胡敏酸的结构特征及其吸附行为

使用0. 5 mol/L NaOH和0. 1 mol/L Na4 P2O7 溶液分别从土壤中提取胡敏酸,并且对其进行了元素分析、红外光谱、固态13C核磁共振的定性、定量研究。结果表明,两种胡敏酸的性质很相似,但也存在一些微小差异,Na4 P2O7 提取的胡敏酸比NaOH提取的具有芳香度较大、聚合度较高、极性官能团含量较多的特点。测定了菲在6个胡敏酸上的吸附等温线, Freundlich模型很好的拟合了所有吸附等温线,相关系数r均在0. 992以上。有机碳分配系数Koc与胡敏酸中极性碳(POC)之间存在明显的线性相关关系,并受到提取剂类型的影响。

贵州红枫湖、百花湖沉积物-水界面营养元素（磷、氮、碳）的生物地球化学作用

富营养化是目前水资源管理的一个主要环境问题。水体中过量的营养元素是引起富营养化的根本原因，其中磷和氮是主要的控制因素。多数湖泊中磷是藻类自然生长的限制因子，因此多年来人们治理富营养化水体的主要策略是减少磷的排放，然而，通过此法成功恢复湖泊生态的例子屈指可数，一个主要的原因就是沉积物中的磷的再释放。因此，沉积物营养元素(尤其是沉积物－水界面上)的生物地球化学过程一直是湖泊科学研究的焦点。本次工作选择贵州的两个人工湖泊—红枫湖、百花湖，通过对磷、氮、碳在沉积物中的化学形态、垂直剖面等方面的研究，结合室内模拟实验和模式计算，揭示了沉积物早期成岩过程中磷、氮、碳的地球化学行为及其潜在的环境效应。尤其是对沉积物磷开展了较深入的研究。红枫湖、百花湖水体中的N／P为46～126，磷是湖泊的限制性营养因子。分析表明，红枫湖、百花湖沉积物中的全磷的平均含量为1300～1500μg.g~(-1)，与其它湖泊相比，红枫湖、百花湖具有较高的磷负荷。根据Ruttenberg提出的化学连续提取法(SEDEX)，可以把沉积物中的磷分为五种形态：(弱)吸附态磷、铁结合态磷、自生磷灰石磷、残留岩屑磷和有机磷。两湖沉积物中以有机磷和铁结合态磷为主，有机磷分别占全磷的60％(红枫湖)和50.3％(百花湖)，铁结合态磷为28.25％(红枫湖)和34％(百花湖)，这在其它湖泊是极少见的，红枫湖、百花湖沉积物磷具有很高的迁移活性。有机物质是沉积物磷的主要载体，沉积物中－部分有机质被保存下来，其余的矿化降解，同时释放出溶解磷(HPO_4~(2-))，这些溶解磷可以扩散到上覆水体为浮游生物吸收利用，或是以其它形态滞留在沉积物中。沉积物孔隙水中NO_3~-、SO_4~(2-)、Fe~(2+)、Mn~(2+)的剖面分布表明，红枫湖、百花湖沉积物最活跃的有机质降解发生在表层2厘米的沉积物内。根据孔隙水HPO_4~(2-)的浓度梯度，可以计算沉积物－水界面HPO_4~(2-)的交换通量(J_s)，红枫湖、百花湖沉积物-水界面磷的扩散通量(J_s)存在明显的季节性变化：在冬春季扩散通量最大，而夏秋季较小，这与传统的认识相反，我们认为这是由于表层沉积物中有机质的矿化降解有关。我们研究了沉积物吸附作用对沉积物磷循环的影响。吸附动力学实验表明，吸附的动力学过程可以用Langmuir或Freundlich方程描述；红枫湖、百花湖沉积物具有很大的理论吸附容量极值(红枫湖的S_m为21.05mgP.g~(-1),百花湖的S_m为15.83mgP.g~(-1));沉积物对磷酸盐的吸附主要是由于其中的未定型的铁氧化物矿物造成的；铁氧化矿物的吸附作用是沉积物中磷滞留的重要机制；经CDB去除铁氧化物处理后，沉积物吸附磷酸根的能力仅为原来的10％。对原状沉积物-界面水柱的释磷实验结果表明：好氧条件下沉积物的溶解磷的释放通量较高，而厌氧条件下相反较低。进一步说明了有机质降解在磷循环中的地位。将沉积物中磷的形态分析数据、孔隙水溶解磷以及吸附盐实验的数据，用于“扩散-平流-反应”模式，结果表明：红枫湖、百花湖沉积物表层有机质(磷)的降解释磷是沉积物-水界面磷交换通量的主要部分，由于沉积物表层易分解有机质的含量较高，铁氧化物的吸附不足以完全阻止沉积物磷酸盐的释放，有机质的氧化降解速率决定了释放通量的大小；而在表层以下的沉积物中铁氧化物的吸附作用是控制孔隙水溶解磷剖面分布的主要因素；红枫湖、百花湖沉积物的整个埋藏历史中(40年)，基本没有稳定自生磷灰石矿物的形成。红枫湖、百花湖沉积物全氮平均为沉积物干重的0.36～0.40％，表层含量为0.69～1.06％，沉积物中的含氮化合物主要85％以上是有机氮，沉积物全氮和有机氮呈现表层富集，随沉积深度增加而减少的剖面特征。红枫湖、百花湖沉积物对固定铵氮的能力较强，固定铵的绝对含量分别为434.05 mg.kg~(-1)和(16.94mg.kg~(-1)，分别相对于总氮含量的13.53％和12.53％。红枫湖、百花湖水体和沉积物孔隙水中氨态氮(NH_4~+)和硝态氮(NO_3~-)的剖面分布表明：在沉积物-水界面上发生着最剧烈的氮循环作用，这也是清除水体氮负荷的最彻底和唯一的机制。沉积物水界面起到向上覆水体的营养供给和对污染水体自然净化的双重功能。红枫湖、百花湖的沉积物柱芯上有机质剖面通常仅表现“降解阶段”和“堆积阶段”，对红枫湖HF980903-1-2柱芯的分析，发现红枫湖沉积物有机质(碳、氮)的降解代谢过程同样包括类似于洱海沉积物的“沉降－降解－堆积”三个阶段，我们认为是样品的分隔精度不足以反映沉积剖面的细节；同时也说明，红枫湖、百花湖沉积物有机质组成中有较多的“新鲜”、活性的组分，它们的快速降解使得沉积物中有机质不能长期保存。研究表明，经过10年堆积埋藏，沉积物有机质大约有35～76％被降解。上层沉积物中(活性)有机质的迅速分解，是引起沉积物－水界面强烈的营养元素循环的重要原因。剖面对比分析显示，红枫湖、百花湖沉积物有机物质分解过程中，有机碳、磷、氮的改造是不同步的，有机碳相对稳定，而含氮化合物和有机磷则相对易于降解。C_(Org): N_(Org): P_(Org)比值的分析结果表明：红枫湖、百花湖沉积物有机质的来源主要是来源于无纤维素植物。较高的C／N、C／P和较低的N／P，反映了小型湖泊受到较多的人为干扰和流域物质输入影响的特点。

