Effect Of Biochar On Adsorption And Transport Oftetracycline Hydrochloride In Aeolian Sandy Soil

Biochar,as a widely used remediation material,has the characteristics of environmental protection,low price,little pollution and excellent remediation effect,and is often used in the treatment of pollutants.Tetracycline hydrochloride（TCH）is the most widely used and most used class of antibiotics.It has stable structure and is difficult to degrade.In recent years,it is often detected in soil and water environment media.TCH can induce bacteria to produce antibiotic resistance genes,resulting in the loss of action of a variety of antibiotics,which poses a potential threat to human health and environmental safety.In this study,TCH was used as the research object to prepare Na HCO₃modified biochar（NBC）.The adsorption and migration of TCH in soil column after adding NBC under different physical and chemical conditions were explored through indoor soil column simulation tests.This study aims to provide theoretical support for predicting the occurrence form,migration and transformation of TCH in soil and the feasibility of using biochar to repair and improve antibiotic-contaminated soil.The main conclusions of this study are as follows:（1）The physical and chemical properties of Na HCO₃-modified biochar were significantly changed compared with the original biochar（BC）.The surface of NBC is loose and porous with abundant pore structure.The specific surface area of NBC is 1.59 times larger than that of BC,and the pore volume is 1.77 times larger.After modification,the functional groups C=C and-COOH on the NBC surface disappeared,and the existing silica on the surface decomposed.It was found that the adsorption capacity of NBC on TCH reached 42.92 mg g^-1.（2）NBC,NBC-1（1%NBC in aeolian sand soil）and aeolian sand soil have different adsorption mechanisms for TCH.The adsorption of aeolian sand and NBC-1 to TCH conforms to Langmuir model（R²reached 0.98 and 0.93,respectively）.The adsorption processes of NBC and NBC-1 on TCH were most consistent with Freundlich model（R²reached 0.92 and 0.96,respectively）.The adsorption of TCH by the three groups conforms to the quasi-second-order adsorption model（R²of 0.99,0.99 and 0.97,respectively）.Thermodynamic adsorption indicates that the adsorption of NBC on TCH is spontaneous and exothermic,while the adsorption of aeolian sand and NBC-1 on TCH is non-spontaneous and endothermic.The adsorption of the three ions on TCH follows the same rule.With the increase of p H of the adsorption system,the increase of ionic strength and the addition of cations,the adsorption of NBC,NBC-1 and wind-sand soil on TCH will be inhibited,and the inhibition effect of bivalent ions on adsorption is stronger than that of univalent ions.（3）Different physical and chemical conditions have different effects on TCH migration in aeolian sandy soil and NBC-1.The experimental results show that the migration behavior of TCH increases with the increase of p H.The effect of velocity on TCH migration in aeolian sandy soil and NBC-1 is not significant.The transport behavior of TCH in aeolian sand and NBC-1 is promoted with the increase of ionic strength in the environment.It was also found that Ca²⁺promoted TCH more significantly than Na⁺.The maximum effluents concentration（C/C₀）and recovery rate of TCH in NBC-1 are smaller than those in aeolian sandy soil.（4）Both clay and humic acid in soil components can promote the adsorption of aeolian sand and NBC to TCH,and inhibit the migration behavior of TCH in soil.Moreover,the inhibition effect was positively correlated with the component content,and the influence behavior was more obvious after the addition of NBC.