Characterization of copper adsorption on oxidized activated carbon

Abstract

Esse artigo discute a adsorção de íon Cu(II) em carvão ativado oxidado com HNO 3 . As modificações introduzidas na superfície do carvão ativado (CA) foram caracterizadas por medidas de área superficial, espectroscopia de absorção no infravermelho, titulação pelo tradicional método de Boehm e titulação potenciométrica. Os dados da titulação potenciométrica foram ajustados através de um método não linear desenvolvido para determinar a concentração e distribuição do pKa dos sítios ácidos ionizáveis presentes na superfície do CA, antes e após a oxidação com HNO 3 . Os estudos de adsorção foram realizados em batelada para a faixa de concentração de 0,08 a 1,75 mmol L -1 em pH = 4,0. Os resultados mostraram que o tratamento do CA com ácido leva à diminuição na área superficial aparente e produz leves modificações na estrutura de poros. Entretanto, a oxidação influenciou fortemente a estrutura química da superfície do CA através do aumento na concentração de grupos ácidos com pKa < 6, causando assim uma melhora significativa na adsorção do íon Cu(II). A maior capacidade de adsorção do CA oxidado foi relacionada à presença de grupos ácidos com pKa < 4, revelando o importante papel destes grupos na adsorção pelo mecanismo de troca iônica. This paper discusses Cu(II) ion adsorption onto oxidized activated carbon with HNO 3 . The modifications introduced on the activated carbon (AC) surface were characterized by surface area measurement, FT-IR spectroscopy, titration by the traditional Boehm procedure, and potentiometric titration. A nonlinear method for fitting acid-base potentiometric titration data was applied to determine the concentration and pKa distributions of the ionizable acidic sites on AC, before and after HNO 3 oxidation. Adsorption studies were conducted in batch mode for the concentration range 0.08 to 1.75 mmol L -1 and pH = 4.0. Results showed that the acid treatment of AC leads to a decrease in apparent surface areas and produces slight modifications in pore structure. However, oxidation strongly influenced the AC surface chemical structures by increasing the concentration of acidic groups with pKa < 6.0, which significantly improved Cu(II) ion adsorption. The uptake enhanced for oxidized carbon was related to the presence of acidic groups with pKa lower than 4, revealing the important role of acidic groups in adsorption by ion-exchange mechanisms.

Sonication-assisted dispersion of carbon nanotubes in aqueous solutions of the anionic surfactant SDBS: The role of sonication energy

“…Prior to the measurement of N 2 adsorption, the CNTs were outgassed at 105°C for at least 24 h. The morphology of the CNT aggregates was obtained using scanning electron microscopy (SEM) (SIRION-100, Fei). The contents of the oxygen-containing acidic functional groups on the CNTs were determined using Boehm's titration method [32].…”

Effect of Chemical Oxidation on the Adsorption Properties of Cationic Dye on Activated Carbons Prepared from Locally Atropa belladonna

“…After oxidation, this band is not observed and a broadening in the intensity of band located at 1630 cm -1 is occurred. Shoulder bands at 1458-1386 cm -1 conjugated with strong band at 1630 cm -1 may be ascribed to the presence of carboxylic acid, carbonyl-carbonates and quinones, also moieties such as C=N, C=C and NH 3 in aromatic rings [5][6][7][8][9][10][11]. Finally, the presence of C-H outof-plane bending vibrations in the aromatic ring is identified by the appearance of small bands at 800-420cm -1 .…”

“…Generally, the adsorption capacity of ACs significantly depended on their surface chemistry and is largely influenced by both quantity and type of the surface functional groups. Accordingly, many studies have considerable interests in the improvement of the surface chemistry properties of ACs via chemical oxidation and reported their relations with the adsorption of dyes and heavy metals in the last two decades [3][4][5][6][7][8][9][10][11][12][13].…”

<b>Comparative study of the adsorption of cadmium and zinc on activated bone char

“…Pearson (1963) affirms that the interaction between soft species is more polarizable than hard ones, and hard acids prefer to bind to hard acids, while soft acids prefer to bind to soft bases. Mesquita, Martelli and Gorgulho (2006) proved that the surface of bovine charcoal contains phosphate group, which was considered a soft base by Huheey et al (1997). Because of this greater affinity, there will be more interactions between Cd 2+ and the charcoal surface, justifying the chemisorption and the results found.…”