疏水性有机污染物的非线性吸附过程及滞后现象的研究

该论文测定了疏水性有机污染物在地质吸附剂上的吸附-解吸等温线,选用合适的模型拟合了这些等温线,并且研究了非线性吸附过程、解吸滞后现象与壤/沉积物异质性之间的关系;得到以下几点认识:1、利用红外光谱仪和核磁共振谱仪研究了土壤/沉积物有机质、土壤胡敏酸的组成.2、测定了菲、蔡、1,3,5-三氯苯在土壤/沉积物及处理样品上的吸附等温线.所有地质吸附剂上的吸附等温线表现出明显的非线性.Freundlic上模型能很好的拟合了有机物的吸附等温线,双区位反应模型(DRDM)能很好的拟合有机物在部分土壤/沉积物及处理样品上的吸附等温线,并且DRDM模型清楚的反映出有机物在低浓度和高浓度下不同的吸附特征.3、对相同土壤/沉积物样品,萘的吸附等温线要比菲的吸附等温线的线性要好些,这与它们的物化性质有关.4、对碱提取后残留土壤测定了菲、茶、1,3,5-三氯苯的吸附-解吸等温线.5、菲和萘在土壤/沉积物及处理样品上的吸附-解吸过程存在明显的滞后现象.

Adsorção de tebutiurom em áreas de recarga do Aqüífero Guarani .

O potencial de contaminação de águas subterrâneas por agrotóxicos depende da mobilidade do produto no solo, que pode ser avaliada de diferentes formas. Uma delas é através da estimativa de parâmetros que podem ser usados como índices relativos de mobilidade, tais como o coeficiente de adsorção de Freundlich. Este coeficiente foi determinado em três solos da Microbacia do Córrego do Espraiado, situada em Ribeirão Preto, SP. Observou-se baixo potencial de adsorção de tebutiurom, o que o torna potencialmente móvel nesses solos. Os resultados sugerem que a Microbacia, situada sobre o Aqüífero Guarani, é suscetível à indução do comprometimento da qualidade de águas subsuperficiais se não houver manejo adequado dos solos agrícolas, e ainda que os cuidados com a aplicação de tebutiurom em solos com menor teor de carbono orgânico e argila devem ser redobrados.

