Optimization Study of the Capacity of Chlorella vulgaris as a Potential Bio-Remediator for the Bio-Adsorption of Arsenic (III) from Aquatic Environments

Reem Mohammed Alharbi; Essam Nageh Sholkamy; Khawla Ibrahim Alsamhary; Neveen Abdel-Raouf; Ibraheem Borie M Ibraheem

doi:10.3390/toxics11050439

Optimization Study of the Capacity of Chlorella vulgaris as a Potential Bio-Remediator for the Bio-Adsorption of Arsenic (III) from Aquatic Environments

Toxics. 2023 May 6;11(5):439. doi: 10.3390/toxics11050439.

Authors

Reem Mohammed Alharbi¹, Essam Nageh Sholkamy², Khawla Ibrahim Alsamhary³, Neveen Abdel-Raouf^{3

4}, Ibraheem Borie M Ibraheem⁴

Affiliations

¹ Department of Biology, College of Science, University of Hafr Al Batin, Hafr Al Batin 39524, Saudi Arabia.
² Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
³ Department of Biology, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia.
⁴ Botany and Microbiology Department, Faculty of Science, Beni-Suef University, Salah Salem Street, Beni-Suef 62511, Egypt.

Abstract

This study examined the ability of the green microalgae Chlorella vulgaris to remove arsenic from aqueous solutions. A series of studies was conducted to determine the optimal conditions for biological arsenic elimination, including biomass amount, incubation time, initial arsenic level, and pH values. At 76 min, pH 6, 50 mgL^-1 metal concentration, and 1 gL^-1 bio-adsorbent dosage, the maximum removal of arsenic from an aqueous solution was 93%. The uptake of As (III) ions by C. vulgaris reached an equilibrium at 76 min of bio-adsorption. The maximum adsorptive rate of arsenic (III) by C. vulgaris was 55 mg/gm. The Langmuir, Freundlich, and Dubinin-Radushkevich equations were used to fit the experimental data. The best theoretical isotherm of Langmuir, Freundlich, or/and Dubinin-Radushkevich for arsenic bio-adsorption by Chlorella vulgaris was determined. To choose the best theoretical isotherm, the coefficient of correlation was used. The data on absorption appeared to be linearly consistent with the Langmuir (q_max = 45 mgg^-1; R² = 0.9894), Freundlich (k_f = 1.44; R² = 0.7227), and Dubinin-Radushkevich (q_D-R = 8.7 mg/g; R² = 0.951) isotherms. The Langmuir and Dubinin-Radushkevich isotherms were both good two-parameter isotherms. In general, Langmuir was demonstrated to be the most accurate model for As (III) bio-adsorption on the bio-adsorbent. Maximum bio-adsorption values and a good correlation coefficient were observed for the first-order kinetic model, indicating that it was the best fitting model and significant in describing the arsenic (III) adsorption process. SEM micrographs of treated and untreated algal cells revealed that ions adsorbed on the algal cell's surface. A Fourier-transform infrared spectrophotometer (FTIR) was used to analyze the functional groups in algal cells, such as the carboxyl group, hydroxyl, amines, and amides, which aided in the bio-adsorption process. Thus, C. vulgaris has great potential and can be found in eco-friendly biomaterials capable of adsorbing arsenic contaminants from water sources.

Keywords: Chlorella vulgaris; Dubinin–Radushkevich; Fourier-transform infrared spectrophotometer (FTIR); Freundlich; Langmuir; arsenic (III); bio-adsorption.

Grants and funding

This research received no external funding.