Optimized Preparation Of Metal-organic Framework Adsorbent And Its Removal Mechanism For Typical Antibiotics From Water

As a novel category of organic pollutants,antibiotics have been frequently detected in natural water environments in recent years.However,due to their biological recalcitrance,traditional water treatment technologies cannot satisfactorily meet the demand for advanced treatment.As a result,developing efficient advanced treatment technologies for antibiotic residues has become a research hotspot in the current environmental field and one of the major problems that urgently needs to be addressed.The adsorption method,featuring high removal efficiency,simple operation and no secondary pollution,exhibits great potential for removing antibiotic pollution in water bodies.The key to the success of the adsorption method lies in the preparation of the adsorbent.The adsorption capacity,stability and recycling performance are crucial indicators for assessing the quality of the adsorbent.Metal-organic frameworks（MOFs）,with their high specific surface area,tunable porous structure and abundant active sites,have significant advantages in the adsorptive removal of antibiotics in water.In this project,the adsorption capacity,stability and recycling performance of MOFs were improved through transition metal doping,alkali activation,high-temperature pyrolysis,and in-situ growth on three-dimensional supports.The adsorption behavior and mechanism of MOFs-based adsorbents towards typical antibiotics in water were investigated.The following are the main contents:（1）Metal-organic frameworks（MOFs）with high porosity have shown potential in environmental remediation.In this study,copper-doped ZIF-8（Cu-ZIF-8）was synthesized using an in-situ process of a zinc metal-organic framework（ZIF-8）at room temperature.The adsorption capacity of Cu-ZIF-8 toward tetracycline hydrochloride（TC）was 2.4 times higher than that of pristine ZIF-8.The effects of adsorbent dosage,initial concentrations,solution p H values,coexisting ions,and reaction temperature on adsorption capacity were investigated.The adsorption process of TC over Cu-ZIF-8 was well-fitted with pseudo-second-order and Langmuir models,suggesting that chemisorption was the dominant mechanism in the adsorption reaction.Furthermore,the Cu-ZIF-8 adsorbent had a homogeneous surface for adsorption.Adsorption thermodynamic studies implied that the adsorption process was spontaneous and exothermic.In addition,the Cu-ZIF-8adsorbent exhibited excellent adsorption performance toward TC in tap water,river water,and pharmaceutical wastewater.The research in this chapter provided a facile and efficient strategy for fabricating MOFs-based adsorbents for water purification.（Chapter 3）（2）The weak coordination between metal and organic bonds in metal-organic frameworks（MOFs）leads to their poor water stability,which limits their application in aqueous reactions.In this study,the integration of KOH activation and high-temperature pyrolysis was applied to fabricate leaf-like zinc-based zeolite imidazole materials（ZIF-L）derived N-doped porous carbon（NPC）adsorbent.It was found that KOH concentration had an effect on the physical structure and chemical property of NPC,and the NPC-0.5 demonstrated the highest adsorption capacity.The morphology,crystalline phase,composition and pore structure of the adsorbent were characterized.KOH activated treatment brought larger surface area and abundant porosity,which were beneficial for the adsorptive reaction.The NPC-0.5 exhibited the highest adsorption capacity of 330.98 mg g^-1,and the adsorption process was a combination of chemical and physical interactions.Moreover,the NPC-0.5 efficiently removed various antibiotics（oxytetracycline and chlortetracycline）and could effectively remove TC from different water bodies（deionized water,tap water and river water）.After being reused for four times,the adsorption property of NPC-0.5 showed a negligible decline.This research proposed a method combining KOH activation and high temperature pyrolysis to prepare ZIF-L-derived nitrogen-doped porous carbon adsorbents with great stability and adsorption performance,which showed huge potential in the remediation of antibiotic-containing wastewater.（Chapter 4）（3）Considering the low recyclability of powder adsorbents when applied in aqueous reactions,the preparation of macroscopically efficient adsorbent materials can solve the above problems.Taking advantage of the 3D iron network and admirable adsorption performance of the Fe-based metal-organic framework（Fe-MIL）,a solvothermal method was used to in-situ grow a series of Fe-MILs（MIL-53（Fe）,MIL-100（Fe）and MIL-101（Fe））onto the iron network.Through various spectroscopic characterizations,the successful growth of Fe-MILs on the3D iron mesh was verified.In addition,the composite 3D material inherits the high adsorption capacity of powdered Fe-MILs and exhibits good recycling performance.Among them,Fe/MIL-100（Fe）exhibited the highest performance towards tetracycline（TC）,with more than 95%of TC being removed at the fifth adsorption cycle.The mechanism indicated that theπ-πand hydrogen bonding interactions between Fe/MIL-100（Fe）and TC molecules played an essential role in the adsorption process.Besides,the Fe/MIL-100（Fe）adsorbent was stable in water with negligible iron leaching in solution.It is worth noting that Fe/MIL-100（Fe）maintained a high adsorption performance towards TC in a wide p H range of 2-10and suffered minor influence from the anion and humic acid in solution.Even in actual aqueous solutions（such as tap water,river water and pharmaceutical wastewater）,the Fe/MIL-100（Fe）adsorbent exhibited high performance.This research provided a new method for synthesizing 3D Fe-MILs adsorbents for wastewater remediation.（Chapter 5）...