Manganese Silicate Eggshell Nanomaterials For The Catalytic Degradation Of Tetracycline In Water

The burgeoning issue of environmental pollution stemming from the overuse of antibiotics has accentuated the pressing need for research into the elimination of antibiotics from water.Chemical catalytic systems,utilizing H₂O₂ and peroxymonosulfate（PMS）as oxidants,hold the potential to ameliorate the present state of antibiotic contamination.The success of such systems hinges upon the selection and design of catalysts,in this regardand,the use of self-preservative eggshell nanocatalysts which effectively tackle the risks of catalyst aggregation and metal ion overflow.However,the customary use of SiO₂ shells containing only a single function may impede the catalytic performance from further improvement.Hence,it is imperative to functionalize the shell of eggshell-structured nanocatalysts.In this study,Fe₃O₄@MnSiO₃ and Co₃O₄/C@MnSiO₃ eggshell nano-catalysts with a multifunctional MnSiO₃ shell were developed utilizing H₂O₂ and PMS as oxidants for the treatment of tetracycline（TC）containing wastewater.Through the exploration of material morphology,surface chemical properties,catalytic performance,stability,applicable conditions and activation and degradation mechanism,the following conclusions are obtained:（1）In this study,the introduction of MnSiO₃ shell was achieved by utilizing Fe₃O₄@SiO₂ and Co₃O₄/C@m SiO₂（CCS）as templates through a hydrothermal method.The synthesized MnSiO₃ shell exhibits the following functionalities:（1）It serves as a protective barrier for the core,mitigating the aggregation of the catalyst during its preparation and reaction processes while minimizing the loss of active sites during the reaction.（2）It endows the catalyst with a high specific surface area and mesoporous channels,facilitating the rapid enrichment of pollutants and providing effective mass transfer pathways across the shell layers.（3）It significantly reduces the leaching of metal ions from the catalyst,leading to a decrease of over 50%in Mnion leaching and a 69%reduction in Co ion leaching,thereby enhancing the environmental compatibility of the catalyst.（4）The eggshell configuration of the MnSiO₃ shell and the core exhibits a pronounced synergistic effect.（5）It exhibits the capability to activate H₂O₂ and generate O₂^-·,thus furnishing a secondary active site for the Fe₃O₄@MnSiO₃ catalyst.（2）The applicable conditions and catalytic degradation mechanisms of the two systems constructed in this study were elucidated.The Fe₃O₄@MnSiO₃/H₂O₂ system demonstrated optimal catalytic degradation performance at p H 3.The Fe₃O₄ core facilitated the activation of H₂O₂ through electron loss,generating highly oxidative·OH species responsible for the degradation of tetracycline.Simultaneously,the MnSiO₃ shell played a supportive role by generating O₂^-·through electron gain from activated H₂O₂,thereby assisting in the degradation of TC.The CCMS/PMS system exhibited its optimum catalytic degradation efficiency at p H 5-9.The Co₃O₄/C（CC）core activated PMS through electron gain and direct electron transfer,producing SO₄^-·and ¹O₂ as active species for TC degradation.Both systems showcased rapid catalytic degradation rates at a reaction temperature of 20°C and exhibited robust resilience against anionic interference.（3）Through meticulous structural modulation and design,the two eggshell-structured nanocatalysts prepared with MnSiO₃ as the shell,namely Fe₃O₄@MnSiO₃ and CCMS,manifested a remarkable synergistic effect between the core and shell.The precisely tailored core-shell architecture achieved an optimal dynamic equilibrium between adsorption-activation-degradation,facilitating the expeditious removal of tetracycline from aqueous environments.Notably,Fe₃O₄@MnSiO₃ with a cavity size of 76 nm displayed a reaction rate of 0.0352 min^-1 for H₂O₂-activated TC degradation,surpassing Fe₃O₄(0.0145 min^-1)by2.4-fold and MnSiO₃(0.0061 min^-1)by 5.8-fold.Similarly,the rate of PMS-activated TC degradation in the CCMS system(0.04026 min^-1)exceeded CC(0.02774 min^-1)by 1.45-fold and MnSiO₃(0.0072 min^-1)by 5.6-fold.