Feasibility study of a soil-based rubberized CLSM

The development of beneficial uses of recycled scrap tires is always in great demand around the world. The disposal of on-site surplus excavated soil and the production of standard engineering aggregates have also been facing increasing environmental and ecological challenges in congested islands, such as Taiwan. This paper presents an experimental study using recycled crumb rubber and native silty sand to produce a lightweight, soil-based, rubberized controlled low strength material (CLSM) for a bridge approach repair. To assess the technical feasibility of this material, the effects of weight ratios of cement-to-water (C/W) and water-to-solid (W/S), and of rubber content on the engineering properties for different mixtures were investigated. The presented test results include flowability, unit weight, strength, settlement potential, and bearing capacity. Based on the findings, we conclude that a soil-based rubberized CLSM with 40% sand by weight and an optimal design ratio of 0.7 for C/W and 0.35 for W/S can be used for the proposed bridge approach repair. Such a mixture has demonstrated acceptable flowability, strength, and bearing capacity. Its lower unit weight, negligible compressibility, and hydrocollapse potential also help ensure that detrimental settlement is unlikely to occur. The results illustrate a novel scheme of CLSM production, and suggest a beneficial alternative for the reduction of scrap tires as well as conservation of resources and environment.     

Silane removal at ambient temperature by using alumina-supported metal oxide adsorbents

Copper, zinc, and cerium oxide adsorbents supported on alumina were used to remove silane gas (SiH4). The adsorbents were prepared using a coprecipitation method and characterized by the inductively coupled plasma mass spectrometry, X-ray powder diffractometer, and Brunauer-Emmett-Teller method (BET). The silane removal efficiency and adsorption capacity of the adsorbents were investigated in this study. Test results showed that the adsorbents containing active species had a removal efficiency >99.9% for SiH4 before breakthrough. Adsorbents containing mixed oxides (CuO-CeO2/ Al2O3 and CuO-ZnO/Al2O3), which showed well-dispersed active species and high BET surface areas, had a greater adsorption capacity than the adsorbents containing single metal oxide. However, when the CuO-ZnO/ Al2O3 adsorbents contain >40 wt% of active metal oxides, the increase of active species lowered the BET surface area leading to a decrease of the adsorption capacity. Additionally, when the content of the active metal oxides was between 20% and 40%, the CuO-ZnO/Al2O3 adsorbents demonstrated higher adsorption capacity.     

The Impact of Typhoon Morakot on Heavy Metals of Dapeng Bay and Pollution from Neighboring Rivers

This study demonstrates that prior to Typhoon Morakot, the index of heavy metals such as Cd, Pb, and Cr was above moderate pollution levels in Dapeng Bay and the three neighboring rivers. During January 2007, the content of Zn metal in Dapeng Bay and Tungkang River was also above moderate pollution levels, while after the Typhoon Morakot event, all metals were at levels below the criteria for low pollution. This work has demonstrated that the samples collected from Dapeng Bay and the three neighboring river systems displayed individual crowd–distribution phenomena, indicating variability between the heavy metal content of sediments collected from Dapeng Bay and the three neighboring rivers. Understanding the spatial and temporal variability of heavy metal pollutants in the sediments of Dapeng Bay, along with pollution sources from three neighboring rivers, provides useful information in the fields of disaster management, habitat recovery, operative management, as well as ecotourism specification.     

Preparation and Properties of Poly (Lactic Acid) Nanocomposites Filled with Functionalized Single-Walled Carbon Nanotubes

This work prepared poly (lactic acid) (PLA)/single-walled carbon nanotubes (SWCNTs) composites using a solution blend method, and investigated the influence of the physical properties of PLA/SWCNTs composites. In order to enhanced interfacial interactions between PLA and SWCNTs, the purified SWCNTs were given functionalisation treatments with a nitric acid/sulfuric acid mixture. These acid-treated SWCNTs (A-SWCNTs) were then grafted with 3-isocyanatopropyl triethoxysilane (A-SWCNTs-Si). When these functionalized SWCNTs were used to fill the PLA matrix, the fractured surface of composite does not present the pullout phenomenon. The dimensional stability obviously increased by a factor of approximately 72. The storage modulus was also significantly improved. The surface resistivity of the PLA/SWCNTs composites decreased from 1 × 10¹⁶ to 2.22 × 10⁴ Ω/cm².     

Evolutions of microbial degradation pathways for parent xenobiotic and for its metabolites follow different schemes

Background and purposes

The pathways used by microorganisms for the metabolism of every xenobiotic substrate are specific. The catabolism of a xenobiotic goes through a series of intermediate steps and lower intermediates (metabolites) appear in sequence. The structure of the metabolites can be similar to the parents due to kinship. The purposes of this study were to examine if the degradation pathways that were developed for a parent xenobiotic are effective to degrade the parent??s lower metabolites, and if the reverse is true.

Materials and methods

The xenobiotic substrates, 2,4-dichlorophenoxyacetic acid (2,4-D, the parent xenobiotic) and its metabolite 2,4-dichlorophenol (2,4-DCP), were independently subjected to acclimation and degradation tests by the biomasses of mixed-culture activated sludge and a pure culture of Arthrobacter sp.

