物理法竹质活性炭制备及净化含铬废水的应用

发布时间：2018-01-03 15:28

本文关键词：物理法竹质活性炭制备及净化含铬废水的应用　出处：《湘潭大学》2015年硕士论文　论文类型：学位论文

【摘要】：活性炭作为一种优良的吸附材料,因具有比表面积大、孔结构发达等优点被广泛应用于化工、环保、医药、食品等诸多行业。随着社会的发展,现代科学和工业对活性炭品质的要求(孔径分布集中有序及特定的表面化学性质)越来越高,定向调控活性炭的孔结构和表面化学性质成为现代活性炭工业研究的核心。我国竹林资源丰富,在竹材加工过程中会产生大量废竹料。本文以废竹料为原料,研究了水蒸气活化对竹质活性炭物理结构以及表面化学性质的影响,并对以竹质活性炭为吸附剂处理含铬废水进行了研究。主要内容如下:(1)以废竹料为原料,经炭化和水蒸气活化两步法制备竹质活性炭,重点研究了活化条件对活性炭物理结构的影响。结果表明提高活化温度、延长活化时间有利于活性炭制造新的微孔,从而提高比表面积和孔容,但是活化时间过长,将引起明显的扩孔效应,最终导致比表面积和总孔容降低。最佳的竹质活性炭制备条件为:炭化温度450℃,炭化时间60 min,活化温度850℃,水蒸气流量0.2 g/min,活化时间120 min,升温速率5℃/min。扫描电镜(SEM)分析表明此条件下的竹质活性炭内部呈发达的网状交联结构。(2)借助多种表征手段对活性炭制备过程中其表面化学性质的变化进行了系统的研究。元素分析、Boehm滴定以及p H测定结果表明炭化料和活性炭主要含C、O元素,表面主要为碱性含氧官能团。与炭化料相比,活性炭材料表面酸性含氧官能团总量降低而碱性含氧官能团总量增加。傅里叶红外(FTIR)图谱表明炭化料与活性炭的差别主要体现在谱图的强度上,活性炭表面官能团包括羟基、甲基、亚甲基、芳香环、羰基和醚键等。X射线光电子能谱(XPS)分析进一步表明水蒸气活化对表面官能团的种类无影响但影响其相对含量。X射线衍射图谱(XRD)分析表明经过高温活化以后活性炭类石墨化程度增高、晶体结构更趋规整。(3)以水蒸气法制备的竹质活性炭作为吸附剂对废水中的Cr(VI)进行了吸附研究。结果表明竹质活性炭具有适合液相吸附Cr(VI)阴离子的物理结构和化学性质。吸附实验表明,Cr(VI)和总铬的去除率随溶液pH的升高而降低,随着活性炭用量的增加,去除率先增加然后保持不变。吸附等温线符合Langmiur模型,在30℃时的最大单层吸附量为193 mg/g。吸附过程自发进行且为吸热过程。吸附动力学符合准二级动力学模型,颗粒内扩散不是吸附过程的唯一速率控制步骤,还有其他机制参与。推测其吸附机理包括四步:表面官能团质子化、活性炭与铬离子之间静电吸引、Cr(VI)表面还原、Cr(III)的吸附或释放。
[Abstract]:Activated carbon as an excellent adsorbent material, because of its large surface area, the pore structure developed is widely used in chemical industry, environmental protection, medicine, food and other industries. With the development of society, the requirements of modern science and industry on the quality of activated carbon (pore size distribution in order and specific surface chemical properties) is more and more high, the pore structure and surface chemical properties of activated carbon directional control has become the core of modern industrial activated carbon. China's bamboo resources rich in bamboo processing will generate a lot of waste bamboo. The waste bamboo as raw material, the water vapor activation of bamboo activated carbon physical structure and the effect of surface chemical properties, and the bamboo activated carbon adsorbent for the treatment of chromium containing wastewater was studied. The main contents are as follows: (1) using waste bamboo as raw material, through carbonization and steam activation of two step preparation of activated bamboo Carbon, focusing on the influence of activation conditions on the physical structure of activated carbon. The results show that the higher activation temperature, activation time. To manufacture new microporous activated carbon, thereby increasing the specific surface area and Kong Rong, but the activation time is too long, will cause the reaming evident effect, resulting in the specific surface area and total pore volume decreased. The preparation conditions of bamboo activated carbon is the best: the carbonization temperature is 450 degrees centigrade, carbonization time 60 min, activation temperature is 850 degrees centigrade, the water vapor flow 0.2 g/min, activation time was 120 min, the heating rate of 5 DEG /min. scanning electron microscope (SEM) analysis showed that the bamboo activated carbon internal conditions were cross-linked structure developed. (2) changes with a variety of characterization methods of preparation of activated carbon in the process of its surface chemical properties were studied systematically. The determination results of elemental analysis, Boehm titration and P H showed that the carbonized material and activated carbon mainly containing C, O elements, surface Mainly for alkaline oxygen containing functional groups. Compared with the carbonized material, activated carbon surface acidic oxygen functional groups and decrease the total amount of alkaline amounts of oxygen-containing groups increased. Fourier transform infrared (FTIR) spectra show that the carbonized material and activated carbon mainly reflected in the difference between the spectral intensity on the activated carbon surface functional groups including hydroxyl, methyl, methylene, aromatic ring, carbonyl and ether bonds such as.X ray photoelectron spectroscopy (XPS) analysis showed that water vapor activation types of surface functional groups had no effect but the relative contents of.X ray diffraction (XRD) analysis showed that after high temperature activation after activated carbon graphitization degree increased, the crystal structure more regular (3). The water vapor preparation of bamboo activated carbon as adsorbent in wastewater on Cr (VI) were studied. The results showed that the adsorption of bamboo activated carbon is suitable for liquid phase adsorption of Cr (VI) and negative ion physical structure Chemical properties. The adsorption experiments show that Cr (VI) and total chromium removal rate increases with the increase of solution pH decreased with the increase of the dosage of activated carbon, the removal rate increased and then remained constant. Langmiur adsorption isotherm model, the maximum adsorption capacity of monolayer at 30 DEG C for 193 mg/g. adsorption process was spontaneous and endothermic process. The adsorption kinetics of the quasi two level dynamic model, the only rate controlling step of particle diffusion is not the adsorption process, there are other mechanisms involved. The adsorption mechanism includes four steps: surface functional groups of protonation, between activated carbon and chromium ion electrostatic attraction, Cr (VI) surface reduction, Cr adsorption (III) or release.

【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ424.1;X703

【相似文献】