Abstract:
In this study, Aloe Vera biomass-based adsorbent was developed for the adsorptive
removal of pharmaceutical wastes from contaminated water. Adsorbent was prepared
from the stem of Aloe vera by chemical (H
3PO4
and NaOH) activation methods. Known
amount of H
3PO4
treated adsorbent was used for batch adsorption experiments to
evaluate the removal efficiency of the adsorbent. Batch adsorption experiments were
carried out at varying amount of adsorbent, pH, contact time and temperature. The
adsorbent was signalized by different analytical instruments such as Fourier Transform
Infrared (FT-IR), thermo gravimetric analysis (TGA/DTG) and X-ray diffraction (XRD).
Fourier Transform Infrared Technique (FT-IR) analysis showed the presence of carboxyl,
and hydroxyl, amine functional groups on the adsorbent surface responsible for
adsorptive active sites. The thermo gravimetric analysis (TGA) curve showed that the
mass loss in the drying stage were 8.63 and 7.56% for air dried and treated adsorbent
respectively. XRD analysis also showed that untreated and acid treated adsorbents
expressed alike characteristic diffraction peaks at2θ values of 15.4
o
and 22.4
o
, which can
be designated to some crystalline cellulose. The peak intensity was increased after strong
acid treatment due to elimination of amorphous compounds. The prepared adsorbent
reveals the highest removal efficiency of 91.92% atpH values of 5.8. This pH
corresponds to the Pzc value of the prepared adsorbent. Beyond Pzc of the adsorbent
percent removal was decreased due to electrostatic repulsion between negatively charged
amoxicillin molecule and adsorbent surface. It was also remarked that removal efficiency
of the adsorbent decreases with increasing temperature suggesting adsorption of
amoxicillin over activated Aloevera is an exothermic process. In such case the highest
removal efficiency of 91.92% was recorded at the operating temperature of 30 ºC, pH of
5.8 adsorbent dose of 1g, and contact time of 30 min. Fitting the experimental data to
different kinetics and isotherms models indicated that the experimental data were well
fitted by the pseudo second order kinetic (R
2
=0.999) and Freundlich isotherm (R
2
=0.998)
models, respectively. The calculated thermodynamic parameters were indicated that the
adsorption process was exothermic (ΔH<0) and spontaneous (ΔG<0) in nature.
Key words: pharmaceutical; amoxicillin; adsorption; aloe vera