Adsorption and removal of Acid orange 7 using industrial essential oil solid by-products of melissa (Melissa officinalis) and yarrow (Achillea millefolium)

Melissa (M) and yarrow (Y) essential oil industry residual biomass was used for decontamination of Acid Orange 7 (AO 7) in model system. Both residues were rich in dietary fibers (DF): the amount of total DF determined for M and Y were 75.26±0.98% and 80.39±1.37%, respectively and the soluble DF were 4.59±0.57% and 5.04±0.43%, respectively. The adsorption process reached equilibrium at the 10th min (1 g M or Y, 20 mL dye water solution (1 mg.mL-1, pH 3.63). The adsorbed amount of AO 7 for M was 19.39±0.12 mg.mL-1 (96.95% efficiency) and for Y: 19.04±0.24 mg.mL-1 (95.20% efficiency). The lower pH favored the decontamination: for M at pH 1.21, the efficiency was 98.70%, and for Y at pH 3.63: 98.55%. Pretreatment of the M and Y residues with 0.1 N HCl led to increase of the adsorption capacity. Both residues compared with three well known adsorbents - aluminum oxide, chromatographic silica gel and activated carbon, showed almost the same efficiency of removal as activated carbon. These results suggested that the M and Y by-products could be successfully employed as renewable and readily available adsorbents for decontamination of water systems containing AO 7.