磁性功能吸附剂的制备及吸附Cr(Ⅵ)的行为

Preparation of magnetic functional adsorbent and its adsorption behavior for Cr(Ⅵ)

以1,6-己二胺、柠檬酸钠和三氯化铁为前驱物,借助溶剂热法制备了磁性功能吸附剂（FMS）,通过调控1,6-己二胺的量制备出3 种磁性功能吸附剂,用于处理含铬（Cr（Ⅵ））废水,探索了吸附时间、初始浓度和pH 值对去除Cr（Ⅵ） 的影响, 得到了最佳的磁性功能吸附剂（FMS3）, 并借助场发射扫描电子显微镜（FESEM）、傅里叶红外光谱（FT-IR）和Zeta 电位表征了磁性功能吸附剂的微观形态. 结果表明： 在25 ℃、pH = 2.0 和吸附剂投加量为1.0 g/L 等条件下,吸附在120 min 内可达到饱和,FMS3最大吸附量为63.78 mg/g. 该吸附规律较好地符合二阶动力学吸附方程和Langmuir 等温吸附模型, 从热力学参数值ΔG°、ΔH°和ΔS°说明此吸附为自发、吸热的熵增加过程,升温益于吸附发生,且可重复使用. 此外,所制备的磁性功能吸附剂为球形颗粒,平均粒径为45-65 nm,表面呈现较强的正电性.

Magnetic functional adsorbents (FMS) were synthesized by solvothermal method with 1,6-hexanediamine, sodium citrate and ferric trichloride as the precursors and three kinds of magnetic functional adsorbents were obtained via changing contents of the 1,6-hexanediamine, respectively. Magnetic functional adsorbents were used to adsorb Cr (Ⅵ) from aqueous solution. The effects of contact time, initial concentration and pH on removing amount of Cr (Ⅵ) were investigated, and the best adsorbent was found to be FMS3, which was characterized by field emission scanning electron microscope (FESEM), Fourier transform infrared spectrometer (FT-IR), and Zeta potential. The experimental results indicated that the highest adsorption capacity of Cr(Ⅵ) was around pH=2 at 25℃with the adsorbent amount of 1.0 g/L, and the adsorption of Cr (Ⅵ) on FMS3 reached equilibrium within 120 min and the saturated adsorption capacity for Cr(Ⅵ) was approximately 63.78 mg/g. The adsorption isotherm can be well described by the adsorption kinetics fitted to the pseudo-second-order model and the Langmuir equation. The thermodynamic parametersΔG°、ΔH° andΔS° indicated that the adsorption was spontaneous and endothermic process with increased entropy, and higher temperature would improve the adsorption. The adsorbent can be repeatedly utilized with no significant loss of adsorption capacity. In addition, the magnetic functional adsorbent FMS3 is spherical particles with the average particle size of 45 - 65 nm, and its surface possesses positive electricity in acidic solution.