Preparação de argilas organofílicas usando diferentes concentrações de sal quaternário de amônio.

INTRODUÇÃO

As esmectitas são largamente usadas numa gama de aplicações devido a sua capacidade de troca de cátions, FDSDFLGDGHGHH[SDQVmRDOWDiUHDHVSHFt¿FDHSRUSRVVXtUHP fortes capacidades de adsorção/absorção [1-4]. Dentro das argilas que tem a capacidade de expandir, a mais comum esmectita dioctaédrica é a montmorilonita.

A montmorilonita possui uma carga negativa na superfície TXHSRGHVHUVXEVWLWXtGDLVRPRU¿FDPHQWH(ODpQDWXUDOPHQWH balanceada pelos cátions inorgânicos trocáveis, tais como Na+ e Ca+2_{, que são geralmente hidratados na presença de água. A} hidratação dos cátions trocáveis e a natureza polar dos grupos silanois (Si-O) conferem uma natureza hidrofílica a superfície da montmorilonita, o que torna essas argilas naturais solventes LQH¿FD]HVSDUDFRPSRVWRVRUJkQLFRV>@

Como os íons metais são substituídos por cátions surfactantes, tais como íons alquilamônio, a natureza da

Preparação de argilas organofílicas usando diferentes

concentrações de sal quaternário de amônio

(Preparation of organophilic clays using different

concentrations of quaternary ammonium salt)

A. A. Silva

_{, F. R. Valenzuela-Diaz}

_{, G. S. V. Martins}

_{, M. G. F. Rodrigues}

1

_{Centro de Ciências e Tecnologia - CCT, Universidade Federal de Campina Grande - UFCG}

Av. Aprígio Veloso 882, Bodocongó, Campina Grande, PB 58109-970

2

_{Departamento de Engenharia Metalúrgica e Materiais, Escola Politécnica da Universidade de S. Paulo}

meiry@deq.ufcg.edu.br

Resumo

(VWXGRXVHDSUHSDUDomRGHDUJLODVRUJDQRItOLFDVFRPRVDOFORUHWRKH[DGHFLOWULPHWLODP{QLR+'70$&ODGLIHUHQWHVFRQFHQWUDo}HV $VDPRVWUDVVHPHFRPWUDWDPHQWRFRPRVDO+'70$&OIRUDPFDUDFWHUL]DGDVSRUGLIUDomRGHUDLRV;DQiOLVHWpUPLFDGLIHUHQFLDO DQiOLVH WHUPRJUDYLPpWULFD PLFURVFRSLD HOHWU{QLFD GH YDUUHGXUD H HVSHFWURVFRSLD GH UDLRV ; SRU HQHUJLD GLVSHUVLYD (QVDLRV GH GLIUDomRGHUDLRV;PRVWUDUDPTXHDGLVWkQFLDEDVDOGDDUJLOD³&KRFRODWH´DQWHVGDPRGL¿FDomRHUDHDSyVWUDWDPHQWRFRPR VDO+'70$&OPHTJpHFRPRVDO+'70$&OPHTJ2SURFHVVRGHLQWHUFDODomRQmRFDXVRXPRGL¿FDo}HV VXEVWDQFLDLVQDPRUIRORJLDGDVSDUWtFXODVGDDUJLOD³&KRFRODWH´

Palavras-chave:DUJLODDUJLODRUJDQR¿OLFD+'70$&O

Abstract

The preparation of organophilic clays using the salt hexadecyltrimethyl ammonium chloride (HDTMA-Cl) at different concentrations was studied. The samples before and after treatment with HDTMA-Cl salt were characterized by X-ray diffraction, differential thermal analysis, thermogravimetric analysis, scanning electron microscopy and X-ray energy dispersive spectroscopy. X-ray GLIIUDFWLRQDQDO\VLVVKRZWKDWWKHEDVDOVSDFLQJRIWKHFOD\³&KRFRODWH´EHIRUHWKHPRGL¿FDWLRQZDVDQGDIWHUWUHDWPHQWZLWK WKH+'70$&OVDOWPHTJDQGZLWK+'70$&/PHTJ7KHLQWHUFDODWLRQSURFHVVGLGQRWFDXVHVXEVWDQWLDO PRGL¿FDWLRQVLQWKHPRUSKRORJ\RISDUWLFOHVRIWKH³&KRFRODWH´FOD\

Keywords: clay, organoclays, HDTMA-Cl.

