Abstract
The multi-walled carbon nanotubes obtained by catalytic chemical vapour deposition synthesis are used as a solid matrix for the adsorption of the Reactive Blue 116 dye and the Reactive Yellow 81 dye from aqueous solutions at different pH values. The batch tests carried out allowed us to investigate the different effects of pH (2, 4, 7, 9 and 12) and of the contact time (2.5 ÷ 240 min) used. The liquid phase was analysed using ultraviolet-visible spectrophotometry in order to characterise the adsorption kinetics, the transport mechanisms and the adsorption isotherms. The adsorption of the optimal dye was observed at pH 2 and 12. The pseudo-first order kinetic model provided the best approximation of experimental data compared to the pseudo-second order kinetic model. The predominant transport mechanism investigated with the Weber and Morris method was molecular diffusion for both Reactive Yellow 81 and Reactive Blue 116, and the equilibrium data were better adapted to the Langmuir isothermal model. The maximum adsorption capacity for Reactive Yellow 81 and Reactive Blue 116 occurred with values of 33.859 mg g−1 and 32.968 mg g−1, respectively.
Highlights
Of all the water volume present on the Earth’s surface, only 0.62% is directly usable by man for vital purposes [1], and in the case of contamination phenomena, the percentage is further reduced.This problem, is found in different territorial contexts; for example, textile wastewater is spilled onto the soil without appropriate treatments, causing serious environmental damage that still persists [2]
The first sample, subtitled “Basis”, represents the stock solution, which was stirred for 24 h without multi-walled carbon nanotubes (MWCNTs) in order to demonstrate the absence of the abatement, which could be caused by the addition of the compounds used for changing the pH
The mass transport was analysed through the Weber and Morris method, concerning molecular diffusion phenomena for the dyes Reactive Blue 116 (RB-116) and Reactive Yellow 81 (RY-81)
Summary
Of all the water volume present on the Earth’s surface, only 0.62% is directly usable by man for vital purposes [1], and in the case of contamination phenomena, the percentage is further reduced. This problem, is found in different territorial contexts; for example, textile wastewater is spilled onto the soil without appropriate treatments, causing serious environmental damage that still persists [2]. The phenomenon of water contamination is an ever-present problem that pushes research to find the most varied solutions These problems can only be addressed through the study and enhancement of different sectors that have in common the purpose of eliminating or reducing the spillage of pollutants into the environment.
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