Results

Activated sludge and Arthrobacter sp. that were acclimated to 2,4-D effectively degraded 2,4-D and the lower metabolites of 2,4-D, typically 2,4-DCP. During the degradation of 2,4-D, accumulations of the lower metabolites of 2,4-D were not found. The degradation pathways acquired from acclimation to 2,4-D are effective for all the metabolites of 2,4-D. However, pathways acquired from acclimation to 2,4-DCP are not effective in the degradation of the parent 2,4-D.

Conclusions

Microorganisms acclimated to 2,4-D evolve their degradation pathways by a scheme that is different from the scheme the microorganisms employ when they are acclimated to the metabolites of 2,4-D.     

The efficacy and cytotoxicity of iron oxide-carbon black composites for liquid-phase toluene oxidation by persulfate

Environmental Science and Pollution Research - This study evaluated the oxidation of toluene (TOL) by persulfate (PS) in aqueous solution in the presence of a Fe3O4-carbon black (CB) composite...     

Deodorization of Dimethyl Sulfide Using a Discharge Approach at Room Temperature

Abstract

The traditional technologies for odor removal of thiol usually create either secondary pollution for scrubbing, adsorption, and absorption processes, or sulfur (S) poisoning for catalytic incineration. This study applied a laboratory-scale radio-frequency plasma reactor to destructive percentage-grade concentrations of odorous dimethyl sulfide (CH₃SCH₃, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS₂) or sulfur dioxide (SO₂). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O₂)/DMS molar ratio slightly improved the removal efficiency. In an O₂-free environment, DMS was converted primarily to CS₂, methane (CH₄), acetylene (C₂H₂), ethylene (C₂H₄), and hydrogen (H₂), with traces of hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), and dimethyl disulfide. In an O₂-containing environment, the species detected were SO₂, CS₂, carbonyl sulfide, carbon dioxide (CO₂), CH₄, C₂H₄, C₂H₂, H₂, formal-dehyde, and methanol. Differences in yield of products were functions of the amounts of added O₂ and the applied power. This study provided useful information for gaining insight into the reaction pathways for the DMS dissociation and the formation of products in the plasmolysis and conversion processes.     

Interactive Analysis of Waste Recycling and Energy Recovery Program in a Small-Scale Incinerator

Abstract

Conflicting goals affecting solid waste management are explored in this paper to find the best implementation of resource recovery with a small-scale waste-to-energy process. Recycling paper and plastic material often leaves a shortage of thermal energy to support incineration that forces operators to supplement the process with auxiliary fuels. Although there are considerable profits to be made from material recovery, the increase of fuel usage causes conflict given that it is cost prohibitive. A series of trials performed on a small-scale 1.5-t/day incineration plant with a cyclone heat recovery system found that material recycling can impede performance. Experimental results are expressed as empirical regression formulas with regard to combustion temperature, energy transfer, and heat recovery. Process optimization is possible if the waste moisture content remains <30%. To test the robustness of the optimization analysis, a series of sensitivity analyses clarify the extent of material recycling needed with regard to plastic, paper, and metal. The experiments also test whether the moisture in the waste would decrease when recycling paper because of its exceptional capacity to absorb moisture. Results show that recycling paper is strongly recommended when the moisture content is >20%, whereas plastic recycling is not necessary at that moisture condition. Notably, plastic recovery reduces the heat needed to vaporize the water content of the solid waste, thus it is recommended only when the moisture content is <10%. For above-normal incineration temperatures, plastic recycling is encouraged, because it removes excess energy. Metal is confirmed as an overall priority in material recycling regardless of the moisture content of the incoming waste.     

Partition and tempospatial variation of gaseous and particulate mercury at a unique mercury-contaminated remediation site

This study investigated the seasonal variation and spatial distribution of gaseous and particulate mercury at a unique mercury-contaminated remediation site located at the near-coastal region of Tainan City, Taiwan. Gaseous elemental mercury (GEM), particulate mercury (PTM), and dustfall mercury (DFM) were measured at six nearby sites from November 2009 to September 2010. A newly issued Method for Sampling and Analyzing Mercury in Air (National Institute of Environmental Analysis [NIEA] Method A304.10C) translated from U.S. Environmental Protection Agency (EPA) Method 10-5, was applied for the measurement of atmospheric mercury in this particular study. One-year field measurements showed that the seasonal averaged concentrations of GEM and PTM were in the range of 5.56-12.60 and 0.06-0.22 ng/m3, respectively, whereas the seasonal averaged deposition fluxes of DFM were in the range of 27.0-56.8 g/km2-month. The maximum concentrations of GEM and PTM were 38.95 and 0.58 ng/m3, respectively. The atmospheric mercury apportioned as 97.42-99.87% GEM and 0.13-2.58% PTM. As a whole, the concentrations of mercury species were higher in the springtime and summertime than those in the wintertime and fall. The southern winds generally brought higher mercury concentrations, whereas the northern winds brought relatively lower mercury concentrations, to the nearby fishing villages. This study revealed that the mercury-contaminated remediation site, an abandoned chlor-alkali manufacturing plant, was the major mercury emission source that caused severe atmospheric mercury contamination over the investigation region. The hot spot of mercury emissions was allocated at the southern tip of the abandoned chlor-alkali manufacturing plant. On-site continuous monitoring of GEM at the mercury-contaminated remediation site observed that GEM concentrations during the open excavation period were 2-3 times higher than those during the nonexcavation period.