Synthesis Of Metal Organic Framework/Graphite Oxide Granules And Their Adsorption Performance For Tetracyclines

Antibiotics are a class of pharmaceuticals that are frequently used in people's daily life.Due to the heavy use of antibiotics and lack of effective regulation and control,they are continuously accumulated in environmental media,which can induce an increase in drug-resistant and resistance genes,and pose potential threats to human health and the ecological environment.Therefore,the efficient removal of antibiotic contamination in water has become one of the research hotspots.Recent studies have shown that adsorption technology is expected to treat antibiotic wastewater quickly and efficiently,however,as a result of the limitations of the traditional adsorbents used widely in current,such as low adsorption capacity,poor separation and regeneration performance,etc.,it is difficult to meet the demand of actual wastewater.This study started from the preparation of aluminum-based MOF/GO?Al-MOF/GO?granules adsorbents with good stability and liquid phase separation performance,regarded the removal of the representative antibiotic tetracyclines?TCS?pollutants in water as the application goal,explored the preparation methods and techniques of MOF/GO powder and granules,and then obtained granular adsorbent with good adsorption properties,separation and regeneration performance and structure stability.At the same time,the adsorption materials were characterized by multiple techniques,and the properties and structure change of Al-MOF/GO before and after molding were investigated.Then,tetracycline?TC?,oxytetracycline?OTC?and chlortetracycline?CTC?were chosen as adsorbates,and used to investigate the adsorption behavior of TC,OTC and CTC onto Al-MOF/GO powder and granules adsorbent,and the adsorption research mainly included influencing factors,adsorption model and adsorption characteristics.The main research contents and conclusions are as follows:?1?Al-MOF/GO granules with good liquid phase separation capacity were prepared for the first time by introducing different ratio SA.SEM results show that Al-MOF/GO granules maintained a distinct rod-like structure of Al-MOF crystals,the Al-MOF/GO crystals were connected by SA fibers,and the blocky shape accumulation of Al-MOF/GO crystals began to appear with the increase of SA dosage;XRD results display that the crystal structure of Al-MOF/GO crystal was less affected by the pelletization process;N₂ adsorption-desorption results present that the porosity and surface area of the sample were decreased with the introduction of SA,while some new mesopores generated,and the optimum amount of SA introduction was 13.8 wt%;Last,FTIR and XPS results indicate that SA and Al-MOF/GO powder were bonded by physical crosslinking.?2?The adsorption influencing factors results show that the adsorption capacity of Al-MOF/GO powder and granules increased with the initial concentration of TCS until the adsorption equilibrium;the TCS adsorption rate on Al-MOF/GO granules was uniformly slowed with time,and reached adsorption equilibrium within about 720 minutes;The solution pH value affected the stability of the Al-MOF framework,and the appropriate pH value was4¹0;Ionic strength had a slight inhibitory effect on the adsorption reaction;Increasing the temperature during the adsorption process can enhance the adsorption.?3?The adsorption model results show that the pseudo second-order model was better fitted with the experimental data for TCS adsorption on Al-MOF/GO powder,suggesting that the chemisorptions may be the rate-limiting step,however,the adsorption behavior of TCS on Al-MOF/GO granules were more suitably described by the pseudo-first-order kinetic model,which demonstrated biphasic kinetics at different rates.For isotherm,the adsorption processes on Al-MOF/GO powder and granules both were dominated by the freundlich model,indicating that surface energies were heterogeneous in the adsorption process.The thermodynamic results display that the adsorption reaction was spontaneous,entropy-increasing,endothermic and the TCS adsorption process on Al-MOF/GO granules might involve a certain chemical adsorption.?4?The adsorption characteristics results exhibit that Al-MOF/GO granules and powder samples had good water stability and regenerability,and Al-MOF/GO granules maintained about 85%of the initial saturated adsorption capacity after 3 cycles of regeneration.Al-N covalent bond,hydrogen bond and?-?stacking together contributed to TC adsorption on Al-MOF/GO granules,while the adsorption of Al-MOF/GO granules for OTC or CTC may involve in cation-?bond,?-?stacking and hydrogen bonding.