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The lack of electron donors in oxygen-rich aquatic environments limits the ability of natural denitrification to remove excess nitrate, leading to eutrophication of aquatic ecosystems. Herein, we demonstrate that electron rich substances in river or lake sediments could participate in long-distance electron rebalancing to reduce nitrate in overlying water. A microstructure containing Dechloromonas and consisting of an inner layer of green rust and an outer layer of lepidocrocite forms in the sediment-water system through synergetic evolution and self-assembly. The microstructure enables long-distance electron transfer from the sediment to dilute nitrate in the overlying water. Specifically, the inner green rust adsorbs nitrate and reduces the kinetic barrier for denitrification via an Fe(II)/Fe(III) redox mediator. Our study reveals the mechanism of spontaneous electron transfer between distant and dilute electron donors and acceptors to achieve denitrification in electron-deficient aquatic systems.

Poly/oligosaccharides are renewable natural resources with abundant chirality. Herein, we develop a general route to prepare optically active particles by using poly/oligosaccharides as both chiral inducers and growth templates. By complexing with Cu(NH

Sulfate scaling, as insoluble inorganic sulfate deposits, can cause serious operational problems in various industries, such as blockage of membrane pores and subsurface media and impairment of equipment functionality. There is limited article to bridge sulfate formation mechanisms with field scaling control practice. This article reviews the molecular-level interfacial reactions and thermodynamic basis controlling homogeneous and heterogeneous sulfate mineral nucleation and growth through classical and non-classical pathways. Common sulfate scaling control strategies were also reviewed, including pretreatment, chemical inhibition and surface modification. Furthermore, efforts were made to link the fundamental theories with industrial scale control practices. Effects of common inhibitors on different steps of sulfate formation pathways (i.e., ion pair and cluster formation, nucleation, and growth) were thoroughly discussed. Surface modifications to industrial facilities and membrane units were clarified as controlling either the deposition of homogeneous precipitates or the heterogeneous nucleation. Future research directions in terms of optimizing sulfate chemical inhibitor design and improving surface modifications are also discussed. This article aims to keep the readers abreast of the latest development in mechanistic understanding and control strategies of sulfate scale formation and to bridge knowledge developed in interfacial chemistry with engineering practice.

The coexistence of aliovalent cations may facilitate the formation of electronic and ionic defects, altering the catalytic properties of manganese oxide. In this paper, a series of mixed-valent manganese oxides (MnOx) were prepared by a hydrothermal route and tested for heterogeneous activation of peroxydisulfate for Orange II degradation in aqueous solution. The morphology, crystal structure and surface chemistry of the MnOx were adjusted by the addition of ethanol in the hydrothermal process. The physicochemical properties were characterized and evidence from X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicated that MnOx exhibited a mixed crystal phase structure of Mn2O3, Mn3O4 and MnO2. The catalytic properties of the three samples prepared with 5%, 10%, and 20% volume fractions of ethanol (denoted as MnOx-5, MnOx-10, and MnOx-20) were found to be related to the valent states of Mn, and MnOx-10 exhibited a better performance with a mole ratio of Mn4+/ Mn2+ close to 1.0. The electrochemical characterization demonstrated that MnOx-10 performed a more effective redox process which may determine the catalytic activity of MnOx. Moreover, quenching tests, electron paramagnetic resonance (EPR) and gas chromatography-mass spectrometry (GC-MS) were used to evaluate the possible activation processes of peroxydisulfate (PDS) and the intermediates of Orange II degradation. This catalyst preparation strategy provides a new idea for the preparation of high-efficiency environmental catalysts.

