Study on the Adsorption Effect of NOR in Reclaimed Water on Montmorillonite

In this study, montmorillonite was used as an adsorbent. The adsorption mechanism of Norfloxacin (NOR) on montmorillonite and the effects of pH, Dissolved Humic Acid (DHA) concentration, and DHA addition order on the adsorption effect were explored using a static adsorption batch experiment method. The aim is to study the adsorption mechanism and influencing factors of antibiotic pollutants in typical clay minerals, and to provide theoretical support for the study of the effects of recycled water on long-term agricultural irrigation. The results showed that the addition of DHA would slow down the initial reaction rate, and 24 and 48 h were selected as the equilibrium time for isothermal adsorption experiments without and with DHA added; As the pH of the solution increases, the adsorption coefficients Kf and KL have the same trend of change, with a maximum value at pH 7.5. The cation exchange interaction of montmorillonite became the main mechanism at lower pH conditions. The concentration and addition order of DHA can have an impact on the adsorption of NOR on montmorillonite. When the initial concentration of NOR is low, the inhibitory effect of DHA on the adsorption of NOR+ and NOR± on montmorillonite becomes more obvious as the concentration of NOR− increases. The promoting effect of DHA on adsorption of NOR on montmorillonite is first strong and then weak. When the initial concentration of NOR is high, as the concentration of DHA increases, DHA has a promoting and then inhibiting effect on the adsorption of NOR+ and NOR− on montmorillonite, DHA exhibits an overall inhibitory effect on the adsorption of NOR± on montmorillonite; When DHA is added first, the adsorption ratio of NOR on montmorillonite will be higher; The main reason for DHA to promote adsorption is the result of co adsorption or cumulative adsorption, while the reasons for inhibiting adsorption mainly include competitive adsorption at sites, solubilization, and the blocking effect of DHA on NOR entering the montmorillonite layer.