Giombo persimmon seed (GPS) an alternative adsorbent for the removal Toluidine Blue dye from aqueous solutions

Abstract

Giombo persimmon seeds (GPS) (Diospyrus kaki L) were used as a novel low-cost adsorbent for the removal of Toluidine Blue dye (TB) from aqueous solution by batch contact adsorption mode at 25°C. The GPS adsorbent was characterized by specific surface area (Brunauer– Emmett–Teller), scanning electron microscopy, infrared spectroscopy (ATR-FTIR), thermal analysis, point of zero charge, and Boehm titration techniques. The effects of initial pH of solution, adsorbent dosage, contact time, and initial dye concentration on TB adsorption were investigated. Kinetic data were evaluated by pseudo-first-order, pseudosecond- order, and Elovich models. The equilibrium adsorption was analyzed by Langmuir, Freundlich, and Sips isotherms models. Desorption studies were also performed. The results indicated that the Elovich model agreed very well with the kinetic data. The equilibrium data of adsorption of TB onto GPS were better fitted using Sips isotherm. The maximum adsorption capacity was 34.73 mg g−1. Good regeneration (93.5%) of GPS adsorbent was obtained using 2.00 mol L−1 CH3COOH as eluent. The GPS adsorbent can be used in the future as an alternative low-cost adsorbent for the treatment of waters contaminated with TB dye.