High-efficiency Removal And Mechanism Of Tetracycline From Water By Electrolysis-assisted NZVI

Among the different antibiotics,tetracycline has received more attention because it exhibits serious environmental problems,including ecological risks and human health damage.Electrochemical technology can effectively remove hard-to-degrade contaminants from the aqueous environment,including heavy metals,dyes,and antibiotics.Nanoscale zero-valent iron（NZVI）is an ideal material for water treatment because of its high reactivity,simple preparation,inexpensive availability,and environmental friendliness.Nanoscale zero-valent iron undergoes spontaneous corrosion,which has a significant impact on the reactivity,stability,and long-term fate of nano-zero-valent iron.To address this critical issue,this research prepared nano-sized zero-valent iron（NZVI）and evaluated its performance and mechanism for tetracycline removal in an electrocatalytic environment.The prepared nano zero-valent iron was uniformly dispersed into the electrolyte,and then a voltage was applied to form an electrically assisted nano zero-valent iron system（E-NZVI）to maintain the continuous reactivity of the nano zero-valent iron.The main research results are as follows:（1）The electrolysis-assisted nano-zero-valent iron was effective in tetracycline removal.At an applied voltage of 4 V,its ability to remove tetracycline at 30 mg/L reached 97.3%,which was6.3 times higher than that of the nano-zero-valent iron system without electrolysis assistance.The electrolysis-induced improvement was mainly attributed to the stimulation of the corrosion of zero-valent iron nanoparticles,which accelerated the release of Fe²⁺.Moreover,Fe³⁺can be electronically reduced to Fe²⁺in the electro-assisted nano-zero-valent iron system,which converts the ineffective iron in the system into the effective iron with reduction ability.And electrolysis assisted to expand the p H range of the electro-assisted nano-zero-valent iron system for tetracycline removal.（2）Due to the direct dispersion of zero-valent iron nanoparticles in the electrolyte in this study,it is conducive to the collection and recycling of the catalyst after the reaction and the treatment,avoiding the secondary contamination of the catalyst after the reaction.（3）Scavenger experiments reveal that the reducing ability of nano-zero-valent iron is accelerated in the presence of electrolysis.Moreover,electrically assisted nano-zero-valent iron can also alleviate the passivation of nano-zero-valent iron,a result demonstrated in TEM-EDS mapping,XRD and XPS analysis of nano-zero-valent iron after electrically assisted reaction.This is mainly due to electron migration,implying that the corrosion products of iron（iron hydroxides and oxides）are not formed mainly near or on the surface of the nano-zero-valent iron.In conclusion,electrolysis-assisted nano-zero-valent iron has high removal efficiency for tetracycline and is a potential water treatment method for removing contaminants.After five cycles of experiments,the nano-zero-valent iron still had high tetracycline removal rates in the electro-assisted system,indicating that the nano-zero-valent iron has good stability and reusability in the electro-assisted system.This study provides a new method to maintain the reduction activity of zero-valent iron nanoparticles and offers a new prospect for using electrochemical technology to treat antibiotic wastewater.