Study On The Effect Of Attapulgite-loaded Nano-zero Valence Iron On The Removal Of Cu And Antibiotics In Water

Heavy metals and antibiotics have been widely detected in water,among which the products of Cu（Ⅱ）and tetracycline antibiotics complexation were also detected.The complexation changed the structural characteristics of these two substances,thus accelerating the migration of Cu（Ⅱ）in the environment and more easily leading to the emergence of tetracycline resistance genes.The combined contamination of Cu（Ⅱ）and tetracycline antibiotics has attracted more and more attention.In view of the abundant and cheap attapulgite clay ore in Gansu Province with high impurities and low utilization rate,and the instability of high-quality adsorbent nano-zero-valent iron itself,this study adopted the liquid phase reduction method,controlled the iron-earth ratio of 1:2,loaded iron on attapulgite,and prepared the nano-zero-valent iron material supported by attapulgite.The problem of agglomeration and oxidation of nano-zero-valent iron was solved,and the adsorption capacity of attapulgite to heavy metal-antibiotic composite pollution was improved.Cu（Ⅱ）and TC,Cu（Ⅱ）and OTC were selected as the target pollutants to explore the adsorption efficiency of attapulgite-loaded nano zero-valent iron on the two composite pollutants,and explore the co-adsorption mechanism.The main research contents and results are as follows:The characterization results of SEM,EDS,XRD,and FT-IR showed that the surface of ATP-n ZVI had abundant carboxyl,hydroxyl,Fe-OH,Fe OOH and additional functional groups,which further improved the stability and reactivity,and could provide favorable conditions for the adsorption of Cu（Ⅱ）and tetracycline antibiotics.The coordination,π-πdispersion and hydrogen bonding effects of ATP-n ZVI on Cu（Ⅱ）and tetracycline antibiotics were verified.The adsorption properties of Cu（Ⅱ）and tetracycline increased by 66.4%and 32.16%,respectively,when the ATP was loaded with zero-valent iron nanoparticles.The adsorption properties of Cu（Ⅱ）and oxytetracycline increased by 49.28%and 25.08%,respectively.The adsorption performance has been significantly improved,and the adsorption performance of Cu（Ⅱ）in composite pollution has been improved even more.After aging,the removal rate of compound contamination did not decrease by more than 2%.This suggests that loading zero-valent iron nanoparticles onto ATP can improve the problems of easy oxidation and unstable adsorption performance of zero-valent iron nanoparticles.The effects of dosage,p H,coexisting ions,time,temperature and other factors on the adsorption of Cu（Ⅱ）and TC,Cu（Ⅱ）and OTC composite pollution by ATP-n ZVI were investigated.The results show that p H has a large influence on the adsorption effect,with the removal rate increasing with p H and then becoming stable.The effect of p H on Cu（Ⅱ）adsorption by materials is greater than that of tetracycline antibiotics.The optimum p H for Cu（Ⅱ）and TC,Cu（Ⅱ）and OTC are 6.Composite pollutants are acidic in natural environments.After the adsorption of ATP-n ZVI,the p H of the solution will tend to be neutral,which is beneficial for the remediation of environmental pollution.The influence degree of ionic strength on the adsorption of two kinds of combined pollution is Ca²⁺>Mg²⁺>Na⁺.Pseudo-second-order kinetic models can be used to adsorb the two recombination contaminations.The adsorption process may be controlled by chemisorption.The Freundlich model can better simulate the adsorption process of Cu（Ⅱ）,while the Langmuir model can better simulate the adsorption process of tetracycline and tetracycline.It is speculated that the adsorption process of Cu（Ⅱ）and TC,Cu（Ⅱ）and OTC on ATP-n ZVI belongs to single molecular layer adsorption.Based on the Tempkin model,it has been concluded that the adsorption mechanism of ATP-n ZVI on compound contamination may be both physical and chemical adsorption.Increasing the temperature helps to adsorb the two recombination contaminations,which is a spontaneous and endothermic process.The adsorption mechanisms of Cu（Ⅱ）may include electrostatic adsorption,surface co-precipitation,ion exchange,surface complexation,physical adsorption,and chemical adsorption.The adsorption mechanisms of tetracycline and tetracycline mainly include surface complexation,physical adsorption,chemisorption,hydrogen bonding,π-πdispersion and electrostatic interaction,and chemisorption is the main adsorption mechanism.The adsorption capacities of Cu（Ⅱ）and TC were 2.985 mmol/g and 2.905 mmol/g,respectively.The adsorption capacities of Cu（Ⅱ）and OTC were 2.257 mmol/g and 2.118 mmol/g,respectively.The adsorption capacity of Cu（Ⅱ）and tetracycline antibiotics is nearly the same,which also proves that the effect of ternary bridging on the adsorption of composite pollution does exist and this effect cannot be ignored.In the composite contaminated solution and material composite system,based on the complexation（coordination）of Cu（Ⅱ）and tetracycline antibiotics and the bridging effect between Cu（Ⅱ）and ATP-n ZVI,a co-adsorption model（ATP-n ZVI-metal ion-antibiotic complex）was initially constructed.It was concluded that the ternary bridging effect of material-metal ion-antibiotic was the reason for the increased adsorption capacity of Cu（Ⅱ）and tetracycline antibiotics in the co-adsorption process.In this paper,the adsorption efficiency and co-adsorption mechanism of attapulgite-loaded nano-zero valence iron on heavy metal-antibiotic composite pollution were investigated,and it was proved that the prepared material had a good removal effect on Cu（Ⅱ）and TC,Cu（Ⅱ）and OTC.In this study,an environmentally friendly and effective adsorbent was prepared to enrich a wide range of applications of attapulgite resources.We have enriched and developed the theory and techniques of adsorption for composite contamination systems and provided theoretical support for further development and application of adsorption removal techniques for heavy metal-antibiotic composite pollution.