Layered Double Oxides/Biomass Composite: Synthesis, Characterization and Treatment of Antibiotic Contaminated Water

A new composite of manganese-iron layered double oxides-biochar (MnFe LDO/BC) was successfully synthesized. The as-prepared composite was characterized using Fourier-transform infrared spectroscopy, scanning electron microscope, X-ray diffractometer and time-resolved spectroscopy. MnFe LDO/BC was applied for the elimination of antibiotic residues like tetracycline (TEC) and metronidazole (MEZ) from contaminated water via adsorption and advanced oxidation processes. The performance of MnFe LDO/BC was evaluated through isotherm studies, reuse efficiency, photocatalytic and adsorption kinetics. The characterization results indicated that the MnFe LDO/BC composite has a sufficient specific surface area of 524.8 m2 /g, saturation magnetization value at 28.5 emu/g, energy band gap of 2.85 eV and photocurrent response of 3.8 µA/cm2 . The maximum adsorption capacity of MnFe LDO/BC for TEC and MEZ was 38.3 mg/g and 40.8 mg/g at pH 3 and 5, respectively. The adsorption behavior fits the Langmuir isotherm and pseudo-second-order models with correlation coefficient R2 ≥ 0.98. The composite demonstrated high photocatalytic efficiency under UV light; TEC and MEZ degradation reached ~98.0% after 60 min of UV light illumination in the presence of 50 mg of MnFe LDO/BC catalyst and 6 mM of H2O2. Under various antibiotics degradation processes, UV/MnFe LDO/BC/H2O2 demonstrated the highest degradation efficiency with a rate constant of 0.266 1/min and lowest energy consumption cost of 0.38$ at 7.56 kWh/m3 which is ~13 times lower than the degradation of TEC and MEZ by the photolytic process under the same conditions. The radical trapping results revealed that the photocatalytic decomposition of TEC iv and MEZ followed a multistage mechanism influenced mainly by  HO and  SO4 radicals and partially by h + and   O2 . The performance of the novel MnFe LDO/BC composite for antibiotics mineralization surpassed several studied catalysts and maintained ~88% reuse efficiency after three consecutive recycling tests. Keywords: Layered double oxide biomass composite; antibiotics elimination; photocatalytic mineralization; antibiotics adsorption.