| An adsorbent, walnut shell based activated corben(MAC) was prepared by the modification of original walnut shell(OWS), which was impregnated with ammonium dihydrogen phosphate solution first.and activated at 460 ℃. The adsorbents were characterized by a variety of techniques such as SEM, FT-IR, XRD,XRF, etc. MAC was used to remove 2,4-dichlorophenoxyacetic acid(2,4-D),chloromycetin and surfactant from aqueous solutions, and secondary adsorption of pchlorophenol(4-CP). Adsorption quantity of MAC for the four pollutants was found to be 123 mg·g-1、84 mg·g-1 、132 mg·g-1 and 96.0 mg·g-1.Variables of the system, including solution p H, temperature, contact time, salt concentration, initial adsorbate concentration and high column, flow rate, were adopted to study their effects on the adsorption. The results showed that MAC had a good adsorption effect, and had slightly better properties under acidic conditions.High concentration of calcium ions was not conducive to adsorption. The results of non-linear regressive analysis were that the Temkin isotherms were better fit the adsorption of 2,4-D, chloromycetin and surfactant on MAC, while the Freundlich and Koble-Corrigan model were better fit the secondary adsorption of 4-CP. Kinetic studies indicated that the four systems followed the Elovich model, and the secondary adsorption also followed Pseudo–second–order model.Thomas and Yan models were used to predict the breakthrough curves of four substances adsorption or secondary adsorption onto MAC using nonlinear analysis method, and both models can fit the breakthrough curves.Results showed that MAC can be used as excellent adsorbents with good efficiency, and low cost. |
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