Effects of Different Level Citric Acid on the Adsorption and Desorption of Sulfonamides in Red Soil

To study the effect of CA on the adsorption and desorption of sulfonamides in red soil can provide theoretical support and scientific basis for the study of remediation of antibiotic contaminated soil. The adsorption and desorption isotherms of sulfadiazine(SDZ), sulfamethoxazole(SMZ) and sulfapyridine(SPD) on red soil treated with different concentrations of CA were set up to clarify the isotherm characteristics and effects of adding different concentrations of CA on the adsorption and desorption of SAs in red soil. The results showed that the adsorption data of red soil to SAs with different initial concentrations under different concentrations CA treatments were consistent with Freundlich, Langmuir and Henry models; the desorption data of red soil to SAs conform to Freundlich and Henry models . Freundlich model parameter n of red soil adsorption SAs with high concentration of CA deviated the farthest from 1. The K_\mathrmF , K_\mathrmd and K_\mathrmL values of red soil adsorbed SAs all showed high concentration > low concentration ≈ control, and the K_\mathrmF and K_\mathrmd values of red soil desorbed SAs all showed high concentration > low concentration ≈ control. High concentration CA treatment improved the adsorption capacity of red soil adsorbed SAs. High concentration of CA treatment significantly increased the adsorption capacity of red soil for SAs, and the adsorption capacity increased by 59.30%–285.30%; the amount of SAs desorbed by red soil was significantly reduced, and the desorption rate was 0.80%–45.88%. The desorption of SAs on red soil hysteresis. High concentration of CA treatment promotes the adsorption and fixation of SAs in red soil, inhibits the desorption of SAs from red soil, and reduces the risk of surface water and groundwater pollution caused by the migration and diffusion of SAs from contaminated soil.