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Adsorption of ciprofloxacin from water by pretreated oat hulls: Equilibrium, kinetic, and thermodynamic studies

Movasaghi, Zahra, Yan, Bei, Niu, Catherine
Industrial crops and products 2019 v.127 pp. 237-250
Fourier transform infrared spectroscopy, adsorbents, adsorption, agricultural industry, byproducts, cellulosic materials, ciprofloxacin, endothermy, kinetics, moieties, oat hulls, pH, pollutants, porosity, scanning electron microscopy, sorption isotherms, surface area, temperature, thermodynamics, water pollution
In this work, a novel and environmentally friendly adsorbent was developed from oat hulls, representative of cellulosic materials abundantly generated as by-products in agriculture industry, for removal ciprofloxacin (CIP) from water. Results of various characterization techniques (e.g. SEM, FTIR, and BET) showed substantial enhancement in porosity, surface functional groups and surface area of the precursor through pre-treatment process. The effects of most influential process parameters of adsorbent dose (0.1–0.8 mg/L), solution pH (3–10), temperature (288, 298, and 318 K) and pre-treatment process on adsorption performance were investigated. The Freundlich isotherm successfully described equilibrium data, suggesting the heterogeneous surface of the adsorbent. The kinetic data were well expressed by the pseudo-second order kinetic model, indicating chemisorption to be the rate-limiting step of the process. The thermodynamic analysis revealed that adsorption was spontaneous (ΔG° < 0), endothermic in nature (ΔH° > 0) and along with increase in randomness (ΔS° > 0). The maximum adsorption capacity of pretreated oat hulls (83 mg/g), at the determined optimum condition, was higher than a number of previously studied adsorbents. This study revealed that oat hulls or similar materials in agriculture industry can be made into adsorbents with high performance for removal of CIP, and similar pharmaceutical or organic pollutants from contaminated water.