Optimization of Sustainable Hybrid Natural–Waste Adsorbent Compositions for Mixed Dye Removal from Aqueous Solutions

Abstract In this study, the removal of a synthetic dye mixture containing anionic (Telon Blue AGLF), cationic (Astrazon Blue BG-200%), and nonionic (Dianix Blue S-BG) dyes from aqueous solutions was investigated using the adsorption method. As an alternative to commonly used commercial adsorbents, three low-cost, naturally abundant, and renewable materials magnolia cone (MC), beidellite (BD), and fly ash (FA) were selected. Unlike many previous studies in the literature, these adsorbents were used simultaneously to explore the potential advantages of combined adsorption. Batch adsorption experiments were conducted by varying the operational parameters, including pH (4–11), contact time (5–60 min), and the individual dosages of three different adsorbents (within the range of 0.01–0.04 g), while keeping the initial dye concentrations constant. A synthetic dye solution was prepared by mixing the three dyes in equal concentrations and volumes. The effects of the selected parameters on dye and total organic carbon (TOC) removal efficiencies were evaluated and optimized using Response Surface Methodology (RSM) based on Central Composite Design (CCD). To assess the structural and surface characteristics of the adsorbents before and after adsorption, Brunauer–Emmett–Teller (BET) surface area analysis and Scanning Electron Microscopy (SEM) were employed. BET analysis revealed surface areas of the adsorbents ranging from 18 to 158.5 m 2 /g. SEM images demonstrated that dye molecules were successfully adsorbed onto the surface and within the pores of the adsorbents. The findings indicate that the simultaneous use of natural and waste-derived materials can offer a sustainable, efficient, and cost-effective approach for the removal of mixed dyes from wastewater.