分子筛负载型吸附剂对典型VOCs的吸附行为特性

以浸渍法制备的分子筛负载铜锰铈(Cu-Mn-Ce/ZSM)为吸附剂,以甲苯、乙酸乙酯和丙酮作为挥发性有机物(VOCs)的典型代表,考察了单组分和混合组分VOCs在吸附剂固定床上的吸附行为。研究表明,Cu-Mn-Ce/ZSM吸附单组分VOCs时,甲苯的吸附穿透时间与饱和吸附量分别为110 min和32.47 mg/g,乙酸乙酯为150 min和52.29 mg/g,丙酮为210 min和86.40 mg/g,可见Cu-Mn-Ce/ZSM对单组分VOCs的吸附能力大小为:丙酮乙酸乙酯甲苯。Cu-Mn-Ce/ZSM吸附混合组分VOCs时,在甲苯与乙酸乙酯的穿透曲线上出现了明显的"驼峰",吸附穿透过程中存在共吸附和竞争吸附行为,甲苯的吸附穿透时间与饱和吸附量降至50 min、10.42 mg/g,乙酸乙酯为95 min、15.12 mg/g,丙酮为105 min、44.37 mg/g。通过Yoon-Nelson模型对单组分VOCs吸附穿透曲线的拟合,表明吸附模型参数可以准确地预测吸附质在固定床上的穿透行为。速率参数k'值计算表明,不同VOCs在固定床上的吸附速率大小为丙酮乙酸乙酯甲苯。     

Mn改性活性炭吸附VOCs性能

采用浸渍焙烧法对活性炭进行负载锰(Mn)改性,考察改性活性炭对甲苯、乙酸乙酯及甲苯-乙酸乙酯二元混合气体的吸附性能.研究表明,活性炭浸渍于1.0％高锰酸钾溶液改性后的吸附性能最好.对于单组分VOCs气体,改性后活性炭对甲苯和乙酸乙酯的吸附量较未改性前分别提高了12.7％和16.3％;对于二元混合VOCs气体,改性后活性炭对甲苯及乙酸乙酯的吸附量分别提高了13.1％和22.9％.BET、SEM、FTIR等分析表明,Mn改性活性炭比表面积变大和总孔容增加是改性后吸附量提高的主要原因.     

NaY沸石分子筛在VOCs处理中的应用

为深入研究分子筛吸附VOCs的性能,采用固定床动态吸附法,对NaY分子筛吸附3种典型VOCs的性能进行了探究,考察了吸附温度、湿度、进气浓度和吸附质物理性质对吸附容量的影响,并探讨了NaY分子筛的循环使用性能;通过Yoon-Nelson模型,从吸附动力学角度,对单组分VOCs吸附穿透曲线进行了拟合。结果表明:NaY分子筛对3种VOCs的吸附饱和时间分别为丙酮355 min,邻二甲苯320 min,乙酸乙酯220 min;相对应的平衡吸附容量分别为丙酮176 mg·g-1,邻二甲苯196 mg·g-1,乙酸乙酯185 mg·g-1。NaY分子筛对VOCs吸附能力排序为邻二甲苯乙酸乙酯丙酮。温度由303 K升至328 K时,3种VOCs吸附容量均分别下降,邻二甲苯下降3.66%,乙酸乙酯下降2.87%,丙酮下降10.0%;VOCs相对湿度为30%时,吸附容量显著降低;进气浓度为660 mg·m-3时,出现吸附交叉的现象;NaY分子筛具有较好的循环使用性;吸附容量与沸点、分子质量存在正相关关系;3种VOCs在NaY分子筛固定床的吸附速率排序为乙酸乙酯邻二甲苯丙酮。YoonNelson模型能够较好地模拟NaY分子筛吸附不同VOCs的过程,为分子筛的工业应用提供了参考。     

混合生活垃圾恶臭特性及评估方法研究

总结了不同区域、不同时段生活垃圾的恶臭特性,发现恶臭特性受垃圾组分、处理处置工艺等因素影响较大,垃圾中转站的主要恶臭组分为乙酸乙酯、甲苯、乙苯等挥发性有机物(VOCs)及氨气,填埋场恶臭组分中含硫化合物和含氧化合物浓度高,堆肥场恶臭组分中苯系物和烃类浓度较高,焚烧厂恶臭组分主要为苯系物。基于复杂多变的生活垃圾恶臭特性,采用综合评分法评价恶臭的环境影响程度,对已报道的生活垃圾恶臭组分进行综合评价,发现生活垃圾降解过程释放的恶臭组分中,二甲二硫、硫化氢、甲硫醇、萘、1,3,5-三甲苯、甲硫醚、甲苯、乙苯、对二甲苯和α-蒎烯等是混合生活垃圾优先控制的恶臭污染物。     

