Nano-zinc hydroxide coated coffee seed-based activated carbon and malahite green removal from aquatic solutions

Keywords: Zinc hydroxide composite, malachite green, kinetic and isotherm, coffee waste, adsorption This work is focused on the development and characterization of coffee waste-based activated carbon (AC) as low-cost, abundantly available, highly efficient and eco-friendly adsorbent. The AC was modified ultrasonically using zinc hydroxide (Zn(OH)2) and used effectively for the removal of malachite green (MG) from aqueous solution. The examined batch adsorption parameters are; initial pH (2-9), adsorbent dose (0.1-0.5 g/100 mL), mixing time (5-120 min), initial MG concentration (25-300 mg/L) and temperature (298-318 K). According to the analyzes, the adsorption capacity of Zn (OH)2-AC increased with the increase in initial dyestuff concentration, pH and temperature, and decreased with increasing Zn (OH)2-AC dose. It has been determined that 0.1 g Zn (OH)2-AC is sufficient to remove 100 mg/L MG in approximately 94% efficiency. Also, ultrasonically activated adsorbent stabilized in a short time like 50 minutes. The XRD, SEM/EDS and FT-IR analysis techniques were conducted to characterize the chemical structure and surface morphology of Zn(OH)2-AC composite before and after adsorption of MG. The Langmuir isotherm model (R2 = 0.97) showed better conventionality than the Freundlich model (R2 = 0.80) with maximum adsorption capacity of 303.03 mg/g at 318 K and pH 7.