This work proposes the use of agro-industrial wastes, specifically peanut hull (HP) and orange peel (OP), as adsorbents for dyes, such as Remazol Golden Yellow RNL-150% (RYG), Gray Reactive BF-2R (RG) and Reactive Turquoise Q-G125 (RT). Characterization by Brunauer-Emmett-Teller indicates that the adsorbents are mesoporous, with pHzpc values of 5.0 for HP and 4.0 for OP. Fourier transform-infrared spectroscopy identified carbonyl and sulphonic groups. The initial pH of the best-adsorbing solution of the three colours was 2.0. Increasing the concentration of the adsorbent promoted an increase in the percentage of removal until saturation of the adsorbent. In a factorial design, the largest value of q was obtained with 0.25 g of the adsorbent, with a particle size of < 0.4 mm and a stirring speed of 300 rpm. Such conditions were used in kinetic studies and studies of adsorption equilibrium. The evolution kinetics were rapid in the first few minutes, and after 180 min the system reached equilibrium. The kinetic model that best fit the experimental data to a 95% confidence level for the F test was the pseudo-second-order model for RYG/HP, RG/OP and RT/OP. There was no significant difference between the kinetic models as evaluated by the F test for RYG/OP, RG/HP and RT/HP. The experimental results indicated favourable dye adsorption characteristics for the adsorbents studied. The results of the F test showed that for RYG and RG, there was no significant difference between the two evaluated models. This study suggests that HP and OP are viable alternatives for the treatment of effluents containing RYG, RG and RT dyes.
The MCM-41 mesoporous molecular sieves have attracted a great deal of interest due to their application in adsorption processes, like in the removal of naphthenic acids, which are directly responsible for acidity and corrosiveness of petroleum. The objective of this work is to explore the synthesis, characterization, and application of Sr-MCM-41 in removing naphthenic acids from a model mixture of aviation kerosene (jet fuel) by adsorption. The adsorbent was characterized and a factorial design was used to determine the best operating conditions. The characterization results indicated that the incorporation of strontium did not compromise the mesoporous structure, and that the material showed a good degree of organization. The factorial design indicated that the highest adsorption capacity was obtained for an acid concentration of 7wt.%, an adsorbent amount of 0.01g, and a stirring speed of 420rpm. This study demonstrates the potential of this adsorbent for the removal of the naphthenic acids that are present in jet fuel.
A B S T R A C TAdsorption of the reactive gray BF-2R dye from an aqueous solution using orange peel as the adsorbent was investigated by the batch method. Experiments characterizing the chemical and physical properties of the adsorbent found that orange peel is a microporous material with a pH zpc 3.9 and containing carboxylic and sulfonic groups. The greatest adsorption capacity was obtained using a 2 3 factorial design for 0.25 g of adsorbent, particle size < 0.419 mm and at 300 rpm. The pseudo-second-order model provided the best fit of the experimental data. The Weber-Morris model indicated that two or more mechanisms control the process. Statistical analysis of the equilibrium studies indicated that there was not a significant difference between the Langmuir and the Fritz-Schlunder models according to an F-test. The results showed that orange peel can remove the reactive gray BF-2R dye.
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