Adsorption And Mechanism Of Mercury In Water By Magnetic Nanocomposites Based On CoFe₂O₄@SiO₂

With the economic globalization and the large-scale development of industrialization,heavy metal pollution of water has caused widespread concern.Mercury is one of the most toxic heavy metals,with persistence,bioaccumulation and ease of migration.Mercury can enter the body through the food chain,causing irreversible damage to human function and the nervous system.Adsorption method is a common heavy metal wastewater treatment methods,with simple,low cost,high efficiency and so on.In this study,the adsorption properties of divalent mercury ions in water were investi-gated by using sulfhydryl/polypyrrole functionalized magnetic nano-cobalt ferrite compo-sites?CoFe₂O₄@SiO₂-SH and PPy-CoFe₂O₄@SiO₂?.The materials were characterized by means of XRD,BET,FTIR,SEM and XPS.The effects of various factors?solution pH,ad-sorbent dosage,coexisting ions,etc.?on the adsorption of mercury were investigated.Re-viewing the regeneration performance of the material and exploring ways to improve its recycling efficiency.The adsorption of mercury from CoFe₂O₄@SiO₂-SH and PPy/CoFe₂O₄@SiO₂ composites were explored by Langmuir and Freundlich adsorption iso-therm model,as well as pseudo-first-order,pseudo-second-order and intra-particle diffusion kinetics models to reveal the mechanism.The results showed that the adsorption of Hg???by Co Fe₂O₄@SiO₂-SH was affected by pH and reached the maximum at pH=8.With the increase of dosage,the adsorption capacity decreased and the removal rate increased.The existence of coexisting ions affected the adsorption of Hg???and Ca²⁺and Cl^-have a great influence.CoFe₂O₄@SiO₂-SH has high recovery loss and great regeneration performance.The adsorption reached equilibrium at 10 h,and the process fitted well with the pseudo-second-order kinetics model.The ad-sorption isotherm fitted the Freundlich model and the maximum adsorption capacity was641.0 mg/g.The adsorption process was exothermic and spontaneous.The adsorption of Hg???by PPy/CoFe₂O₄@SiO₂ was also affected by pH and reached the maximum at pH=8.With the increase of dosage,the adsorption capacity decreased and the removal rate increased.The existence of coexisting ions affected the adsorption of Hg???and Ca²⁺and SO₄^2-have a great influence.The regeneration performance of PPy/CoFe₂O₄@SiO₂ is great.The adsorption reached equilibrium at 8 h,and the process fitted well with the pseudo-second-order kinetics model.The adsorption isotherm fitted the Langmuir model and the maximum adsorption capacity was 680.2 mg/g.The process was endothermic and spontaneous.