Paraquat Adsorption,Degradation, and Remobilization in Tropical Soils of Thailand

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with K _f values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0–5 cm layer under field conditions and in the 0–1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT₅₀ at 36–46 days and DT₉₀ around 119–152 days.     

Sorption and desorption of sulfentrazone in Brazilian soils

This study was undertaken to obtain information about the behavior of sulfentrazone in soil by evaluating the sorption and desorption of the herbicide in different Brazilian soils. Batch equilibrium method was used and the samples were analyzed by high performance liquid chromatography. Based on the results obtained from the values of Freundlich constants (Kf), we determined the order of sorption (Haplic Planosol < Red-Yellow Latosol < Red Argisol < Humic Cambisol < Regolitic Neosol) and desorption (Regolitic Neosol < Red Argisol < Humic Cambisol < Haplic Planosol < Red-Yellow Latosol) of sulfentrazone in the soils. The process of pesticide sorption in soils was dependent on the levels of organic matter and clay, while desorption was influenced by the organic matter content and soil pH. Thus, the use of sulfentrazone in soils with low clay content and organic matter (low sorption) increases the probability of contaminating future crops.     

活性炭吸附处理电镀废水中的EDTA

采用颗粒活性炭对模拟废水中EDTA进行批式吸附实验,在实验中考察了恒温振荡器的振荡速度、温度、pH值等因素对吸附的影响,同时探讨了吸附等温线模型和吸附动力学模型。实验结果表明,在25％时活性炭对EDTA的吸附平衡时间为40h。在pH值为5．0、温度为25℃、振荡器振荡速度为200r／min、活性炭粒径为1～2mm、活性炭加入量为10g／L的情况下,EDTA的浓度在48h内由368．8mg／L降低至76．34mg／L,对应的COD值从305．9mg／L降低为67．21mg／L,去除率达到了79．3％。活性炭对EDTA的吸附符合Langmuir吸附等温线模型,其吸附行为可以用准二级吸附动力学模型来描述。     

稻壳基活性炭的制备及其对亚甲基蓝吸附的研究

以稻壳为原料,采用K2CO3活化法和H3P04活化法制备了比表面积为1312m^2／g和682m^2／g的活性炭,通过扫描电子显微镜（SEM）、X-射线衍射仪（XRD）对样品进行了表征,并将孔隙发达的活性炭样品用于对亚甲基蓝的吸附,结果表明,K2CO3活化法制备的活性炭样品具有更多的微孔结构;随着亚甲基蓝溶液初始浓度的增加、活性炭吸附时间的延长,亚甲基蓝的去除率呈现逐渐降低和逐渐增大的变化规律,当pH值为6时,活性炭对亚甲基蓝的吸附效果最佳;稻壳基活性炭对亚甲基蓝的吸附等温线符合Langmuir模型,Qm最高可达476．2mg／g;热力学参数△G^0△H^0和△S^0均为负值,表明稻壳基活性炭对亚甲基蓝的吸附是一个自发的放热反应。     

改性花生壳粉对钙离子的吸附特性研究

利用改性花生壳粉吸附去除水中产生硬度的主要离子钙离子,考察了改性花生壳粉的吸附动力学和吸附平衡特性,并利用傅立叶红外光谱（FTIR）对其结构特性进行了表征。结果表明,钙离子吸附量的85％发生在45min时,其吸附平衡基本在4h内完成,可以通过准二级吸附动力学准确地表征该吸附过程,且改性花生壳粉对钙离子的吸附能够很好地遵循Langmuir等温吸附模型。当pH由2升高至12时,钙离子吸附量随之增加,且在强碱性时吸附效果尤为显著。在花生壳粉固定床吸附实验中,钙离子的穿透曲线很好地遵循Thomas方程。通过FTIR分析发现,改性花生壳粉中较高含量的不饱和基团（C=C,C=O）和C-O官能团在对钙离子的吸附过程中作用最强。     

