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利用氨水-氯化铵体系在pH 9～10时具有缓冲能力的特点,以其作为沉淀剂成功合成了镁铝水滑石(Mg3Al-Cl-LDHs),采用XRD、FT-IR、TG-DTA等手段对材料结构进行表征,并测试了合成Mg3Al-Cl-LDHs样品对溶液中Cr(Ⅵ)的吸附性能。研究结果表明,缓冲溶液法制备的Mg3Al-Cl-LDHs材料晶相单一,晶面生长的有序程度较高,结晶度较好。晶胞参数a=0.3106 nm,c=2.367 nm,粒子尺寸约为36.44 nm。其热分解过程包括水滑石层间结构水脱除和层板羟基脱水、氯离子分解两个步骤。Mg3Al-Cl-LDHs对Cr(Ⅵ)的吸附主要发生在0～1 h内,随着时间的增长吸附量先增加后趋于平缓;温度对Cr(Ⅵ)吸附量影响不大,在常温下即可进行;随着pH值的减小,饱和吸附量先增大后减小,在pH 6时吸附效果较好;2价与3价竞争阴离子比1价阴离子对吸附性能的影响更大。在最佳吸附条件下,Mg3Al-Cl-LDHs对Cr(Ⅵ)的饱和吸附量可达58.73 mg/g,有望应用于实际Cr(Ⅵ)废水处理。
Ammonia-ammonium chloride system was used as a precipitating agent to synthesize Mg3Al-Cl-LDHs with pH value of 9-10. XRD, FT-IR and TG-DTA Means were used to characterize the structure of the material and the adsorption of Cr (Ⅵ) in the solution by the sample of Mg3Al-Cl-LDHs was tested. The results show that Mg3Al-Cl-LDHs prepared by the buffer solution has a single crystalline phase, a higher ordered degree of crystal growth and a better crystallinity. The unit cell parameters are a = 0.3106 nm, c = 2.367 nm and particle size about 36.44 nm. The thermal decomposition process includes the removal of water from the interlaminar structure of the hydrotalcite and the dehydration of the hydroxylamine and the chloride ion. The adsorption of Cr (Ⅵ) by Mg3Al-Cl-LDHs occurred within 0-1 h, and the adsorption increased first and then became gentle with the increase of time. The temperature had little effect on the adsorption of Cr (Ⅵ) Can be carried out. With the decrease of pH value, the saturated adsorption capacity firstly increases and then decreases, and the adsorption effect is better at pH 6; the bivalent and trivalent competition anions have a greater influence on the adsorption performance than monovalent anions. Under optimal adsorption conditions, the saturated adsorption capacity of Cr (Ⅵ) by Mg3Al-Cl-LDHs was 58.73 mg / g, which is expected to be applied to the treatment of actual Cr (Ⅵ) wastewater.