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Synthesis and characterization of pistachio shell/nanodiopside nanocomposite and its application for removal of Crystal Violet dye from aqueous solutions using central composite design

ABSTRACT In this study, diopside nanoparticles were immobilized on activated carbons prepared from pistachio shells (AC/DIOP) to produce an inexpensive nanocomposite. The AC/DIOP nanocomposite was characterized using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and field emission scanning electron microscopy (FESEM). The pore volume, the pore size distribution, and the specific surface area of the nanocomposite were calculated using BET technique. The effects of four parameters including pH, contact time (min), adsorbent dose (g), and initial dye concentration (mg/L) were studied by response surface methodology (RSM) based on the central composite design (CCD). The optimal condition for removal of Crystal Violet up to 97.46% was found to be; pH 7.5, contact time: 10 min for 198.8 mg of adsorbent dosage for 20 mg/L of initial dye concentration in 25 ml of the solution. The efficiency of the synthesized adsorbent for removal of Crystal Violet (CV) was investigated. Adsorption equilibrium and kinetic data were fitted with the Langmuir monolayer isotherm model (qmax: 196.08 mg/g and R2: 0.9801) and pseudo-second-order kinetics mechanism (R2: 0.9998). Thermodynamic parameters (R2: 0.9537, ΔH°: 175.005 kJ/mol, ΔG°: −10.089 kJ/mol, and ΔS°: 0.9674 kJ/mol K) were calculated and indicating adsorption to be an endothermic and spontaneous process. Regeneration investigation showed that AC/DIOP can be reused impressively, indicating that the adsorbent was a promising one for the removal of CV from aqueous solutions.