Preparation Of Functionalized Alginate Composite And Its Adsorption Efficiency For Tetracycline And Copper Ions In Water

In the livestock industry,antibiotics and trace metals are often used as growth promoters in feed,but most of them are excreted by the animals in metabolic or raw form.Therefore,it is urgent to combat the problem of compound pollution.The adsorption method is widely used because of its simplicity,economy and lack of pollution to the environment.In order to solve the competing adsorption of common materials in compound pollution problems,this paper designs a hydrogel with sodium alginate as the core material and cross-linked with Fe³⁺to form a three-dimensional porous mesh structure,and takes into account the low mechanical strength,poor stable adsorption and weak recycling and regeneration ability of single alginate gel spheres by wrapping Fe₃O₄ and GO in them,the introduction of Fe₃O₄ both increases the adsorption The introduction of Fe₃O₄ both increases the adsorption sites and improves the magnetic separation properties of the material.GO not only has a huge specific surface area,but also contains a large number of oxygen-containing functional groups such as hydroxyl and carboxyl groups on its surface and edges,which has a good effect on the removal of antibiotics and heavy metal ions,thus preparing functional sodium alginate gel spheres GO/Fe₃O₄-SA-Fe³⁺.The SEM,TEM and XRD results showed that GO/Fe₃O₄-SA-Fe³⁺had good morphological characteristics and stable crystallinity.The specific surface area,pore characteristics,stability and magnetic strength of the material were further analysed by TGA,BET and VSM characterisation,thus demonstrating the successful preparation of GO/Fe₃O₄-SA-Fe³⁺.Combining the results of bulk adsorption experiments with FT-IR,XPS and zeta potential characterisation methods,the adsorption mechanism was investigated and the following conclusions were obtained.（1）In a single system,the adsorption of tetracycline hydrochloride or copper ions by the material showed a large dependence on pH,and the study showed that the best adsorption effect was achieved at pH=6.Under the optimum adsorption conditions,the adsorption processes of tetracycline hydrochloride or copper ions both satisfied the proposed secondary kinetic model and the Langmuir model,where the equilibrium times of GO/Fe₃O₄-SA-Fe³⁺for tetracycline hydrochloride or copper ions were about48 h and 28 h,respectively,and the maximum equilibrium adsorption capacities were37.36 mg/g and 15.19 mg/g,respectively.in the cyclic stability and simulated wastewater experiments,GO/Fe₃O₄-SA-Fe³⁺still maintained a high adsorption capacity for pollutants and demonstrated a good regenerative stability as well as strong magnetic separation,thus proving the practical application potential of GO/Fe₃O₄-SA-Fe³⁺.（2）In the composite system,the adsorption capacities of GO/Fe₃O₄-SA-Fe³⁺for both tetracycline hydrochloride and copper ions were increased to different degrees at the optimum pH conditions.A study of the adsorption mechanism showed that the simultaneous removal of both involved two effects,both competitive and facilitative.The main mechanisms involved in the removal of tetracycline hydrochloride by GO/Fe₃O₄-SA-Fe³⁺were electrostatic interaction,π-πstacking,hydrogen bonding and complexation of Fe³⁺with TC.GO/Fe₃O₄-SA-Fe³⁺relies on the oxygen-containing functional groups on the surface of GO/Fe₃O₄-SA-Fe³⁺for the removal of copper ions.The oxygen-containing functional groups act as a common adsorption site for both,thus leading to competition.Also,in the complex system,the addition of copper ions or tetracycline hydrochloride at low concentrations will form complexes,thus increasing the adsorption capacity of each other in solution,but when copper ions or tetracycline hydrochloride are added at higher concentrations,the increased competition will weaken the complexation of Cu-TC.The above study shows that GO/Fe₃O₄-SA-Fe³⁺has great potential for the treatment of complex pollution with tetracycline hydrochloride and copper ions,and solves the problem of competing pollutant adsorption during the treatment process,which provides reference and guidance for practical application.