Measurement and modeling of single- and multi-component adsorption equilibria of VOC on high-silica zeolites

From pure and binary gas adsorption equilibria measurements carried out using a volumetric method for three volatile organic compounds (methyl ethyl ketone, toluene (TOL), and 1,4-dioxane) on two high-silica zeolites, desaluminated faujasite Y (Fau Y) and ZSM-5 (Sil Z), co-adsorption was investigated and modeled. Apart from steric exclusion taking place with TOL-containing mixtures on Sil Z, micropore filling was similar to distillation since the component with the lower volatility adsorbed preferentially. At low coverage, chemisorption on specific sites happened in favor of polar or major compound, whereas at saturation the adsorbent was selective for the minor compound. Second, a quantitative prediction of binary equilibria was performed using the ideal adsorbed solution theory (IAST), examining the influence of pure component adsorption fitting model. The efficiency of correlations when extending AST to real mixture behavior was satisfactory in most cases. For engineering purposes, Fau Y is to be considered as a high-adsorption capacity adsorbent, whose selectivity can be described qualitatively by the distillation analogy and predicted quantitatively with the IAST in case of quasi-ideal mixtures.     

木质素在土壤改良和修复中的研究及应用进展

具有酚羟基、醇羟基、羧基等极性基团的木质素,因具有较高的络合性,能够被用于提高植物对土壤中养分的利用效率,改良土壤团粒结构,提高土壤酶活;同时,木质素能够通过离子交换及络合作用,吸附去除土壤中的污染物,引发微生物对有机污染物的降解,从而起到修复污染土壤的作用。本文综述了木质素在土壤改良和修复方面的作用原理,介绍了木质素作为土壤改良剂、固沙剂和污染物吸附剂的应用效果。最后,对木质素在此领域的研究和应用进展进行了总结,并对其未来发展提出了相应的建议。     

Water Activity Calculation by Direct Measurement of Vapor Pressure

An improved method for calculation of water activity from vapor pressure manometric data, which takes into account the volume expansion of nonadsorbing gases, the initial pressure in the desiccant flask and the pressure exerted by the desiccant, was developed. The water activity of pure water was measured over a range of nonadsorbing gas pressures and initial pressures in the desiccant flask. Standard deviations in a_w of pure water calculated using no corrections, corrections for volume expansion only, and full corrections were 0.221, 0.011, and 0.005, respectively. Correction only for volume expansion may under some conditions result in larger errors than when no corrections are made at all. Based on the improved equation, an experimental modification which reduces loss of water from samples during measurement was proposed.     

水分活度的蒸汽压测定法的研究

本文在水分活度(a_w)的蒸汽压测定法(VPW)的研究中发现Lewicki的测定装置及计算公式中尚未考虑到干燥瓶的容积和干燥剂吸湿后剩余水汽压强对a_w测定结果的影响。本研究在Lewicki的装置中添加一个恒温水浴以减少测定过程中温度的变化,又在该装置的油压计中增加了一个加热器用于排除硅油中的空气,并对干燥瓶的容积和干燥剂的吸湿特征进行了探讨。依据理想气体的特性,提出了一个改进后的a_w计算公式。实验结果:(1)标准品(NaCl饱和水溶液)a_w测定的均值和标准差,依Lewicki方法为0.764和0.013,依本文方法为0.754和0.003;与文献公认值相比,相对误差由Lewicki的小于1.5％减少到改进后的小于0.15％。(2)样品(调味鱼干片)的a_w定的均值和标准差,依Lewicki方法为0.657和0.023,依本文方法为 0.635和 0.008.     

改良剂施用量对Cd污染土壤修复及烤烟Cd积累的影响

为了研究改良剂施用量对重金属Cd污染植烟土壤的修复效果,在湖北恩施“清江源”科技园区采取盆栽方法,人工模拟Cd污染,试验研究了不同改良剂用量对土壤中总Cd、交换态Cd及烤烟叶片中Cd含量的影响。结果表明,施用改良剂使植烟土壤pH值升高,阳离子交换量显著增加,交换性Cd含量显著降低。施用改良剂显著降低了烤烟中部叶Cd积累量,最大降幅达51.59%     

AM真菌和牛粪对铅污染土壤的修复效应

铅污染会对环境和人体健康产生较大风险,如何修复污染土壤、降低农产品中的铅残留值得深入研究。在温室盆栽条件下研究了接种丛枝菌根(AM)真菌、施加牛粪及复合处理对铅污染土壤的修复效应和机理。结果表明,在所有铅污染水平下,接种AM 真菌、施加牛粪和复合处理均显著促进烟草生长,改善烟草磷营养。复合处理在所有铅污染水平下均降低烟草铅残留量,而施加牛粪仅在轻度和中度铅污染水平下、接种AM 真菌仅在重度污染水平下作用显著。土壤pH 升高,铅有效性降低。可见,AM 真菌和有机肥对铅污染地区优质烟叶生产及铅污染土壤的植物修复具有一定的应用潜力。     

重金属污染土壤固化/稳定化修复技术的研究

重金属污染土壤的修复问题一直是国内外研究课题的难点.目前,对此类污染土壤的处理主要包括物理、化学、生物等修复方法,其中,物理法主要包括:客土法、换土法和深耕翻土法;而化学法主要包括:固定/稳定化技术、土壤淋洗技术和氧化还原技术;生物法主要包括植物修复和生物治理.基于以上方法,在重金属污染土壤的治理修复过程中,最常用的方...     