VXSHUItFLHpGUDVWLFDPHQWHPRGL¿FDGD(QTXDQWRDVDUJLODV QDWXUDLVVmRJHUDOPHQWHKLGURItOLFDVDVDUJLODVPRGL¿FDGDV FRP RV VXUIDFWDQWHV RUJDQRItOLFDV VmR KLGURIyELFDV RX RUJDQRItOLFDV>@$VDUJLODVRUJDQRItOLFDVVmRIDFLOPHQWH solvatadas e expandidas por vários solventes orgânicos, o que torna as argilas organofílicas atrativas para adsorventes seletivos, agentes gelatinosos de sistemas orgânicos, etc.

intercalação dos cátions quaternários de amônio entre os espaços interlamelares dos argilominerais. Os autores concluem ainda, que para os solventes utilizados nesse estudo, o inchamento é inferior aos obtidos anteriormente com outras argilas do (VWDGRGD3DUDtED>@)RLIHLWRRHVWXGRVREUHDLQÀXrQFLDGD FRQFHQWUDomRGHDUJLODGHDQDVGLVSHUV}HVDTXRVDV de partida, para obtenção de argilas organofílicas e estudo de LQFKDPHQWR HP WUrV VROYHQWHV >@ R PDWHULDO REWLGR GHVWD preparação apresentou distâncias interlamelares superiores a QP)RLWDPEpPYHUL¿FDGRTXHRVPDWHULDLVTXHDSUHVHQWDUDP maiores valores de inchamento, obtidos usando concentrações LQLFLDVGHDUJLODHQWUHH

8OWLPDPHQWH DV DUJLODV RUJDQRItOLFDV YrP JDQKDQGR notoriedade por estarem sendo utilizadas na obtenção de QDQRFRPSyVLWRV EHQWRQLWDVSROtPHURV XP QRYR WLSR GH material com amplo potencial de uso, principalmente nas LQG~VWULDV DXWRPRWLYDV H GH HPEDODJHQV >@ (VWH WUDEDOKR faz parte de uma série que vem pesquisando a obtenção e caracterização de argilas organofílicas, visando seu uso na indústria petrolífera, no tratamento de substâncias FRQWDPLQDGDV H QD REWHQomR GH QDQRFRPSyVLWRV VLOLFDWR SROtPHURV /HYDQGRVH HP FRQVLGHUDomR TXH R (VWDGR GD Paraíba possui as maiores reservas brasileiras de argilas esmectíticas, este estudo foi realizado para obter e caracterizar XPDDUJLOD³&KRFRODWH´QDFLRQDOPRGL¿FDGDFRPRVDOFORUHWR KH[DGHFLOWULPHWLODP{QLR *HQDPLP &7$& YLVDQGR VXD XWLOL]DomRQXPVLVWHPDGHVHSDUDomRyOHRiJXD

EXPERIMENTAL

Utilizou-se na preparação de argilas bentoníticas RUJDQRItOLFDVDEHQWRQLWDSROLFDWL{QLFD³&KRFRODWH´IRUQHFLGD pela empresa Dolomil Ind. Ltda. na sua forma bruta, peneiradas HP SHQHLUD $%17 PP VHP PRGL¿FDomR GDV propriedades químicas. Utilizou-se o sal quaternário de amônio FRPHUFLDOEUDVLOHLURGHQRPLQDGRFORUHWRGHKH[DGHFLO7ULPHWLO DP{QLR*HQDPLP&7$&FRPGXDVUHODo}HVDUJLODVDO PHTJGHDUJLODHPHTJGHDUJLODUHVSHFWLYDPHQWH >@(VSHFL¿FDo}HVGRVDO*HQDPLP&7$&6ROXomRHP HWDQRODIyUPXODGH&GH&HGH& fornecedor Clariant.

Para a preparação da argila organofílica seguiu-se duas HWDSDV QD SULPHLUD D DUJLOD FKRFRODWH SROLFDWL{QLFD IRL WUDQVIRUPDGD SDUD D IRUPD VyGLFD XWLOL]DQGR XPD GLVSHUVmR DTXRVDFRPFRQFHQWUDomRGHHPSHVRGHDUJLODGHVDJUHJDGD e moída. Acrescentou-se à dispersão aquosa solução de FDUERQDWR GH VyGLR FRQFHQWUDGR QD SURSRUomR GH PHT J GH DUJLOD VHFD VRE DJLWDomR FRQVWDQWH H DTXHFLPHQWR DWpž&SRUPLQXWRVQDVHJXQGDHWDSDDGLFLRQRXVHD VROXomRGHVDOTXDWHUQiULRGHDP{QLR*(1$0,1&7$& DHDSyVDGLomRFRPSOHWDGRVDODJLWRXVHSRUPLQ SDUD¿OWUDomRDYiFXRHPVHJXLGD2VVyOLGRVREWLGRVIRUDP FRORFDGRV HP HVWXID D “ ž& SRU K H GHVDJUHJDGRV H SHQHLUDGRVHPSHQHLUD$%17PP

$VDPRVWUDVDSyVWUDWDPHQWRFRPRVDOTXDWHUQiULRGH DP{QLRVmRGHQRPLQDGDVGDVHJXLQWHVIRUPDDVDUJLODVTXH IRUDPWUDWDGDVFRPRVDO*HQDPLP&7$&FRPDUHODomR

