Adsorption behavior of methylene blue onto waste-derived adsorbent and exhaust gases recycling

Abstract

A waste-derived adsorbent was prepared from waste carbon, which was obtained from the production process of monosodium glutamate, by microwave heating under ultrasonic spray conditions for removing methylene blue (MB) from wastewater. The preparation process was performed at 840 °C for 17 min with an ultrasonic spray rate of 2 mL min⁻¹ produced by ultrasonic spray equipment. Ultrasonic spray was successfully used for the preparation of an adsorbent from waste carbon for the first time. An adsorbent was also prepared under a steam atmosphere. The MB adsorption number of the adsorbent prepared under ultrasonic spray conditions increased by 15.27% in comparison to that prepared under a steam atmosphere under similar experimental conditions. The exhaust gases that were obtained during the preparation process of the adsorbent had a certain heating value, as the major components were carbon monoxide and hydrogen. The exhaust gases have promising utility as a heat source, which would significantly alter the commercial manufacturing process. The physicochemical properties of the adsorbent were investigated via N₂ adsorption, TG/DTG, SEM, FTIR, XPS and zeta potential measurements. Analyses of the adsorption mechanism prove that CO bonds in the adsorbent play an important role in the adsorption process of MB, as proved by zeta potential measurements and XPS analysis. The above-mentioned analyses show that an adsorbent with good MB adsorption performance can be prepared from waste carbon under ultrasonic spray preparation conditions and fuel gas can be obtained at the same time, which achieves the comprehensive utilization of waste resources.