Preparation Of Manganese-Cerium-based Oxide Composite Nanomaterials And Study On The Performance And Mechanism Of Tetracycline Removal From Water

Antibiotics are a new type of environmental pollutants,and tetracycline(TC)is a common broad-spectrum antibiotic among antibiotics,which is widely used in animal husbandry and aquaculture.These pollutants entering the water body will pose a serious threat to human health.Due to the drug resistance of bacteria,it is difficult to remove them by biodegradation.Therefore,adsorption and other non biodegradation methods show advantages in TC treatment because of their low cost,environmental friendliness,simple operation process and wide range of raw materials of adsorbents.Nanomaterials have high chemical properties because of their small particle size and large specific surface area,and the unsaturated surface will increase the number of functional groups on the surface.At the same time,nanomaterials show high adsorption capacity due to their unique morphological and structural characteristics.Therefore,the use of nanomaterials to treat TC in water is a promising.Among them,nanomaterials based on manganese and cerium have attracted extensive attention because of their low cost and high activity,and the combination of the two can improve the redox performance of mixed oxides and improve their adsorption and catalytic activity.In this paper,manganese-cerium-based oxide composite nanomaterials were prepared by solvothermal method and coprecipitation method and used to remove TC from water.In order to detect the specific structure of the adsorbent,the micro morphology and main element composition of the adsorbent were studied by means of scanning electron microscope(SEM),energy dispersive spectroscopy(EDS),X-ray diffractometer(XRD),fourier transform infrared spectroscopy(FT-IR)and Zeta potential;At the same time,the experimental results were fitted by various models such as adsorption kinetics,adsorption isotherm and adsorption thermodynamics,and the removal mechanism of TC by composites was analyzed.In addition,the effects of different reactant ratio,adsorbent dosage and solution p H on the adsorption properties and the reusability of the composites were also studied.The main research contents and conclusions of this paper are summarized as follows:(1)A manganese-cerium co-doped iron-based MOFs composite oxide nanomaterial(Mn Ce/MIL-100)was prepared by solvothermal method,which showed significant removal ability of TC.It was found that the removal efficiency of TC could reach 90%when the concentration of TC was 10 mg/L,the dosage of adsorbent was 15 mg and p H was 6.In addition,the adsorption kinetics of TC on Mn Ce/MIL-100 can be well described by pseudo second-order model.At room temperature,the adsorption capacity is up to203.252 mg/g,which is consistent with the Langmuir isotherm.Through thermodynamic analysis,it is found that this process has the characteristics of absorbing heat,and this absorption is spontaneous.At the same time,Mn Ce/MIL-100 still maintained good TC adsorption capacity after five cycles,showing good repeatability.The infrared spectrum analysis showed that after Mn Ce/MIL-100 reacted with TC,the stretching vibration of aromatic ring group and the bending vibration of-CH₃appeared.(2)An iron-manganese-cerium composite oxide(Fe MC)with higher adsorption rate was prepared by coprecipitation method.The ratio of reactants was optimized in the preparation process,and efficient adsorption performance was obtained.The results show that under the condition of p H 4,the adsorption and removal performance of Fe MC for TC is the best.In addition,the adsorption of TC on Fe MC follows pseudo-second-order kinetics,and the equilibrium data agree well with the Langmuir isotherm,indicating that chemisorption and monolayer adsorption are dominant.According to the Langmuir isotherm,the maximum adsorption capacity of Fe MC on TC at room temperature is214.133 mg/g.The study of adsorption thermodynamics shows that the adsorption process is spontaneous and endother.Regeneration experiments show that the prepared Fe MC adsorbent has high stability,and the performance attenuation is small after repeated use for five times.The prepared adsorbent has the application prospect of efficient removal of antibiotics.(3)In order to further explore the adsorbents with high adsorption capacity,wide p H adaptation range and fast adsorption rate,a copper-manganese-cerium composite oxide(Cu MC)was prepared by coprecipitation method.When the molar ratio of Cu/Mn/Ce was1:1:3,the adsorption capacity of the prepared sample to remove TC was the highest.The results showed that Cu MC showed a TC removal rate of more than 95%in a wide p H range.In addition to electrostatic effect,there are other effects,such as?-?conjugation and hydrogen bonding,which participate in the adsorption process.The adsorption of TC by Cu MC followed the pseudo-second-order kinetic model(R~2=0.996),and the isotherm followed the Langmuir model(R~2=0.997).The maximum adsorption capacity was 344.828mg/g at room temperature.Thermodynamic parameters confirmed that the adsorption of TC on Cu MC was endothermic and spontaneous,and there was affinity between adsorbent and adsorbate.At the same time,the removal of TC by Cu MC has good reusability,and the removal rate is still more than 91%after 5 cycles.It is an excellent adsorption material that can be reused.Infrared analysis shows that Cu MC adsorbent can efficiently adsorb TC,which is related to the stretching vibration of Mn-OH and Ce-o,and?-?conjugation and hydrogen bonding are involved in the adsorption process.