Study On Adsorption Characteristics Of Sulfonamides In Wastewater By Bentonite-steel Slag Composite Particles

In recent years,the extensive use and even abuse of antibiotics have caused serious environmental pollution and destroyed the inherent ecological balance of the environment.In this paper,bentonite-steel slag composite particles were selected as adsorbents,and the adsorption characteristics of sulfamethoxazole?SMZ?and sulfamethazine?SM2?in water were studied by OECD Guideline batch equilibrium method.The removal effect of the adsorbent on sulfonamide antibiotics was determined and the mechanism of removal was analyzed.Kinetic experiments showed that the adsorption process of bentonite-steel slag composite particles for two sulfonamides was most in accordance with Elovich equation,and the equilibrium time of adsorption kinetics was 24 hours.Freundlich equation fitted the adsorption data of sulfonamides on bentonite-steel slag composite particles best.The isothermal adsorption curves of sulfamethoxazole and sulfamethazine belonged to L-type.When two sulfonamide antibiotics were mixed,the adsorption capacity decreased,and there was competitive adsorption between sulfonamides,but the adsorption equilibrium time determined by kinetics had no effect.The competitive adsorption process of sulfamethoxazole/sulfamethazine on composite particles is more in line with Elovich model.The adsorption capacity of composite particles for two sulfonamide antibiotics at low concentration was little affected by temperature.In competitive adsorption system,with the increase of antibiotic concentration,the competitive effect is gradually enhanced,and sulfamethoxazole is dominant in the whole competitive system.The competitive adsorption of two sulfonamide antibiotics under alkaline condition?7<pH<12?is more intense than that under acidic condition?2<pH<7?.The adsorption capacity of both sulfonamides decreases with the increase of pH.The single factor experimental results showed that the higher the temperature,the worse the adsorption effect of the composite particles on SMZ.Combined with practical considerations,the temperature should be set to 25?when the composite particles are used to adsorb sulfamethoxazole in wastewater.The increase of pH value will inhibit the adsorption and lead to the decrease of adsorption capacity.2<pH<7,the amount of adsorption changed obviously.According to the actual situation,pH should be controlled between 6 and 7.In the presence of different cations,the adsorption capacity?K_f?of bentonite-steel slag composite particles to sulfamethoxazole in water was M⁺?Na⁺?K⁺?>M²⁺(Ca²⁺?Mg²⁺?Zn²⁺).Under the same ionic medium conditions,increasing the concentration of ionic solution will reduce the adsorption capacity of sulfamethoxazole in water by bentonite-steel slag composite particles.Within the range of 0.05⁰.25 g/L,the adsorption capacity of sulfamethoxazole on bentonite-steel slag composite particles increased rapidly at first and then tended to be flat with the increase of the dosage.When the dosage is 0.15 g/L,the adsorption and removal effect of sulfamethoxazole in wastewater is the best.