Resin Adsorption Behavior And Mechanism Of Removing Antibiotics

In our country, extensively applications of antibiotics are line with increasing environmental risk. Aiming at the typical antibiotics (tetracycline and sulfonamide antibiotics), the adsorption behaviors on hyper-crosslinked resins (MN-200, NDA-150), aminated resins (MN-100, MN-150), macroporous resin XAD-4and activated carbon F-400were studied in this paper, which could offer theoretical support in treating and recycling antibiotics wastewater. The main study contents were listed as follows:1. Adsorption of tetracycline and sulfonamide antibiotics onto the four resinsThe results of static adsorption kinetics showed the adsorption data of tetracycline and sulfonamide antibiotics were fitted to the pseudo-second-order kinetic model by nonlinear regression (R2>0.99), indicating the pore size was the main effect on the adsorption rate. The equilibrium time for mesoporous resin XAD-4was the shortest, while the equilibrium time for F-400was the longest because of its high microporosity. The equilibrium times for MN-200and MN-150were between those for F-400and XAD-4because of their bimodal pore size distribution.The effect of solution chemistry on the adsorption behavior and mechanism had been studied by static adsorption experiments in this paper:(1) the effect of pH:it was found that the higher percentages of neutral species in the solution, the more adsorption amount of tetracycline and sulfonamide antibiotics on the adsorbents, which indicated the contribution of force between the molecules (such as π-π-EDA interaction, hydrophobic effects) was stronger than those between the functional groups on the adsorption process;(2) the effect of ion concentration:adsorption amounts increased with the rise of sodium chloride concentration. This might largely result from the well-known salting out effect and electrostatic interactions. And in this process, the IR spectra of resins showed hydrogen bonding, electrostatic effect and π-π conjugate made great contribution to the adsorption process;(3) the effect of temperature:adsorption isotherms of antibiotics on resins could be better fitted with Freundlich model (R2>0.99). And the adsorption coefficient (Kd) of XAD-4decreased with the rise of temperature, which showed the hydrophobic effect played a main role on the adsorption process. The adsorption amount of those two antibiotics on the MN-200was largest. It was observed that the high surface area and bimodal pore size distribution of resins appeared to be important for the adsorption of antibiotics. The adsorption capacity of MN-200was more than that of MN-150because of its higher surface area, so the functional groups of MN-150were not the main interaction in adsorption process. And the adsorption capacity of MN-200was more than XAD-4because of its bimodal pore size distribution.2. The study of dynamic adsorption and elution of antibioticsThe study of static elution showed the elution effect of sodium hydroxide was not good, which indicated the functional group of resins had no role on the process of elution and the chemistry adsorption was not major on the process of adsorption. But the elution effect of ethanol was better than sodium hydroxide on the elution process on resins, especially XAD-4, so it was also proved that the main mechanism of resins was the force between the molecules. For F-400, the elution effect of sodium hydroxide and ethanol was not good due to pore filling effect. The dynamic adsorption and elution of TC on MN-200was studied. The results showed that the ideal conditions of adsorption were:2000mg/L and1.0mL/min, and the ones of elution were:0.03mL/min and80%ethanol solution.