沸石分子筛和活性炭吸附/脱附甲苯性能对比

考察了甲苯在NaY型沸石分子筛(简写为NaY)、13X型沸石分子筛(简写为13X)、Hβ型沸石分子筛(简写为Hβ)、MCM-22型沸石分子筛(简写为MCM-22)和ZSM-5型沸石分子筛(简写为ZSM-5)上的吸附/脱附性能,同时与椰壳活性炭(AC)的吸附/脱附性能进行对比.结果表明,各吸附剂对甲苯的平衡吸附量大小依次为:AC>NaY>Hβ>13X>MCM-22>ZSM-5,甲苯从吸附剂表面脱附难易程度依次为:AC>NaY、13X>Hβ>MCM-22>ZSM-5>ZSM-5对甲苯的平衡吸附量和吸附强度都最小,这是由于甲苯无法进入ZSM-5的内部孔道造成的;在低甲苯质量浓度(<1 000 mg/m3)时.NaY平衡吸附量超过AC,因此NaY更适合应用在低浓度有机废气吸附治理中,Langmuir吸附方程比Freundlich吸附方程更符合沸石分子筛吸附甲苯的行为.     

用于氨氮去除的13X分子筛／PES膜吸附剂的制备与性能表征

针对氨氮排放对环境造成的污染以及给人类带来的危害这一问题,将分子筛吸附与膜技术相结合,以13x分子筛为功能颗粒,以聚醚砜（PES）为膜的基质材料,以二甲基乙酰胺（DMAc）为溶剂,通过相转化法制备了不同13x分子筛填充量的13x／PEs膜吸附剂。研究发现,随着13x分子筛填充量的增加,膜的指状孔变得细密、短小,其吸附容量,断裂强度都在增加,但是水通量逐渐降低。料液温度与pH值对吸附性能的影响表明,该膜吸附剂在293K,pH=7时对氨氮有较好的吸附容量,可达21．69mg／g;吸附热力学研究表明,该类型膜吸附剂对氨氮的吸附等温线符合Langmuir方程。     

选择性去除香烟烟气中亚硝胺的研究

沸石具有选择性吸附和催化去除亚硝胺的功能.使用沸石添加剂和/或微波辐射预处理,可将香烟侧流烟气中致癌性物质亚硝胺的含量降低约50%,主流烟气中降低60-90%,能有效地减轻吸烟对于环境的污染.     

Lead sorption by a Mexican,clinoptilolite-rich tuff

Goal, Scope and Background The retention of lead by a Mexican, clinoptilolite-rich tuff from Oaxaca (Mexico) at different pH values was evaluated and the lead sorption mechanisms on the zeolitic material in this work were discussed. Methods Isotherms were determined using lead nitrate solutions (initial pH values between 2 and 5) at 303 K. After the equilibrium was reached, the content of lead in the liquid phases was determined by atomic absorption spectrometry. The elemental composition of the clinoptilolite-rich tuff before and after the lead sorption process was evaluated by electron microscopy. Results The maximum ion exchange capacity of the Mexican, clinoptilolite-rich tuff for lead was 1.4 meq/g at pH 3, considering an ion exchange mechanism in the absence of any precipitated or hydrolyzed lead species in the sorption process or any change in the zeolite network. Langmuir and Freundlich isotherms were also considered in this work for comparison purposes. Discussion It is important to consider the nature of the sorption processes before choosing a model to describe the interaction between the metal ions and the sorbent. Conclusions The chemical lead speciation, the pH, as well as the characteristics of the clinoptilolite-rich tuff are important factors to be considered on the lead sorption process by natural zeolites. The chemical species involved in that process are Na⁺ from the zeolite and Pb²⁺ from the aqueous solution at pH 2 and 3, so that the ion exchange mechanism explains the lead sorption processes by the clinoptilolite-rich tuff through the ion exchange isotherms. The sodium, Mexican, clinoptilolite-rich tuff is a potential adsorbent for lead from aqueous solutions. Recommendations and Perspectives The natural zeolite-rich tuffs are very important as ion exchangers for the treatment of polluted water due to their sorption properties and low cost. The sorption behavior of each natural material depends on their composition. Mexican, clinoptilolite-rich tuff from Oaxaca (Mexico) could be used for the treatment of waste water contaminated with lead. It would be important to propose this material as an alternative as waste water treatment, because it shows good selectivity for the removal of heavy metals from water.     

