Agricultural by-products as granular activated carbons for adsorbing dissolved metals and organics

Johns, Mitchell M.; Marshall, Wayne E.; Toles, Christopher A.

doi:10.1002/(sici)1097-4660(199802)71:2<131::aid-jctb821>3.0.co;2-k

Cited by 200 publications

(95 citation statements)

References 6 publications

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“…The copper solutions used in the equilibrium experiments were prepared with deionized water and CuSO 4 •5H 2 O (Biotec). The analytic curve was obtained with Titrisol Merck solution.…”

Section: Methodsmentioning

confidence: 99%

“…[3][4][5] Each method has merits and limitations. Adsorption processes are very versatile and efficient, and have received considerable attention in recent years.…”

Section: Introductionmentioning

confidence: 93%

“…Washing with NaOH solutions effectively dissolves the soluble residues generated during oxidation; however, Na + ions cannot be completely eliminated during the thermal treatment and can remain in the micropores. 17 In contrast, the use of NH 4 OH under reflux ensures that only H + and OH -ions occupy the surface acidic and basic sites after rinsing with water and drying at 100 °C.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of copper adsorption on oxidized activated carbon

Mesquita¹,

Martelli²,

Gorgulho³

2006

J. Braz. Chem. Soc.

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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.

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“…The copper solutions used in the equilibrium experiments were prepared with deionized water and CuSO 4 •5H 2 O (Biotec). The analytic curve was obtained with Titrisol Merck solution.…”

Section: Methodsmentioning

confidence: 99%

“…[3][4][5] Each method has merits and limitations. Adsorption processes are very versatile and efficient, and have received considerable attention in recent years.…”

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of copper adsorption on oxidized activated carbon

Mesquita¹,

Martelli²,

Gorgulho³

2006

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

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“…The adsorption is greatest for the carboxylic functionalized tubes, but is also significant for asprepared tubes and for activated carbon as a high-surface-area reference material. Oxygen containing surface functional groups are likely sites for cation adsorption [44,45]. Figure 12 explores the effect of wash medium composition on the removal of bioavailable iron from SWCNTs.…”

Section: Measurement Origin and Removal Of Bioavailable Ironmentioning

confidence: 99%

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

Liu

Guo

Morris

et al. 2008

Carbon

124

110

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There is substantial evidence for toxicity and/or carcinogenicity upon inhalation of pure transition metals in fine particulate form. Carbon nanotube catalyst residues may trigger similar metal-mediated toxicity, but only if the metal is bioavailable and not fully encapsulated within fluid-protective carbon shells. Recent studies have documented the presence of bioavailable iron and nickel in a variety of commercial as-produced and vendor "purified" nanotubes, and the present article examines techniques to avoid or remove this bioavailable metal. First, data are presented on the mechanisms potentially responsible for free metal in "purified" samples, including kinetic limitations during metal dissolution, the re-deposition or adsorption of metal on nanotube outer surfaces, and carbon shell damage during last-step oxidation or one-pot purification. Optimized acid treatment protocols are presented for targeting the free metal, considering the effects of acid strength, composition, time, and conditions for post-treatment water washing. Finally, after optimized acid treatment, it is shown that the remaining, non-bioavailable (encapsulated) metal persists in a stable and biologically unavailable form up to two months in an in vitro biopersistence assay, suggesting that simple removal of bioavailable (free) metal is a promising strategy for reducing nanotube health risks.

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“…One of most common toxic metals found in waters waste is leas, which is toxic even at a trace level (Johns 1998). In Figure 1 a diagram of lead species in aqueous solution as a function of pH, is shown.…”

Section: Introductionmentioning

confidence: 99%

Pb2+ adsorption from aqueous solutions on activated carbons obtained from lignocellulosic residues

Giraldo

Moreno–Piraján

2008

Braz. J. Chem. Eng.

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-Activated carbons obtained from cane sugar bagasse (ACB), African palm pit (ACP) and sawdust (ACS) were prepared through an impregnated with HNO 3 and thermal treatment in an atmosphere in N 2 /steam water at 1173 K. Adsorption isotherms of N 2 at 77 K and of CO 2 at 273 K were determined for the activated carbons for which surface area and pore volume values were from 868 to 1100 m 2 g -1 and from 0.27 to 0.55cm 3 g -1 , respectively. These results were correlated, with the ones obtained for adsorption the adsorption isotherms of Pb 2+ in aqueous solutions. Impregnation of the lignocellulosic materials with nitric acid produced acid-type activated carbons with total acid site contents between 4.13 and 6.93 mmol g -1 and pH at the point of zero charge values between 2.7 and 4.1, which were within range of the adsorption, at different pH values, since they determined, the surface charge of the activated carbons. Adsorption isotherms of Pb 2+ at different pH values (2-8) at 298 K were determined. The ion adsorption capacity on ACB, ACP and ACS were 13.7, 15.2 and 17.5 mg.g -1 , respectively. Experimental data were fitted to the Langmuir and Freundlich models and all cases the former fit better. The highest values for the quantity adsorbed on the monolayer, qm, were at pH 4, whereas the surface, charge of activated carbons was negative and the lead species mainly present was Pb 2+ . For higher pHs, the quantity of Pb 2+ adsorbed decreased, and this had an important effect on adsorption, the surface characteristics of the solids and the hydroxilated lead species that were formed in the system.

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Agricultural by-products as granular activated carbons for adsorbing dissolved metals and organics

Cited by 200 publications

References 6 publications

Characterization of copper adsorption on oxidized activated carbon

Characterization of copper adsorption on oxidized activated carbon

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

Pb2+ adsorption from aqueous solutions on activated carbons obtained from lignocellulosic residues

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