A new method for remedial treatment of contaminated clayey soils by electrokinetics coupled with permeable reactive barriers

This paper presents the results of preliminary investigations into the potential application of a remediation system that couples the electrokinetic (EK) remediation with the permeable reactive barrier (PRB) concept. Atomizing slag was adopted as a PRB reactive material for freshing groundwater contaminated with either inorganic or organic substances. Laboratory experiments were performed with variable conditions including (i) type of pollutant, (ii) processing time, and (iii) the application of PRB system during the EK processing. From the results of the preliminary investigations, the coupled technology of EK with PRB system could effectively remediate contaminated groundwater in situ without extracting pollutants from subsurface through the effectiveness of the reactions between the reactive materials and contaminants.     

Using sewage sludge as a permeable reactive barrier for remediation of groundwater contaminated with lead and phenol

We investigated the efficiency of granular dead anaerobic sludge (GDAS) biosorbent as a permeable reactive barrier for remediation of groundwater contaminated with lead–phenol (Pb-Ph) present simultaneously. Batch tests were performed to characterize the equilibrium sorption properties of the GDAS and sandy soil in the Pb-Ph containing aqueous solutions. Computer solutions (COMSOL) Multiphysics 3.5a software was used for simulating the two-dimensional equilibrium transport of lead–phenol including the sorption process through the saturated sandy soil in the presence of GDAS. A good agreement between the predicted and experimental results was recognized with the root-mean-squared error not exceeding 0.049.     

可渗透反应墙原位修复污染地下水研究进展

可渗透反应墙是一种替代抽提技术的创新型地下水原位修复技术。在实际工程中大量不同种类的填料被应用在墙体上,通过吸附、沉淀、氧化还原和生物降解等作用,可处理包括重金属、苯系物、卤代烃、芳香烃、农药以及无机阴离子等污染物。综述了可渗透反应墙的结构、去除污染物机理、优缺点以及活性填料的应用,详细介绍了可渗透反应墙技术的最新研究进展,指出该技术虽已得到广泛认可,但其长期性能尚待实践证明。     

Heterotrophic/autotrophic denitrification (HAD) of drinking water: prospective use for permeable reactive barrier

This work aims to explore the use of an innovative denitrification process developed by our group for groundwater remediation. This process is coupling heterotrophic-autotrophic denitrification processes (HAD) supported by cotton and zero-valent iron (ZVI). In the experimental part, the effect of two amounts of ZVI (150 and 300 g), two nitrate (100 and 220 mg/l) and phosphate (3 and 6 mg/l) inlet concentrations on nitrate removal performance is investigated in two parallel continuous fed plug-flow reactors. The possible in-situ application of the proposed system in permeable reactive barriers (PRB) is further discussed. The HAD showed higher volumetric nitrate removal ratio (VNR) than the cotton supported heterotrophic denitrification one, and VNR increased with the amount of ZVI packed in the reactors. Ammonium production by the reductive action of iron was kept on acceptable level adjusting the contact time between water and ZVI. Iron release from ZVI decreased with time to negligible value (<0.5 mg/l) thanks to the formation of iron green rust compounds (GR). The HAD seems to be adequate for PRB systems, because both cellulose-based material and ZVI have been used in reactive trench for site remediation. Moreover, the proposed process could have the function for removal of nitrate and priority pollutants, such as chlorinated ethenes, simultaneously.     

地下水硝酸盐污染来源分析及治理方法

地下水硝酸盐污染已日趋严重,已经在很大程度上影响了环境和人类的健康。系统地对硝酸盐污染的来源进行了介绍和分析,并且详细地阐述了要治理地下水硝酸盐的污染必须要从源头防止和局部治理两方面着手;同时也综合性地比较了各种治理方法的优缺点。最后综合分析得出结论。     

低渗透地层测试技术探索与应用

低渗透地层在进行地层测试时往往存在取样困难、压力恢复资料品质不高等问题,影响对地层特性的评价,进而影响对储层改造措施的评价。依据地层特点将低渗透地层划分为三种类型储层,对不同类型储层采用不同的测试工艺技术,可解决地层样品取样难的问题并且提高测试资料质量。     

