Adsorption of heavy metal ions from aqueous solution by carboxylated cellulose nanocrystals

A novel nanoadsorbent for the removal of heavy metal ions is reported.Cotton was first hydrolyzed to obtain cellulose nanocrystals(CNCs).CNCs were then chemically modified with succinic anhydride to obtain SCNCs.The sodic nanoadsorbent(NaSCNCs) was further prepared by treatment of SCNCs with saturated NaHCO 3 aqueous solution.Batch experiments were carried out with SCNCs and NaSCNCs for the removal of Pb 2+ and Cd 2+.The effects of contact time,pH,initial adsorption concentration,coexisting ions and the regeneration performance were investigated.Kinetic studies showed that the adsorption equilibrium time of Pb 2+ and Cd 2+ was reached within 150 min on SCNCs and 5 min on NaSCNCs.The adsorption capacities of Pb 2+ and Cd 2+ on SCNCs and NaSCNCs increased with increasing pH.The adsorption isotherm was well fitted by the Langmuir model.The maximum adsorption capacities of SCNCs and NaSCNCs for Pb 2+ and Cd 2+ were 367.6 mg/g,259.7 mg/g and 465.1 mg/g,344.8 mg/g,respectively.SCNCs and NaSCNCs showed high selectivity and interference resistance from coexisting ions for the adsorption of Pb 2+.NaSCNCs could be efficiently regenerated with a mild saturated NaCl solution with no loss of capacity after two recycles.The adsorption mechanisms of SCNCs and NaSCNCs were discussed.     

城市污水回用示范工程

本文阐述了城市污水回用的重要作用.介绍了国家科技攻关项目城市污水回用示范工程建设背景及概况、水质指标及效益分析.     

岷江上游半干旱区耕地生产潜力分析——以茂县静州村为例

以茂县静州村为例，从几个主要影响因素出发分析了岷江上游半干旱区耕地的生产潜力。并对生产潜力的估算及其订正系数的依据方法有的改进，运用于分析之中，结果可行。计算结果表明，静州村耕地生产潜力平均可达１２４１３．４ｋｇ／ｈｍ＾２，目前产量仅有９０００ｋｇ／ｈｍ＾２，还大有潜力可挖。     

A SIMPLIFIED MODEL FOR PREDICTING DAILY TRANSMISSION LOSSES IN A STREAM CHANNEL1

ABSTRACT: A simplified approach for modeling transmission losses in a stream is presented. A theory relating seepage from a channel with the depth of flow is simplified to a one-parameter relationship. A power relationship is then utilized for the stage-discharge relationship, which is coupled with the seepage relationship. This combined equation is integrated over the channel reach to arrive at a general model for seepage loss through the reach, with one parameter needing calibration. An example is provided showing the development of the relationship and the calibration technique for the parameter. The results are shown, emphasizing the use of the model for simulation of channel transmission losses at low and moderate flow conditions.     

Environmental perspectives of pupils: the development of an attitude and behaviour scale

Summary The object of this study was to construct a measurement instrument to assess two different environmental world views of adolescents and, additionally, to address the adolescents' verbal commitment and actual behaviour. Using a multiple-choice questionnaire the instrument was designed to identify and measure the existing factors that underlie concern for ecological/environmental problems and behaviour towards environment/nature in the age group of 10 to 16 year old pupils. Within the traditional tripartite model covering cognitive, affective and behavioural components the study selected items that made up the majority of corresponding subscales from various previous studies. Using factor analysis the configuration of the scale's dimensionality was stated. Based on the responses of approximately 2000 Bavarian pupils, subscales were extracted via factor analysis and, subsequently, addressed to different segments of environmental concern ranging from attitudes to verbal commitment and actual behaviour. Correlation coefficients and the standardized Cronbach's -values were also surveyed. Additionally, a Kruskal-Wallis analysis was applied in order to locate the subscales' influences on sociodemographic variables such as gender and age and self-reported variables such as the pleasure of being a pupil and school performance. The further purpose of the present study is to provide the basis for follow-up comparisons of preferences and values in pupils within other countries.

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Résumé Le but de la présente étude est la réalisation d'un système de mesure pour l'évaluation de différents niveaux de conscience par rapport à la nature et à la protection de l'environnement, ainsi que des comportements actuels ou envisagés. Le système de mesure s'appuie sur un questionnaire à choix multiples pour évaluer les différents facteurs qui déterminent les niveaux de conscience et les comportements correspondants chez les adolescents de 10 à 16 ans. Dans le cadre du modèle à trois niveaux, qui comprend des composantes cognitives, affectives et comportementales, un grand nombre d'items, en partie issus d'études antérieures, ont été sélectionnés pour former les sous-catégories nécessaires. La configuration des catégories a été garantie par une analyse factorielle.Sur la base des réponses d'environ 2000 élèves, des sous-catégories ont été définies, qui vont depuis les positions de départ jusqu'au comportement actuel. En outre, nous avons défini les coefficients de corrélation, ainsi que les valuers Cronback-Alpha, et une analyse des régressions a été effectuée, qui prend en compte les influences, par exemple, des variables sociodémographiques comme le sexe et l'âge, des résultats scolaires ou de la manière dont l'école est perçue par chacun.La présente étude représente la base aussi bien pour des investigations comparatives entre pays, que pour l'évaluation de l'influence d'un enseignement extra-scolaire adopté.