The development of the bionic water channel aims to replace the possible use of natural aquaporins (AQPs) for water purification, while retaining the ability of natural AQPs to carry out ultra-fast water transport and repel ions. Carbon nanotube channels (CNTCs) are a convenient membrane-based model system for studying nano-fluidic transport that replicates a number of key structural features of biological membrane channels. In this report, we describe protocols for CNTCs synthesis by ultrasound-assisted cutting of long CNTs in the presence of lipid amphiphiles. CNTCs have a similar thickness to the lipid membrane and high affinity for it. The ultra-short high-affinity CNTCs have high permeability and ion selectivity. The water permeability of the CNTCs is 1936 &plusmn, 123 &mu, m/s, which is 2.3 times that of natural AQPs, and completely rejects salt ions. In general, carbon nanotubes represent a multifunctional nanopore building module for creating high-ranking functional bionic materials. This study has reference significance for the design of new bionic water channel and the actual development of bionic membrane based on CNTs.

Covalently-bound organic silicate-aluminum hybrid coagulants (CBHyC) have been shown to efficiently remove low molecular weight organic contaminants from wastewater. However, the interaction dynamics and motivations during the coagulation of contaminant molecules by CBHyC are limited. In this study, a molecular dynamics (MD) simulation showed that CBHyC forms core-shell structure with the aliphatic carbon chains gather inside as a core and the hydrophilic quaternary ammonium-Si-Al complexes disperse outside as a shell. This wrapped structure allowed the coagulant to diffuse into solutions easily and capture target contaminants. The adsorption of anionic organic contaminants (e.g., diclofenac) onto the CBHyC aggregates was driven equally by van der Waals forces and electrostatic interactions. Cationic organic contaminants (e.g., tetracycline) were seldom bound to CBHyC because of substantial repulsive forces between cationic molecules and CBHyC. Neutrally-charged organic molecules were generally bound through hydrophobic interactions. For adenine and thymine deoxynucleotide, representatives of antibiotic resistance genes, van der Waals forces and electrostatic interaction became the dominant driving force with further movement for adenine and thymine, respectively. Driving forces between target contaminant and coagulant directly affect the size and stability of formed aggregate, following the coagulation efficiency of wastewater treatment. The findings of this study enrich the database of aggregation behavior between low molecular weight contaminants and CBHyC and contribute to further and efficient application of CBHyC in wastewater treatment.

Graphene oxide (GO) coating has recently been reported as a novel approach to increase membrane flux of membrane distillation (MD), yet the phenomena underlying the process are still not fully understood. In this study, a mathematical model based on capillary-film assumption was developed and validated with the results (R

The development of large surface-area and high conductivity electrode is a prerequisite for the construction of high-performance microbial fuel cells. Herein, we report an innovative approach to the fabrication of such high-performance electrodes via the welding assembly of 3D interconnected carbon nanotubes (CNTs) on a carbon-fiber (CF) paper electrode. The minimized interfacial ohmic loss between CNTs and the CF scaffold endowed the microbial fuel cells with the welding-assembled CNT-CF electrodes excellent electrochemical properties with the maximum power density of 2015.6 mW m −2 , 10.0 times higher than that obtained with the untreated CP/CNT (499.8 mW m −2 ) carbon paper anode. As compared to the conventional chemical vapor deposition (CVD) growth technique for fabricating CNT- CF electrodes, this welding assembly approach is more versatile and much easier for up-scaling; on this basis, our work may pave a new avenue to the large-scale production of high-performance microbial fuel cells.

Widespread application of anammox process has been primarily limited to the high sensitivity of anammox consortia to fluctuations of temperature. However, the metabolic acclimation of anammox consortia to decreased temperature remains unclear, which is the core of developing potential strategies for improving their low-temperature resistance. Here, we operated anammox reactors at 25 °C and 35 °C to explore the acclimation mechanism of anammox consortia in terms of metabolic responses and cross-feedings. Accordingly, we found that the adaptation of anammox consortia to ambient temperature (25 °C) was significantly linked to energy conservation strategy, resulting in decreased extracellular polymeric substance secretion, accumulation of ATP and amino acids. The expression patterns of cold shock proteins and core enzymes caused the apparent metabolic advantage of Candidatus Brocadia fulgida for acclimation to ambient temperature compared to other anammox species. Importantly, strengthened cross-feedings of amino acids, nitrite and glycine betaine benefited adaptation of anammox consortia to ambient temperature. Our work not only uncovers the temperature-adaptive mechanisms of anammox consortia, but also emphasizes the important role of metabolic cross-feeding in the temperature adaptation of microbial community.

