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Title: Adsorption of red azo dyes on multi-walled carbon nanotubes and activated carbon : a thermodynamic study.
Authors: Ferreira, Guilherme Max Dias
Ferreira, Gabriel Max Dias
Hespanhol, Maria C.
Rezende, Jaqueline de Paula
Pires, Ana Clarissa dos Santos
Gurgel, Leandro Vinícius Alves
Silva, Luis Henrique Mendes da
Issue Date: 2017
Citation: FERREIRA, G. M. D. et al. Adsorption of red azo dyes on multi-walled carbon nanotubes and activated carbon: a thermodynamic study. Colloids And Surfaces A-Physicochemical And Engineering Aspects, v. 529, p. 531-540, set. 2017. Disponível em: <>. Acesso em: 15 set. 2017.
Abstract: Carbonaceous materials have been extensively studied as highly efficient adsorbents for the removal of dyes from wastewater. However, investigations of thermodynamic aspects of the interactions between these materials and dyes remain scarce. This paper describes the thermodynamics of the interactions between the Ponceau 4R (PR), Congo Red (CR), and Allura Red (AR) dyes and multi-walled carbon nanotubes (MWCNTs). The interactions between the dyes and activated carbon (AC) were also evaluated for comparison. The investigation used a combination of adsorption isotherms and isothermal titration nanocalorimetry (ITC) measurements, and a thermodynamic approach provided full characterization of the adsorption process. For both MWCNT and AC, the amount of adsorbed dye (ΓD) increased in the order ΓD (PR) < ΓD (AR) < ΓD (CR), and the adsorption capacity normalized by the adsorbent specific area was up to 5.6 times higher for MWCNT. The maximum amount adsorbed (ΓD,max) reached values of up to 2.00 μmol m−2 for CR adsorption on MWCNT. For both adsorbents, the process of dye adsorption was enthalpically driven and entropically unfavorable. All the thermodynamic parameters depended on the surface coverage and the structures of both dye and adsorbent. The adsorption enthalpy change (ΔadsH) and entropy change (TΔadsSref) values were higher than −137.0 kJ mol−1 and −114.2 kJ mol−1, respectively. In addition to the structural differences between MWCNT and AC, the ITC data suggested that the adsorption sites are heterogeneous and that the dyes preferentially adsorb on the more hydrophilic sites on the adsorbent surfaces.
ISSN: 0927-7757
metadata.dc.rights.license: O periódico Colloids and Surfaces A: Physicochemical and Engineering Aspects concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 4211380272452.
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