Biochar Derived from Treated Lotus Stem and Adsorption of Phthalic Acid Esters

Abstract

Phthalic acid ester (PAE), a plasticizer, is increasingly being detected in different environments. These compounds can gravely affect the human endocrine system. The present study aims to prepare adsorbents that can effectively adsorb PAE pollutants. To fabricate a better carbon structure than conventional biochar, the sodium hydroxide solution was used as a hydrolyzing agent to pretreat the biomass in order to weaken the bonds in lignin, cellulose, and hemicellulose. As a result, biochar with a special porous carbon structure is obtained. To study the characteristics of the biochar and its adsorption properties, dimethyl phthalate (DMP)—a PAE—was selected as the adsorbate. The morphology and structural composition of the biochar were examined via an environment scanning electron microscope with a field emission gun (SEM), surface area analyzer (BET), Fourier transform infrared spectrometer (FTIR), thermal gravimetry (TG/DTG), X-ray diffractometry (XRD), and Raman spectroscopy. The BET data of the biochar increased by 125.3 times than that of the original biochar. The layer spacing and the surface functional groups of the pretreated biochar also increased. After performing the micro-morphological regulation of biomass using sodium hydroxide, the adsorption performance of biochar with regard to PAE effectively improved and an adsorption capacity of 125 mg/g was observed for DMP. The adsorption kinetics and thermodynamic experiments showed that DMP adsorption by biochar follows the Langmuir and pseudo-second-order models.