Background: Bacterial interaction and communication via quorum sensing (QS) received extensively attention, as it can coordinate bacterial behavior and activity through the QS signal molecules in microbial community. Though the exchange of public goods regulated by QS have been explored in pure culture, how signal sense, transmit, and affect the social traits through regulating public goods in complex communities remains unclear. Results: The levels of public goods (e.g. extracellular polymeric substances (EPS) and amino acids) changed significantly when exogenous diffusion signal factor (DSF), a kind of QS molecules, was added. Approaches involving meta-omics and hierarchical signalling network construction give insight into that anammox species ( Jettenia caeni , AMX1) and Proteobacteria -affiliated bacterium (PRO1) can sense and transit DSF signals, thus directly regulating the production and exchange of public goods via the secondary messenger c-di-GMP regulator, Clp. In detail, these two kinds of species can supply more costly amino acids for DSF-Secretor species (like AMX2, CFX1, CFX3, and PRO4) after sensing DSF. Meanwhile, DSF-Secretor species encoded diverse genes involved in hydrolysis of extracellular protein and carbohydrate and genes involved in transportation of peptides and sugars. The exogenous DSF-inducement also leads to the high expression of these genes, which indicated DSF-Secretor species helped anammox bacteria scavenge extracellular detritus. This process can be considered as a feedback of public goods supply by anammox bacteria, as this process contributed to create a suitable environment for anammox bacteria growth. Namely, DSF can bridge bacterial interactions through regulating public goods. Furthermore, the trade-off induces discrepant metabolic loads of different microbial clusters and community succession. It illustrated the potential to artificially alleviate metabolic loads and thus increase proliferation rate for certain bacteria through QS. Conclusions: DSF can bridge interactions of anammox bacteria and DSF-Secretor species through regulating production and exchange of public goods using Clp regulator. Deciphering microbial interactions via QS provides insights for understanding the molecular evolution of QS in microbial community.

In marginal marine settings, understanding the role that clay minerals play in the transfer of metal cations from the water column to the seafloor is important if the composition of modern muds is to be used as a proxy for the precursors of ancient shale deposits. In this study, we conducted potentiometric titrations of three naturally abundant clay minerals (kaolinite, montmorillonite and illite) in 0.56 M NaCl electrolyte solutions to ascertain the surface reactivity of each clay mineral at seawater ionic strength. Our results demonstrate that all three clay minerals were increasingly anionic as pH increases from 3 to 9, with montmorillonite having the highest negative-charge. The potentiometric titrations and adsorption data were modeled using both non-electrostatic (NEM) and electrostatic (constant-capacitance model, CCM) surface complexation models (SCMs). A two-site surface complexation model, that included one basal siloxane surface site (≡X−) and one amphoteric edge site (≡SOH), provided an excellent fit for the protonation data of each mineral. Cd(II) adsorption experiments were conducted to quantify the magnitude of cation adsorption, which showed that 10 g montmorillonite, illite, and kaolinite powder could bind an equivalent of 4.7 × 10−4 g, 4.3 × 10−4 g, and 4.0 × 10−4 g of Cd, respectively, under conditions relevant to seawater (initial Cd concentration of 8.9 × 10−6 M, and pH = 8). To place this value into the context of modern riverine clay inputs to the ocean, 13.5 × 109 tons of total suspended sediment are deposited annually (Milliman and Meade, 1983) of which 10 to 25% is clay (Manheim et al., 1970; Schroeder et al., 2015). The total amount of Cd adsorbed to suspended clay minerals entering the modern oceans could then amount to approximately 104 to 105 tons per year. The results of this study highlight the potential role of clay minerals in transporting metals from the ocean water column to the seafloor.

