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金属盐改性石英砂的制备及其吸附重金属性能研究
Experimental Study on Preparation and Heavy Mental Adsorption Capability of Metallic Salt Modified Quartz Sands
【作者】 付静;
【作者基本信息】 浙江工业大学 , 市政工程, 2010, 硕士
【摘要】 重金属离子是一种危害极大的污染物,为了提高石英砂对重金属离子的吸附性能,采用改性剂对石英砂表面进行改性,提高其对重金属离子的吸附效果。本试验以石英砂为载体,以氯化铝和氯化镁为改性剂,采用碱性沉积法制备了铝盐改性石英砂和镁盐改性石英砂。通过改性前后石英砂比表面积的测定、扫描电子显微镜的观察和拍照以及X射线衍射仪的鉴定,对改性前后石英砂的表面特性进行了表征和分析。结果表明,与石英原砂相比,铝盐改性砂和镁盐改性砂的比表面积显著增大,分别是石英原砂的9.38倍和6.12倍。改性后的石英砂表面粗糙度明显增大,孔隙密而多,铝盐改性砂表面主要成分为Al(OH)3,镁盐改性砂表面的主要成分为Mg(OH)2。以含Zn2+、Cd2+的废水为处理对象,考察了改性前后石英砂对Zn2+、Cd2+的吸附性能。试验结果表明,pH值是影响吸附性能的主要因素,在pH中性条件下,铝盐、镁盐改性石英砂和石英原砂的Zn2+去除率分别为68%、54%和41%,随着pH值增加,吸附效果提高,当pH值接近9时,铝盐、镁盐改性砂的Zn2+去除率均在95%左右。铝盐改性石英砂、镁盐改性石英砂和石英原砂,在pH中性条件下,Cd2+去除率分别为59%、47%和39%,随着pH值增加,吸附效果提高,当pH值接近9时,铝盐、镁盐改性砂的Cd2+去除率分别为71%和67%。利用制备好的两种改性石英砂,对电镀镀锌废水进行了动态试验研究。结果表明,改性石英砂对锌的去除效率有较大的提高。铝盐改性的石英砂在前5个小时之内,一直保持70%左右的去除效率,但是在5小时之后,去除效率下降较快。镁盐改性石英砂对锌的高去除率有效时间稍短,为3小时左右,去除率大约保持在60%左右。根据两种改性砂吸附Zn2+、Cd2+的试验数据,对改性石英砂吸附重金属离子的机理、吸附等温线和吸附动力学行为进行了初步分析和探讨。分析结果表明,两种改性砂对Zn2+、Cd2+的吸附以化学吸附为主。对Zn2+、Cd2+的吸附均符合Langmuir吸附等温式,吸附过程更好的符合准二级反应动力学模型。
【Abstract】 Heavy metal ion is a severe pollutant. In order to improve the heavy metal ion adsorption capability of quartz sands, the quartz sands are modified by applying relevant modifier. In this experiment, two kinds of modified filter material were prepared, in which quartz sand was chosen as a carrier to be coated with aluminium chloride and magnesium chloride by the deposition process at alkaline condition, respectively. By comparing the pre-modified and post-modified physical characteristics of quartz sands surface, through specific surface area test, SEM (Scanning Electron Microscope) inspection, XRD (X-Ray Diffractometer) and etc, the results reveals that the specific surface areas of aluminium chloride and magnesium chloride modified sands were increased to 9.38 and 6.12 times compared to the original quartz sands. What’s more, the surface roughness of modified sands was also improved obviously and the surface porosity was greatly denser than that of original one. The major components of the two modified sands surface were Al(OH)3 and Mg(OH)2.Additionally, by analyzing the possible influences of modifying condition to wasted water containing Zn2+、Cd2+, the research shows that the pH value was an important factor on the heavy metal removal by the modified sands. The removal rates of Zn2+ by aluminium chloride、magnesium chloride modified sands and original quartz sands were 68%、54% and 41% under the condition of pH value with 7.00. It was also found the removal efficiency was enhanced with the increase of pH value, and the removal rates of Zn2+ by the two modified sands were both above 95% under the condition of 9.0. In the same way, when pH value equal 7.00, the removal rates of Cd2+ by aluminum chloride、magnesium chloride modified sands and original quartz sands were 59%、47% and 39%. The removal efficiency was also enhanced with the increase of pH value. When pH value was near 9.0, the removal rates of Cd2+ by aluminum chloride、magnesium chloride modified sand were 71% and 67%.The continuous experimental study on the treatment of galvanized wastewater using the two modified quartz sands was also conducted. It was shown that the removals of Zn2+ improved a lot. In the first 5 hours of the filtration,the removal rate of Zn2+ of aluminum chloride modified sands was kept of 70%, nevertheless, after 5 hours, it reduced quickly. In contrast, the removal rate of Zn2+ by magnesium chloride modified sands was about 60% in the first 3 hours.Ultimately the experimental data and research on theory and kinetics of heavy metal adsorption capability demonstrate that the adsorption of the two modified sands was dominated by chemical reaction. The adsorption isotherms of Zn2+ and Cd2+ both have the high consistency with Langmuir adsorption mode. Furthermore, the analysis of the two modified sands adsorption kinetics of Zn2+ and Cd2+ discovers that two modified sands adsorption reaction is more likely to satisfy Lagergren kinetic rate equationⅠ.
【Key words】 modified quartz sand; adsorption; heavy mental; adsorption isotherm; kinetic;