Study On The Adsorption Properties Of Pseudophysalis Seed Gum Composite Aerogel For Tetracycline

In recent years,antibiotics,as an important drug for the treatment of bacterial infections,have been widely used in medical and health,livestock breeding,food industry and other fields.However,due to the incomplete metabolism of antibiotics in humans and animals,most antibiotics enter the soil and water environment in their original form.These antibiotics are difficult to be completely degraded,and their degradation intermediates are more toxic.If not properly treated,it is easy to cause water pollution and damage the ecological environment of aquatic organisms.Therefore,the removal of antibiotics in the environment is of great significance to protect the ecological environment.At present,there are many methods to remove antibiotics,including ozone oxidation,photocatalytic degradation,microbial degradation,electrochemical decomposition,adsorption and so on.The adsorption method which can adsorb antibiotics from the environment to the surface of adsorbent is considered to be an effective method to remove antibiotics.Compared with other removal methods,adsorption method has the advantages of low power consumption,low cost,high efficiency,simple operation and no secondary pollution.Nicandra physalodes（L.）Gaertn seed gum（NPG）is a colorless,odorless,non-toxic edible colloid on the surface of Nicandra physalodes（L.）Gaertn seed.As a component of traditional Chinese medicine NPG is used in food,medical and other fields.The main component of NPG is the mixture of polysaccharides with galacturonic acid as the main chain.When metal ions such as Cu²⁺,Ca²⁺and Ni²⁺exist in aqueous solution,NPG will crosslink with metal ions to form a gel with a space network structure.Biomass aerogels have the advantages of no pollution,easy recovery and biodegradation.Based on these characteristics,NPG material is expected to become a new type of biomass adsorption material.Based on the above background,the main work of this paper is as follows:（1）Hydrogel spinning was used to prepare nickel loaded NPG-Ni²⁺.The scanning electron microscope（SEM）,Fourier transform infrared spectrometer（FT-IR）,thermogravimetric analyzer and surface area analyzer（BET）were used to characterize material.The adsorption mechanism of NPG-Ni²⁺was studied by simulating tetracycline water environment.The effects of p H,temperature,amount of adsorbent and contact time on the adsorption performance of TC were studied.It was found that when the temperature is 303K,the dosage is 10 mg,and the initial concentration of TC is 200 mg/L,the maximum adsorption capacity is 102.68mg/g.The Langmuir isothermal model and quasi second-order kinetic model can better describe the adsorption process,which indicates that the adsorption process is a monolayer adsorption on the homogeneous surface of adsorbent and is dominated by chemical driving force.Thermodynamic analysis shows that the adsorption reaction is a spontaneous exothermic process within the experimental temperature range.The adsorption desorption cycle experiment showed that the recycling performance of NPG-Ni²⁺material was poor,which needed to be further improved.According to the results of experiment,it is speculated that the adsorption of TC by NPG-Ni²⁺is mainly driven by n-πinteraction and cationic bond bridge.（2）Because of the poor effect of NPG-Ni²⁺gel on TC removal and poor reuse.Based on the effect of Cu²⁺on TC in the water environment,NPG-Cu²⁺was prepared by wet spinning.The morphology of the material was characterized by various instruments.The effects of p H,temperature,adsorbent dosage and contact time on the adsorption of TC by NPG-Cu²⁺were studied by static adsorption experiments.The results showed that the maximum adsorption capacity of NPG-Cu²⁺gel material reached 216.18mg/g when the temperature was 323K,the dosage of adsorbent was 10mg,and the initial concentration of TC was 140mg/L.The higher the temperature,the better the adsorption process.The adsorption process is spontaneous endothermic.The experimental data are more consistent with the Freundlich model and the quasi second order kinetic model,which indicates that the adsorption may be dominated by chemical adsorption on the heterogeneous surface of the adsorbent.The 4 sorption desorption cycle tests of the material showed that the removal rate of TC solution by NPG-Cu²⁺gel line to 100 mg/L can still reach over 60%,which has good reusable property.The results of experiments suggest that the adsorption of TC by NPG-Cu²⁺is mainly driven by hydrogen bond,electrostatic interaction,n-πinteraction and cation bond bridge.（3）The unique three carboxyl structure of citric acid makes citric acid chelate with metal ions and promote the binding with TC.In order to further improve the adsorption efficiency of NPG-Cu²⁺to TC,NPG/CA was prepared by using two valent metal ion as crosslinking agent.The composite was characterized by various techniques,and its adsorption behavior was studied in simulated tetracycline polluted water environment.The experimental results show that the adsorption behavior of tetracycline on NPG/CA composite can be well described by Freundlich model and quasi second-order kinetic model,which indicates that the adsorption of TC by NPG/CA materials occurs on the heterogeneous surface of gel wire and the adsorption process is dominated by chemical driving force.The maximum adsorption capacity of NPG/CA was 231.93mg/g at 293K,10mg of adsorbent and 140mg/L of TC.The experimental data showed that the adsorption of tetracycline on NPG/CA was easier in the low temperature environment.The adsorption behavior of TC on the composite material was spontaneous exothermic.The results of experiments suggest that the adsorption process of NPG/CA to TC is mainly driven by hydrogen bond,n-πinteraction,cation bridge.and electrostatic interaction.