The low electronic conductivity of sulfur and the high solubility of polysulfides seriously hinder the practical application of lithium–sulfur (Li–S) batteries. Therefore, the incorporation of sulfur into carbon-based materials is considered as a suitable solution. Here, a porous pomelo biochar/graphene composite (PBG) was prepared via a simple and green method combining hydrothermal carbonization and KOH activation. The obtained material was used as a host to encapsulate sulfur for the cathode of Li–S batteries, and the three-dimensional pore structure with enhanced conductivity is beneficial for the utilization of sulfur and absorption of soluble polysulfides. As a result, the PBG-S composite (63.3 wt% sulfur) delivered an initial discharge capacity of 1053 mA h g−1 at 0.1C (1C = 1675 mA g−1) and retained 418 mA h g−1 at 3C, even with a high sulfur loading of 4.0 mg cm−2. In addition, the performance of the composite was further improved by reducing the content of sulfur to an appropriate ratio in the PBG-S composite. The optimized PBG-S composite (48.6 wt% sulfur) exhibited a high initial discharge capacity of 1368 mA h g−1 at 0.1C and retained 638 mA h g−1 at 3C, and the discharge capacity remained as high as 664 mA h g−1 and 354 mA h g−1 even after the 200th and 600th cycles at 1C, respectively. The results indicated that PBG, with excellent electrochemical properties, is an ideal electrode material for lithium–sulfur batteries, and can also be prepared economically on an industrial scale.

A novel strategy was presented for the synthesis of graphene-based film electrodes by electrolyte-induced hydrothermal reduction of holey graphene oxide based films. After hydrothermal treatment, the reduced holey graphene films (rHGFs) maintained their flexibility, integrity and porosity, which resulted from the electrolyte-induced balance between electrostatic repulsion and π–π attraction. The trapped electrolyte (H2SO4) between graphene layers can prevent aggregation, and the resulting supercapacitor exhibits a high specific capacitance in the sulfuric acid electrolyte. Benefitting from the in-plane pores and oxygen-containing groups on graphene sheets, the rHGF electrode exhibits a high specific capacitance of 260 F g−1 (297 F cm−3) with remarkable rate performance in a three-electrode system. To evaluate the practical application, flexible all-solid-state supercapacitors based on the rHGF electrode with PVA/H2SO4 gel electrolyte were prepared, and the device exhibits remarkable cycling stability. The areal capacitance and volumetric energy density were 56 mF cm−2 and 1.41 W h cm−3, respectively. This work demonstrated a cost-effective and simple technique to prepare compact graphene films with continuous ion channels and showed great importance on the design of flexible, portable and highly integrated supercapacitors.

The lignite activated coke-facilitated activated sludge (LAC/AS) process has proved to be an effective method for increase of phenol biodegradability, yet the interactions between LAC toxicity mitigation and microbial community shift remain unclear. In this study, the phenol degradation rate under different shock-stress for 51 days were investigated. LAC/AS system can tolerate higher phenol shock stress but phenol removal rate starts to descend at 200 mg/L. The system settling performance deteriorated as the filamentous bulking appeared after 40 days but the phenol removal rate was maintained. The results indicated that the microbial community tend to shift for phenol biodegradation when the effect of LAC toxicity mitigation subdued. However, the SVI increased sharply from 40 to 226 mL/g in a relatively long operation period along with the increase of floc size and reduction of TB EPS. Flavobacterium and Bacteroides were the dominated species in the LAC/AS bulking system, correlating to the sustained phenol removal. This work enhances our understanding on the interactions between LAC and microbial community in LAC/AS system, which can be employed for further optimizing LAC/AS technology.

