Vermiculitas tratadas quimicamente na obtenção de sólidos microporosos como precursores para híbridos inorgânico-orgânicos com aplicações adsortivas

• Ano de defesa: 2009
• Autor(a) principal: Alves, Ana Paula de Melo
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal da Paraí­ba; BR; Química; Programa de Pós-Graduação em Química; UFPB
• Palavras-chave em Português: Híbridos inorgânico-orgânicos; Vermiculita; Organoargilas; Argilas ativadas; Silanização; Hybrid inorganic-organic; Vermiculite; Organoclays; Activated clays; Silylation; CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: https://repositorio.ufpb.br/jspui/handle/tede/7172

The selective leaching of clay minerals is an important method in the preparation of porous silicates presenting as a simple, effective and low cost route. In this study, vermiculite was submitted to acid treatment at concentrations 1, 2, 3, and 4 mol dm-3, resulting the precursor solids named as VacX (x=1 a 4), respectively. The lixiviated matrices and vermiculite reacted covalently with the organosilanes aminepropyl-, propyletilenediamine-, propyldietilenetriamine- and glycidoxypropyltrimethoxisilane (GPTS). The hybrid Vac3G, derived from silanization reaction between Vac3 and GPTS, was submitted to subsequent reactions with ethyl, propyl, butyldiamines and 2- aminepiridine resulting in the entrance of new basic centres. The products were characterized by chemical analysis, infrared spectroscopy, X-ray diffraction, 29Si and 27Al NMR in solid state, SEM, and pore volume and surface area determination. The lixiviation of sodic vermiculite originated the restructured porous solids with high superficial area showing the values133, 334, 673 e 575 m2 g-1 for VacX where X = 1,2,3,4, respectively. These solids and sodic vermiculite reacted covalently with each organosilane through methoxyl groups of silane and the hydroxyl surface of matrices. Independently of solid, it was observed that the lixiviation favored the reactivity of activated matrices compared with sodic vermiculite, showing the Vac3 as more reactive comparing with others solids. All modified solids presented high nitrogen content showing the values of 6,31 %. The set of modified vermiculites containing aminepropyl group was applied as adsorbent for divalent cations as copper and nickel in aqueous solution. These solid showed highest affinity for Ni2+ than Cu2+ ions as illustrated by Nf values of 2,97 and 1,23 mmol g-1, respectively. Clay porous solids obtained of leaching treatment of vermiculite are potential substrates for grafting of silanes showing important applications as adsorbents for contaminant species as heavy metals.