Adsorption of crystal violet on polystyrene microplastics in aqueous: optimization, modeling, and assessment of isotherms and kinetics

Abstract

The global increase in plastic production has significantly contributed to the contamination of aquatic environments with MPs. This study examined the adsorption of CV dye onto PS MPs in aquatic ecosystems. BBD was utilized to optimize adsorption conditions and evaluate the effects of key independent variables on the adsorption process. The sorption experiments were conducted using reaction mixtures containing PS at levels ranging from 0.1 to 1.5 g/L and CV at concentrations of 5 to 20 mg/L. The pH levels of the samples were adjusted to range from 4 to 10, while the duration of interaction varied between 10 and 60 min. The findings revealed that the optimal sorption rate for CV (84.96%) was achieved at a CV level of 12.5 mg/L, a PS dosage of 1 g/L, a pH level of 7, and an interaction duration of 35 min. In this investigation, the ZP of PS particles transitioned from − 45.6 to − 16.8 mV following the sorption of CV. Furthermore, the kinetics of CV sorption were most accurately described by the pseudo-first-order model, demonstrating a high R² value of 0.99. The Langmuir isotherm (R² = 0.99) further confirmed the presence of significant interactions between the dye molecules and the surface of the sorbent, with the highest sorption capacity quantified at 6.25 mg/g. This study highlights the role of PS microplastics as carriers of harmful dyes, such as CV, in aquatic environments. It underscores the urgent need for further research into the environmental consequences of microplastic pollution and the development of strategies to mitigate their impact.