Silica-alumina-niobia (SiO2/Al2O3/Nb2O5) matrix obtained by the sol-gel processing method: new material for online extraction of zinc ions

Abstract

No presente trabalho foi avaliado um novo material como adsorvente, SiO 2 /Al 2 O 3 /Nb 2 O 5 (designado SiAlNb), empregado na determinação e pré-concentração online de Zn 2+ por um método espectrofotométrico por injeção em fluxo. O método de pré-concentração é baseado na adsorção de Zn 2+ em meio alcalino (pH 9,0) sobre a superfície de SiAlNb. A etapa de eluição é realizada usando solução de HNO 3 e é seguida da reação dos íons Zn , respectivamente. De acordo com o modelo linear de Langmuir, a capacidade máxima de adsorção foi de 7,0 mg de Zn 2+ por grama de SiAlNb. O método proposto foi aplicado com sucesso na determinação de Zn 2+ em amostras de água (lago, mineral e torneira) e material certificado de referência (TORT-2 Lobster Hepatopancreas).In the present work, a new material, SiO 2 /Al 2 O 3 /Nb 2 O 5 (designated as SiAlNb), was evaluated as an adsorbent in a flow injection spectrophotometric method for online preconcentration and determination of trace amounts of Zn 2+ ions. The preconcentration method is based on Zn 2+ adsorption onto the surface of SiAlNb in alkaline medium (pH 9.0). The elution step is carried out using HNO 3 solution, followed by reaction of the Zn 2+ ions with 1-(2-piridylazo)-2-naphtol (pan) in ammoniacal buffer solution (pH 9.3) containing of SiAlNb. The proposed method was successfully applied to the Zn 2+ determination in water samples (lake, mineral, tap) and certified reference material (TORT-2 Lobster Hepatopancreas).

Development and application of graphite-SiO 2 /Al 2 O 3 /Nb 2 O 5 -methylene blue (GRP-SiAlNb-MB) composite for electrochemical determination of dopamine

“…Higher intense peaks in the region of 1067-1158 cm À1 , were observed, as expected for the material SiAlNb, which corresponds to the Si-O stretches in the SiAlNB matrix (Tarley et al, 2010). The band at 964 cm À1 is attributed to either the Si-OH and Si-Nb stretches, while the signals at 790, 577 and 434 cm À1 are assigned, respectively to stretching modes of Si-O-Si, Nb-O-Nb and deformation of Si-O-Si (Marco et al, 2013a,b).…”

“…Tris [hydroxymethyl] aminomethane (Trizma), 4-[2-hydroxyethyl] piperazine-1-ethanesulfonic acid (HEPES), piperazine-1,4-bis[2-ethanesulfonic acid] (PIPES), sodium hydroxide, nitric acid, acetic acid and mineral oil were acquired from Sigma-Aldrich Ò (St. Louis, MO, USA). The material SiO 2 /Al 2 O 3 /Nb 2 O 5 (designated as SiAlNb), obtained by sol-gel process, was prepared according to previously described procedure (Costa et al, 2011;Tarley et al, 2010). All other reagents were of analytical grade, and their solutions were prepared with distilled and deionized water (resistivity: >18 MX cm À1 , 25°C; Millipore Ò Milli-Q Ò purification system, Bedford, MA, USA).…”

“…Recently, our research group has reported the outstanding features of ternary mixed oxide (SiO 2 /Al 2 O 3 /Nb 2 O 5 ) to strongly adsorb DNA in the MWCNT/SiO 2 /Al 2 O 3 /Nb 2 O 5 / DNA composite for electrochemical determination of promethazine and amitriptyline as well as to preconcentrate metal ions (Marco et al, 2013a,b;Costa et al, 2011;Tarley et al, 2010). Dopamine (DA), 3,4-dihydroxyphenylethylamine, is an important phenolic compound which occurs naturally as neurotransmitter in the mammalian central nervous system.…”

Síntese de óxidos mistos SiO2 /Mn xOy para aplicação na reação de redução de O2

“…Si(OEt) 4 + xM(OR') y SiO 2 /M x O y + 4EtOH + xyR'OH O produto formado (SiO 2 /M x O y ) apresenta uma estrutura de poros que permite a imobilização de espécies eletroativas, possibilitando o desenvolvimento de novos eletrodos quimicamente modificados e novos materiais para pré-concentração de íons metálicos [5][6][7][8][9][10]. Esses óxidos mistos são também bons adsorventes para a remoção de íons metálicos de meios aquosos, em função de apresentarem sítios ácidos e grandes áreas de superfície [9].…”

Adsorption studies of Cd(II) onto Al2O3/Nb2O5 mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

“…Apart from available adsorbents, such as ion-imprinted polymers [7], carbon nanotubes [8], natural adsorbents [9], activated carbon [10] and polymeric resins [11], the development of new synthetic materials with relevant properties through variation of their chemical compositions and/or physical dimensions has currently attracted the attention of researchers around the world. An efficient solid-phase adsorbent should present a stable and insoluble porous matrix containing suitable active groups that interact with heavy metal ions, large surface area, high wettability, absence of swelling effect and high adsorption capacity [12]. In this sense, inorganic adsorbents such as the Al 2 O 3 , ZrO 2 and Nb 2 O 5 oxides show these characteristics slightly and, depending on adsorption pH, they have amphoteric properties.…”