地下水硝酸盐迁移转化规律分析

地下水硝酸盐污染已日趋严重,已经在很大程度上影响了环境和人类健康。分析了地下水硝酸盐的迁移转化过程,并指出要从空间和时间两方面综合研究硝酸盐的迁移转化规律。最后,就今后地下水硝酸盐迁移转化规律的研究方向提出展望。     

Layered double hydroxides:Scale production and application in soil remediation as super-stable mineralizer

Soil contamination by heavy metals has presented severe risks to human health through food chain.As one of the most promising remediation technologies,in-situ immobilization strategy has been widely adopted in practice.However,considering the large quantities of contaminated soil,it is still a huge challenge to design low-cost amendments with strong and long-term immobilization ability.Layered double hydroxides(LDHs) have drawn tremendous attention in fundamental research and practical applicati...     

透水砖防堵技术研究与展望

透水砖的铺设能有效地降低城市的洪涝风险,是海绵城市建设的重要环节.透水砖在使用过程中,因雨水径流中颗粒物的累积效应,导致透水性能降低,使用寿命缩短.笔者综述了透水砖的孔隙结构、堵塞机理以及透水砖的防堵塞技术.透水砖的表面和内部孔隙因截留雨水径流中的颗粒物而产生堵塞,堵塞位置和程度受透水砖孔隙结构、雨水径流颗粒物性质及流...     

Fe~0可渗透反应墙处理地下水污染的研究现状与展望

阐述了Fe⁰可渗透反应墙(permeable reactive barrier,PRB)技术在处理污染物时可能发生的反应机理及研究现状,主要介绍了零价铁的吸附共沉淀作用、电化学腐蚀作用、化学还原以及生物还原作用。同时指出零价铁作为填料的不足之处,并且展望了PRB技术今后的研究方向。     

Pilot plant investigations of thermal remediation of tar-contaminated soil and oil-contaminated gravel

Pilot plant studies were conducted to assess the feasibility of remediation of coal tar-contaminated soil and oil-contaminated gravel by incineration in a fluidized bed combustor and the same equipment converted to a calciner, with environmentally acceptable performance. Besides adequate decontamination and emission control, effort was devoted to treat the special feedstocks with difficult handling properties by use of the conventional combustion and feeding systems. Combustor modeling of the incineration process was carried out to estimate the decontamination performance in targeted operations using experimental data. Analysis of the results showed that satisfactory decontamination of the soil and gravel could be achieved and the emission of pollutants in the flue gas could be effectively controlled. Recovery of heat energy from the incinerated material was also considered.     

Design considerations for groundwater remediation using reduced metals

Use of reduced metals has attracted much attention since it possesses a great potential for eliminating reducible contaminants in groundwater such as heavy metals and chlorinated compounds. However, products of metal-mediated reactions for many chlorinated hydrocarbons have not clearly been identified. In addition, consumption of the metals, generation and release of metal ions, formation of insoluble metal oxides and hydroxides on the clean metal surface, and rise of pH inevitably accompany the reactions. Due to these properties of metal-mediated reactions, the reaction rate could decrease as the reaction proceeds, and effluent quality could decay. It was shown in this study using chlorine mass balance and GC analysis that chloroform is formed from carbon tetrachloride by reduced iron. It is also well-known that nitrate is reduced mostly to ammonia by metals, which indicates that the metal process is inappropriate for denitrification of nitrate-contaminated aquifers. These results indicate that groundwater remediation using metal process requires careful consideration for the safety of reaction products. It was also shown that mixing rate strongly affects reaction rate since metal-mediated reaction occurs on the surface of metals. In addition, reaction rate was decreased due to metal hydroxide deposition on the surface of metal granules that was seen by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. Generation of iron ions (consumption of reduced iron) released from reduction of zero-valent iron was also shown by using an ion chromatograph (IC). In this study, some methods were suggested to solve the above-mentioned problems. Acid washing appeared effective for removing corrosion products on the surface of metal granules, by which a reduction rate could be maintained high for an extended time of reaction. Use of iron sulfide decreased an extent of pH rise during metal-mediated reaction; thereby precipitation of insoluble metal (hydr)oxides is expectedly decreased. It was also shown that inexpensive iron scrap instead of fine metal powders can be used for metal processes.     

