Kinetic study on the photo-catalytic degradation of pyridine in TiO2 suspension systems

It has been generally agreed that pyridine can be effectively mineralized in aerated TiO2 slurries using near-UV irradiation. The knowledge on the kinetics of the system possesses both practical and theoretical values. The present study, on the base of Langmuir-Hinshewood mechanism, illustrates a pseudo first-order kinetic model of the degradation with the limiting rate constant of 3.004 mg l(-1) min(-1) and equilibrium adsorption constant 2.763 x 10(-2) l mg(-1), respectively. The degradation efficiency in alkali is a little higher than that in acid with a minimum at about pH = 5, which is explained by the formation of acid-pyridine in acidic surrounding together with the amphoteric nature of the TiO2 surface. The promotion of H2O2 on the photo-degradation ties in its supplying proper amount of (OH)-O-. radicals for the inducement stage before surface redox reactions. (C) 2004 Elsevier B.V. All rights reserved.

东北草甸棕壤对重金属铅的吸附行为研究

研究了重金属铅(Pb2+)在东北草甸棕壤上的吸附行为,探讨了吸附机理.结果表明,重金属铅(Pb2+)在东北草甸棕壤上的吸附动力学符合准二级吸附速率方程,吸附等温线为Langmuir型;随pH增大,吸附量在pH=2~4范围内急剧增大,而在pH=4~6范围内基本不变;惰性电解质(NaNO3)的存在可明显抑制Pb2+的吸附,随NaNO3浓度的增大,吸附量先急剧下降,后趋于平缓.Pb2+在草甸棕壤颗粒上的吸附机理包括离子交换吸附和表面功能基团键合作用吸附,其中表面功能基团键合作用吸附又可分为化学键合吸附和静电键合吸附,前者形成内络合层,后者形成外络合层.

Activated carbons chemically modified by concentrated H2SO4 for the adsorption of the pollutants from wastewater and the dibenzothiophene from fuel oils

The surface properties, porosities, and adsorption capacities of activated carbons (AC) are modified by the oxidation treatment using concentrated H2SO4 at temperatures 150-270 degreesC. The modified AC was characterized by N-2 adsorption, base titration, FTIR, and the adsorption of iodine, chlorophenol, methylene blue, and dibenzothiophene. The treatment of AC with concentrated H2SO4 at 250 degreesC greatly increases the mesoporous volume from 0.243 mL/g to 0.452 mL/g, specific surface areas from 393 m(2)/g to 745 m(2)/g, and acidic surface oxygen complexes from 0.071 meq/g to 1.986 meq/g as compared with the unmodified AC. The base titration results indicate that the amount of acidic surface oxygen groups on the modified AC increases with increasing the treatment temperatures and carboxyls and phenols are the most abundant carbon-oxygen functional groups. The carboxyl groups, COO- species, and hydroxyl groups are detected mainly for the sample treated at 250 degreesC. The mesoporous properties of the AC modified by concentrated H2SO4 were further tested by the adsorption of methylene blue and dibenzothiophene. The AC modified by concentrated H2SO4 at 250 degreesC has much higher adsorption capacities for large molecules (e.g., methylene blue and dibenzothiophene) than the unmodified AC but less adsorption capacities for small molecules (e.g., iodine). The adsorption results from aqueous solutions have been interpreted using Freundlich adsorption models.

短刺小克银汉霉对偶氮染料刚果红的脱色

为探索真菌对染料的脱色特性,利用分离得到的短刺小克银汉霉对偶氮染料刚果红进行了脱色研究.短刺小克银汉霉菌丝球能在3h内使刚果红脱色率达到96%以上.在通气脱色体系中研究了短刺小克银汉霉菌丝球在不同pH值、脱色温度、摇床转速、盐度等条件下对刚果红脱色效果的影响.研究结果表明,短刺小克银汉霉菌丝球在温度为33℃,pH6.5,摇床转速120r/min的条件下对刚果红具有最大脱色率,染料溶液中盐浓度对脱色率有一定影响,但影响不大.在刚果红50~200mg/L质量浓度范围内,小克银汉霉菌丝球对刚果红吸附脱色动力学符合拟二级动力学方程(R2>0.999).菌丝球对刚果红的吸附等温线可用Langmuir和Freundlich等温方程模型表达,其中Langmuir方程能更好地描述菌丝球对染料的吸附行为(R2>0.999).