Measurement of Water Activity of Salt Solutions and Foods by Several Electronic Methods as Compared to Direct Vapor Pressure Measurement

The Kaymont-Rotronics Hygroskop DT, the Beckman-Sina and the Protimeter were tested for their ability to measure water activity (a_w) of five foods over the 0.11 – 0.85 a_w range. Each instrument was calibrated at 30 ± 0.1°C against ten saturated salt solutions using a modification of the AOAC Method 32.004-32.009. Regression of the reading versus true a_w, as determined by the vapor pressure manometer (VPM), gave high r² values for the saturated salt solutions between 0.32 – 0.85 a_w. An error of approximately 0.01 a_w units was found using the 1 hr data but no significantly better regression line was found using the 24-hr data as compared to I hr data. Measurement of the a_w of five foods, however, gave values differing by an average of 0.051 a_w units as compared to the VPM readings. This study demonstrates justification of the FDA cutoff a_w value of 0.85 for low-acid foods as a margin of safety.     

废弃遗留地重金属污染土壤治理与修复案例研究

土壤重金属污染主要来自农药、废水、污泥和大气沉降等,重金属污染物在土壤中移动性很小,不易被分解,易随食物链进入人体,潜在危害大.文章选取了废弃遗留地重金属污染土壤治理案例为研究重点,对项目概况、修复工艺选择、方案设计、修复效果评估进行分析,为各地实施重金属污染场地治理与修复提供参考.     

生物过程模型化与控制中空气湿度的测量

在好氧发酵等生物过程中通入的空气 ,其水分含量即湿度对氧的传递速率、微生物细胞的呼吸和生长、发酵液体积以及补料稀释率都将产生很大的影响 ,并进而影响发酵过程产率 .对发酵过程进行模拟和对不可测变量进行间接计算 (即所谓软测量 )时 ,如果忽视空气的湿度 ,计算和模拟结果将产生很大的偏差 .因此 ,对好氧发酵过程来说 ,必须高度重视空气湿度的测量和控制 .     

Effective thermal conductivity of potato during frying: Measurement and modeling

Abstract

The effective thermal conductivities of potato were measured at various stages of the frying process. Samples were taken at 30 s intervals during frying, and two different methods (line heat source and modified Fitch method) were used to measure the effective thermal conductivity. An iterative Kopelman model was used for the prediction of thermal properties. The effective thermal conductivity decreased as frying time increased. The variation of experimental measurements by both methods and modeling were within 10% over most of the range studied. The probe method yielded values that were not significantly different than the modified Fitch method. Lower standard deviations were obtained with the modified Fitch method.     

Research Watch: Remediation of radionuclide-contaminated soil

Bioremediation.     

Measurement of Fibre Tuft Weight in an Air Duct using Optical Methods

The feasibility of using a Charge-Coupled Device (CCD) linescan camera to evaluate the weight of fibre tufts moving in an air duct is reported. A theoretical study of the measurement of the light transmission of fibre tufts is presented and the theoretical models are verified by experimental results. The accuracy of the results is improved by a modification of the air duct shape. The fibre tuft speed and the optical uniformity are also discussed.     

Air injection into concentrated maple sap during processing: impact on syrup composition and flavour

BACKGROUND: Air injection (AI) is a relatively new process used during maple sap thermal processing to increase the profitability of maple syrup production by increasing the production of more economically valuable light‐coloured syrup. The effects of applying this technology in conjunction with existing practices employed to increase the efficiency of maple production, such as reverse osmosis (RO), are unknown. The main objective of this work was to investigate the effects of AI on syrup chemical composition and flavour when applied to maple sap concentrated by RO. RESULTS: The chemical composition and flavour of syrup produced simultaneously with and without AI from a common source of maple sap concentrated by RO were compared. The chemical composition of maple syrup produced with AI was within ranges previously published for maple syrup. Syrup produced with AI was significantly lighter in colour than syrup produced without AI from the same sap concentrate (P < 0.001). Although syrup produced with AI contained fewer volatile flavour compounds and had a flavour distinguishable from that of syrup produced without AI from the same concentrated sap, the flavour properties of AI syrup were consistent with those of light‐coloured maple syrup. CONCLUSION: The results indicate that AI can be used in conjunction with RO to effectively increase the economic efficiency of maple syrup production without detrimental impacts on maple syrup properties. Copyright © 2009 Society of Chemical Industry     

Correction Factors for Nondestructive Measurement of Residual Volume of Air in Retort Pouches

A destructive and a nondestructive method of estimating residual volume of air in retort pouches were compared. The difference between the volumes of air given by two techniques were found to be significant (P < 0.05) by paired t-test. An indirect calculation method was developed for estimation of internal pressure at neutral buoyancy and when used in conjunction with Archimedes’ Principle and Boyle's Law significantly improved the results. This method of calculating residual air in flexible pouches did not show any significant difference (P > 0.01) when compared to the standard destructive technique. The procedure outlined is easy to use.     

