ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Sustainable heavy metal removal: optimization of adsorption onto oxidized brewery spent grains via response surface methodology

Çiğdem Ay

Faculty of Science and Art, Department of Chemistry, Kütahya Dumlupınar University, Kütahya, Turkey

E-mail: cigdem.ay@dpu.edu.tr

Received: 27 June 2025  Accepted: 24 November 2025

Abstract:

Using inexpensive, sustainable adsorbents, including industrial agricultural waste, to remove heavy metals from wastewater treatment is of great interest, as it presents a major environmental problem. The adsorption capacity of brewery-spent grains (BSG) for copper(II) ions (Cu(II)) was examined in this study and was found to increase by oxidation (O@BSG) from 32.51 to 74.48 mg g⁻¹. The adsorption process was optimized using the Box-Behnken design (BBD), and the highest adsorption capacity (30.21 mg g⁻¹) was obtained at pH 5.57, 22.44 mg O@BSG, and 156.98 mg L⁻¹ initial Cu(II) ion concentration. A quadratic mathematical model was formulated to predict the responses. The analysis of variance (ANOVA) demonstrated a significant impact of pH on the adsorption of Cu(II) ions. The models that best describe the adsorption process were pseudo-second-order kinetics and the Langmuir isotherm model. The monolayer adsorption capacity was 69.26 mg g⁻¹. The thermodynamic analysis indicated that the process is spontaneous and endothermic, as well as an increase in disorder at the solid-liquid interface. In conclusion, O@BSG was shown to have significant potential as an economical, efficient, and sustainable adsorbent for Cu(II) removal.

Keywords: Adsorption; Analysis of variance; Brewery-spent grains; Box-Behnken design

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04549-9

Chemical Papers 80 (3) 2755–2774 (2026)