Raw and treated Avokado waste to remove Bemacid Red-ETL dye from aqueous solution: kinetics and theoretical physics modeling

The raw and modified surface of agricultural waste of Avokado was investigated in the adsorption of textile dye Bemacid Red. Phosphoric Acid, sodium hydroxide, and Acetone were used to treat the adsorbent surface. Batch mode studied the effects of experimental parameters: solution pH, contact time, initial dye concentration and temperature. The fit of the kinetics data was performed by the pseudo-first and second-order models. Whereas the adsorption isotherm data was performed by the statistical physics models. The Batch results reveals that the contact time and initial concentration have a positive effect on adsorption capacity, however, the two other parameters have a negative effect. From the kinetic modeling results, it was observed that the pseudo-second order fit well the data with a height determination coefficient (0.971< R2 < 0.984). On the other side the double layer with two energies from the tested physical models proves to be the best model to explain the Bemacid Red dye adsorption mechanism (0.0991<R2<0.999 for the raw and treated Avokado). The modeling analysis indicated that dye molecules occurred via parallel orientation onto raw and NaOH-treated Avokado at 20 °C and via non-parallel orientation at temperature greater than 20 °C. In summary the NaOH-treated Avokado gives an important affinity towards Bemacid Red dye and can be classified as a low and efficient adsorbent.