Abstract
Four different types of multi-walled carbon nanotubes (MWCNTs) were used and compared for the treatment of benzoic acid contaminated water. The types of nanotubes used were: (1) non-purified (CNTsUP), as made; (2) purified (CNTsP), not containing the catalyst; (3) oxidized (CNTsOX), characterized by the presence of groups such as, –COOH; (4) calcined (CNTs900), with elimination of interactions between nanotubes. In addition, activated carbon was also used to allow for later comparison. The adsorption tests were conducted on an aqueous solution of benzoic acid at concentration of 20 mg/L, as a model of carboxylated aromatic compounds. After the adsorption tests, the residual benzoic acid concentrations were measured by UV-visible spectrometry, while the carbon nanotubes were characterized by TG and DTA thermal analyses and electron microscopy (SEM). The results show that the type of nanotubes thermally treated at 900 °C has the best performances in terms of adsorption rate and amounts of collected acid, even if compared with the performance of activated carbons.
Highlights
Non-purified (CNTsUP ), purified (CNTsP ) and oxidized (CNTsOX ) carbon nanotubes were characterized in previous work, to which reference should be made to investigate their characteristics [39]
The purification treatment leads to a slight lowering of efficiency compared with non-purified carbon nanotubes
The oxidation and calcination pretreatments at 900 ◦ C proved to be decisive for increasing the adsorption capacity
Summary
Carbon nanotubes can be advantageously used above all in the treatment of water contaminated by pollutants, thanks to their extraordinary adsorbing properties [5,6,7,8,9]
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