Acid Orange 7 adsorption onto quaternized pistachio shell powder from aqueous solutions

Pistachio shell powder (PSP) was chemically modified using the quaternizing agent N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride, under strong alkaline conditions. In order to acquire a thorough understanding of their chemical and structural properties, samples were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EXD), elemental analysis, X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. The characterization results showed that the quaternary ammonium groups were successfully grafted onto the PSP molecular structure and morphology of PSP has changed. The potential of quaternized pistachio shell powder (QPSP) in removing Acid Orange 7 (AO7) dye from aqueous solutions under batch conditions was investigated. Adsorption experiments were carried out as a function of initial solution pH, contact time, initial dye concentration, adsorbent dose, and salt concentration. Studies on the effect of pH revealed that initial solution pH had little effect on adsorption. The kinetic results showed that pseudo-second-order kinetic model adequately represented the adsorption of AO7 onto QPSP. Compared to the Freundlich isotherm model, the Langmuir isotherm model fitted well with the equilibrium data with high correlation coefficients. The maximum adsorption capacity of QPSP estimated from the Langmuir isotherm model was 215.5 mg.g(-1). It was also observed that QPSP showed excellent reusability that the value of adsorbed amount of AO7 onto QPSP decreased only by 3.0% of initial value after five consecutive adsorption-desorption cycles. This work indicated that QPSP could be used as an adsorbent to remove AO7 from aqueous media.