Transportation fuel production by combination of LDPE thermal cracking and catalytic hydroreforming

Fuel production from plastics is a promising way to reduce landfilling rates while obtaining valuable products. The usage of Ni-supported hierarchical Beta zeolite (h-Beta) for the hydroreforming of the oils coming from LDPE thermal cracking has proved to produce high selectivities to gasoline and diesel fuels (>80%). In the present work, the effect of the Ni loading on Ni/h-Beta is investigated in the hydroreforming of the oils form LDPE thermal cracking. h-Beta samples were impregnated with Ni nitrate, calcined and reduced in H₂ up to 550 °C to achieve different Ni contents: 1.5%, 4%, 7% and 10%. Larger and more easily reducible metal particles were obtained on Ni 7%/h-Beta and Ni 10%/h-Beta. Hydroreforming tests were carried out in autoclave reactor at 310 °C, under 20 bar H₂, for 45 min. Ni content progressively increased the amount of gases at the expenses of diesel fractions, while gasoline remained approximately constant about 52–54%. Maximum selectivity to automotive fuels (～81%) was obtained with Ni 7%/h-Beta. Ni loading also enhanced olefins saturation up to Ni 7%/h-Beta. High cetane indices (71–86) and octane numbers (89–91) were obtained over all the catalysts. Regarding the different studied Ni contents, Ni 7%/h-Beta constitutes a rather promising catalyst for obtaining high quality fuels from LDPE thermal cracking oils.     

Enhancing Diatom Growth by Using Zeolites to Change Seawater Composition (4 pp)

- Aims and Scope. The purpose of this study was to test whether two zeolites produced synthetically (products of zeolitic nature, PZN) could influence either the yield of a diatom culture or the chemical changes in the cultures. For this purpose, Phaeodactylum tricornutum was used as test organism in a culture medium of natural seawater enriched with N and P having negligible amounts of ammonia. Methods The PZN ZEBEN-06 and ZESTEC-56 were used in parallel experiments. The composition of trace metals and organic compounds with chelate activity in the culture media, were determined by anodic or cathodic stripping voltammetry. The impact of leaching silicon on the algal yield was evaluated by comparing the growth in the presence or absence of PZN, in seawater enriched or not-enriched with silicon. Results and Conclusions Both PZN significantly promoted the algal yield even in the absence of added silicon, a limiting nutrient for diatom growth. The PZN acted as a silicon buffer while providing a source of silicon required for growth. In addition, PZN released into the seawater small but significant amounts of the limiting micro-nutrient manganese (its concentration doubled during the experiments), while simultaneously removing relatively high quantities of zinc from the seawater. The presence of PZN inhibited the releasing of chelated compounds. These changes (sorption/desorption) caused by the PZN in the concentrations in the solutions used as culture media of P. tricornutum were probably responsible for the differences in both the diatom and exudation observed in the tested cultures.     

改性沸石对焦化废水中COD的去除研究

本文研究了沸石经NaCl、NaOH、HDTMA（溴化十六烷基三甲胺）改性后对焦化废水中的COD的去除效果。比较得出HDTMA改性沸石对COD的去除能力较好．而且废水的色度明显减小。接着进一步研究了该废水处理过程中的影响因素，包括吸附时间、烘干温度、改性剂HDTMA的浓度、pH值等。结果表明，HDTMA改性沸石处理焦化废水可使其COD的浓度降低至150mg／L以下，达到污水综合排放二级标准。     

阳离子表面活性剂用量对改性沸石吸附铬酸根的影响

用不同量阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)对天然沸石改性,并制备不同改性程度的改性沸石,测定沸石对CTAB的吸附量,比较几种沸石对铬酸根的吸附性能及其与改性沸石胶体Zeta电位的关系,探讨沸石对铬酸根的吸附机制及沸石再生后对铬酸根的吸附能力.结果表明,随着CTAB加入量的增加,它在沸石表面的吸附量显著增加,制备的改性沸石对铬酸根吸附性能显著提高.改性后沸石胶体的Zeta电位由负变正,而且随着CTAB用量的增加,Zeta电位正值增加.铬酸根在改性沸石表面的吸附量随离子强度增加而减小,而且改性沸石吸附的铬酸根大部分可以被中性盐解吸,说明铬酸根的吸附以静电作用机制为主.改性剂用量在0.15～0.3 mol·kg-1范围内,改性沸石再生后仍对铬酸根有很好的吸附性能,可以循环使用.     

溴化十六烷基吡啶改性沸石对水中菲的吸附作用

采用不同浓度的溴化十六烷基吡啶(CPB)溶液对天然沸石进行改性,制备得到了单层和双层CPB改性沸石,并通过批量吸附实验考察了这两种CPB改性沸石对水中菲的去除作用.结果表明,单层和双层CPB改性沸石对水中菲均具备良好的吸附能力.CPB改性沸石对水中菲的去除率随吸附剂投加量的增加而增加,而CPB改性沸石对水中菲的单位吸附量随吸附剂投加量的增加而降低.CPB改性沸石对水中菲的吸附动力学过程满足准二级动力学模型.CPB改性沸石对水中菲的吸附平衡数据可以采用线性模型和Freundlich模型加以描述.CPB改性沸石对水中菲的吸附过程是一个自发和放热的过程.单层CPB改性沸石吸附水中菲的机制主要是疏水作用,双层CPB改性沸石吸附水中菲的机制主要是有机相分配作用.当双层CPB改性沸石的CPB负载量为单层CPB改性沸石的CPB负载量的2倍时,前者对水中菲的吸附能力略微强于后者.以上结果表明,双层和单层CPB改性沸石均可以用于水中菲的去除;为节约成本,单层CPB改性沸石与双层CPB改性沸石相比更适合用于水中菲的去除.