Study On Adsorption-Desorption Characteristics Of Sulfonamide Antibiotics In Sediment

In recent years,with the extensive use of antibiotics,the pollution of antibiotics in water is becoming more and more serious.As an important part of water body,sediment can enrich pollutants in water by adsorption and make it become a“reservoir”of pollution.Sulfonamides are one of the largest antibiotics produced,used and sold in China,which are widely used in animal husbandry,aquaculture,medical and other industries.Therefore,in this paper,three typical sulfonamides,sulfachloropyridazine（SCP）,sulfamethoxazole（SMZ）and sulfamethoxazole（SMA）,were selected as research objects to study their adsorption-desorption behavior in sediments.The effects of temperature,pH,cation type of cation strength and organic matter on the adsorption-desorption behavior were discussed.The main research results are summarized as follows:（1）The adsorption-desorption process of sediment for three kinds of sulfonamides can be divided into three stages:fast,slow and equilibrated adsorption,and all reach the adsorption-desorption equilibrium in 720min.The adsorption capacity of SCP,SMZ and SMA at equilibrium is 71.4%,69.3%and 59.1%of the adsorption capacity,respectively.Both the quasi-first-order kinetic modeland the quasi-second-order kinetic model well described the adsorption kinetic process of the three antibiotics in the sediment,and the correlation coefficients were highly are significant（p<0.01）.（2）Both the Langmuir model and the Freundlich models could well fit the isothermal adsorption-desorption process of the three antibiotics in sediment,and there was a very significant correlation（p<0.01）.The adsorption-desorption ability of sediment to three kinds of sulfonamides antibiotics is SCP>SMZ>SMA.（3）During different temperatures（15℃,25℃,35℃）,the adsorption-desorption capacity of the three sulfonamides increased with the increase of temperature,and under the experimental conditions,ΔG<0 and|ΔG|<40KJ·mol,ΔH>0,ΔS>0,indicating that the whole reaction process is spontaneous,endothermic and disordered.（4）The equilibrium adsorption capacity of SCP,SMZ and SMA on the sediment decreased with the increase of pH,and alkaline condition was not conducive to the adsorption of sulfonamides.（5）The inhibition ability of K⁺,Ca²⁺,Mg²⁺cations on the adsorption-desorption of SCP、SMZ and SMA is as follows:K⁺<Ca²⁺<Mg²⁺,means that the higher the ion valence is,the less conducive to the adsorption of sulfonamides in the sediment,and the adsorption capacity of the three sulfonamides in the sediment decreases with the increase of Ca²⁺concentration in the background solution.（6）The adsorption-desorption capacity of the three sulfonamides increased with the increase of biochar content.Compared with the control group,after adding 2%,5%,and 8%biochar,the adsorption capacity of SCP,SMZ and SMA in the sediment increased by 35.8%～134.4%,45.9%～166.2%and 67.6%～185.7%;The desorption amount increased by 34.1%～57.8%,28.7%,～62.0%and 31.8%～64.0%,respectively.