Sulfonamide antibiotics sorption by high silica ZSM-5: Effect of pH and humic monomers (vanillin and caffeic acid)

Abstract

Sulfonamides (SAs) in the aquatic environment are a serious threat to human health, environmental ecology and water reuse. Natural organic matter and SAs are known to compete for adsorption sites on adsorbent. SAs adsorption by high silica ZSM-5 (HSZSM-5) affected by humic monomers remains unclear. The impact of representative humic monomers (HMs) (caffeic acid (CA) and vanillin (VNL)) on the sorption of SAs by HSZSM-5 at different pH was evaluated for the first time. Fourier transform infrared and X-ray photoelectron spectroscopy were used to obtain the group transformations. The presence of HM did not change the main adsorption mechanism of SAs on pristine and loaded HSZSM-5 (pH-dependent and hydrophobic interaction). Lewis acid-base electron interaction, π-π electron donor-acceptor (EDA), and H-bonding had a positive contribution to the adsorption of SAs by HSZSM-5 after HM coating. However, HM coating and competition reduced the adsorption capacity of HSZSM-5 towards SAs. In co-introduction system of HM and SAs, the reaction between CO in HM and N–H in SAs resulted in SAs and HM co-adsorbed on HSZSM-5. Meanwhile, CA concentration <20 mg/L was in favor of SMX adsorption. The findings give an insight into the interactions among HM and SAs in high silica zeolites adsorption system, thereby improving SAs removal in actual water.