VOCs和水在Y型分子筛表面的竞争吸附

采用水热处理方法合成了具有不同硅铝比的超稳Y型分子筛,考察了苯、甲苯、二甲苯、苯乙烯和乙酸乙酯与水在Y分子筛表面的竞争吸附。结果表明,随着Si/Al比的增加,Y分子筛表面的有机分子选择性吸附位数量增加,有机分子竞争吸附能力增加。低硅Y型分子筛只有在吸附偶极距>1.0的高极性有机分子时才能与水分子产生有力的竞争吸附,而高硅超稳Y分子筛则对偶极距在0～0.5范围的有机分子就表现出很强的竞争吸附能力。     

生物滴滤-生物过滤组合工艺处理汽车喷漆废气中试研究

采用中试规模的生物滴滤-生物过滤组合工艺设备处理某汽车厂喷漆车间废气,研究了组合式反应器对废气的净化效果和2处理单元对污染组分的去除能力及微生物特性.该汽车厂喷漆车间废气中的主要组分为甲苯、二甲苯、乙酸乙酯、乙酸丁酯、丁醇、丙酮和甲基丙基甲酮.组合式反应器对废气中的污染物有较好的处理效果,但不同的污染组分在不同处理单元...     

应用POMS复合膜分离去除废气中挥发性有机污染物

依靠POMS平板单层膜或POMS卷式膜上选择性分离层的选择性溶解和渗透作用,常温负压分离回收废气中乙酸乙酯等挥发性有机污染物(VOC)组分.结果表明,膜两侧操作压差和原料气流量对乙酸乙酯分离效率影响较大;当原料气处理量为1.770 0～2.810 0 m3/(m2·h)、膜两侧操作压差为0.08 MPa,POMS卷式膜乙酸乙酯渗透速率可达7.86 × 10-7 mol/(s·m2·Pa);乙酸乙酯为1 500～4 500 mg/m3时,其去除率可达80%.测得几种VOC组分在POMS复合膜中的溶解吸附量都比较可观,由此预测该膜处理废气中VOC可取得很好的净化效果.甲苯在POMS复合膜中的溶解吸附量低于乙酸乙酯,其实验测得渗透速率也小于乙酸乙酯.甲苯去除率也能达到80%.     

泥炭对甲苯的吸附-解吸行为研究

用热处理方法对泥炭进行活化改性,探讨了对甲苯的吸附性能及影响因素,并研究了甲苯在泥炭上的吸附/解吸行为。结果表明,粒径在0.6～1 mm之间的泥炭在160℃热处理5 h,在pH为7的条件下对甲苯有良好的吸附效果,对甲苯的吸附量为0.32 mg/g。泥炭对甲苯的吸附在20 min内基本达到平衡,可用二级吸附速率方程进行拟合。甲苯在泥炭上的吸附和解吸均呈现明显的非线性,用Langmuir模型能较好地描述,泥炭对甲苯的饱和吸附量为0.939 mg/g。甲苯在泥炭上的平均解吸率为6.393%,并且出现了滞后现象,表明苯系物与泥炭有较强的结合能力。研究结果为应用泥炭作为PRB装填介质进行原位修复甲苯污染的地下水提供了理论依据。     

风道式光催化反应器降解VOCs的效果分析

针对室内挥发性有机化合物(VOCs),搭建了带风道式反应器的模拟环境舱实验系统,选取甲醛、甲苯和苯为目标污染物,研究了光催化对各污染物的降解性能及其之间的相互影响。通过装置的优化,还对紫外光下目标VOC降解的主要副产物进行了检测。结果表明,单组分VOC的降解实验中,该净化器对3种污染物均具有良好的降解效果,其中对甲苯和苯的降解性能相似,对甲醛的降解性能更优。2组分VOCs降解实验中,目标组分会受到另一组分的不同程度影响;甲苯和苯无论是作为影响组分还是目标组分其实验结果均较接近;甲醛对甲苯、苯的降解影响明显大于两者的相互影响,即甲醛对两者的降解反应阻碍更大。甲苯的主要副产物为苯、苯甲醛和苯甲酸,苯的主要副产物为苯酚。     

新装饰装修房屋室内空气中的苯系物调查

对新装饰装修房屋室内的一类主要有机苯系污染物进行了调查,调查采用吸附柱采集、GC/MS 和GC-FID测定,检测了321家居室内的苯系物.检出的苯系物有12种,苯平均浓度为0.068 mg/m^3,有86.9%的居室符合《室内空气质量标准》（GB/T18883-2002）规定的限量值,甲苯、二甲苯平均浓度分别为0.14 mg/m^3和0.41 mg/m^3,符合《室内空气质量标准》规定限值的居室分别达85.4%和73.3%.苯系物约占室内空气中TVOC的62%,浓度由低到高分别是苯、甲苯、乙苯和二甲苯,其中二甲苯中的间二甲苯占二甲苯总量的55% .     

