Experimental design and modeling of ultrasound assisted simultaneous adsorption of cationic dyes onto ZnS: Mn-NPs-AC from binary mixture

• ZnS: Mn-NPs-AC were used for the simultaneous removal of dyes from aqueous solution.
• Derivative spectrophotometric method for resolve of spectra overlap of MG and MB.
• Dyes removal significantly were accelerated under application of ultrasound.
• Response surface methodology was used to optimize the process variables.
• The MB and MG adsorption data were best followed by Langmuir and pseudo-second order models.

The manganese impregnated zinc sulfide nanoparticles deposited on activated carbon (ZnS: Mn-NPs-AC) which fully was synthesized and characterized successfully applied for simultaneous removal of malachite green and methylene blue in binary situation. The effects of variables such as pH (2.0–10.0), sonication time (1–5 min), adsorbent mass (0.005–0.025 g) and MB and MG concentration (4–20 mg L−1) on their removal efficiency was studied dy central composite design (CCD) to correlate dyes removal percentage to above mention variables that guides amongst the maximum influence was seen by changing the sonication time and adsorbent mass. Sonication time, adsorbent mass and pH in despite of dyes concentrations has positive relation with removal percentage. Multiple regression analysis of the experimental results is associated with 3-D response surface and contour plots that guide setting condition at pH of 7.0, 3 min sonication time, 0.025 g Mn: ZnS-NPs-AC and 15 mg L−1 of MB and MG lead to achievement of removal efficiencies of 99.87% and 98.56% for MG and MB, respectively. The pseudo-second-order model as best choice efficiency describe the dyes adsorption behavior, while MG and MB maximum adsorption capacity according to Langmuir was 202.43 and 191.57 mg g−1.