A new method for determination of adsorption and desorption coefficients of pesticides with soil column liquid chromatography

The adsorption and desorption coefficients of atrazine, methiocarb and simazine on a sandy loam soil were measured in this study with soil column liquid chromatographic (SCLC) technique. The adsorption and desorption data of all the three pesticides followed Freundlich isotherms revealing the existence of hysteresis. In comparing with other methods, SCLC method showed some characteristics such as rapidity, online and accuracy.

Indices de sorción de fósforo en algunos molisoles de la pradera pampeana

p.145-154

Adsorción de fósforo en algunos suelos argentinos : 1-condiciones experimentales e isotermas de adsorción

p.165-174

Adsorption isotherm models for basic dye adsorption by peat in single and binary component systems

Coloured effluents from textile industries are a problem in many rivers and waterways. Prediction of adsorption capacities of dyes by adsorbents is important in design considerations. The sorption of three basic dyes, namely Basic Blue 3, Basic Yellow 21 and Basic Red 22, onto peat is reported. Equilibrium sorption isotherms have been measured for the three single component systems. Equilibrium was achieved after twenty-one days. The experimental isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson, Temkin and Toth isotherm equations. A detailed error analysis has been undertaken to investigate the effect of using different error criteria for the determination of the single component isotherm parameters and hence obtain the best isotherm and isotherm parameters which describe the adsorption process. The linear transform model provided the highest R2 regression coefficient with the Redlich-Peterson model. The Redlich-Peterson model also yielded the best fit to experimental data for all three dyes using the non-linear error functions. An extended Langmuir model has been used to predict the isotherm data for the binary systems using the single component data. The correlation between theoretical and experimental data had only limited success due to competitive and interactive effects between the dyes and the dye-surface interactions.

Cooperativism, entrepreneurship and economic development: a linking theoretical model

Cooperatives, as a kind of firms, are considered by many scholars as an remarkable alternative for overcoming the economic crisis started in 2008. Besides, there are other scholars which pointed out the important role that these firms play in the regional economic development. Nevertheless, when one examines the economic literature on cooperatives, it is detected that this kind of firms is mainly studied starting from the point of view of their own characteristics and particularities of participation and solidarity. In this sense, following a different analysis framework, this article proposes a theoretical model in order to explain the behavior of cooperatives based on the entrepreneurship theory with the aim of increasing the knowledge about this kind of firms and, more specifically, their contribution to regional economic development.

Investigations on the adsorption of acidic gases using activated dolomite

In this work activated dolomite adsorption was investigated for removal of acidic gaseous pollutants. Charring was found to be an effective method for the activation of dolomite. This thermal processing resulted in partial decomposition, yielding a calcite and magnesium oxide structure. Adsorbents were produced over a range of char temperatures (750, 800 and 850 °C) and char times (1–8 h). The surface properties and the adsorption capability of raw and thermally treated dolomite sorbents were investigated using porosimetry, SEM and XRD. The sorbates individually investigated were CO2 and NO2. Volumetric equilibrium isotherm determinations were produced in order to quantify sorbate capacity on the various sorbents. The equilibrium data were successfully described using the Freundlich isotherm model. Despite relatively low surface area characteristics of the activated dolomite, there was a high capacity for the acidic gas sorbates investigated, showing a maximum of 12.6 mmol/g (554 mg/g) for CO2 adsorption and 9.93 mmol/g (457 mg/g) for NO2 adsorption. Potentially the most cost effective result from the work concerns the adsorptive capacity for the naturally occurring material, which gave a capacity of 9.71 mmol/g (427 mg/g) for CO2 adsorption and 4.18 mmol/g (193 mg/g) for NO2 adsorption. These results indicate that dolomitic sorbents are potentially cost effective materials for acidic gases adsorption.

Marine micro and macro algal species as biosorbents for heavy metals

This paper reviews some practical aspects of the application of algal biomass for the biosorption of heavy metals from wastewater. The ability of different algal species to remove metals varies with algal group and morphology, with the speciation of specific metals and their competition with others in wastewater, and with environmental or process factors. The scattered literature on the uptake of heavy metals by both living and dead algal biomass - both macroalgae and immobilized microalgae - has been reviewed, and the uptake capacity and efficiency of different species, as well as what is known about the mechanisms of biosorption, are presented. Data on metal uptake have commonly been fitted to equilibrium models, such as the Langmuir and Freundlich isotherm models, and the parameters of these models permit the uptake capacity of different algal species under different process conditions to be compared. Higher uptake capacities have been found for brown algae than for red and green algae. Kelps and fucoids are the most important groups of algae used for biosorption of heavy metals, probably because of their abundant cell wall polysacchrides and extracellular polymers. Another important practical aspect is the possibility of re-using algal biomass in several adsorption/desorption cycles (up to 10 have been used with Sargassum spp), and the influence of morphology and environmental conditions on the re-usability of algal tissue is also considered.

