Spectroscopic and macroscopic studies of the adsorption of arsenate and phosphate on polynuclear aluminum organomineral precipitates

Aluminum organic coprecipitates play important roles in the transport of oxyanions in soil environment.A new polynuclear aluminum organomineral precipitate(Al13-oxalate precipitate) was prepared to investigate the adsorption behavior of arsenate and phosphate on noncrystalline aluminum precipitates.Important thermodynamic parameters for adsorption reaction were evaluated using macroscopic adsorption data and equations.The result showed that,the adsorption reaction basically is a diffusion process.FTIR spectroscopic studies have provided evidence for the formation of two different types of complexes in substrate,protonated bidentate and deprotonated bidentate complexes at pH 4 and pH≥6,respectively.The classic competitive adsorption and XPS studies both indicated that phosphate has stronger chemical interaction with substrate than arsenate.The findings of XPS studies revealed that the precipitate substrate can act as Lewis acid when adsorbing oxyanions.     

Solute transport in sand and chalk: a probabilistic approach

A probabilistic approach is used to simulate particle tracking for two types of porous medium. The first is sand grains with a single intergranular porosity. Particle tracking is carried out by advection and dispersion. The second is chalk granulates with intergranular and matrix porosities. Sorption can occur with advection and dispersion during particle tracking. Particle tracking is modelled as the sum of elementary steps with independent random variables in the sand medium. An exponential distribution is obtained for each elementary step and shows that the whole process is Markovian. A Gamma distribution or probability density function is then deduced. The relationships between dispersivity and the elementary step are given using the central limit theorem. Particle tracking in the chalky medium is a non‐Markovian process. The probability density function depends on a power of the distance. Experimental simulations by dye tracer tests on a column have been performed for different distances and discharges. The probabilistic approach computations are in good agreement with the experimental data. The probabilistic computation seems an interesting and complementary approach to simulate transfer phenomena in porous media with respect to the traditional numerical methods. Copyright © 2006 John Wiley & Sons, Ltd.     

针铁矿和蒙脱石对菲的吸附解吸行为与热力学研究

采用批量振荡吸附平衡法设计针铁矿和蒙脱石对菲的吸附解吸试验,对比研究了针铁矿和蒙脱石对菲的吸附解吸行为,并考察了不同K+浓度的溶液对蒙脱石吸附菲的影响,比较分析了线性吸附模型和Freundlich吸附模型描述矿物吸附等温线的准确性,并从吸附热力学角度探讨了矿物的吸附机理。结果表明:针铁矿和蒙脱石对菲的吸附解吸均表现出明显的非线性和解吸滞后现象;相对于线性吸附模型来说,针铁矿和蒙脱石对菲的吸附解吸更符合Freundlich吸附模型;与蒙脱石相比,针铁矿对菲的吸附更为显著,且具有更好的稳定性;溶液中软阳离子K+的存在使蒙脱石对菲的吸附能力得到显著提高;菲在蒙脱石和针铁矿上的吸附过程是一个自发放热,同时伴随着熵值减小的过程;随着温度的升高,蒙脱石和针铁矿对菲的吸附能力均减弱。     

广东清远市漂流旅游优势与竞争态势分析

广东清远市作为中国第一个也是目前唯一一个“中国漂流之乡”,近几年来,漂流旅游发展得如火如荼,已经成为广东漂流旅游发展得最成功、最成熟的地方以及全国最著名漂流地之一。笔者认为清远市发展漂流旅游的优势在于其气候和资源、区位交通、客源市场及规模集聚效应等方面,其目前面临着来自省内同类产品和非同类产品以及周边省区同类产品的竞争。要实现清远市漂流旅游的可持续迅速发展,需要做好清远漂流旅游品牌整体形象的塑造、多功能综合性漂流旅游区的建设、漂流旅游安全管理、从业人员的总体素质、对外宣传营销以及漂流旅游发展的总体规划等六方面的工作。     

Coastal Pollution Mitigation with Lime and Zero Valent Iron

The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb²⁺, Cd²⁺, Ni²⁺) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO₄ ^3?, CrO₄ ^2?, SeO₄ ^2?)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems.     

