Conversion of phosphorus and nitrogen in lincomycin residue during microwave-assisted hydrothermal liquefaction and its application for Pb2+ removal

Treatment of antibiotic fermentative residue (AFR) produced from pharmaceutical industries and their application in the environment has been gaining researchers' interest. In this study, lincomycin residue (LMR, the type of AFR) was treated with microwave-assisted hydrothermal liquefaction (MW-HTL) in a temperature range 120-210 degrees C, transforming effect of phosphorus (P) and nitrogen (N) functional groups in LMR samples was characterized with elemental analysis, XRD, XPS, FT-IR, and P-extraction, and utilized LMR samples for Pb2+ removal from aqueous solutions. The temperature had a significant impact on P and N functional groups conversion justified by characterization techniques and also responsible for Pb2+ adsorption. LMR hydrochar produced at 210 degrees C was accounted highest Pb2+ adsorption capacity (57.4 mg g(-1)), higher four folds than raw LMR (13.8 mg g(-1)). To understand the mechanism and rate defining phase of adsorption equilibrium isotherm and kinetic models were applied systematically. Adsorption results of LMR and its derived hydrochar samples found connectivity with Langmuir and pseudo-first-order isotherm models. Adsorption mainly occurred as ion-exchange dependent on the substitution of metal ions (Pb2+) to Ca2+ ions present in P-materials, and surface adsorption dependent on surface functional groups of LMR samples. Better operation feasibility of MW-HTL treated LMR, elaboration of P and N conversion behavior and high sorption of Pb2+ ions could make LMR a frontrunner for heavy metals immobilization. (C) 2019 Elsevier B.V. All rights reserved.