Adsorption Of Antibiotics And Phosphates By Biochar Of Aquatic Plants In Wetland

Wetland is an important part of the surface natural ecosystem,which has a variety of ecological functions and significant economic value in terms of water conservation,pollutant degradation and biodiversity protection.Aquatic plants in wetland play an important role in it.Biochar is a highly carbonized porous substance produced by pyrolysis of carbon-rich biomass under hypoxia or oxygen restriction conditions.Article takes a typical wetland aquatic plant reeds and lotus as the research object,explores the reed straw biochar and lotus stalk biomass charcoal adsorption characteristics of norfloxacin antibiotics in water environment,and based on this,reed biochar has carried on the modification of magnesium ions,before and after modification are studied magnesium phosphate adsorption characteristics of water environment.The results show that:?1?The yield,average pore diameter,and contents of H,O and N elements of biochar from reed straw and lotus stem all showed a trend of decreasing with the increase of pyrolysis temperature,while the contents of ash,p H value,specific surface area?BET?,total pore volume and element C increased with the increase of pyrolysis temperature.The adsorption amount of norfloxacin antibiotics Reed Straw Biochar>Lotus Stem Biochar.Among them,the biochar fired from reed straw at 700?had the largest adsorption capacity of norfloxacin antibiotics,up to 4.94 mg·g^-1.?2?The adsorption isotherm of norfloxacin on the lotus stem biochar prepared at 300?,500?and 700?conforms to the Freundlich equation?R²>0.98?.The adsorption isotherm of norfloxacin on the reed straw biochar prepared at 300?,500?and 700?conforms to the Langmuir equation?R²>0.91?.The adsorption kinetics of norfloxacin by reed straw biochar was in accordance with the quasi-first-order kinetic equation?R²>0.89?,and the adsorption mechanism was physical adsorption.The adsorption kinetics of norfloxacin by lotus stem biochar conforms to the quasi-second-order kinetic equation?R²>0.94?,and the adsorption mechanism is the joint action of physical adsorption and chemical adsorption.Through the analysis of the intergranular diffusion model,the adsorption rates of the two biochars may be determined by surface adsorption,liquid film diffusion and intergranular diffusion.?3?Morphology characteristics before and after modification of biochar magnesium ion in reed straw were characterized by scanning electron microscopy?SEM?and X-ray energy spectrum analysis?EDS?,indicating that magnesium ion was successfully loaded on the surface of biochar.Morphology characteristics of magnesium modified biochar before and after phosphate adsorption were characterized by SEM,EDS,Fourier transform infrared spectrometer?FTIR?and X-ray diffraction analysis?XRD?,shows that phosphate is mainly adsorbed on magnesium modified biochar in the form of Mg HPO₄ and Mg₃?PO₄?₂.?4?Adsorption kinetics experiments show that the adsorption process of phosphate by magnesium modified reed straw biochar conforms to the quasi-second-order kinetic model,and the adsorption mechanism is the joint action of physical adsorption and chemical adsorption.The adsorption rate is determined by surface adsorption,liquid film diffusion and particle diffusion.The adsorption isotherm analysis shows that the adsorption process conforms to Langmuir equation and is a single molecule layer adsorption.?5?The co-existing ion and desorption experiments showed that Cl^-,SO₄^2-,HCO₃^-and CO₃^2-inhibited the adsorption of phosphate by magnesium modified biochar,among which the inhibition effect of HCO₃^-and CO₃^2-was more obvious.After three times desorption,magnesium modified biochar can completely release the adsorbed phosphorus,which is conducive to the reuse of magnesium modified biochar.?6?The adsorption effect of reed straw biochar on phosphate in water environment is poor,but the adsorption effect on phosphate is significant after magnesium ion modification.When the ambient temperature was 308 K,the concentration of hexahydrate magnesium chloride was 2 mol·L^-1,the dosage was 2.0 g·L^-1,and the p H was 7.0,the adsorption effect of magnesium modified biochar on phosphate was the best,and the adsorption amount reached 2.37 mg·g^-1.