基于“钻石模型”的我国地理信息产业国际竞争力分析

利用波特"钻石模型"理论,从生产要素、需求条件、结构与竞争、相关支持产业、政府推动和机会等六个方面对我国地理信息产业竞争力进行了分析,找到了我国地理信息产业在国际发展道路上存在的优势和不足,并提出相应对策。     

不同形态洛美沙星在高岭土上的吸附特性

本研究采用批实验方法探究了不同形态洛美沙星(LOM)在高岭土上的吸附特性。LOM吸附动力学结果符合准二级反应动力学方程,吸附等温数据可用Langmuir方程很好地拟合。随着溶液pH值增大,洛美沙星吸附量先增大后减小,且pH值在洛美沙星pKa1与pKa2间吸附量达到最大。不同形态LOM在高岭土上的吸附量排序为LOM^±>LOM^+>LOM^-。溶液离子强度和无机阳离子种类对LOM^+在高岭土上的吸附影响十分微弱,但均明显抑制了LOM^±的吸附,且离子强度越大,抑制作用越明显。不同无机阳离子抑制程度排序为Mg^2+>Ca^2+>K^+>Na^+。LOM^+在高岭土上的吸附机理主要是内层络合和阳离子交换;LOM^±在高岭土上的吸附机理主要是阳离子交换、氢键作用和静电引力作用;LOM^-与高岭土表面存在较大静电斥力,导致吸附量很小,可能是外层表面络合引起少量的吸附。     

Quantitative Gas-in-place Comparison of Original and Bitumen-free Lacustrine Shale

Residual bitumen in organic-rich shale of oil windows exists widely, and its effect on the gas storage capacity of shale could be two-fold. Bitumen could occupy and block the nanopores of shale, thereby reducing the gas storage capacity. On the other hand, gas could be dissolved in bitumen in shale gas reservoirs, leading to enhanced gas storage capacity. To quantify the effect of bitumen on the gas-in-place (GIP) estimation of lacustrine organic-rich shale, the micropore characteristics and methane sorption capacity of original and bitumen-free shale from the Triassic Yangchang Formation of the Ordos Basin, combined with the methane dissolution capacity for the isolated bitumen, were analyzed and compared. GIP for the original and bitumen-free shale in the depth range of 500–2500 m was evaluated. The results show that micropores in the shale samples were mainly related to organic matter. Clay mineral-hosted pores contributed slightly to microporosity. Bitumen significantly reduced the micropore surface area and volume of the original shale, with average percentages of 28.09% and 51.26%, respectively. The methane sorption capacity decreased after bitumen removal. When normalized to the original shale mass, the sum of the methane sorption capacity for bitumen-free shale and the methane dissolution capacity for isolated bitumen was similar to the methane sorption capacity of the original shale, indicating that the lack of methane absorbed on bitumen is the main reason for the decrease in methane sorption capacity after bitumen removal. The contribution of absorbed methane on bitumen to sorbed methane in shale could be higher than 36.23%. Dual effects of bitumen on shale GIP were observed. A high content of bitumen (1.12%) increased the GIP of the shale samples, with an average percentage of 23.5% in the depth range of 500–2500 m, while a low content of bitumen (0.06%) decreased the GIP, with an average percentage of 13.6%.     

“一带一路”主要国家和地区的海洋学研究态势分析

本文使用文献计量学方法对"一带一路"框架中的主要国家和地区在海洋研究方面的论文发表情况进行了综合分析,探讨并分析了"一带一路"国家与地区的科研竞争力,以及我国在海洋研究方面与"一带一路"国家和地区的国际合作情况,为相关研究和决策提供参考依据。