渗入固结型混凝土防腐涂料的研究

混凝土具有多孔结构,水和离子可通过混凝土的孔隙渗入于混凝土内部,对混凝土造成腐蚀。以环氧树脂和糠醛/丙酮制备了渗入固结型混凝土防腐涂料 (PSEp),其中糠醛/丙酮混合物为反应性溶剂。制得的涂料具有优异的润湿性能,能够渗入砂浆固结体(水灰比为0.5)的孔隙中并原位交联 (渗入深度可达4.0 mm),从而对混凝土孔隙进行封闭。该涂料渗入混凝土后与之形成复合增强层,其粘附力(拉拔强度)比混凝土提高130%。同时,混凝土表面抗离子渗入能力提高,其电通量从3 400 C下降至130 C。因此,该涂料可有效用于混凝土防腐。     

Design formulae for reactive barrier membranes

Polymers films and membranes with immobile and irreversible reactive sites can provide significant barrier properties for packaging materials. The reactive term that consumes the mobile species in the governing transport equations for such materials is a function of both the mobile species and the immobilized reactive sites, leading to non-linear partial differential equations that typically have to be solved numerically. Here we present analytic design formulae to estimate the time varying flux, kill time and time lag through homogenous reactive membranes, obviating the need to numerically solve the model's non-linear equations.Modeling reveals three regimes for the time varying flux. For early times most reactive sites are still present, and an initial flux plateau is observed. For intermediate times, a moving reaction front is found to travel across the film coupled with an increasing flux of the mobile species. Finally, for long times when most reactive sites are consumed, the transient flux approaches its steady value. Analytic design equations characterizing the flux in these three regimes are developed based on perturbation theory and matched asymptotic expansions. They agree closely with the exact numerical solutions. Algebraic formulae for the kill time, time lag and speed of the reaction front also correspond to the full numerical solutions.     

Control of Shear Dispersion by the Permeable Porous Wall of a Capillary Tube

The transfer of a neutral nonreacting mass species was studied in a capillary tube with a permeable porous wall, under the effect of combined pressure-driven and electro-osmotic flows or simply combined flows (CF). An exact expression for the shear dispersion coefficient in a tube under the influence of CF is derived, which remains constant when λ_D, inversely propotional to the permeability of the porous medium, is smaller than 1 or larger than 100 for a constant Péclet number. In addition, the equivalent one-dimensional governing equations for the concentrations of species in the tube and the permeable porous medium under the influence of CF are obtained. The proposed model is compared and verified with several existing models in the literature.     

Development of electrokinetic-flushing technology for the remediation of contaminated soil around nuclear facilities

The effects of a flushing by a pump on an electrokinetic-flushing remediation of contaminated soil were estimated. The soils were sampled from the sites around nuclear facilities which were built on a high hydro-conductivity of sandstone. An electrokinetic-flushing equipment with a pump was manufactured to estimate the effect of a flushing on an electrokinetic-flushing remediation. In order to select an optimal reagent suitable to the characteristics of a soil near nuclear facilities, 4 experiments were executed with 4 candidate reagents selected from 12 reagents and the results of the experiments are as follows. The removal efficiencies of cobalt and cesium from the contaminated soil with the acetic acid were the highest, which were 92.1% and 83.1%, respectively. The effluent solution volume generated from an electrokinetic remediation was very smaller and it was 5% below that from a soil washing. Next, the results from a comparison of an electrokinetic-flushing remediation and an electrokinetic remediation revealed that the removal efficiencies of Co²⁺ and Cs⁺ by an electrokinetic-flushing remediation for 5 days were increased by 25% and 35% when compared to those by the electrokinetic remediation, but the effect of a flushing by the electrokinetic-flushing equipment started to decrease after 5 days. The removal efficiencies of Co²⁺ and Cs⁺ by an electrokinetic-flushing remediation for 15 days were increased by 6.8% and 7.7% when compared to that by an electrokinetic remediation. Namely, the higher the hydro-conductivity of a soil was, the larger the effect of a flushing was on an electrokinetic-flushing remediation.     

