Magnetic resonance imaging of nonaqueous phase liquid during soil vapor extraction in heterogeneous porous media

Soil vapor extraction (SVE) is commonly used to remediate nonaqueous phase liquids (NAPLs) from the vadose zone. This paper aims to determine the effect of grain size heterogeneity on the removal of NAPL in porous media during SVE. Magnetic resonance imaging (MRI) was used to observe and quantify the amount and location of NAPL in flow-through columns filled with silica gel grains. MRI is unique because it is nondestructive, allowing three-dimensional images to be taken of the phases as a function of space and time. Columns were packed with silica gel in three ways: coarse grains (250-550 microm) only, fine grains (32-63 microm) only, and a core of fine grains surrounded by a shell of coarse grains. Columns saturated with water were drained under a constant suction head, contaminated with decane, and then drained to different decane saturations. Each column was then continuously purged with water-saturated nitrogen gas and images were taken intermittently. Results showed that at residual saturation, a sharp volatilization front moved through the columns filled with either coarse-grain or fine-grain silica gel. In the heterogeneous columns, the volatilization front in the core lagged just behind the shell because gas flow was greater through the shell and decane in the core diffused outward to the shell. When decane saturation in the core was above residual saturation, decane volatilization occurred near the inlet, the relative decane saturation throughout the core dropped uniformly, and decane in the core flowed in the liquid phase to the shell to replenish volatilized decane. These results indicate that NAPL trapped in low-permeability zones can flow to replenish areas where NAPL is lost due to SVE. However, when residual NAPL saturation is reached, NAPL flow no longer occurs and diffusion limits removal from low-permeability zones.     

Pretreatment of apramycin wastewater by catalytic wet air oxidation

IntroductionPharmaceuticalindustrybecomesmoreandmoreimportantallovertheworld .InChina ,therearemorethan30 0plantsmanufacturingantibioticproduction .However,theplantsoftenproducealotofwastewatercontaininghighconcentrated,colortoxicorganiccompounds.Ifthepol…     

高通量中子发生器排放气体中氚的去除研究 Ⅰ.催化剂活性测定

中子发生器运行过程中,由于在氚钛靶片上发生氘氚置换及靶片升温等原因,氚钛靶上的一部分氚将脱离靶而随离子源的氚气及真空系统洩漏的空气等一起被排放出来,对工作环境造成危害。     

Determination of hydroxyl radicals in TiO2/Ti photoelectrocatalytic oxidation system using Fe(phen)3 2+ spectrophotometry

A new method of determining the cumulate concentration of hydroxyl radicals in the TiO₂/Ti photoelectrocatalytic(PEC)oxidation system was established by o-phenanthroline-Fe(Ⅱ)(Fe(phen)₃²⁺) spectrophotometry and using anion     

掺杂ZrO_2、TiO_2、γ－Al_2O_3对Pt、Pd／Al_2O_3燃烧

运用ＸＲＤ、ＢＥＴ、ＤＴＡ等测试技求，研究并考察了掺杂ＺｒＯ＿２、ＴｉＯ＿２、ｒ－Ａｌ＿２Ｏ＿３对Ｐｔ－Ｐｄ／Ａｌ＿２Ｏ＿３燃烧催化剂性能的影响，结果表明，ＺｒＯ＿２对Ａｌ＿２Ｏ＿３晶相的γ型转为α型有明显的抑制作用，而ＴｉＯ＿２的添入则起促进作用；高温引起催化剂活性下降的主要原因是作为第一载体的Ａｌ＿２Ｏ＿３的比表面积和孔容减少以及Ａｌ＿２Ｏ＿３晶态从γ型转为α型所造成的。     

富氧条件下氢部分选择性催化还原NO研究

研制成功了低钯含量活性非均布Pd Al2 O3催化剂 ,实现了富氧条件下 ,氢部分选择性催化还原NO过程。实验表明在该催化剂上 ,低温、富氧条件下NO的转化率高达 80 %～ 10 0 %。室温下 (～ 2 0℃ ) ,NO对氢氧反应有强烈的抑制作用 ,氢氧反应进行后 ,NO还原反应开始明显进行 ,其与氢氧反应为竞争的平行反应     

[Cu—γ—Al2O3]催化剂处理染料废水工艺条件研究

采用「Ｃｕ－γ－Ａｌ２Ｏ３」催化剂对由活性艳红Ｘ－３Ｂ配制的ＣＯＤｃｒ为５７００ｍｇ／Ｌ色度３１００倍的实际染料废水进行了催化氧化试验，试验表明，在控制ｐＨ＝４－５，Ｈ２Ｏ２用量为５．０ｍｇ／Ｌ，催化剂用量为３．０ｇ／Ｌ，ｔ＝７０℃和反应时间为２ｈ条件下，可获得ＣＯＤｃｒ去除率为７７％－７８％，脱色率为９９％的良好效果，且催化剂可再生使用。     

Mesoporous molecular sieve-based materials for catalytic oxidation of VOC: A review

As the main contributor of the formation of particulate matter as well as ozone, volatile organic compounds(VOCs) greatly affect human health and the environmental quality. Catalytic combustion/oxidation has been viewed as an efficient, economically feasible and environmentally friendly way for the elimination of VOCs. Supported metal catalyst is the preferred type of catalysts applied for VOCs catalytic combustion because of the synergy between active components and support as well as its flexi...     

正丁胺在Pt／NM催化剂上完全氧化反应机理的研究

研究了正丁胺在Ｐｔ／ＭＮ催化剂上氧化过程的产物分布，结果表明，在氧大大过量的条件下，正丁胺氧化反应速率与正丁胺浓度无关，表现为零级反应，尾气中ＮＯｘ浓度随反应温度升高出现极大值，相应的温度为４１０℃，最大生成率９４％，在此基础上，初步讨论了正丁胺氧化的反应机理，并解释了ＮＯｘ浓度出现极大值的原因。     

钯、铜、锰、铈三效催化剂性能研究

应用脉冲－火焰反应装置、ＸＲＤ、ＴＰＲ和氢氧滴定技术来研究Ｐｄ－Ｃｕ－Ｍｎ－Ｃｅ－Ｏ三效催化剂的性能。实验结果表明，不同的制备Ｐｄ－Ｃｕ－Ｍｎ－Ｃｅ－Ｏ催化剂的方法，则催化活性各不相同。在分层制备的催化剂中，催化性能主要以外层组分性能为主；以混合浸渍法制备的样品中，ＣｕＭｎ＿２Ｏ＿４相消失，Ｃｕ－Ｍｎ－Ｃｅ－Ｏ表面氧环境发生变化；表面活性剂的添加改变了Ｐｄ的分布，使催化剂表面易于还原；这些改变均对催化剂的三效性能发生影响。催化剂表面的有效贮氧量与三效活性没有明显的关系。