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Dr. Franz Bogner is the senior author to whom correspondence should be addressed. Manfred Wilhelm is based at the Institut für Medizinische Statistik, Technische Universität, Ismaninger Straße 22, D-81675 München, Germany.     

The enhancement of photodegradation efficiency using Pt–TiO2 catalyst

This study investigates the mechanism of photosensitization and the recombination of excited electron–hole pairs affected by depositing platinum (Pt) on the surface of titanium dioxide (TiO₂). A new catalyst of Pt–TiO₂ was prepared by a photoreduction process. Being model reactions, the photocatalytic oxidation of methylene blue (MB) and methyl orange (MO) in aqueous solutions using the Pt–TiO₂ catalyst was carried out under either UV or visible light irradiation. The experimental results indicate that an optimal content of 0.75%Pt–TiO₂ achieves the best photocatalytic performance of MB and MO degradation and that the Pt–TiO₂ catalyst can be sensitized by visible light. The interaction of Pt and TiO₂ was investigated by means of UV–Vis absorption spectra, photoluminescence emission spectra, and X-ray photoelectron emission spectroscopy. The Pt⁰, Pt²⁺ and Pt⁴⁺ species existing on the surface of Pt–TiO₂, and the Ti³⁺ species existing in its lattice may form a defect energy level. The Pt impurities, including Pt, Pt(OH)₂, and PtO₂, and the defect energy level absorb visible light more efficiently in comparison with the pure TiO₂ and hinder the recombination rate of excited electron–hole pairs.     

Role of amination of a polymeric adsorbent on phenol adsorption from aqueous solution

Adsorption of seven phenols, one aromatic carboxylic acid and one sulfonated aromatic acid from aqueous solution, by a hypercrosslinked polymeric adsorbent (CHA-111) and the derivative animated by dimethylamine was compared. The results of different adsorption isotherms indicated that amino group on the polymeric matrix played a significant role on adsorption of almost all the employed compounds. For most employed compounds adsorption capacities increase to different degree and significantly for those with lower value of pK(a). It may be attributed to the enhanced adsorbent-adsorbate interaction for amino group introduced on the polymeric matrix. The empirical Freundlich isotherm equation was employed to interpret the adsorbent-adsorbate interaction. The adsorption enthalpy change indicated the uptake of phenols on MCH-111 to be an enhanced physical adsorption because of the hydrogen-bonding interaction. Adsorption kinetic study of phenols on CHA-111 and MCH-111 was also conducted and amino group on the matrix will reduce the adsorption rate for change of pore size distribution and loss of macroprous volume as well as the hydration effect on the surface partly.     

Movement of bromacil and hexazinone in soils of Hawaiian pineapple fields

Bromacil and hexazinone have been heavily used to control weeds in the pineapple fields in central Oahu, Hawaii, USA, since 1970s and 1980s, respectively. The last application prior to this study was at a rate of 0.6 kg active ingredient (a.i.) ha(-1) for hexazinone and 1.8 or 3.4 kg (a.i.) ha(-1) for bromacil in the six study fields during June-October 1998. Soils were collected from 0 to 1860 cm below the surface in January-May 1999 to survey the residue profiles of the two herbicides. Stratoprobe sampling showed to be an efficient and convenient method for deep soil cores. Bromacil was detected in all the soil samples above 60 cm (105-1338 ng g(-1) dry weight) and in 74% of the samples above 400 cm (26-473 ng g(-1)). Trace amounts of bromacil (90-113 ng g(-1)) were detected in some of the samples collected from as deep as 1540 cm. Hexazinone was detected in three of the six fields at 0-60 cm only (86-107 ng g(-1) dry weight). The more frequent detection of bromacil at higher concentrations than hexazinone is related to the prolonged higher application rates of bromacil in the fields and its higher persistence and mobility in soil.     

Changes in soil solution Zn and pH and uptake of Zn by arbuscular mycorrhizal red clover in Zn-contaminated soil

Red clover plants inoculated with Glomus mosseae were grown in a sterile pasture soil containing 50 mg Zn kg(-1) in 'Plexiglas' (acrylic) containers with nylon net partitions (30 microm mesh) designed to separate the soil into a central root zone and two outer zones for hyphal growth with no root penetration. Two porous plastic soil moisture samplers were installed in each pot, one in the root compartment and the other in one of the hyphal compartments. The soil in the outer compartments was amended with one of the four application rates of Zn (as ZnSO4) ranging from 0 to 1000 mg kg(-1). Non-mycorrhizal controls were included, and there were five replicates of each treatment in a randomised block in a glasshouse. Uninoculated plants received supplementary P to avoid yield limitation due to low soil P status. Plants grew in the central compartment for nine weeks. Soil moisture samples were collected 4, 24 and 62 days after sowing to monitor changes in the Zn concentration and pH of the soil solution. At harvest, the mean mycorrhizal infection rate of inoculated plants ranged from 29% to 34% of total root length and was little affected by Zn application. Root and shoot yields were not affected by mycorrhizal infection. Plant Zn concentration and uptake were lower in mycorrhizal plants than non-mycorrhizal controls, and this effect was more pronounced with increasing Zn application rate to the soil. Soil solution Zn concentrations were lower and pH values were higher in mycorrhizal treatments than non-mycorrhizal controls and the mycorrhiza effect was more pronounced at higher Zn application rates. The protective effect of mycorrhiza against plant Zn uptake may have been associated with changes in Zn solubility mediated by changes in the soil solution pH, or by immobilisation of Zn in the extraradical mycelium.