Preparation Of "Adsorption-catalysis" Bifunctional Bimetallic Oxide And Its Tetracycline Removal From Water

In recent years,due to the overuse of antibiotics in fields such as human medicine and animal husbandry,high-risk antibiotics are ubiquitous in various ecosystems from terrestrial to aquatic environments,and even in surface and direct drinking water,posing a major threat to human health and the ecological environment.To comply with the trend of sustainable and green development and effectively solve the increasingly serious problem of antibiotic pollution in water bodies,various technologies for efficient removal of antibiotics have been developed,such as membrane separation,advanced oxidation,adsorption,and biodegradation.However,the above single technology is often difficult to meet the needs of actual antibiotic wastewater treatment,so the coupling technology of multiple treatment methods has gradually attracted attention.Among them,adsorption-photocatalytic coupling technology has great potential in the treatment of antibiotic pollution because of its green,high efficiency,and energy-saving advantages.Therefore,it is very important to develop a low-cost,efficient,and harmless adsorption-catalytic dual-function catalyst.Based on the above background,this paper intends to use the“precursor-calcination method”to prepare bimetal oxide-based catalysts（LDOs）,so that it has the dual function of adsorption and catalysis,and select tetracycline（TC）as the representative of antibiotic,through the construction of an adsorption-photocatalytic system for efficient adsorption and catalytic oxidation of tetracycline in water.The specific research content and conclusions are as follows:（1）A series of LDOs were prepared by high-temperature calcination with layered bimetal hydroxide（LDHs）as the precursor,and the adsorption-catalytic degradation system was constructed.The optimal synthesis conditions were optimized by adjusting the technological parameters such as metal type,metal proportion,and calcination temperature.The results show that:Compared with LDHs,the adsorption-catalytic activity of LDOs-based catalysts is improved.When the metal type of the plate is Zn-Al,the metal ratio,and the calcination temperature are 2:1 and 400℃respectively,the prepared Zn₂Al₁@LDO₄₀₀ has the highest adsorption-catalytic activity.The removal rate of TC can reach 86.13%under visible light irradiation for 180 min.In addition,after five cycles of Zn₂Al₁@LDO₄₀₀,the TC removal rate was not significantly reduced,indicating excellent photostability and reusability.（2）Using Zn₂Al₁@LDO₄₀₀ as an adsorbent,the adsorption effect and reaction mechanism of TC were systematically investigated.The results show that the adsorption of Zn₂Al₁@LDO₄₀₀ to TC confirms the Langmuir model and pseudo-second-order kinetic model,indicating that the procs are heterogeneous monolayer adsorption limited by chemisorption.Thermodynamic calculation shows that high temperature is more conducive to the adsorption of TC by Zn₂Al₁@LDO₄₀₀.Fourier infrared spectroscopy（FT-IR）,X-ray diffraction spectroscopy（XRD）,and scanning electron microscopy（SEM）were used to analyze the solid samples after TC adsorption equilibrium,which confirmed that a variety of mechanisms were involved in the adsorption process of tetracycline,including electrostatic interaction,complexation,and structural“memory effect”.（3）The effects of different environmental factors on the photocatalytic degradation of TC under visible light conditions were evaluated by a degradation kinetics experiment system with Zn₂Al₁@LDO₄₀₀ as the photocatalyst.The results show that Zn₂Al₁@LDO₄₀₀ has better environmental adaptability,the more catalyst dosage,the smaller the initial concentration of pollutants,and the higher the photocatalytic degradation efficiency of TC.When the catalyst dosage is 0.5 g/L,the initial concentration of tetracycline is 50 mg/L,and the p H is 7,the TC degradation efficiency is the highest,and the reaction process conforms to the quasi-first-order kinetic model.In addition,the order of the interference intensity of the influence of different anions on TC removal was Cl^-≈NO₃^-<PO₄^3-.（4）The results of the free radical shielding experiment and electron paramagnetic resonance（EPR/DMPO）test showed that the active species involved in TC degradation in Zn₂Al₁@LDO₄₀₀ photocatalytic system were h⁺,?O₂^-,and?OH,among which h⁺and?O₂^-were the main oxidation.The adsorption-catalysis process of Zn₂Al₁@LDO₄₀₀ on TC is mainly to adsorb TC to the surface of the catalyst through physical and chemical effects.After the catalyst is excited by visible light,electron-hole pairs are generated,and strong oxidizing radicals?O₂^-and?OH are generated to achieve the synergistic degradation of TC.