铅锌矿区重金属污染土壤修复植物及其制浆造纸性能研究

介绍了某废弃铅锌矿区土壤重金属污染情况,筛选出矿区内几种对重金属污染土壤修复性能好的优势植物,并以优势植物为原料进行蒸煮实验,研究其制浆造纸性能和安全性。结果表明,实验矿区土壤Pb、Zn、Cd含量均超过国家土壤环境二级标准;筛选的6种主要优势植物中,桑树、五节芒、蜈蚣草对重金属的富集能力强,可作为重金属污染土壤修复的主要优势植物;当蒸煮用碱量（以Na₂O计）和硫化度均为20%时,蜈蚣草蒸煮粗浆得率仅31.1%,卡伯值和无机物含量较高,分别为19.4和9.55%;而用五节芒和桑树蒸煮粗浆得率较高,分别为48.4%和45.1%,卡伯值较低,分别为7.8和13.8;用蜈蚣草浆抄造纸张的耐破度、撕裂度、抗张强度均非常低,而用五节芒浆和桑树浆抄造纸张的强度性能较好。并且五节芒浆和桑树浆成纸的重金属含量接近我国国家标准对食品包装用原纸的理化指标要求。     

VOC and particulate emissions from commercial cigarettes: analysis of 2,5-DMF as an ETS tracer

Emissions of particulate matter (PM) and a broad suite of target volatile organic compounds (VOCs) in total, main-stream (MS) and side-stream (SS) smoke emissions are measured for six types of commercial cigarettes. The suitability of 2,5-dimethyl furan (DMF) as a tracer for environmental tobacco smoke (ETS) is investigated using laboratory results and a field study of 47 residences. Over 30 VOCs were characterized in cigarette smoke, including several that have not been reported previously. "regular tar", "low tar", menthol, and nonmenthol cigarettes showed only minor differences in PM and VOC emissions. When total emissions are considered, PM emissions averaged 18 +/- 2 mg cigarette(-1) and VOC emissions averaged 3644 +/- 160 mg cigarette(-1). DMF appears to satisfy all requirements for a tracer, namely, uniqueness, detectability, similar emission factors across tobacco products (211 +/- 16 microg cigarette(-1)), consistent proportions to other ETS compounds, and behavior similar to other ETS components in relevant environments. On the basis of field study results, DMF more reliably indicated smoking status than occupant-completed questionnaires, and cigarette smoking was responsible for significant fractions of benzene (50%), styrene (49%), and other VOCs in the smoker's homes.     

Direct measurement of VOC diffusivities in tree tissues: impacts on tree-based phytoremediation and plant contamination

Recent discoveries in the phytoremediation of volatile organic compounds (VOCs) show that vapor-phase transport into roots leads to VOC removal from the vadose zone and diffusion and volatilization out of plants is an important fate following uptake. Volatilization to the atmosphere constitutes one fundamental terminal fate processes for VOCs that have been translocated from contaminated soil or groundwater, and diffusion constitutes the mass transfer mechanism to the plant-atmosphere interface. Therefore, VOC diffusion through woody plant tissues, that is, xylem, has a direct impact on contaminant fate in numerous vegetation-VOC interactions, including the phytoremediation of soil vapors and dissolved aqueous-phase contaminants. The diffusion of VOCs through freshly excised tree tissue was directly measured for common groundwater contaminants, chlorinated compounds such as trichloroethylene, perchloroethene, and tetrachloroethane and aromatic hydrocarbons such as benzene, toluene, and methyl tert-butyl ether. All compounds tested are currently being treated at full scale with tree-based phytoremediation. Diffusivities were determined by modeling the diffusive transport data with a one-dimensional diffusive flux model, developed to mimic the experimental arrangement. Wood-water partition coefficients were also determined as needed for the model application. Diffusivities in xylem tissues were found to be inversely related to molecular weight, and values determined herein were compared to previous modeling on the basis of a tortuous diffusion path in woody tissues. The comparison validates the predictive model for the first time and allows prediction for other compounds on the basis of chemical molecular weight and specific plant properties such as water, lignin, and gas contents. This research provides new insight into phytoremediation efforts and into potential fruit contamination for fruit-bearing trees, specifically establishing diffusion rates from the transpiration stream and modeling volatilization along the transpiration path, including the trunk and branches. This work also has importance in other plant-VOC interactions, such as potential uptake from the atmosphere for hydrophobic compounds and also uptake from vapor-phase soil contaminants.     

浅谈凹印烟包中挥发性有机化合物的检测与控制

目前,烟草行业《卷烟条与盒包装纸中挥发性有机化合物的测定顶空-气相色谱法》和《卷烟条与盒包装纸中挥发性有机化合物的限量》两项标准相继发布、实施,这将极大地促进我国烟包印刷行业向绿色、环保、低危害方向发展,改善员工的工作环境。凹印作为烟包印刷的主要加工工艺,印刷过程中使用了大量有机溶剂,如何充分理解烟包中挥发性有机化合物（VOC）控制相关标准,