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. 2019 Mar 4;9(1):3356.
doi: 10.1038/s41598-019-39945-1.

Adsorption of Methylene Blue and Pb2+ by using acid-activated Posidonia oceanica waste

Randa R Elmorsi  1 , Shaimaa T El-Wakeel  2 , Waleed A Shehab El-Dein  3 , Hesham R Lotfy  4 , Wafaa E Rashwan  5 , Mohammed Nagah  6 , Seham A Shaaban  7 , Sohair A Sayed Ahmed  5 , Iman Y El-Sherif  2 , Khaled S Abou-El-Sherbini  8
Affiliations

Adsorption of Methylene Blue and Pb2+ by using acid-activated Posidonia oceanica waste

Randa R Elmorsi et al. Sci Rep. .

Abstract

Dead leaves of seagrass Posidonia oceanica were activated by using one mol L-1 acetic acid and used as an eco-adsorbent for the removal of methylene blue (MB) and Pb2+ from aqueous solutions. The seagrass was characterized by chemical and physical measurements that confirmed the acid-activation of seagrass. The favourable conditions for MB and Pb2+ adsorption onto the activated seagrass (SGa) were determined to be a pH range of 2-12 and ≥6, an adsorbent dosage of 3.0 and 0.5 g L-1, respectively, and a shaking time of 30 min, which are suitable for a wide range of wastewaters. The equilibrium data were analysed using the Langmuir, Freundlich and Dubinin-Raduskavich-Kaganer (DRK) adsorption isotherm models. The Freundlich and DRK models best describe the adsorption processes of MB and Pb2+, on SGa with capacities of 2681.9 and 631.13 mg g-1, respectively. The adsorption isotherm fitting and thermodynamic studies suggest that the adsorption mechanism of MB may combine electrostatic and physical multilayer adsorption processes, in which MB may be present as monomers as well as dimers and trimers which were confirmed from UV spectroscopy whereas Pb2+ is chemically adsorbed onto SGa. The pseudo-2nd-order kinetic model was utilized to investigate the kinetics of adsorption processes. The removal process was successfully applied for MB-spiked brackish waste water from Manzala Lake, Egypt, with removal efficiencies of 91.5-99.9%.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
TGA (a) and pH-metric titration versus 0.0073 mol L−1 KOH (b) of SG before and after acid treatment of SGp and SGa.
Figure 2
Figure 2
FTIR absorption spectra of SGa, SGp, SGa-2 MB and SGa-100 MB.
Figure 3
Figure 3
Effect of solution pH on the percent removal efficiency of MB or Pb2+ onto SGa.
Figure 4
Figure 4
The effect of shaking time on the removal efficiency (%) of MB or Pb2+ applying initial pH values 5.8 and 5.3 and adsorbent dosage of 5 and 0.5 g L−1, respectively, on the adsorbents SGa or SGp.
Figure 5
Figure 5
Plot of t/qt versus t for the application of pseudo 2nd order kinetic model. Ci of MB and Pb2+ are 200 and 20 mg L−1, SGa adsorbent dosage of 5 and 0.5 g L−1, and initial pH values 5.8 and 5.3, respectively.
Figure 6
Figure 6
Effect of dosage on the removal efficiency of MB and Pb2+ by SGa.
Figure 7
Figure 7
Adsorption isotherms of MB or Pb2+ onto SGa (a) and their linear fitting to Langmuir (b), Freundlich (c) and DRK (d) adsorption models. ε (adsorption potential) = RTln(11+Ce).
Figure 8
Figure 8
Effect of MB concentration on its UV absorption spectra in aqueous solutions.
Figure 9
Figure 9
Effect of temperature on ∆Gads of the adsorption of MB on SGa.
Figure 10
Figure 10
Thermal analysis of SGa loaded with MB (6.44 mEq g−1).
See this image and copyright information in PMC

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