我国地下水污染控制与修复研究

随着经济的发展,各种环境污染物进入土壤系统污染地下水,直接或间接地威胁到生态环境和人类健康。对地下水污染现状、修复技术进展以及控制措施等进行了分析,指出了地下水污染控制与修复的意义和重要性。     

A concept of reactive compatibilizer‐tracer for studying reactive polymer blending processes

A concept called reactive compatibilizer‐tracer is proposed. The latter bears reactive groups capable of reacting with its counterpart on forming a copolymer for in situ compatibilization, and fluorescent labels allowing determining very small amounts of the in situ formed compatibilizer and formation of micelles when it occurs. Owing to this concept, it is shown that a reactive compatibilizer may be very efficient at the beginning of a reactive blending process and may suddenly become completely inefficient, resulting in an abrupt and drastic increase in size of the dispersed phase domains. © 2015 American Institute of Chemical Engineers AIChE J, 62: 359–366, 2016     

Optimized design of multilayer barrier films incorporating a reactive layer. III. Case analysis and generalized multilayer solutions

In part III of this series of articles, we present the analysis of transient permeation through two‐layer reactive–passive (RP) film designs, the analysis extension to multilayer structures, and optimized design solutions for multilayer barriers incorporating immobile noncatalytic oxygen scavenger within one of the layers. The reduction of oxygen ingress into a package within a certain timeframe depends on two factors: extension of the scavenger exhaustion time and reduction of the transient transmission rate through the film during that time. The optimal design for the scavenger exhaustion time involves exposure of the reactive layer to the package contents and its protection from high levels of environmental oxygen by the best possible passive barrier layer. The film barrier properties can be further optimized by the selection of the matrix material to place the scavenger in. Reducing the initial transmission rate requires the placement of the scavenger within a layer with the lowest diffusivity of the matrix polymer. When one chooses between two layers with different material transport properties in which to put the scavenger, the optimal solution for the ingress depends on the desired time to provide an improved barrier. The lifetime of the scavenger in the RP film is shortened for design 1, when the diffusivity of the reactive layer is smaller than that of the passive layer, compared to RP design 2, with the layer matrix sequence reversed, but the transient transmission rate is greatly reduced on average for the former. If the desired time to provide a barrier does not exceed the scavenger exhaustion time for RP design 1, the lowest diffusivity material should be used as a matrix for the innermost layer loaded with the scavenger. Otherwise, the highest possible passive barrier should be placed into the film external layer to minimize the total ingress during longer times. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1966–1977, 2006     

Photocatalytic activity of metal nanoparticle-decorated titanium dioxide for simultaneous H2 production and biodiesel wastewater remediation

A set of metal nanoparticle-decorated titanium dioxide(M_x/TiO_2; where x is the percent by mass, %)photocatalysts was prepared via the sol-immobilization in order to enhance the simultaneous hydrogen(H_2)production and pollutant reduction from real biodiesel wastewater. Effect of the metal nanoparticle(NP) type(M = Ni, Au, Pt or Pd) and, for Pd, the amount(1 %–4 %) decorated on the surface of thermal treated commercial TiO_2(T_(400)) was evaluated. The obtained results demonstrated that both the type and amount of decorated metal NPs did not significantly affect the pollutant reduction, measured in terms of the reduction of chemical oxygen demand(COD), biological oxygen demand(BOD) and oil grease levels, but they affected the H_2 production rate from both deionized water and biodiesel wastewater, which can be ranked in the order of Pt_1/T_(400) Pd_1/T_(400) Au_1/T_(400) Ni_1/T_(400). This was attributed to the high difference in work function between Pt and the parent T_(400). However, the difference between Pt_1/T_(400) and Pd_1/T_(400) was not great and so from an economic consideration, Pd/TiO_2 was selected as appropriate for further evaluation. Among the four different Pd x/TiO_2 photocatalysts, the Pd_3/TiO_2 demonstrated the highest activity and gave a high rate of H_2 production(up to135 mmol·h_(-1)) with a COD, BOD and oil grease reduction of 30.3%, 73.7% and 58.0%, respectively.