Reversibly enhanced aqueous solubilization of volatile organic compounds using a redox-reversible surfactant

Surfactant-enhanced remediation (SER) is an effective method for the removal of volatile organic compounds (VOCs) from contaminated soils and groundwater. To reuse the surfactant the VOCs must be separated from the surfactant solutions. The water solubility of VOCs can be enhanced using reversible surfactants with a redox-acive group, (ferrocenylmethyl)dodecyldimethylammonium bromide (Fcl2) and (ferrocenylmethyl)tetradecanedimethylammonium bromide (Fcl4), above and below their critical micelle concentrations (CMC) under reducing (I⁺) and oxidative (I²⁺) conditions. The CMC values of Fcl2 and Fcl4 in I⁺ are 0.94 and 0.56 mmol/L and the solubilization of toluene by Fcl2 and Fcl4 in I⁺ for toluene is higher than the solubilization achieved with sodium dodecyl sulfate, cetyltrimethylammonium bromide and Trition X-114. The solubilization capacity of the ferrocenyl surfactants for each tested VOCs ranked as follows: ethylbenzene > toluene > benzene. The solubilities of VOCs by reversible surfactant in I⁺ were 30% higher than those in I²⁺ at comparable surfactant concentrations. The effects of Fcl4 concentrations on VOCs removal efficiency were as follows: benzene > toluene > ethylbenzene. However, an improved removal efficiency was achieved at low ferrocenyl surfactant concentrations. Furthermore, the reversible surfactant could be recycled through chemical approaches to remove organic pollutants, which could significantly reduce the operating costs of SER technology.     

Effect of C/N ratio, aeration rate and moisture content on ammonia and greenhouse gas emission during the composting

Gaseous emission (N₂O, CH₄ and NH₃) from composting can be an important source of anthropogenic greenhouse gas and air pollution. A laboratory scale orthogonal experiment was conducted to estimate the effects of C/N ratio, aeration rate and initial moisture content on gaseous emission during the composting of pig faeces from Chinese Ganqinfen system. The results showed that about 23.9% to 45.6% of total organic carbon (TOC) was lost in the form of CO₂ and 0.8% to 7.5% of TOC emitted as CH₄. Most of the nitrogen was lost in the form of NH₃, which account for 9.6% to 32.4% of initial nitrogen. N₂O was also an important way of nitrogen losses and 1.5% to 7.3% of initial total nitrogen was lost as it. Statistic analysis showed that the aeration rate is the most important factor which could affect the NH₃ (p = 0.0189), CH₄ (p = 0.0113) and N₂O (p = 0.0493) emissions significantly. Higher aeration rates reduce the CH₄ emission but increase the NH₃ and N₂O losses. C/N ratio could affect the NH₃ (p = 0.0442) and CH₄ (p = 0.0246) emissions significantly, but not the N₂O. Lower C/N ratio caused higher NH₃ and CH₄ emissions. The initial moisture content can not influence the gaseous emission significantly. Most treatments were matured after 37 days, except a trial with high moisture content and a low C/N ratio.     

Visible light responsive N-F-codoped TiO2 photocatalysts for the degradation of 4-chlorophenol

Visible light responsive N-F-codoped TiO₂ photocatalysts exhibit a higher catalytic activity than N-doped TiO₂ for the degradation of 4-chlorophenol due to the synergistic effect of nonmetal elements.     

Modification of Ce02-ZrO2 catalyst by potassium for NOx-assisted soot oxidation

Potassium-modified ceria-zirconia catalyst was synthesized by wetness impregnation method. The ageing treatment was performed in static air at 800℃ for 20 hr to evaluate the thermal stability of the catalyst. The catalysts were characterized by X-ray diffraction,BET surface area, oxygen storage capacity, NOx-temperature programmed desorption and soot-temperature programmed oxidation measurements. By introduction of potassium, the maximum soot oxidation rate temperature (Tm) of the ceria-zirconia based catalyst decreased from 525 to 428℃ in the presence of NO under a loose contact mode. The shift of Tm of the K-modified catalyst after ageing is only 15℃. The enhanced activity of the aged catalyst mainly lies in the promotional effect of potassium on the NOx/oxygen storage cacity as well as the soot-catalyst contact.     

Structural and electrochemical properties of annealed La1-xYxNi3.55Mno.4Alo.3Coo.75 hydrogen storage alloys

The effects of the annealing and partial substitution of Y for La on the structural and electrochemical properties of La_1-xY_xNi_3.55Mn_o.4Al_o.3Cr_o.75 (x = 0, 0.1 and 0.2) alloys were reported in the present work. The single-phased CaCu₅-type structure was retained after La was partially substituted by Y. However, the increase of Y content leads to decrease of the lattice parameters and the unit-cell volume. The annealed La_o.9Y_o.1Ni_3.55Mn_o.4Al_o.3Co_o.75 alloys shows typical isometric microstructure, indicating that the composition segregation is improved by annealing. Y substitution for La in the alloys is effective to improve the electrochemical properties at both room temperature and high temperature. A critical substitution content of Y is found at x = 0.1.     

Cadmium removal from wastewater by sponge iron sphere prepared by hydrogen reduction

A new type of sponge iron sphere (NSIS) with 1-5 mm diameter, made of concentrated iron powder and possessed high activity and intension, was prepared by mini-pellet sintering integrated with H₂ direct reduction. Static state experiment has been carried on to investigate the Cd²⁺ removal efficiency from wastewater by the NSIS and to explore the Cd²⁺ removal reaction kinetics. It was suggested that initial pH value and Cd²⁺ original concentration had significant influence on Cd²⁺ removal percentage. Cd²⁺ removal percentage decreased significantly with the increasing of Cd²⁺original concentration whether the original pH value be adjusted to 3.0 or without adjustment. The results showed that the Cd²⁺ removal process followed the first order reaction because the reaction order was from 0.803 to 0.996. The apparent reaction rate constant between Cd²⁺ and NSIS was from 0.0025 to 0.1000 (mg·L^?1)^1-n·min^?1. Compared with SIS reduced by charcoal reduction, NSIS deoxided by hydrogen possessed higher activity, and could remove the same quantity of Cd²⁺ within a shorter period of time.     

基于REOF方法的辽宁气候舒适度区域特征分析

基于辽宁省50个气象站1964-2008年的气象资料,采用适应东北地区的人体舒适度计算公式及分级标准,得出辽宁省近45年历年人体各舒适度级别日数,使用旋转经验正交分解法(REOF),对辽宁省气候舒适度进行区域划分,并分析了各区域气候舒适度的空间分布特征和变化趋势.结果表明:(1)根据前4个旋转倚载向量场高载荷区分布,将...     

低温等离子体-催化协同降解挥发性有机废气

低温等离子体-催化协同技术适合于各类挥发性有机物的治理,特别是大气量低浓度的有机废气的处理.高效催化剂的加入可 以显著提高等离子体反应中有机废气的降解效率,减少有害副产物的生成以及提高反应器的能量利用率.从反应器、催化剂以及背景气体等方面探讨了该技术实现产业化需要解决的问题,结合低温等离子体与催化剂的相互作用、等离子体...     

不同进水条件对SBR工艺脱氮除磷效能的影响

采用人工配水,研究进水在不同pH值,碳源类型,碳氮比条件下,厌氧/好氧/缺氧(A/O/A)sBR工艺对生物法脱氮除磷效能的影响.结果表明:不同的进水条件对反应器的影响较大,当pH值为7.5,乙酸钠为碳源,碳氮比为1.4时,反应器运行效果最佳,系统对PO43--P,NH4+-N的去除率分别达到97.28%,99.5%.N...