| Wastewater containing heavy metals such as chromium has been recognized as one of the difficult problems by the environment protection community. In the current, the problem of prevalence method for removing chromium is high cost and low efficiency. Adsorption of Cr(Ⅵ) with the advantages of low cost and simple operation, its core technology lies in the selection of excellent adsorbent. Therefore, screening of low cost adsorbent is the hot issues in the study of removing Cr(Ⅵ). Crops waste which was rich in cellulose become an important source of low-cost adsorbent.In the paper, the modified cationic adsorbent (MPS) was modified by amine reaction with peanut shell (PS) that using epichlorohydrin as etherifying agent, N,Ndimethylformamide as dissolvent, triethylenetetramine as cross-linking agent and introduce amino group. In order to test the adsorption property of Cr(Ⅵ) with MPS, static and dynamic adsorption experiments were taken in the study. In the static sorption tests, MPS dosage, initial Cr(Ⅵ) concentration, pH, temperature and contact time was carried out as experimental parameters. Column sorption and regeneration test was carried out in the dynamic tests. The adsorption isotherms fitting of the adsorption process of Cr(Ⅵ) with MPS were described by Langmuir and Freundlich adsorption models, and the adsorption process was described by dynamic fitting.The experiments show that the modified peanut shells on the Cr (VI) adsorption capacity is only around1.7mg/g, while after modification to132.38mg/g. In the static sorption experiments, the optimal MPS dosage was determined as1g/L when the initial Cr(VI) concentration was100mg/L. And the oscillation adsorption time was120min with experiments. When pH was1.0to6.0, the removal rate of Cr (Ⅵ) were between91.0%and95.9%, while the removal rate decreased significantly as pH>6.0. The Cr(Ⅵ) adsorption capacity with MPS increased as the temperature increases, which indicates that the adsorption process was endothermic reaction. The adsorption capacity of Cr (Ⅵ) with MPS was138.3mg/g in the dynamic adsorption experiments, which was93.9%of the maximum adsorption capacity Qmax (147.3mg/g) at25℃. It was shown as high adsorption efficiency. Hydrochloric acid was chosen as the eluent to assess the regeneration capacity of MPS. The regeneration efficiency was up to82.6%, indicating that the dominant in the adsorption process was ion exchange, and there was some irreversible process as chemical adsorption. MPS samples before and after adsorption were characterized by Zeta potential, infrared and Raman spectrum. With FTIR spectra analysis of MPS, the raw material surface was introduced amino group. Zeta potential analysis resulted that the modified PS surface was positive charged, apparently show the modification effect. The mechanism analysis of the experiment results showed the existence of chemical adsorption and ion exchange in the adsorption process.The experimental results show the high adsorption capacity of Cr (Ⅵ) and good regeneration performance, which indicates MPS is an effective adsorbent of chromium-containing wastewater and has broad application prospects. This article is the relevant theoretical reference for practical application of MPS. |
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