Journal
JOURNAL OF COLLOID AND INTERFACE SCIENCE
Volume 541, Issue -, Pages 101-113Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2019.01.078
Keywords
Oxytetracycline; Metal ions; Nano-hydroxyapatite; Ternary complexation; Adsorption mechanism
Categories
Funding
- National Natural Science Foundation of China [51579099, 51521006, 51879105]
- Program for Changjiang Scholars and Innovative Research Team in University [IRT-13R17]
- Hunan Provincial Innovation Foundation for Postgraduate [CX2016B134]
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In this study, interaction of oxytetracycline (OTC) onto nano-hydroxyapatite (nHAP) was evaluated as affected by pH and metal ions. Results showed that the adsorption process of OTC was highly pH- and metallic species-dependent. The amount of sorbed OTC at four pH were in the order of pH 8.0 > pH 10.0 > pH 5.5 > pH 3.0 and reached equilibrium around 120 min, indicating adsorption affinity of four species to nHAP followed the order of OTC- > OTC2- > OTC +/- > OTC+. Adding metal ions greatly increased the distribution coefficient (K-d) of OTC between adsorbents and aqueous phases, following the order of Fe3+ > Cu2+ > Pb2+ > Cd2+ = Ca2+ in the pH range of 3.0-10.0. Moreover, the co-adsorption behavior of OTC and heavy metals onto nHAP was also explored at pH 5.5 for the first time. OTC adsorption was significantly enhanced with the co-existence of 0.25 mmol/L Cu2+ or Pb2+. Inversely, the presence of 0.25 mmol/L OTC slightly led to the improvement of Cu2+ adsorption and depression of Pb2+ adsorption, yet Pb2+ adsorption was obviously promoted with the co-existence of 0.1 mmol/L OTC. Meanwhile, adsorption of OTC and Cd2+ showed unapparent variation in single or binary systems. The bridging effect involving metal ions, O- and N- containing groups in OTC molecules, and CaOH or POH sites of nHAP resulted in the formation of ternary complexes which were responsible for the promotion of their adsorption, while dissolution-precipitation was another key mechanism with the co-existence of Pb2+. (C) 2019 Elsevier Inc. All rights reserved.
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