NaOH-Activated Fly Ash Adsorbent in Copper(II) Metal Ion Removal from Laboratory Wastewater

Abstract

The discharge of untreated laboratory wastewater containing highly toxic copper(II) poses a significant environmental risk, highlighting the need for an effective and low-cost treatment material. At the same time, the accumulation of coal fly ash from Indonesia’s electricity sector requires sustainable waste valorization strategies. Addressing these dual environmental challenges, this study proposes a 'waste-to-treat-waste' approach by evaluating NaOHactivated fly ash (FA-NaOH) to reduce copper(II) ion levels in laboratory wastewater. FTIR characterization of FA-NaOH identified functional groups including –OH, Si–O, and Al–O, which are responsible for metal ion binding. Adsorption experiments using a copper(II) model solution determined the optimum operating conditions. The optimum adsorbent dosage was 2 g per 100 mL with a contact time of 60 minutes, achieving 99.07% copper(II) removal. Application of the optimized conditions to actual laboratory wastewater achieved 77.10% removal. The lower efficiency indicates the influence of competing heavy metals and other constituents in the wastewater matrix. Although FA-NaOH effectively lowers copper(II) levels, the treated wastewater did not fully comply with regulatory requirements. Therefore, additional pretreatment is recommended to enhance adsorption performance. These findings demonstrate the potential of FA-NaOH as an effective alternative adsorbent for heavy metal removal from laboratory wastewater.