Cost-Effective Removal of Cu(II) and Cd(II) from Wastewater Using Walnut Shell-Immobilized Amberlite XAD-4 as a Sorbent

Abstract In this study, a cost-effective and environmentally friendly solid-phase extraction (SPE) method using walnut shell-immobilised on Amberlite XAD-4 (WNS-XAD-4) was developed to pre-concentrate and determine Cu(II) and Cd(II) ions in water samples prior to flame atomic absorption analysis (FAAS). The low-cost adsorbent, prepared by immobilizing waste walnut shells on Amberlite XAD-4 (WNS-XAD-4), was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermal Gravimetric Analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. Under optimal conditions, the method achieved recoveries of 95.7% for Cu(II) and 100% for Cd(II) using 5.0 mL of 1.5 mol L −1 HNO 3 as eluent. The detection limits were found as 0.582 μg L −1 for Cu(II) and 0.03 μg L −1 for Cd(II) with preconcentration factors of 10 and 40, respectively. The accuracy of the method was validated using the certified aquatic plant reference material BCR-670 and successfully applied to various real water samples, including those from Lake Van, Billoris Spa, tap water, salt water and wastewater from Siirt, Turkey.