吹扫捕集/气相色谱/质谱法测定水体中54种常见挥发性有机物的研究

运用吹扫捕集/气相色谱/质谱(P＆T/GC/MS)法对水体中54种常见的挥发性有机物(VOCs)进行了测定.结果表明,VOCs的色谱分离情况较好,平均加标回收率为88.5%～117.0%,相对标准偏差为0.71%～8.50%,准确度和精密度均符合有关分析测试的要求;方法检出限为0.10～0.61μg/L,远低于<地表水环境质量标准>(GB 3838-2002)、<生活饮用水卫生标准>(GB3838-2002)及国外相关标准的限值;54种VOCs的线性范围不同,低沸点的VOCs线性范围较宽,高沸点的VOCs的线性范围较窄,因此在分析VOCs样品配制标准工作曲线时,应注意不同沸点VOCs的线性范围.     

活性炭吸附和脱附-等离子体氧化净化有机废气的研究

根据滑动弧放电等离子体适于降解高浓度有机物废气的特性,结合活性炭吸附法,提出了吸附器的吸附浓缩和热脱附-等离子体氧化净化有机废气的方法。在活性炭吸附过程中,最初2 h内甲苯净化率达到100%,随着时间的增加净化率下降;在热脱附滑动弧放电等离子体净化过程中,甲苯降解效率最高为97.3%。将滑动弧放电等离子体反应器出口气相产物收集进行FT-IR检测,发现放电后有CO2、CO、H2O和NO2产生,并分析了甲苯的降解机理。     

Adsorption and desorption characteristics of semiconductor volatile organic compounds on the thermal swing honeycomb zeolite concentrator

The use of a honeycomb zeolite concentrator and an oxidation process is one of the most popular methods demonstrated to control volatile organic compound (VOCs) emissions from waste gases in semiconductor manufacturing plants. This study attempts to characterize the performance of a concentrator in terms of the removal efficiencies of semiconductor VOCs (isopropyl alcohol [IPA], acetone, propylene glycol methyl ether [PGME], and propylene glycol monomethyl ether acetate [PGMEA]) under several parameters that govern the actual operations. Experimental results indicated that at inlet temperatures of under 40 degrees C and a relative humidity of under 80%, the removal efficiency of a zeolite concentrator can be maintained well over 90%. The optimal rotation speed of the concentrator is between 3 and 4.5 rph in this study. The optimal rotation speed increases with the VOCs inlet concentration. Furthermore, reducing the concentration ratio helps to increase the removal efficiency, but it also increases the incineration cost. With reference to competitive adsorption, PGMEA and PGME are more easily adsorbed on a zeolite concentrator than are IPA and acetone because of their high boiling points and molecular weights.     

Effects of several low-molecular weight organic acids and phosphate on the adsorption of acid phosphatase by soil colloids and minerals

Adsorption of acid phosphatase on goethite, kaolinite and two colloids from the soils in central and south China in the presence of organic acids and phosphate was studied. With the increase of anion concentration, the ability in decreasing enzyme adsorption followed the sequence: phosphate>tartrate>oxalate>acetate. Acetate showed promotive effect on enzyme adsorption at lower anion concentrations whereas oxalate, tartrate and phosphate compete effectively with enzyme in a broad range of anion concentration. The adsorption isotherms of enzyme in most of the anionic systems studied conformed to the Langmuir equation. Phosphate reduced the affinity of enzyme on goethite more significantly than the other anions. However, tartrate decreased the affinity of enzyme on soil colloids and kaolinite to a greater extent than phosphate, oxalate and acetate. This observation suggested that the impact of anions on enzyme adsorption varies with anionic type and the surface characteristics of soil components. The influence of the addition order of ligand on enzyme adsorption was found greater in tartrate and phosphate systems. In general, simultaneous introduction of ligand and enzyme into the system had the lowest enzyme adsorption, showing more competition between ligand and enzyme molecules in this system. Data from this work indicated that the status and activity of enzyme in certain soil microenvironments especially the rhizosphere where various organic and inorganic ligands are active can be altered and may be completely different from the bulk soil.     

