Activated carbons (ACs) with well–developed microstructure and high microporosity were obtained from biomass by potassium hydroxide activation. The preparation process consisted in producing carbon materials in the ratios of activating agent to raw material 70:30, 50:50, 30:70 and 25:75 (w/w) characterized by thermal analysis coupled to spectroscopy (TG–DTA / FT–IR), scanning electron microscopy (SEM), N2 adsorption isotherms at –196 ºC and activation isotherm at 500 and 600 ºC for 3.0 h. Specific surface areas (SBET) within 728 and 1712 m2 g-1 and (Smic) within 1054 and 1923 m2 g-1 were obtained, while the micropores surface area was calculated using the Dubinin-Astakhov (DA) equation and the pore size distribution calculated from density functional theory (DFT) was found to be in the range 1.09 – 1.77 nm. Adsorption isotherms were fitted using Langmuir and Freundlich non–linear models and the adsorption capacity determined for methylene blue dye was between 27.13 and 459.20 mg g-1.

The use of dyes in the commercialization of fuel is usually associated with protection of the source and destination. It is used as "markers" to identify and guarantee the identity of the specific product of a particular manufacturer to discourage theft, tampering and disclosure of the quality of solvent or fuel. This work presents a critical analysis on the state of the art about the available analytical methods for identification and quantification of dyes used as markers of solvents and fuels, as well as evaluation of the physical-chemical staining and laws surrounding their use and commercialization.

An analytical method based on high-performance liquid chromatography with electrochemical detection has been developed and applied to the determination of Solvent blue 14 (SA-14) and Solvent red 24 (SV-24) in fuel samples. The dyes were better separated on C18 column, using a mobile phase composed of acetonitrile and ammonium acetate (90:10, v/v). Detection was carried out at an oxidation potential of +0.85V. The detector response was linear at concentration range of 7.50×10-8 - 1.50×10-6 mol L-1 (r = 0.997) for SA-14 and SV-24, respectively. The method was used to quantify these dyes in fuels samples with satisfactory accuracy and precision.