短刺小克银汉霉菌丝球对孔雀绿的吸附研究

利用分离得到的短刺小克银汉霉对三苯甲烷类染料孔雀绿进行了吸附脱色研究。当染料质量浓度为100mg·L-1时,短刺小克银汉霉菌丝球能在3h内使孔雀绿脱色率达到92%以上。在通气脱色体系中研究了短刺小克银汉霉菌丝球在不同pH、脱色温度、摇床转速等条件下对孔雀绿脱色效果的影响。研究结果表明,短刺小克银汉霉菌丝球在温度为35℃,pH为10,转速为150r·min-1的条件下对孔雀绿具有最大脱色率,脱色时间在180min时达到吸附平衡。孔雀绿质量浓度为25～100mg·L-1,小克银汉霉菌丝球对孔雀绿吸附脱色动力学符合拟二级动力学方程(R2>0.99)。菌丝球对孔雀绿的吸附符合Langmuir等温吸附方程(R2>0.998),饱和吸附量达到1250mg·g-1。对吸附了染料的菌体进行解吸研究,发现用异戊醇作为解吸剂的解吸率最高,可以达到93%,解吸过程符合二级动力学方程(R2>0.99)。

活性炭负载Fe(Ⅲ)吸附剂去除饮用水中的As(Ⅴ)

利用活性炭负载水合铁氧化物制备了复合吸附剂,并用于饮用水中As(Ⅴ)的去除.研究了活性炭种类、粒度、溶液pH值、Fe(Ⅲ)盐浓度和干扰离子等对As(Ⅴ)去除的影响.结果表明,煤质活性炭作为基质负载水合铁氧化物比椰壳炭和果壳炭具有更好的除砷效果.随着炭粒度降低,除砷效率显著增加.在pH3～9范围内,活性炭负载水合铁氧化物可有效吸附As(Ⅴ).F-,Cl-,SO42-的加入对As(Ⅴ)的去除效率基本无影响,而SiO32-和PO43-则明显抑制As(Ⅴ)的去除.Langmuir模型比Freundlich模型能更好地描述复合吸附剂对As(Ⅴ)的吸附平衡.动力学研究表明,As(Ⅴ)吸附反应可用二级速率方程描述.

Adsorption of arsenite and arsenate on amorphous iron hydroxide

Adsorption isotherms in solutions with ionic strengths of 0.01 at 25°C were measured over the arsenite and arsenate concentration range 10−7−10−3 M and the pH range 4–10. At low concentrations, these isotherms obeyed equations of the Langmuir type. At higher concentrations the adsorption isotherms were linear, indicating the existence of more than one type of surface site on the amorphous iron hydroxide adsorbent. Removal of arsenite and arsenate by amorphous iron hydroxide throughout the concentration range were determined as a function of pH. By careful selection of the relative concentration of arsenic and amorphous iron hydroxide and pH, removals on the order of 92% can be achieved.

人工湿地基质净化磷素的吸附剂性能

通过基质磷素等温吸附实验,研究了砂子、水淬渣、钢渣3种人工湿地基质净化磷素的效果.结果表明:Freundlich和Langmuir等温吸附曲线方程均能较好地描述上述基质磷素吸附的过程,其磷素理论饱和吸附量依次为钢渣12 500 mg.kg-1,水淬渣3 333 mg.kg-1,砂子270 mg.kg-1.基质吸附饱和后,磷素解吸实验表明:水淬渣磷素解吸率最低,为0.68%;砂子的解吸率最高,为7.59%.虽然钢渣的吸附量最大,但其水溶液pH显强碱性,不适合湿地植物的生长;水淬渣作为一种工业废料,磷素吸附量为砂子的12倍左右,解吸率为砂子的1/10,而且对植物生长无明显危害,是一种比较有应用前景的湿地除磷材料.