Adsorption of imidazolinone herbicides on ferrihydrite-humic acid associations.

Adsorption of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was studied on two binary systems (ferrihydrite-humic acid) prepared by treating ferrihydrite (Fh) immediately after its precipitation with a soil humic acid (HA) at different loadings (4% and 8% HA content), and on a blank ferrihydrite sample prepared in the same way, but without HA addition. Imidazolinone adsorption on pure Fh and on the 4% Fh-HA decreased with increasing of the herbicide hydrophobicity (imazaquin相似文献   

Investigation on the influence of methanol on adsorption and leaching of pesticides with soil column liquid chromatography

The effect of methanol of low concentration on adsorption and leaching of atrazine and tebuconazole was studied in this paper. The adsorption coefficients and the retardation factors (R^m) of pesticides on EUROSOIL 3# log-linearly decreased as volumetric fraction of methanol (f^c) was increased in the binary solvent mixtures of methanol and water. These data are consistent with solvophobic theory formerly outlined for describing the adsorption and transport of hydrophobic organic chemicals from mixed solvents. Nevertheless, the adsorption of these pesticides in soil–water system slightly increased when the soil was pre-washed with methanol in comparison with that pre-washed with water (pure water system). Furthermore, their adsorption coefficients were still higher in binary solvent systems with methanol of very low concentrations, i.e. f^c<0.03 for atrazine and f^c<0.01 for tebuconazole, than those in pure water system. The adsorption coefficients (logK^w) of atrazine and tebuconazole predicted by solvophobic theory were 0.5792 and 1.6525, respectively, and their experimental logK^w were 0.3701 and 1.6275 in pure water system. Obviously, the predicted logK^w of the two pesticides was higher than the experimental log K^w in pure water system. The predicted K^w and the retardation factor (R^w) in pure water system by solvophobic theory are thus possibly inaccurate.     

Zr—Fe双组分复合除砷吸附剂的优化制备及性能评价

实验发现，铁氧化物或铁的羟基氧化物对As（V）有较好的吸附性能，而锆氧化物或锆水合氧化物则对As（Ⅲ）有优异的吸附选择性，但其使用的pH通常要在〉9的条件下。通过简单的共沉淀法制备了Zr-Fe双组分复合吸附剂，在制备过程中通过优化制备条件如：沉淀剂浓度、金属离子总浓度、金属离子配比、反应温度、反应时间及吸附剂价格等因素，最终合成出了对As（V）和As（Ⅲ）都具有良好吸附能力的吸附剂。这种吸附剂在中性条件下对As（V）和As（Ⅲ）的最大吸附量为62mg／g和118mg／g。     

Zr-Fe双组分复合除砷吸附剂的优化制备及性能评价

实验发现,铁氧化物或铁的羟基氧化物对As(V)有较好的吸附性能,而锆氧化物或锆水合氧化物则对As(Ⅲ)有优异的吸附选择性,但其使用的pH通常要在9的条件下。通过简单的共沉淀法制备了Zr-Fe双组分复合吸附剂,在制备过程中通过优化制备条件如:沉淀剂浓度、金属离子总浓度、金属离子配比、反应温度、反应时间及吸附剂价格等因素,最终合成出了对As(V)和As(Ⅲ)都具有良好吸附能力的吸附剂。这种吸附剂在中性条件下对As(V)和As(Ⅲ)的最大吸附量为62 mg/g和118 mg/g。     

Adsorption and Desorption Characteristics of Semiconductor Volatile Organic Compounds on the Thermal Swing Honeycomb Zeolite Concentrator

Abstract

The use of a honeycomb zeolite concentrator and an oxidation process is one of the most popular methods demonstrated to control volatile organic compound (VOCs) emissions from waste gases in semiconductor manufacturing plants. This study attempts to characterize the performance of a concentrator in terms of the removal efficiencies of semiconductor VOCs (isopropyl alcohol [IPA], acetone, propylene glycol methyl ether [PGME], and propylene glycol monomethyl ether acetate [PGMEA]) under several parameters that govern the actual operations. Experimental results indicated that at inlet temperatures of under 40 °C and a relative humidity of under 80%, the removal efficiency of a zeolite concentrator can be maintained well over 90%. The optimal rotation speed of the concentrator is between 3 and 4.5 rph in this study. The optimal rotation speed increases with the VOCs inlet concentration. Furthermore, reducing the concentration ratio helps to increase the removal efficiency, but it also increases the incineration cost. With reference to competitive adsorption, PGMEA and PGME are more easily adsorbed on a zeolite concentrator than are IPA and acetone because of their high boiling points and molecular weights.