6 g L-1 of M-Mg/ Fe to remove 96.7% of the phosphate. The pseudo-second order model presented a good fit to the experimental data of BC-Mg/Fe with the effluent, while for M-Mg/Fe it was the Elovich model, corroborating that the chemical mechanisms may have been important in the phosphate adsorption, adsorption equilibrium being reached, respectively, in 240 and 600 minutes. Thus, the high adsorptive capacity of BC-Mg/Fe and the efficiency of phosphate removal in effluents evidenced the great potential of this material for post-treatment of effluents.
Phosphorus (P), despite being an essential nutrient for plant growth, when in excess in aquatic environments can lead to eutrophication. Thus, its removal from wastewater is essential to prevent contamination of water bodies. While conventional wastewater treatment processes are usually inefficient in removing phosphorus, biochars have shown to be very promising in removing this pollutant, especially when chemically modified to increase adsorption performance. Thus, this work aimed to produce a biochar composite from coffee husks, modified with magnesium and iron compounds, and its application in the post-treatment of swine slaughterhouse wastewater to remove phosphorus. The performance of the composite was compared with unmodified biochar (BC) and with a mixture of Mg and Fe compounds (M-Mg/Fe). The pyrolysis conditions for preparing the materials were a residence time of 2 hours at 480ºC, with an initial heating rate of 22.8ºC min-1 . For the characterization of the materials, analysis of yield, pH, point of zero charge (PCZ), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (DRX), scanning electron microscopy (SEM) and dispersive energy (EDS). Adsorption studies of the materials with synthetic phosphorus solution were carried out, evaluating the effect of pH, ionic strength, as well as adsorption kinetics and equilibrium studies. Phosphate adsorption in slaughterhouse wastewater was evaluated by adsorbent dosage test and adsorption kinetics assays. By morphological analysis, BC had a very irregular surface with exfoliation and pores, while BC-Mg/Fe had a rough structure, with the presence of channels and amorphous surface deposits. M-Mg/Fe showed the formation of cubic phases and overlapping layers. The pH effect test showed that BC has a low phosphate adsorption capacity, with the highest observed efficiency of 15.7% (pH 12.0), while BC-Mg/Fe and M-Mg/Fe obtained 99, 3 and 98.8% adsorption efficiency, respectively, at pH 2.0 and 7.0). The presence of chloride ions, in the ionic strength test, did not influence the phosphate adsorption by BC-Mg/Fe and M-Mg/Fe (removals ≥ 99.0%). The Elovich model best fitted the experimental data for BC-Mg/Fe and M-Mg/Fe, indicating that chemisorption may be an important mechanism in the removal of phosphate by these adsorbents. The adsorption equilibrium for these materials was reached, respectively, after 360 and 600 minutes. The Sips isotherm best fitted the experimental BC-Mg/Fe data, with an estimated maximum adsorption capacity (qmax) of 216.47 mg g-1 . For M-Mg/Fe, it was the Redlich-Peterson isotherm, with qmax of 133.52 mg g-1 . For the tests with swine slaughterhouse wastewater, the dose of 4 g L-1 of BC-Mg/Fe was enough to remove 97.0% of phosphate present in the effluent, while 6 g L-1 of M-Mg/ Fe to remove 96.7% of the phosphate. The pseudo-second order model presented a good fit to the experimental data of BC-Mg/Fe with the effluent, while for M-Mg/Fe it was the Elovich model, corroborating that the chemical mechanisms may have been important in the phosphate adsorption, adsorption equilibrium being reached, respectively, in 240 and 600 minutes. Thus, the high adsorptive capacity of BC-Mg/Fe and the efficiency of phosphate removal in effluents evidenced the great potential of this material for post-treatment of effluents.
Descrição
Dissertação de Mestrado defendida na Universidade Federal de Lavras
Palavras-chave
hidróxido duplo lamelar, adsorção de fosfato, remoção de fosfato, tratamento terciário, lamellar double hydroxide, phosphate adsorption, phosphate removal, tertiary treatmen
Citação
SILVA, Laís Miguelina Marçal da. Remoção de fósforo de efluente utilizando biocarvão de casca de café modificada com magnésio e ferro. 2023. 95 p. Dissertação (Mestrado em Engenharia Ambiental)–Universidade Federal de Lavras, Lavras, 2023