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

Nada K Alharbi; Mayasar I Al-Zaban; Fawziah M Albarakaty; Sayed F Abdelwahab; Sedky H A Hassan; Mustafa A Fawzy

doi:10.3390/life12040585

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

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

Authors

Nada K Alharbi¹, Mayasar I Al-Zaban¹, Fawziah M Albarakaty², Sayed F Abdelwahab³, Sedky H A Hassan^{4

5}, Mustafa A Fawzy⁶

Affiliations

¹ Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia.
² Department of Biology, Faculty of Applied Science, Umm Al-Qura University, P.O. Box 715, Makkah Al Mukarramah 21955, Saudi Arabia.
³ Department of Pharmaceutics and Industrial Pharmacy, College of Pharmacy, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.
⁴ Department of Biology, College of Science, Sultan Qaboos University, Muscat 123, Oman.
⁵ Department of Botany and Microbiology, Faculty of Science, New Valley University, El-Kharga 72511, Egypt.
⁶ Biology Department, Faculty of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.

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.