Investigation of Citrus reticulata peels as an efficient and low-cost adsorbent for the removal of safranin orange dye

ABSTRACT

Safranin orange (SO) is a cationic dye widely used in industrial sectors. It becomes a threat to the aquatic ecosystem once it reaches water resources, directly affecting photosynthetic activity and dissolved oxygen rate. In view of this scenario and considering the large production of agro-industrial waste, which provides significant disposal costs and environmental impacts, the agricultural by-products such as mandarin peels (MP) are being used as biosorbent materials. Thus, this work proposed the use of MP for SO adsorption. The material was characterized by SEM, zeta potential, and FTIR analysis, in which it was possible to verify heterogeneous porous morphology, predominantly negative surface, and organic functional groups that facilitate adsorption. The results were promising, wherein the maximum adsorption capacity was 464 mg g^–1 (318 K), 0.4 g L^–1 adsorbent concentration, 120 min equilibrium time and removal percentage of 84.75%. The experimental data showed a better fit to the Langmuir and pseudo-second order mathematical models. The thermodynamic analysis inferred spontaneous, endothermic, and reversible character for SO adsorption onto MP. The main proposed adsorptive mechanisms were hydrogen bonds, π-interactions, and electrostatic interactions. In addition, the reuse of MP showed good efficiency since the adsorption capacity was maintained above 50% after four cycles (from 77.90 to 41.55 mg g^–1). Moreover, when evaluating the effect of pH and ionic strength, it verified that the adsorption efficiency was not reduced. Therefore, when compared with other materials, the versatility and potential applicability of MP as a low-cost adsorbent for wastewater treatment is notable.

GRAPHICAL ABSTRACT

KEYWORDS:

• Biosorbent
• Mandarin peels
• agro-industrial residue
• dye removal
• wastewater

Acknowledgements

This work was supported by the National Council for Scientific and Technological Development (CNPq) and Higher Education Personnel Improvement Coordination (CAPES) Financing Code 001. The authors also thank the Complex of Research Support Center (COMCAP) of the State University of Maringá (UEM) for the characterisation analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author, Angélica Marquetotti Salcedo Vieira, upon reasonable request.

Additional information

Funding

This work was supported by the National Council for Scientific and Technological Development (CNPq) and Higher Education Personnel Improvement Coordination (CAPES) Financing Code 001.