Amine-functionalized magnetic biochars derived from invasive plants Alternanthera philoxeroides for enhanced efficient removal of Cr(VI): performance, kinetics and mechanism studies

In this study, novel magnetic biochars derived from Alternanthera philoxeroides and modified by different amines (hexanediamine, melamine, and L-glutathione) were successfully prepared by hydrothermal carbonization and employed as an efficient adsorbent for Cr(VI). When pH =2.0, T=25 degrees C, c(0) =100 mg/L, and the dosage of biochars is 0.05 g, the maximum adsorption capacity of Cr(VI) by pristine biochar (BAP) was 42.47 mg/g and modified biochars (MFBAP, MEBAP, LBAP) was 80.58, 62.26, and 55.66 mg/g, respectively. It was found that hexanediamine and melamine could enhance the S-BET of biochars, while L-glutathione could reduce its S-BET, which could be supported by BET measurement and SEM images. Adsorption kinetics and isotherm studies showed that the Cr(VI) adsorption process of MFBAP followed Elovich kinetic model and Langmuir isotherm, respectively, which means that it was mainly a chemical adsorption process. The characterization results proved that -NH2 derived from amines plays a significant role in removing Cr(VI), which is mainly degraded by complexation reaction, electrostatic interaction, and reduction. In sum, the biochar modified by amines has excellent Cr(VI) adsorption performance, highly enhanced S-BET, and excellent recyclability, which is a promising candidate for solving the problem of invasive plants and wastewater treatment.

Automated summary

In this study, novel magnetic biochars derived from Alternanthera philoxeroides and modified by different amines were prepared and used as efficient adsorbents for Cr(VI) removal. Hexanediamine and melamine enhanced the specific surface area of biochars, while L-glutathione reduced it. The adsorption process of modified biochars mainly followed chemical adsorption. Amines played a significant role in removing Cr(VI) through complexation, electrostatic interaction, and reduction. The amine-modified biochars exhibited excellent adsorption performance, enhanced specific surface area, and good recyclability, making them promising candidates for invasive plant control and wastewater treatment.