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. 2022 Apr 14;12(4):585.
doi: 10.3390/life12040585.

Kinetic, Isotherm and Thermodynamic Aspects of Zn2+ Biosorption by Spirulina platensis: Optimization of Process Variables by Response Surface Methodology

Nada K Alharbi  1 , Mayasar I Al-Zaban  1 , Fawziah M Albarakaty  2 , Sayed F Abdelwahab  3 , Sedky H A Hassan  4   5 , Mustafa A Fawzy  6
Affiliations

Kinetic, Isotherm and Thermodynamic Aspects of Zn2+ Biosorption by Spirulina platensis: Optimization of Process Variables by Response Surface Methodology

Nada K Alharbi et al. Life (Basel). .

Abstract

The aim of this study was to assess the efficiency of Spirulina platensis for removing Zn2+ ions from the aqueous solutions. The optimized conditions of 4.48 g/L algal dose, pH of 6.62 and initial zinc concentration of 29.72 mg/L obtained by response surface methodology were employed for Zn2+ biosorption by S. platensis and up to 97.90% Zn2+ was removed, showing that there is a favorable harmony between the experimental data and model predictions. Different kinetic and equilibrium models were used to characterize the biosorption manner of Spirulina as a biosorbent. The kinetic manner of Zn2+ biosorption was well characterized by the pseudo-second-order, implying that the adsorption process is chemical in nature. The Langmuir and Dubinin-Radushkevich isotherm models were best fit to the equilibrium data. The maximum adsorption capacity of the Langmuir monolayer was 50.7 mg/g. Furthermore, the thermodynamic analysis revealed that Zn2+ biosorption was endothermic, spontaneous and feasible. As a result of biosorption process, FTIR, SEM, and EDX investigations indicated noticeable alterations in the algal biomass's properties. Therefore, the dried Spirulina biomass has been shown to be cost-effective and efficient for removing the heavy metals, particularly zinc ions from wastewater, and the method is practicable, and environmentally acceptable.

Keywords: Spirulina platensis; biosorption; equilibrium isotherm models; pseudo-second order; response surface methodology; zinc.

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Conflict of interest statement

There were no conflicts of interest from the authors.

Figures

Figure 1
Figure 1
FT-IR spectra of algal biomass (A) before, and (B) after Zn2+ ions biosorption.
Figure 2
Figure 2
SEM images of algal biomass (A) before, and (B) after Zn2+ ions biosorption.
Figure 3
Figure 3
EDX image of algal biomass (A) before, and (B) after Zn2+ ions biosorption.
Figure 4
Figure 4
Effect of (A) Contact time, and (B) Initial Zn2+ ions concentration on removal efficiency.
Figure 5
Figure 5
Response surface plots showing the influence of interactive parameters on Zn2+ ions removal efficiency (A) algal dosage and pH, (B) algal dosage and initial Zn2+ concentration, and (C) pH and initial Zn2+ concentration.
Figure 6
Figure 6
Different kinetic model plots (A) Pseudo-first order, (B) Pseudo-second order, and (C) Intraparticle diffusion model.
Figure 7
Figure 7
Different isotherm model plots (A) Langmuir, (B) Freundlich, and (C) Dubinin–Radushkevick model.
Figure 8
Figure 8
(A) Effect of temperature on the biosorption process, and (B) plot of lnKc against 1/T for the determination of thermodynamic parameters.
See this image and copyright information in PMC

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