Usability of spent Salvia officinalis as a low-cost adsorbent in the removal of toxic dyes: waste assessment and circular economy

ABSTRACT

The removal of methylene blue (MB) and maxilon yellow (MY) dyes from aqueous solutions was investigated by an adsorption process using spent Salvia officinalis (SSO) for the first time. The operating conditions and mechanisms for the MB-SSO and MY-SSO adsorption systems were determined. FTIR-ATR and SEM-EDAX analyses were also performed to characterise the adsorbent. Optimum conditions in each system were similarly obtained, excluding pH (5.7 for MB and 6.5 for MY). The dye removal efficiency was 78% for MB and 56% for MY. It was observed that experimental data fits Freundlich isotherm (R² ≈ 0.97) and pseudo-second-order kinetic (R² ≈ 0.99) model in both systems. The maximum adsorption capacities of SSO for MB and MY dyes were determined as 16.53 and 11.79 mg g⁻¹, respectively. The pseudo-second-order kinetic model revealed that adsorption efficiency was affected by a number of active sites on the adsorbent and the concentration of the dye. The thermodynamic parameters confirmed that adsorption was spontaneous, exothermic and physisorption in both adsorption systems. The results indicate that SSO can be used as a promising adsorbent material for removal of MB and MY dye from aqueous solutions. However, in order to remove high dye concentrations, SSO must be activated.

KEYWORDS:

• Spent Salvia officinalis
• toxic dyes
• low-cost adsorbent
• waste assessment
• circular economy

CRediT authorship contribution statement

Zuleyha Bingul: Conceptualization, Conducting experiments, Calculation. Elanur Adar: Investigation, Calculation, Writing-review&editing.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. No funds were used in this study.

Supplementary material

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