Biosorption of cadmium from aqueous solution by combination of microorganisms and chitosan: response surface methodology for optimization of removal conditions

Abstract

The food-grade adsorbents of Saccharomyces cerevisiae (10⁸ CFU/mL), Bifidobacterium longum (10⁸ CFU/mL) and chitosan (1%w/v) alone or in combination were used for biosorption of cadmium (Cd) from aqueous solution. Among the tested adsorbents, combination of B. longum and chitosan had the highest efficiency. Therefore, biosorption process with B. longum/chitosan as the most efficient biosorbent was optimized by variables of pH (3–6), temperature (4–37 °C), contact time (5–180 min) and Cd concentrations (0.01–5 mg/L) using RSM. Twenty-seven tests were carried out and the data fitted to the second-order polynomial models. Results revealed that 99.11% of Cd was reduced within 180 min at concentration of 2.5 mg/L, pH 6 and temperature of 20.5 °C that were considered as the optimal conditions for Cd removal. The trend of isotherm was more fitted to the Langmuir model and maximum biosorption capacity was obtained about 3.61 mg/g. The pseudo-second-order fitted the biosorption kinetics for Cd ions. The B. longum/chitosan biosorbent exhibited the high affinity to Cd ion in the presence of coexisting metal ions. It could remove 81.18% of Cd from simulated gastrointestinal tract. Thus, B. longum/chitosan can have good potential as an effective adsorbent for Cd biosorption from aqueous solutions and human body.

Keywords:

• Aqueous solutions
• biosorption
• cadmium
• chitosan
• isotherm

Acknowledgements

We gratefully thank from the National Nutrition and Food Technology Research Institute (NNFTRI), Food Safety Research Center and Shahid Beheshti University of Medical Sciences of Iran for the efforts in promoting the knowledge and this work was supported financially by them.

Data availability statement

Data will be available on request.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.