Optimization of trypan blue and brilliant green dyes photocatalytic degradation and adsorption of lead(II) and chromium (VI) heavy metal ions by copper sulfide nanoparticles

The use of nanoparticles for to remove organic pollutants and heavy metals is a rapidly expanding field in environmental sciences. However, process optimization for practical, real-world applications is still underexplored. In this work, copper sulfide nanoparticles prepared from a single-source precursor were characterized using SEM, TEM, EDX, FTIR, and UV-visible spectroscopy. The copper sulfide nanoparticles demonstrated high photocatalytic degradation efficiency of trypan blue (TB) and brilliant green (BG) dyes. The as-prepared nanoparticles efficiently removed lead(II) (Pb²⁺) and chromium(VI) (Cr⁶⁺) ions. Response surface methodology (RSM) with a Box-Behnken design (BBD) was employed to optimize reaction time, pH, and nanoparticle dosage. The optimal conditions for TB degradation were pH 10.91, 77.46 minutes, and 4.999 g/L, while for BG, they were pH 3, 70 minutes, and 5 g/L. For Pb²⁺ removal, optimal conditions were pH 7.06, 100.38 minutes, and 0.94 g/L, and for Cr⁶⁺ removal, pH 3.03, 168.20 minutes, and 0.98 g/L. Under these optimal conditions, CuS nanoparticles achieved up to 99.35% degradation for TB, 100% for BG, 100% removal for Pb²⁺, and 98.54% for Cr⁶⁺. ANOVA confirmed the models' significance, with high regression coefficients (R²: 0.9852 for BG, 0.9846 for TB, 0.9980 for Pb²⁺, and 0.9901 for Cr⁶⁺). The CuS photocatalyst remained stable over three reuse cycles, with minimal efficiency reduction (8.88% for TB and 19.01% for BG). This study demonstrates the effectiveness of copper sulfide nanoparticles in environmental remediation and highlights the practicality of using RSM to optimize nanoparticles as efficient materials to remove organic dyes and heavy metal-laden wastewater.