改性木屑的制备及其对铜离子的吸附研究

发布时间：2018-06-30 17:10

  本文选题：重金属 + Cu~(2+)　； 参考：《北京化工大学》2016年硕士论文

【摘要】：近年来,随着现代工业的快速发展,重金属的开采和应用越来越广泛,大量含重金属的废水没有经过达标处理就排放到环境中,造成了巨大的安全隐患,直接威胁到人体健康和生态环境。因此,有效地处理重金属废水已成为当今环保领域中一个亟待解决的重要问题。传统的处理工艺往往只能将重金属废水降低到一定浓度,不能将它们从水体中完全除去。而吸附法其材料来源广,对低浓度的重金属离子具有较高的去除能力,可以有效地达到排放标准,是一种很有前途的重金属废水处理方法。常用的吸附剂是活性炭,但其价格偏贵,在应用中受到限制。目前针对活性炭等较为昂贵的问题,人们正在研制各种高效低廉的吸附剂。木屑是一种林业废弃物,廉价易得,且产量巨大,由于它表面为多孔结构且本身含羟基官能团,是一种应用前景广泛的重金属吸附剂,但木屑吸附量不大,往往需要通过改性提高其吸附性能。本文用热解+NaOH浸泡的方法制备改性木屑,并对其改性条件进行优化；采用表征手段观察了改性前后木屑表面结构的变化；通过间歇实验,考察了pH、初始浓度、吸附时间、投加量、粒径、离子强度等因素对改性木屑吸附Cu2+的影响；在相同条件下,将改性木屑对Cu2+的吸附效果与活性炭和原木屑进行比较；并进行吸附等温线、吸附动力学和热力学参数研究,进一步揭示木屑对重金属离子的吸附过程,探讨改性木屑吸附铜离子的机理。研究结果表明：木屑的最佳改性条件为：热解条件(热解温度240℃、热解时间45min)以及浸泡条件(NaOH溶液的浸泡时间3h、NaOH溶液的浸泡浓度0.4mol/L、NaOH溶液浸泡的浸渍比1：20)：与原始木屑相比,改性木屑的比表面积变大,表面相对平整光滑且出现了一些明显的孔隙,羟基增多；对于初始浓度为20mg/L的铜离子溶液,在吸附时间为180min, pH为5,投加量为4g/L的最佳吸附条件下,改性木屑对Cu2+的去除率可以达到99%,处理后的Cu2+剩余浓度低于国家要求的废水排放一级标准(0.5 mg/L)；与原木屑和活性炭相比,改性木屑的平衡时间缩短了60min,吸附速率提高了50%；改性木屑对铜离子的吸附符合Langmuir等温模型,最大吸附量为31.25mg/g,是原始木屑吸附量的8倍,是活性炭的3倍,准二级反应动力学模型能更好的描述改性木屑对铜离子吸附反应的动力学；改性木屑对Cu2+的去除是化学吸附和物理吸附共同作用的结果。
[Abstract]:In recent years, with the rapid development of modern industry, the mining and application of heavy metals is becoming more and more extensive. It is a direct threat to human health and ecological environment. Therefore, the effective treatment of heavy metal wastewater has become an important problem in the field of environmental protection. The traditional treatment process can only reduce the heavy metal wastewater to a certain concentration and can not completely remove them from the water. The adsorption method is a promising treatment method for heavy metal wastewater because of its wide source of materials, high removal capacity of heavy metal ions with low concentration, and can meet the discharge standard effectively. The commonly used adsorbent is activated carbon, but its price is too high, so it is limited in application. At present, for the more expensive problems such as activated carbon, people are developing various kinds of high-efficiency and low-cost adsorbents. Wood sawdust is a kind of forestry waste, which is cheap and easy to get, and its yield is huge. Because of its porous structure and hydroxyl functional group, it is a kind of heavy metal adsorbent with wide application prospect, but the adsorption amount of wood chips is not large. It is often necessary to improve the adsorption performance by modification. In this paper, the modified sawdust was prepared by the method of pyrolysis NaOH soaking, and the modification conditions were optimized. The changes of the surface structure of the wood chips before and after modification were observed by means of characterization, and the pH, initial concentration and adsorption time were investigated by intermittent experiments. The effects of adding amount, particle size and ionic strength on the adsorption of Cu _ 2 by modified wood scraps were studied. Under the same conditions, the adsorption effect of modified wood chips on Cu _ 2 was compared with that of activated carbon and raw wood chips, and the adsorption isotherm was carried out. The adsorption kinetics and thermodynamic parameters were studied to reveal the adsorption process of heavy metal ions and the mechanism of copper ion adsorption by modified sawdust. The results show that the optimum modification conditions of sawdust are pyrolysis conditions (pyrolysis temperature 240 鈩，

本文编号：2086204