It is a challenge to achieve pure graphene foams with a desired monolithic structure in order to take advantage of the excellent properties of graphene-based macroscopic assemblies. Here, we introduced a confinement fabrication strategy to prepare nitrogen doped reduced graphene oxide foams (NrGFs) through a one-step hydrothermal process. The melamine foam (MF) skeleton was removed during the hydrothermal reaction, and the NrGF retained its desired monolithic structure by the confinement of solution ionic strength. Due to the “roof-tile-like” microscopic morphology with high N-doping (9.88 at%), the free-standing graphene foam electrode exhibited excellent capacitive performance. The resulting NrGF-based symmetric supercapacitor displayed a remarkably enhanced specific capacitance of 260 F g−1 at 0.1 A g−1 and 173 F g−1 at 20 A g−1 in an aqueous electrolyte. Moreover, the facility of fabrication makes it a promising material in many contexts for large scale production, such as energy storage, environmental remediation and strain sensors. Furthermore, this synthesis strategy can be expanded to prepare other pure macroporous foams or composites by using different building blocks (such as CNTs and MXene).

The power generation performance of a microbial fuel cell (MFC) greatly depends on the relative amount of electricigens in the anodic microbial community. Running the MFC multiple times can practically enrich the electricigens, and thus improve its power generation efficiency. However, Gram-positive electricigens cannot be enriched well because of their thick non-conductive peptidoglycan layer. Herein, we report a new Gram-positive electricigen enrichment method by regulating the peptidoglycan layer of the bacteria using lysozyme. Lysozyme can partially hydrolyze the peptidoglycans layer of Gram-positive Firmicutes to improve the permeability of cell wall, and thus enhance its electricity generation activity. The stimulation of Gram-positive electricigen endows MFCs a high power generation community structure, which results in the power density 42% higher than that of the control sample. Our work has provided a new and simple method for optimizing the anode community structure by regulating weak electricigens in the community with lysozyme.

The low yield of anaerobic ammonium oxidation (anammox) biomass has attracted great attention because of its difficulty to be abundantly enriched. Patterns of substrate supply greatly influence microbial metabolism and behavior. The present study proposed that low nitrogen strength was beneficial to anammox biomass yield and nitrogen removal when comparing a membrane bioreactor (MBR) operated at low nitrogen strength with short hydraulic retention time (HRT) (R-low; influent: fixed at 100 mg-N L−1) and one operated at high nitrogen strength with long HRT (R-stepwise; influent: 100-700 mg-N L−1). Different nitrite concentrations in the two MBRs would indicate discrepant environments, and inevitably resulted in the discrepant microbial responses for anammox community. In particular, we found that at low nitrogen strength, increased activities of purine and pyrimidine metabolism pathways provided more abundant nucleic acids for bacterial proliferation. More active reaction of lipid and protein synthesis favored the synthesis of cellular structure. Importantly, the metabolism of cheaper amino acids was more active under low nitrogen strength, which was coupled with higher metabolic flux and potentially more active exchange of costly amino acids as public goods. In this way, more energy could be saved and applied to biomass yield. Higher active bacterial diversity and more positive interactions among bacterial species in R-low further favored biomass yield and nitrogen removal. The present study highlighted the significant effect of substrate supply patterns on anammox, which is meaningful to overcome the current bottleneck of deficient anammox biomass for application in wastewater treatment.

Pollution caused by volatile organic compounds (VOCs) and odorous pollutants in the air can produce severe environmental problems. In recent years, the emission control of VOCs and odorous pollutants has become a crucial issue owing to the adverse effect on humans and the environment. For treating these compounds, biotrickling filter (BTF) technology acts as an environment friendly and cost-effective alternative to conventional air pollution control technologies. Besides, low concentration of VOCs and odorous pollutants can also be effectively removed using BTF systems. However, the VOCs and odorants removal performance by BTF may be limited by the hydrophobicity, toxicity, and low bioavailability of these pollutants. To solve these problems, this review summarizes the design, mechanism, and common analytical methods of recent BTF advances. In addition, the operating conditions, mass transfer, packing materials and microorganisms (which are the critical parameters in a BTF system) were evaluated and discussed in view of improving the removal performance of BTFs. Further research on these specific topics, together with the combination of BTF technology with other technologies, should improve the removal performance of BTFs.

