Removal Of Contaminants From Aqueous Solutions Using Hop (Humulus Lupulus L.) Agricultural By-Products

Abstract

Agricultural wastes can be used as an alternative to the existing sorbents for the removal of metals or synthetic dyes from contaminated liquids. In this work, the fine powdered biomass of the hop (Humulus lupulus L.) variety Osvald's clone 72 and variety Bohemie as a sorbent for the removal of Cd from aqueous solutions of CdCl₂ spiked with radionuclide ¹⁰⁹Cd and synthetic dyes thioflavine T (ThT) or methylene blue (MB) from single dye solutions under conditions of batch systems was used. The maximum sorption capacity Q = 264 µmol Cd/g (d.w.) was found in the case of the leaf biomass of hop (H. lupulus L.) variety Osvald's clone 72 at the initial concentration of CdCl₂ 10,000 µmol/dm³, whereby the sorption capacity decreased in the order Q_leaves : Q_stems : Q_roots = 1.0 : 0.8 : 0.7. The sorbed amount of Cd was removed from the hop biomass with the following increasing desorption efficiency of the extraction reagents: deionised H₂O << 0.1 mol/dm³ HCl ≤ 0.1 mol/dm³ EDTA-Na₂. Similarly as in the case of Cd sorption, the kinetics of ThT and MB sorption by the leaf biomass of the hop (H. lupulus L.) variety Bohemie were also showed as two-phase processes. The maximum sorption of ThT approx. Q = 19 mg/g (d.w.) and MB approx. Q = 70 mg/g (d.w.) were found within the range of the initial values of pH 4 – 7. The sorption of both dyes by the leaf biomass from single dye solutions decreased with increasing biomass concentration and on the other hand increased with increasing the initial concentrations of ThT or MB. The process of ThT and MB sorption was better described by the Langmuir model than the Freundlich model of sorption isotherm. From the obtained values of Q_max, it was found that in the case of MB the dried leaf biomass showed more than 2-times higher sorption capacity (Q_max = 184 mg/g; d.w.) in comparison with the value predicted for ThT. Obtained results suggest that dried plant biomass of hop (H. lupulus L.) as agricultural by-products can be used as a potential sorbent for both types of studied contaminants.