Avaliação da capacidade de adsorção de Zn(II) em solução por geopolímeros preparados com resíduos industrais
Arquivos
Data
2022-11-22
Autores
Santos, Aysline Duarte 
Orientadores
Shinzato, Mirian Chieko
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Os geopolímeros são materiais cimentantes formados por uma cadeia polimérica inorgânica amorfa, cuja composição é baseada em aluminossilicatos. A estrutura química dos geopolímeros é semelhante à de materiais zeolíticos, porém com uma microestrutura não cristalina. Devido a suas características químicas e estruturais esses materiais podem apresentar elevada eficiência de adsorção. Nesse contexto, o presente trabalho teve como objetivo avaliar a capacidade de adsorção de zinco (Zn2+) em solução por geopolímeros preparados com metacaulinita (MK) e resíduos sólidos da indústria de alumínio conhecido como lama vermelha (LV). Foram preparados geopolímeros contendo somente MK e misturas de MK e diferentes proporções de LV (10%, 30% e 50%). Inicialmente determinou-se a capacidade de troca catiônica (CTC) dessas amostras e, em seguida, escolheu-se aquelas que apresentaram valores de CTC mais elevados (MK= 3,45 meq g-1; LV 10%= 2,67 meq g-1). Esses materiais foram caracterizados (mineralogicamente, grupos funcionais e capacidade de troca catiônica) e utilizados em testes de adsorção em batelada para analisar a sua eficiência em reter os íons de Zn2+ sob duas condições (tempo e concentração inicial). Ambas as amostras apresentaram os mesmos grupos funcionais que são típicos de materiais zeolíticos. As fases cristalinas encontradas na análise por difratometria de raios X correspondem àqueles presentes originalmente na metacaulinita (quartzo e muscovita). Os resultados dos testes de remoção de Zn2+ em função do tempo (30 a 180 min) revelaram que todas as amostras de geopolímero apresentaram elevada eficiência (cerca de 99%) em adsorver Zn2+ de uma solução contendo 500 mg L-1. Os resultados do teste de batelada em função da concentração inicial de Zn2+ revelaram por meio da análise dos modelos de isotermas de adsorção, que as capacidades máximas de adsorção das amostras de MK e LV 10% correspondem a 63,01 mg g-1 e 53,55 mg g-1, respectivamente. Mesmo após serem adsorvidos, verificou-se por meio de testes de dessorção em meio aquoso e ácido, que os geopolímeros são capazes de manter grande parte do Zn2+ retidos em sua estrutura, liberando muito pouco para o ambiente. Portanto o uso de geopolímeros como adsorventes para conter metais pesados é bastante promissor.
Geopolymers are cementing materials formed by an amorphous inorganic polymeric chain, whose composition is based on aluminosilicates. The chemical structure of geopolymers is similar to that of zeolitic materials, but with a non-crystalline microstructure. Due to their chemical and structural characteristics, these materials can present high adsorption efficiency. In this context, the present work aimed to evaluate the adsorption capacity of zinc (Zn2+) in solution by geopolymers prepared with metakaolinite (MK) and solid waste from the aluminum industry known as red mud (LV). Geopolymers were prepared containing only MK and mixtures of MK and different proportions of LV (10%, 30% and 50%). Initially, the cation exchange capacity (CTC) of these samples was determined and, then, those that presented the highest CTC values were chosen (MK= 3.45 meq g-1; LV 10%= 2.67 meq g-1). These materials were characterized (mineralogically, functional groups and cation exchange capacity) and used in batch adsorption tests to analyze their efficiency in retaining Zn2+ ions under two conditions (time and initial concentration). Both samples showed the same functional groups that are typical of zeolitic materials. The crystalline phases found in the analysis by X-ray diffractometry correspond to those originally present in metakaolinite (quartz and muscovite). The results of Zn2+ removal tests as a function of time (30 to 180 min) revealed that all geopolymer samples showed high efficiency (about 99%) in adsorbing Zn2+ from a solution containing 500 mg L-1. The results of the batch test as a function of the initial concentration of Zn2+ revealed, through the analysis of the adsorption isotherm models, that the maximum adsorption capacities of the MK and LV 10% samples correspond to 63,01 mg g-1 and 53,55 mg g-1, respectively. Even after being adsorbed, it was verified through desorption tests in aqueous and acidic media that the geopolymers are able to keep a large part of the Zn2+ retained in their structure, releasing very little to the environment. Therefore, the use of geopolymers as adsorbents to contain heavy metals is very promising.
Geopolymers are cementing materials formed by an amorphous inorganic polymeric chain, whose composition is based on aluminosilicates. The chemical structure of geopolymers is similar to that of zeolitic materials, but with a non-crystalline microstructure. Due to their chemical and structural characteristics, these materials can present high adsorption efficiency. In this context, the present work aimed to evaluate the adsorption capacity of zinc (Zn2+) in solution by geopolymers prepared with metakaolinite (MK) and solid waste from the aluminum industry known as red mud (LV). Geopolymers were prepared containing only MK and mixtures of MK and different proportions of LV (10%, 30% and 50%). Initially, the cation exchange capacity (CTC) of these samples was determined and, then, those that presented the highest CTC values were chosen (MK= 3.45 meq g-1; LV 10%= 2.67 meq g-1). These materials were characterized (mineralogically, functional groups and cation exchange capacity) and used in batch adsorption tests to analyze their efficiency in retaining Zn2+ ions under two conditions (time and initial concentration). Both samples showed the same functional groups that are typical of zeolitic materials. The crystalline phases found in the analysis by X-ray diffractometry correspond to those originally present in metakaolinite (quartz and muscovite). The results of Zn2+ removal tests as a function of time (30 to 180 min) revealed that all geopolymer samples showed high efficiency (about 99%) in adsorbing Zn2+ from a solution containing 500 mg L-1. The results of the batch test as a function of the initial concentration of Zn2+ revealed, through the analysis of the adsorption isotherm models, that the maximum adsorption capacities of the MK and LV 10% samples correspond to 63,01 mg g-1 and 53,55 mg g-1, respectively. Even after being adsorbed, it was verified through desorption tests in aqueous and acidic media that the geopolymers are able to keep a large part of the Zn2+ retained in their structure, releasing very little to the environment. Therefore, the use of geopolymers as adsorbents to contain heavy metals is very promising.