Removal of methylene blue via adsorption using magnetic char derived from food waste

Abstract

In this work, the char residue from hydrothermal liquefaction of food waste was chemically treated with potassium hydroxide and modified to prepare magnetic char (MC) adsorbent for removal of methylene blue (MB). The char was modified to prepare MC with improved surface properties and to enhance MB adsorption. The surface chemistry and textural properties of the developed modified char were analyzed by Fourier transform infrared spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, and point of zero charge. Raw char and various treated char and MC prepared at different conditions were used for MB adsorption at selected conditions to identify the best performing adsorbent for further testing in the parametric study. The influence of pH (2-12), adsorbent dosage (0.05-0.15 g), and initial MB concentration (50-250 mg/L) was studied for 30 min at room temperature to determine the conditions for maximum adsorption capacity and removal efficiency of MB using MC. The results show successful impregnation of magnetic nanoparticles (MNP) on activated char for effective MB adsorption and also for MC separation after adsorption. The adsorption capacity of MB achieved approximately 59.8 mg/g with the maximum removal efficiency of 59.8% using selected MC at the conditions of pH 10 and 0.05 g of MC dosage for 30 min. The finding shows that MC has a potential as an effective adsorbent to remove dyes from wastewater and has an advantage to separate adsorbent using magnet.