Pressure-assisted ozonation of PCB and PAH contaminated sediments

Sediment contamination by recalcitrant organics such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) is prevalent and of a great concern. Remediation efforts are hampered by the hydrophobic nature of the contaminants that limits their availability as well as by the sediment matrix that limits their exposure to treatment agents. Using contaminated sediment samples from the Passaic River, St. Louis River, Waukegan Harbor, and Wells National Estuarine Research Reserve, this research demonstrated a new ozonation technique that incorporates rapid, successive cycles of pressurization (690 kPa) and depressurization, enabling more effective treatment than conventional ozonation would. Conventional ozonation reached maximum 60% and 40% removal of PAHs from the Passaic River (40 mg kg(-1) initially) and St. Louis River sediment (520 mg kg(-1) initially), respectively, in 1h; however, removals ceased despite prolonged treatment for 2h. The pressure-assisted technique removed 96% of PAHs from both river sediments within 1h; it completely removed both PAHs (16 mg kg(-1) initially) and PCBs (5.1 mg kg(-1) initially) from the Waukegan Harbor sediment in 0.5 h. The heightened treatment is explained by soil aggregate fracturing upon pressure cycles that exposes the contaminants as well as by the confluence of hydrophobic contaminants and O(3) at the gas-liquid interface in the presence of microbubbles. The technique is expected to accelerate O(3) treatment of a wide range of organic contaminants, and it may provide treatment to dredged and stored contaminated sediment.     

天然Na基膨润土吸附处理高浓度PAM废水的研究

研究了PAM在天然钠基膨润土上的吸附行为,将其应用于含高浓度PAM（100～200 mg/L）的生产废水处理。静态条件下,膨润土的吸附平衡时间为1.5 h,最有效的吸附材料投加量为100 mg/100 mL水样。实验证明,低温度变化范围和弱酸、弱碱条件对PAM的吸附行为不产生显著影响。在最佳吸附动力学条件下,以活性炭做参比,利用实验的结论对化工厂中PAM生产废水进行吸附处理,结果表明,在对PAM废水中对PAM的吸附量分别可达到30.1和22.4 mg/g,膨润土是性价比较高的吸附处理材料。     

土壤分离菌株去除水溶液中铅离子研究

金属及微生物种类、pH和接触时间是决定生物吸附效果的关键因素.从受铅污染的土壤中分离出5株有生物吸附铅离子能力的菌株,并鉴定吸附能力最强的菌株1为芽孢杆菌;试验了pH、接触时间和初始铅离子浓度对该芽孢杆菌生物吸附铅的影响,在温度为25℃时,pH值3.0、初始铅离子浓度250 mg/L、吸附时间不超过15 min有最大吸附量92.27 mg/g,此时去除率为73.82%,且25℃吸附平衡基本符合Langmuir等温模型.因此,用该芽孢杆菌生物吸附去除水溶液中铅是可行的.     

厌氧颗粒污泥对五氯酚(PCP)的吸附、解吸及生物降解

以未驯化污泥接种的升流式厌氧污泥床反应器可形成降解五氯酚（PCP）的颗粒污泥．颗粒污泥去除PCP的主要机制是生物降解作用,而不是生物吸附作用．PCP在颗粒污泥上的吸附和解吸符合Freundlich等温方程,吸附和解吸的Freundlich常数K、1/n分别为0.7857mg/gSS、0.5079和1.1095mg/gSS、0.3782,部分PCP被不可逆吸附．与其它活或死的生物材料相比,本试验形成的颗粒污泥对PCP吸附量较小．该方程较准确地表达了UASB反应器内厌氧颗粒污泥对PCP吸附量的变化规律．     

Nitrous oxide gas removal by using compost-based biofilter medium

This paper is aimed at introducing our research result in the efficiency in removing nitrous oxide gas (N2O) by using compost as a medium filter,which is actually a kind of manure derived from cow faeces at Kukusan Kelurahan farm containg wood chips and some other microorganisms.Practically speaking,N2O is a major greenhouse gas,whose continuous presence in the atmosphere is expected to last over a 100 years and produce its radiative warming effect just next to CO2.In spite of its rather small concentration in the atmosphere,it is the Number Four largest greenhouse gas contributor to the overall global warming,behind carbon dioxide,methane and water vapour.The biofiltration experiments we have conducted to explore its removing rate of N2O from flue gas help us to find various operating factors in the biofilter system.So far as we know,N2O gas has been fed from the top of the column.It was flowing through the column when it is made to get circulated with a peristaltic pump for 6 hours.The data obtained in our paper prove to be in conformity with the Langmuir adsorption model.The highest N2O gas removing efficiency can be made to be as high as 70.22% at the highest biofilter length of 50 cm with the gas flowing rate of 200 mL/min.The results of this research have finally been modeled by the Langmuir adsorption isotherm formula with its K value obtained being 16.949 L/mol.