Institute of Fundamental Technological Research

In this study, eco-friendly Fe3O4-lignin (FeL) and Fe3O4-carbon-based lignin (FeCL) were synthesized, characterized, and applied for the adsorption of tetracycline (TRC) and ceftriaxone (CEF). Comparative characterization showed that the BET-specific surface area of FeCL is 27 m2/g more than that of FeL. The difference in their morphologies is insignificant, and the particle sizes range between 5 and 15 nm. There is a reduction in the oxygen content and hydroxyl group of FeCL as shown from the EDS and FTIR spectra respectively, compared with FeL. The adsorption capacity for the removal of TRC at 333 K is 156 and 148 mg g−1 by FeL and FeCL, respectively; while that of CEF are virtually the same. FeL and FeCL adsorption capacity for TRC increases with temperatures (endothermic), but decreases (exothermic) for CEF. The combination of experimental and computational approaches gave insight into the mechanisms of the adsorption process. The mechanisms of TRC and CEF adsorption by FeL and FeCL are the electrostatic attraction, hydrophobic, and π-π interaction, while only FeL shows the possibility of hydrogen bond with both TRC and CEF. The study demonstrated that the synthesized material can be reused for up to 3 cycles without an alarming loss of efficiency capacity.
Graphical abstract

Lignin,antibiotics,Adsorption mechanisms,Thermodynamics

Adsorption and photocatalytic degradation techniques for removing various contaminants have received broad consideration and acceptance due to their advantages over conventional wastewater treatment techniques. Iron- based materials are among several groups of adsorbents, and photocatalysts that have proven to be effective in pharmaceuticals-based pollutants removal from wastewater. Pharmaceutical drug removal is accompanied by several mechanisms, so there is a deep need for a better understanding of the complexity and development of wastewater treatment using iron-based materials. Therefore, this review examined the mechanism of adsorption
and photocatalysis degradation of pharmaceuticals in aqueous solutions by iron-based materials. The adsorption of pharmaceutical drugs was found to be influenced by changes in the solution pH. The mechanism of removal of
these contaminants by iron-based materials through adsorption occurred via electrostatic, π-π, and hydrogen bond interactions among others. In the case of photocatalysis, the first mechanism occurred through the for-
mation the hydroxyl radicals due to highly reactive species (electrons and holes) that partook in the reaction processes, while the second mechanism is related to the formation of hydrogen peroxide, H2O2, by photo-
generated electrons in the conduction band and with the well-known photo dissolution of iron oxide leading to free Fe2+ and Fe3+ ions. The overall idea of this review is to provide useful information on the mechanisms of
adsorption and photocatalytic degradation of pharmaceutical contaminants using iron-based materials. The re-view summarizes the current understanding and the advances in the pharmaceutical-bearing effluent treatment using nanostructured adsorbents and photocatalysts, including future developments for a cleaner and safer environment.

Mechanism,Iron-based materials,Pharmaceutical drugs,Adsorption,Photo(degradation)