In the paper, we demonstrated the controlled fabrication of nanostructured graphene/copper phthalocyanine/layered double hydroxide (G/TSCuPc/LDH) films by layer-by-layer assembly. The G/TSCuPc/LDH-modified electrodes exhibited remarkable photoelectric performance, and its light absorption and resistance were increased with the increase of the film thickness. The electroactivity of the film was enhanced by the incorporation of graphene into TSCuPc. The 20-layer film electrode generated higher photocurrent than the G/TSCuPc electrode, suggesting orderly assembled phthalocyanine layer between LDH and graphene layers and the efficient charge separation and electron transfer in the novel system.

In this research, a hybrid nonlinear grey-prediction and quota allocation model (HNGP-QAM) wasdeveloped for supporting optimal planning of China's carbon intensity reduction at both departmentaland provincial levels in 2020. At such dual levels, HNGP-QAM can not only help forecast carbon intensityand its fluctuations over the concerned period, but also facilitate the identification of China's carbonintensity reduction target in 2020 and the corresponding quotas for minimizing the total abatement cost.Two scenarios were developed based on multiple governmental policies and allocation schemes amongprovinces and departments. The results showed that the total abatement cost would be 92.07 and98.93 10 9 , as well as 180.57 and 194.19 10 9 RMB (It is another shortname for China Yuan) for pro-vincial and departmental allocation schemes under the reduction ratios of 40 and 45%, respectively.Furthermore, the west, the east, and the central China would be allocated the emission assignments thatwould be accounting for 48.53, 28.26, and 23.21% of the total national emission reduction, respectively.The obtained results were particularly useful for multi-level governments in providing information toidentify the carbon intensity reduction target, conducting emission reduction assignments amongprovinces and departments, as well as supporting relevant policy-making. The results also suggested thatthe developed HNGP-QAM be applicable to similar engineering and planning problems.© 2014 Elsevier Ltd. All rights reserved.

Electrochemical oxidation of p-nitrophenol was examined using different anodic materials, including Ti/boron-doped diamond (BDD), Ti/SnO2-Sb/PbO2, and Ti/SnO2-Sb anodes. The results demonstrated that Ti/BDD anodes had a much stronger mineralization performance than the other two anodes. Furthermore, it was found that hydroxyl radicals could mainly exist as free hydroxyl radicals at BDD anodes, which could react with organic compounds effectively. This implied that the dominant mechanism for a much higher mineralization capacity of BDD anodes would be attributed to the existence of free hydroxyl radicals in the BDD anode cell rather than adsorbed hydroxyl radicals on the BDD anode. To further corroborate this hypothesis, electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) was examined at the Ti/BDD, Ti/SnO2-Sb/ PbO2, and Ti/SnO2-Sb anodes, respectively. The study revealed that for Ti/BDD electrodes,the degradation rate of p-substituted phenols (k) increased with the increase of Hammett's constant (sigma), which confirmed the dominance of free hydroxyl radicals at BDD anodes and its effective reaction with organics therein. For Ti/SnO2-Sb/PbO2 electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of initial surface concentration Gamma (representing the adsorption capacity of phenols to electrode surface), which indicated that organic compounds mainly reacted with adsorbed hydroxyl radicals at PbO2 anodes. For Ti/SnO2-Sb electrodes, however, k increased with the increase of the integrated parameter S (representing the effects of both sigma and Gamma), which implied that organic compounds reacted with both adsorbed hydroxyl radicals and free hydroxyl radicals at SnO2 anodes.

A simulated wastewater containing the monoazo dye C.I. Acid Orange 7 was electrolytically treated using a three-dimensional electrode reactor equipped with granular activated carbon as particle electrode. The activated carbon fiber cathode was more effective than either a graphite or a stainless steel cathode due to its larger surface area which was beneficial to the electrogeneration of H(2)O(2). Under the reaction conditions of 20 V and 3.0 g L(-1) Na(2)SO(4) at pH 3.0, decrease in the COD of up to 80%, and in the TOC by up to 72% were achieved and almost the complete decolorization of the dye was secured after 180 min electrolysis. Furthermore, decay of the dye followed a pseudo-first-order reaction in the first 60 min treatment. The three-dimensional electrode system generated more hydroxyl radicals than a two-dimensional system due to the formation of microelectrodes under applied high potential. (C) 2007 Elsevier Ltd. All rights reserved.

