Synthesis, characterization, and response surface methodology-based parametric optimization of copper-modified LSX zeolite for efficient cyanide ion removal

Cyanide contamination from industrial and mining effluents poses a serious environmental and public health risk. This study reports the synthesis, characterization, and parametric optimization of copper-modified low-silica X (Cu-LSX) zeolite for efficient cyanide ions (CN⁻) removal. The adsorbent was prepared by hydrothermal synthesis and copper ion exchange, and characterized using Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy, and Brunauer-Emmett-Teller (BET). The results show that Cu-LSX possesses a higher surface area (432.1 m²/g) than unmodified LSX (285.2 m²/g), along with improved porosity, stability, and a preserved crystalline structure. SEM image confirmed the formation of a porous morphology, which is suitable for adsorption. The equilibrium adsorption isotherm analysis for CN⁻ on the Cu-LSX zeolite showed that the Langmuir model (R² = 0.9975) provided a slightly better fit than the Freundlich model (R² = 0.9930). This suggests that CN⁻ adsorption proceeds predominantly via monolayer coverage on a homogeneous surface, indicating the Langmuir isotherm as the more appropriate model for describing the adsorption process. Optimization of process parameters using response surface methodology (RSM) (central composite design (CCD)) revealed an optimal CN⁻ removal efficiency of 96.7 %. The two-factor interaction (2FI) model provided the best fit (R² = 0.997), confirming the reliability of the predictions. These findings demonstrate that Cu-LSX zeolite is a robust, high-capacity adsorbent with significant potential for industrial wastewater treatment applications.