文摘
Dried powder of alligator weed root (AWR), a promising biosorbent, was employed to remove tetracycline (TC) from aqueous solution, using acid-pretreated AWR (HAWR) for comparison. The effects of ionic strength, pH, and environmentally coexisting substances on the adsorption of TC on AWR were also investigated. The results indicated a negligible impact of ionic strength but a significant effect of solution pH on the adsorption, with apparent inhibition observed in relatively acidic or alkaline pH regions. The impact of coexisting substances on TC adsorption depended on the species and concentration of interfering components. The mechanism of desorption was explored using NaCl/MgCl2 solution and cyclohexane–methanol mixture, revealing intense TC adsorption on the AWR surface. The biosorbent was characterized using various techniques, including inductively coupled plasma (ICP), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and zeta potential and N2 adsorption/desorption analyses. The results of the ICP, SEM–EDS, and FTIR analyses indicated that metals including Mn, Fe, and Al were enriched mainly over the AWR surface with metal (hydr)oxide (MHO) morphology. When the MHOs were denuded by HCl solution pretreatment, the resulting HAWR totally lost the adsorption capability. Based on the nature of AWR and TC as well as the adsorption/desorption performance, MHOs over the AWR surface were verified to play an essential role in driving adsorption via surface complexation. Furthermore, MHO-based complexation provides a reliable explanation for the TC adsorption/desorption performance. The obtained results will aid adsorption mechanism elucidation and potential applications of such low-cost biosorbent.