The photoacoustic (PA) amplitude spectra of Eu(Dbm) 3 Phen, Eu 0.8 Gd 0.2 (Dbm) 3 Phen and Eu 0.8 Nd 0.2 (Dbm) 3 Phen complexes (Dbm: dibenzoylmethane; Phen: phenanthroline) have been measured, and the PA phase data of the different complexes calculated. The PA amplitude spectra combined with the luminescence spectra reflected the variation of the luminescence efficiency, and the PA phase is directly relative to the lifetime of Eu 3+5 D 0 level. The luminescence efficiency and the lifetime of Eu 3+5 D 0 level increase when Gd 3+ is introduced, while they decrease greatly when Nd 3+ is added, which is due to the different intermolecular energy transfer processes. The models of energy transfer and relaxation processes of Eu 0.8 Gd 0.2 (Dbm) 3 Phen and Eu 0.8 Nd 0.2 (Dbm) 3 Phen are established.

Photoacoustic spectroscopy (PAS) is useful in the study of non-crystalline solids. By using PA amplitude and phase spectra, together with IR and fluorescence spectra, the variation of the energy levels and luminescence efficiencies and the intramolecular relaxation processes of silica gels doped with rare earth complexes with salicylic acid have been studied in comparison with their corresponding pure complexes. After the complexes are doped into silica gels, the PA and emission peaks of the ligands show a shift, but the peaks of rare earth ions do not apparently shift. The complex molecules are dispersed in the silica gel, this reduces concentration quenching. In addition, the relatively rigid host structure of silica gel limits the vibrations of the ligands, which decreases the non-radiative transition and increases the lifetime of Tb 3+ .

Electrochemical oxidation of some p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) with electron-donating and -withdrawing substituents was studied to reveal the relationship between the structure and the electrochemical reactivity of p-substituted phenols using a boron-doped diamond electrode by voltammetry and bulk electrolysis. Voltammetric study shows that the oxidation peak potentials of p-substituted phenols become more positive with an increase of Hammett's constants, that is, the direct electrochemical oxidation of p-substituted phenol with an electron-withdrawing group is more difficult than that of p-substituted phenol with an electron-donating group. However,the p-substituted phenols with electron-withdrawing groups are degraded faster than those with electron-donating groups in bulk electrolysis, which is opposite to the result obtained on the Pt electrode. These results indicate that the p-substituted phenols are mainly degraded by indirect electrochemical oxidation with hydroxyl radicals on a boron-doped diamond electrode. Under the attack of hydroxyl radicals, the release of p-substituted groups from the aromatic ring is the rate-limiting step. Since electron-withdrawing groups are easy to be released, the p-substituted phenols with these groups are degraded faster than those with electron-donating groups. Therefore, the degradation rates of the p-substituted phenols rise with an increase of Hammett's constants.

Department of Chemistry, Shandong University, Jinan, 250100, China E-mail : zhangply@yahoo.com.cn Department of Chemistry, Teacher's College of Qingdao University, Qingdao, 266071, China Manuscript received 5 June 2000, revised 2 April 2001, accepted 17 April 2001 The adsorption of a cationic polyelectrolyte onto quartz surface from aqueous solution has been studied using an electrode-separated piezoelectric sensor (ESPS). The adsorption process has been monitored in situ in Britton-Robinson buffer at different concentrations of polyelectrolyte. The adsorption mechanism is described. The adsorption density is influenced by pH and electrolyte concentration.

The deviation of magnetization (M) relaxation from logarithmic time dependence is due to both the low pinning potential influenced by the driving energy formed by the gradient of flux lines and the large thermal activation. Considering the structural relaxation of the vortex state under the action of the driving force and thermal activation, the dependence of M on time t can be obtained as M=A+Bt−β, where A, B, and β keep constant at a given field and temperature.