Abstract
Background organic matter significantly influences the removal of emerging contaminants in natural water. In this work, the adsorption of ciprofloxacin (CPX) onto a series of magnetic multifunctional resins (GMA10-GMA90) in the presence and absence of humic acid (HA) was conducted to demonstrate the effect of HA. Both hydrophobic and ion exchange interactions contributed to CPX adsorption. Negative charge-assisted hydrogen bonds also participated in the adsorption process, resulting in the high adsorption amount of anionic CPX onto the negatively charged GMA30 under basic solutions. HA could impact CPX adsorption not only as a competitive adsorbate but also as an additional adsorbent. At pH 5.6, the additional adsorption sites provided by adsorbed HA molecules on the resins dominated and thus facilitated the adsorption process. While at pH 10, HA inhibited the adsorption of CPX by directly competing for ion exchange sites and coexisting with CPX in the solution. The ratio of the amount of CPX adsorbed by dissolved HA to that by the resin reached as high as 1.61 for GMA90. The adsorbed HA molecules onto the resins could provide additional adsorption sites for CPX as proven by the enhanced CPX adsorption in HA-preloading systems at pH 5.6.
Highlights
natural organic matter ® (NOM), which comprises a complex mixture of organic molecules that vary in size and chemical structure, is ubiquitous in drinking water sources and seriously affects emerging contaminants (ECs) purification by adsorbents
NOM, which comprises a complex mixture of organic molecules that vary in size and chemical structure, is ubiquitous in drinking water sources and seriously affects ECs purification by adsorbents
Compared with the copolymerization monomers, the absorbance peaks at ~976 cm−1 and ~3400 cm−1 of the resins correspond to the C–N stretching vibration and the O–H in-plane bending vibration, respectively, which confirms the successful introduction of the –N+(CH3)[3] group after amination[29,30]
Summary
NOM, which comprises a complex mixture of organic molecules that vary in size and chemical structure, is ubiquitous in drinking water sources and seriously affects ECs purification by adsorbents. For single adsorbate adsorption experiments, 100 mL of solutions with an initial concentration of 0.03 mmol/L CPX or 20 mg/L HA were shaken at 150 rpm and 293 K with 0.01 g of each resin in 250 mL conical flasks.
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