The removal of dyes from textile wastewater: a study of the physical characteristics and adsorption mechanisms of diatomaceous earth

The feasibility of using diatomite for the removal of the problematic reactive dyes as well as basic dyes from textile wastewater was investigated. Methylene blue, Cibacron reactive black and reactive yellow dyes were considered. Physical characteristics of diatomite such as pH(solution), pH(ZPC), surface area, Fourier transform infrared, and scanning electron microscopy were investigated. The surface area of diatomite was found to be 27.80 m(2) g(-1) and the pH(ZPC) occurred around pH of 5.4. The results indicated that the surface charge of diatomite decreased as the pH of the solution increased with the maximum methylene blue removal from aqueous solution occurring at basic pH of around (1011). Adsorption isotherms of diatomite with methylene blue, hydrolysed reactive black and yellow dyes were constructed at different pH values, initial dye concentrations and particle sizes. The experimental results were fitted to the Langmuir, Freundlich, and Henry models. The study indicated that electrostatic interactions play an important role in the adsorption of dyes onto diatomite. A model of the adsorption mechanism of methylene blue onto diatomite is proposed. (C) 2003 Elsevier Ltd. All rights reserved.

Comparison of optimised isotherm models for basic dye adsorption by kudzu

This study assesses the use of dried (5% w/w moisture) kudzu (Peuraria lobata ohwi) as an adsorbent medium for the removal of two basic dyes, Basic Yellow 21 and Basic Red 22, from aqueous solutions. The extent of adsorption was measured through equilibrium sorption isotherms for the single component systems. Equilibrium was achieved after 21 days. The experimental isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson, Temkin and Toth isotherm equations. A detailed error analysis was undertaken to investigate the effect of using different error criteria for the determination of the single component isotherm parameters. The performance of the kudzu was compared with an activated carbon (Chemviron F-400). Kudzu was found to be an effective adsorbent for basic dye colour removal, though its capacity for colour removal was not as high as an activated carbon, the potential appeared to exist to use it as an alternative to activated carbon where carbon cost was prohibitive. (C) 2002 Elsevier Science Ltd. All rights reserved.

Adsorption of basic dyes from aqueous solution onto activated carbons

The aim of this research is to compare the adsorption capacity of different types of activated carbons produced by steam activation in small laboratory scale and large industrial scale processes. Equilibrium behaviour of the activated carbons was investigated by performing batch adsorption experiments using bottle-point method. Basic dyes (methylene blue (MB), basic red (BR) and basic yellow (BY)) were used as adsorbates and the maximum adsorptive capacity was determined. Adsorption isotherm models, Langmuir, Freundlich and Redlich-Peterson were used to simulate the equilibrium data at different experimental parameters (pH and adsorbent particle size). It was found that PAC2 (activated carbon produced from New Zealand coal using steam activation) has the highest adsorptive capacity towards MB dye (588 mg/g) followed by F400 (476 mg/g) and PAC 1 (380 mg/g). BR and BY showed higher adsorptive affinity towards PAC2 and F400 than MB. Under comparable conditions, adsorption capacity of basic dyes, MB, BR and BY onto PAC 1, PAC2 and F400 increased in the order: MB <BR <BY. Redlich-Peterson model was found to describe the experimental data over the entire range of concentration under investigation. All the systems show favourable adsorption of the basic dyes with 0 <R-L <I (C) 2007 Elsevier B.V. All rights reserved.

Prediction of bisolute dye adsorption isotherms on activated carbon

The removal of acid dyes, Tectilon Blue 4R, Tectilon Red 2B and Tectilon Orange 3G, from single solute, bisolute and trisolute solutions by adsorption on activated carbon (GAC F400) has been investigated in isotherm experiments. Results from these experiments were modelled using the Langmuir and Freundlich adsorption isotherm theories with the Langmuir model proving to be the more suitable. The Ideal Adsorbed Solution (IAS) model was coupled with the Langmuir isotherm to predict binary adsorption on the dyes. The application of the IAS theory accurately simulated the experimental data with an average deviation of approximately 3% between modelled and experimental data.