土壤中镉的吸附解吸研究进展

首先概述了国内外关于土壤对镉的吸附解吸的基本研究方法与实验条件。用于吸附解吸实验的土样以通过20目筛为宜,而不同形式的支持电解质及其离子浓度的选择对实验结果有很大影响,应由实验的具体目的和要求确定合适的实验条件。位于土壤颗粒表面的各吸附点位与镉的结合能的能量高低不一,可将土壤对镉的吸附作用区分为专性吸附和非专性吸附。可用传统的或融入新参数的吸附等温线表达土壤对镉的吸附过程,土壤对镉的吸附性能可用综合因子来形容,如吸附势、吸持率、平均分配系数、Langmuir方程的常数k和Freundlich方程的系数k等表达方式,同时寻找这些综合因子与土壤基本理化性质之间的关系。文章最后讨论了影响吸附过程的主要环境因子,并就土壤pH和水分条件的影响机制进行了分析。

Platinum-coated gold nanoporous film surface: Electrodeposition and enhanced electrocatalytic activity for methanol oxidation

This report describes the preparation of Pt-nanoparticle-coated gold-nanoporous film (PGNF) on a gold substrate via a simple "green" approach. The gold electrode that has been anodized under a high potential of 5 V is reduced by freshly prepared ascorbic acid (AA) solution to obtain gold nanoporous film electrode. Then the Pt nanoparticle is grown on the electrode by cyclic voltammetry (CV).

Near-infrared emission from novel tris(8-hydroxyquinolinate)lanthanide(III) complexes-functionalized mesoporous SBA-15

A novel mesoporous material covalently bonded with 8-hydroxyquinoline (HQ) was synthesized (designated as Q-SBA-15). The 5-formyl-8-hydroxyquinoline grafted to.(3-aminopropyl)triethoxysilane, that is, alkoxysilane modified 8-hydroxyquinoline (Q-Si), was used as one of the precursors for the preparation of the Q-SBA-15 material. On the basis of the other function of the Q-Si of coordinating to lanthanide (Ln) ions, for the first time, the LnQ(3) complexes (Ln = Er, Nd, Yb) have been covalently bonded to the SBA-15 materials.

Fabrication of Superhydrophobic Cellulose-Based Materials through a Solution-Immersion Process

An industrial waterproof reagent [(potassium methyl siliconate) (PMS)] was used for fabricating a superhydrophobic surface on a cellulose-based material (cotton fabric or paper) through a solution-immersion method. This method involves a hydrogen bond assembly and a polycondensation process. The silanol, which was formed by a reaction of PMS aqueous solution with CO2, Was assembled on the cellulose molecule surface via hydrogen bond interactions. The polymethylsilsesquioxane coatings were prepared by a polycondensation reaction of the hydroxyl between cellulose and silatiol. The superhydrophobic cellulose materials were characterized by FTIR spectroscopy, thermogravimetry, and surface analysis (XPS, FESEM, AFM, and contact angle measurements).

Effect of Freeze-Thawing on Lipid Bilayer-Protected Gold Nanoparticles

In this study, varieties of lipid bilayer-protected gold nanoparticles (AuNPs) were synthesized through a simple wet chemical method, and then the effect of freeze-thawing on the as-prepared AuNPs was investigated. The freeze-thawing process induced fusion or fission of lipid bilayers tethered on the AuNPs. The UV-vis spectra and transmission electron microscopy experiments revealed that the disruption of lipid bilayer structures on the nanoparticles led to the fusion or aggregation of AuNPs.

Simple Electrochemical Route to Nanofiber Junctions and Dendrites of Conducting Polymer

We first report a simple and rapid electrochemical approach to synthesize novel nanofiber junctions and dendrites of conducting poly(o-phenylenediamine) without any surfactant or template. Through controlling some parameters such as the time and potential of electrodeposition and concentration of the reactant, nanofiber junctions and dendrites of conducting polymer can be easily obtained on the solid surface.

Environmentally friendly synthesis of highly monodisperse biocompatible gold nanoparticles with urchin-like shape

We report a facile and environmentally friendly strategy for high-yield synthesis of highly monodisperse gold nanoparticles with urchin-like shape. A simple protein, gelatin, was first used for the control over shape and orientation of the gold nanoparticles. These nanoparticles, ready to use for biological systems, are promising in the optical imaging-based disease diagnostics and therapy because of their tunable surface plasmon resonance (SPR) and excellent surface-enhanced Raman scattering (SERS) activity.