Mg (OH)2@粉煤灰复合材料对重金属离子的去除研究

根据“粒子设计”思想,以粉煤灰为载体,采用非均匀形核法制备了一种核壳结构粉煤灰负载纳米氢氧化镁复合材料,并对其吸附废水中Cu （II）、Ni （II）和Pb （II）性能进行研究.采用扫描电子显微镜（SEM）、EDS能谱、比表面积分析仪（BET）、X射线衍射（XRD）、红外光谱（FTIR）等技术对包覆前后的复合粉体进行了表征.结果表明,复合粉体表面均匀包覆了大量纳米氢氧化镁和少量水合碳酸镁,比表面积增大到原来（粉煤灰1.79m²/g）的30多倍,平均孔径由11nm增加至14.7nm.平均孔隙宽度从12.8nm增加至15.4nm.粉煤灰表面的Si-O-Si、Si-O-C与氢氧化镁之间形成Si-O-C-O-Mg和Si-O-Mg-OH.复合粉体材料去除重金属的效率明显高于原粉煤灰和氢氧化镁,其单位饱和吸附量分别达到了216.30、116.50、160.96mg/g.根据Zeta电位、FTIR及模拟方程分析了复合粉体吸附重金属离子机理,结果表明复合粉体材料对重金属离子通过沉淀反应、静电吸引、离子交换等方式进行吸附,吸附过程等温线符合Langmuir等温模型,动力学符合颗粒内扩散模型,热力学符合自发吸热反应.通过解吸再生试验发现,经过5次循环再生利用后,复合粉体对重金属离子的去除率达到50%以上,这说明复合粉体在吸附过程中具有良好的再生性能.

Study on removal of heavy metal ions by mg (OH)2@fly ash composite

Nano-magnesium hydroxide@fly ash composite with core-shell structure was prepared with non-uniform nucleation method taking fly ash as the carrier, MgCl₂ and NaOH as reaction coating agents according to the idea of "particle design" and its adsorption properties of Cu(II), Ni(II) and Pb(II) in wastewater were studied. The composite powders before and after coating were characterized by scanning electron microscopy (SEM), energy dispersive (EDS), specific surface area analyzer (BET), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The results show that the surface of the composite powder is uniformly coated with a large amount of nano-magnesium hydroxide and a small amount of hydrated magnesium carbonate, the specific surface area increased to more than 30 times of the original (fly ash 1.79 m²/g), the average pore size increased from 11 nm to 14.7 nm, and the average pore width increased from 12.8 nm to 15.4nm, respectively. Si-O-C-O-Mg and Si-O-Mg-OH are formed between Si-O-Si, Si-O-C and magnesium hydroxide on the surface of fly ash. The removal efficiency of heavy metals by the composite powder is significantly higher than that of fly ash, and the unit saturated adsorption capacity reaches 216.30, 160.96 and 116.50 mg/g. According to Zeta potential, FTIR and simulation equations, the adsorption mechanism of heavy metal ions by composite powder was analyzed. The results show that the composite adsorbs heavy metal ions through precipitation reaction, electrostatic attraction and ion exchange, etc. The adsorption process isotherm, the kinetics and the thermodynamics conform to the Langmuir isotherm model, intraparticle diffusion model and spontaneous endothermic reaction, reapectively. The desorption experiment indicates that the composite powder has a good regeneration performance in the adsorption process.