Synthesis and Application of FeMg-Modified Hydrochar for Efficient Removal of Lead Ions from Aqueous Solution
Jelena Petrović, Marija Koprivica, Marija Ercegović, Marija Simić, Jelena Dimitrijević, Mladen Bugarčić, Snežana Trifunović
Abstract
This study explores the utilization of waste grape pomace-derived hydrochar as an efficient adsorbent for lead (Pb2+) removal from aqueous solutions. Hydrochar was produced via hydrothermal carbonization (HTC) at 220 °C, followed by doping with magnesium and iron salts, and subsequent pyrolysis at 300 °C to obtain Fe/Mg-pyro-hydrochar (FeMg-PHC). The material’s structural and morphological changes after Pb2+ adsorption were examined using FTIR. FTIR revealed chemisorption and ion exchange as key mechanisms, shown by decreased hydroxyl, carbonyl, and metal–oxygen peaks after Pb2+ adsorption. Adsorption tests under varying pH, contact time, and initial Pb2+ concentrations revealed optimal removal at pH 5. Kinetic modeling indicated that the process follows a pseudo-second-order model, suggesting chemisorption as the dominant mechanism. Isotherm analysis showed that the Sips model best describes the equilibrium, with a maximum theoretical adsorption capacity of 157.24 mg/g. Overall, the simple two-step synthesis—HTC followed by pyrolysis—combined with metal doping yields a highly effective and sustainable adsorbent for Pb2+ ion removal from wastewater.