Application of ZnS:Ni Loaded on Sponge-Activated Carbon as an Efficient Adsorbent for Dye Removal

In the present work, a ZnS:Ni loaded on sponge-activated carbon (SAC) was synthesized and applied as an effective adsorbent to remove bromophenol blue (BPB) dye from aqueous solutions. Various techniques such as Fourier-transform infrared, X-ray diffraction, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Brunauer-Emmett-Teller (BET) were used to characterize ZnS:Ni–SAC. The effective parameters such as BPB concentration, amount of ZnS:Ni–SAC, ultrasonic time, and pH of the aqueous solution were investigated and optimized by response surface methodology. To investigate the accuracy and reliability of the proposed method, the analysis of variance was used based on p-values and F-test. The optimal values of the parameters were obtained using the desirability function, and they were as follows: 15 mg L⁻¹ BPB concentration, 20 min sonication time, 18 mg of ZnS:Ni–SAC, and pH = 7. To evaluate the adsorption mechanism and calculation of maximum adsorption capacity, different adsorption isotherms were studied, and according to the obtained results, the Langmuir isotherm model showed the highest compatibility due to its higher R² (0.997). Also, the proposed adsorbent represented good adsorption capacity (125 mg g⁻¹). Moreover, kinetic studies proved the applicability of the pseudo-second-order model (R² = 0.986) compared to other models. The achieved results confirmed the applicability of ZnS:Ni–SAC as a versatile adsorbent for the removal of BPB.