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Removal of sulfamethoxazole from solution by raw and chemically treated walnut shells
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Resumo(s)
Purpose: The sorption of sulfamethoxazole, a frequently
detected pharmaceutical compound in the environment, onto
walnut shells was evaluated.
Methods: The sorption proprieties of the raw sorbent were chemically modified and two additional samples were
obtained, respectively HCl and NaOH treated. Scanning
electron microscopy, Fourier transform infrared spectroscopy,
X-ray photoelectron spectroscopy, and thermogravimetric
(TG/DTG) techniques were applied to investigate the
effect of the chemical treatments on the shell surface morphology
and chemistry. Sorption experiments to investigate
the pH effect on the process were carried out between pH 2
and 8.
Results: The chemical treatment did not substantially alter
the structure of the sorbent (physical and textural characteristics)
but modified the surface chemistry of the sorbent
(acid–base properties, point of zero charge—pHpzc). The
solution pH influences both the sorbent’s surface charge
and sulfamethoxazole speciation. The best removal efficiencies
were obtained for lower pH values where the neutral
and cationic sulfamethoxazole forms are present in the
solution. Langmuir and Freundlich isotherms were applied
to the experimental adsorption data for sulfamethoxazole
sorption at pH 2, 4, and 7 onto raw walnut shell. No
statistical difference was found between the two models
except for the pH 2 experimental data to which the
Freundlich model fitted better.
Conclusion: Sorption of sulfamethoxazole was found to be
highly pH dependent in the entire pH range studied and for
both raw and treated sorbent.
Descrição
Palavras-chave
Sulfamethoxazole Pharmaceutical Sorption Walnut shell Chemically modified
Contexto Educativo
Citação
Editora
Springer Verlag