Preparation of activated carbon from Zilla spinosa biomass by means of microwave for efficient bio-sorption of hazardous methylene blue colorant from water

Biochars and their activated carbons derived from sustainable materials constitute an extensive use in adsorbing several hazardous substances due to their excellent characteristics and their high efficiencies. In this work, an economic and prompt method was adopted to prepare activated carbon from low-cost, abundant, and sustainable ligno-cellulosic Zilla spinosa fruits chemically activated with zinc chloride (ZnCl₂) in a laboratory microwave apparatus. The experiments were carried out at different mixing ratios (1:1, 2:1, and 1:2), microwave power (580 W, 640 W, and 720 W), and microwave time (60, 90, 120, 180, and 240 s). The obtained activated carbon was analyzed using a number of techniques which include Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) surface area, X-ray fluorescence (XRF), X-ray diffraction (XRD), and thermogravimetric-differential thermal analysis (TGA-DTA). The optimal conditions for the design of activated carbon with the maximum adsorption ability of methylene blue (390 mg/g) were as follows: carbonization temperature of microwave power = 640 w, radiation time = 180 s, Zilla to ZnCl₂ ratio of 2:1. The dye uptake mechanism fulfilled first-order kinetic and Freundlich models. Overall, it has been proven that the prepared activated carbons, due to simplicity of synthesis and ease of recuperation from solution, could be proficiently used for water purification systems.