PHTJGHDUJLODVmRGHQRPLQDGDVDUJLOD* indica a relação argila/sal e o G indica o sal Genamim-&7$& SRU H[HPSOR &KRFRODWH * DV WUDWDGDV FRP RVDO*HQDPLP&7$&FRPDUHODomRPHTJGH DUJLODVmRDUJLOD*SRUH[HPSOR&KRFRODWH*

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Difração de raios X (DRX) - difratômetroShimadzu ;'5 FRP UDGLDomR N_A GR FREUH FRP WHQVmR N9 FRUUHQWHP$SDVVRHPQ e tempo por passo de 1 s. 2REMHWLYRGHVWDWpFQLFDpYHUL¿FDUDH[LVWrQFLDGHPLQHUDLV DFHVVyULRVTXDUW]RIHOGVSDWRHGHDUJLORPLQHUDLV

Análise térmica (ATD/TG) - equipamento Shimadzu, com vazão de 100 mL/min de ar desde temperatura ambiente até 1000 ºC, com taxa de aquecimento 10 ºC/min. Alfa-alumina foi utilizada como material de referência. Estas WpFQLFDVSHUPLWHPDYDOLDUDWHPSHUDWXUDGHPRGLÀFDomRH GHFRPSRVLomRGRVDORUJDQRFORUDGRQRPDWHULDO

Microscopia eletrônica de varredura (MEV) - A amostra QD IRUPD GH Sy IRL ¿[DGD QR SRUWDDPRVWUD FRP ¿WD DGHVLYD GH FDUERQR H UHFREHUWD FRP XPD ¿QD FDPDGD GH RXUR QXP PHWDOL]DGRU $V PLFURJUD¿DV SDUD DQiOLVH GD PRUIRORJLD GDV DPRVWUDVIRUDPREWLGDVQRPLFURVFySLRHOHWU{QLFRGHYDUUHGXUD 3KLOLSV ;/ HTXLSDGR FRP R VLVWHPD GH HVSHFWURVFRSLD GH UDLRV;SRUHQHUJLDGLVSHUVLYD('6(VWDWpFQLFDpLQGLFDGD para o estudo da morfologia dos cristais individuais dos minerais argilosos, bem como para a análise química elementar.

RESULTADOS E DISCUSSÃO

Com a troca do sódio pelo cátion do sal quaternário HDTMA-Cl, ocorre a expansão da camada da PRQWPRULORQLWD(VWDH[SDQVmRpGHWHFWDGDSRUGLIUDomRGH

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[Figure 1: X-ray diffraction patterns of the “Chocolate” clay ZLWKRXWPRGLÀFDWLRQDQGPRGLÀHGZLWKGLIIHUHQWFRQFHQWUDWLRQVRI HDTMA-C1 salt.]

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[Figure 2: DTA (a) and TG (b) curves of the “Chocolate” clay ZLWKRXWPRGLÀFDWLRQDQGPRGLÀHGZLWKGLIIHUHQWFRQFHQWUDWLRQVRI HDTMA-C1 salt.]

)LJXUD 0LFURJUDÀDV HOHWU{QLFDV GH YDUUHGXUDV GD DUJLOD ´&KRFRODWHµVHPWUDWDPHQWR

GHVKLGUR[LOL[DomR GR DUJLORPLQHUDO 2 SLFR H[RWpUPLFR D ž&pHVWUXWXUDOFDUDFWHUtVWLFRGDGHVWUXLomRGRUHWLFXODGR cristalino. A curva de análise térmica diferencial obtida para D DUJLOD ´&KRFRODWHµ WUDWDGD FRP R VDO +'70$&O FRP FRQFHQWUDomRGHPHTJPRVWUDXPSLFRHQGRWpUPLFRQD faixa de 20 ºC a 100 o&DWULEXtGRjSHUGDGHiJXDOLYUHHXP

SLFRH[RWpUPLFRTXHRFRUUHHQWUHž&Hž&DWULEXtGRj

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>)LJXUH 6(0 PLFURJUDSKV RI WKH ´&KRFRODWHµ FOD\ PRGLÀHG with HDTMA-C1 salt, 0.8 meq/g of clay .]

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>)LJXUH 6(0 PLFURJUDSKV RI WKH ´&KRFRODWHµ FOD\ PRGLÀHG with HDTMA-C1 salt, 1.0 meq/g of clay .]

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[Figure 6: EDS microanalysis spectrum of the clay “Chocolate”. (a) without treatment, (b) with treatment with salt HDTMA-Cl in the ratio of 0,8meq/g of clay and (c) with treatment salt HDTMA-Cl in the ratio of 1,0meq/g of clay.]

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CONCLUSÕES

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AGRADECIMENTOS

Os autores deste trabalho agradecem, em especial, ao 35+$130&7SHORDX[tOLRGHEROVDGHPHVWUDGR

REFERÊNCIAS

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