Magnetic normalization of particle size effects in a heavy metal pollution study of intertidal sediments from the Yangzte Estuary

Magnetic, granulometric and geochemical analyses were conducted on an intertidal sediment core from the Yangtze Estuary to evaluate the possibility of normalizing samples for particle size effects in a heavy metal pollution study by means of magnetic proxies. It has been found that the magnetic parameter_ϰARM, indicating fine grained ferrimagnetic minerals, correlates well with the clay content and organic matter concentration of the sediments._ϰARM also shows significant relationship with heavy metals. Therefore_ϰARM is proposed as a proxy for clay content in the sediments, and can be used to compensate for the particle size effect in sedimentary heavy metal records, where magnetic minerals are not subject to significant post-depositional alteration.

     

Distribution and forms of phosphorus in tidal flat sediments of the Yangtze Estuary and coast

The distribution and forms of phosphorus (P) were investigated in the tidal flat sediments of the Yangtze Estuary and coast. The total P contents in surface sediments range from 18.0 to 31.4 μmol · g-1 along the southern coast. The spatial and temporal distribution of P in tidal flats is closely related to the location and pollution resources, especially in association with the variation of hydrodynamic conditions. Significant variations in the forms of P in different sites were observed. P bonded with Ca(Ca-P) is the dominant mineral form in all surface sediments, organic P(Org-P) is lower. Most P is of unstable form, suggesting that P has larger potential activity. P accumulation is the main behavior process between water and sediment in the coastal environment of the Yangtze Estuary.     

330 MW燃煤机组异相凝并对重金属排放控制的实验研究

湖北某电厂1号机组容量为330 MW，配备双室四电场静电除尘器，为了考察异相凝并技术对细颗粒物以及重金属脱除效率的影响，对1号机组除尘器前后，脱硫塔后进行颗粒物与重金属采样测试。结果表明，在烟道中喷射凝并吸附剂后，ESP入口颗粒态重金属占比增加，其中，Se元素在PM_2.5和PM₁₀上增加尤为明显，而气态的重金属含量有所降低，表明凝并吸附剂增强了颗粒态重金属的凝并效果，小颗粒态与气态重金属通过异相凝并过程转移至大颗粒态。喷入凝并吸附剂后，石膏中重金属含量显著降低，说明能够进入脱硫石膏的重金属含量减少，异相凝并提升了ESP对重金属的脱除作用；在尾部烟道末端烟囱排放口采样点，重金属含量相较于未喷入凝并吸附剂的工况，有着明显的降低，表明了经过异相凝并之后，排放至大气中的重金属显著减少，异相凝并对于重金属的控制起到关键作用。     

Effect of the reaction parameters on the particle size in the dispersion polymerization of 2‐hydroxyethyl and glycidyl methacrylate in the presence of a ferrofluid

The precipitation of Fe₃O₄ from an aqueous solution with ammonium hydroxide produced nanoparticles that were coated with a layer of oleic acid [or, in some cases, poly(ethylene oxide) or poly(vinylpyrrolidone)] before their dispersion into the organic phase. The encapsulation of magnetite nanoparticles in poly(2‐hydroxyethyl methacrylate) or poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) microparticles was achieved by dispersion polymerization in toluene/2‐methylpropan‐1‐ol. Magnetic poly(glycidyl methacrylate) microparticles were obtained in the presence of poly(ethylene oxide) at the magnetite/monomer interface. The particles containing up to 20 wt % iron maintained their discrete nature and did not aggregate. The effect of the reaction medium polarity, the concentrations of the monomer, initiator, and stabilizer, and the temperature on the particle size, particle size distribution, and iron and oxirane group contents was studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1848–1863, 2003     

A study of a newly synthesized ligand and its metal complexes in bulk and nano size and metal uptake efficiency

A newly synthesized ligand derived from 2-amino thiophenol and benzoic anhydride and its Co(II), Cd(II), La(III) (in bulk and nano size), and Gd(III) complexes was investigated and characterized. The maximum elimination capacity of the newly synthesized ligand was investigated towards the removal of Co(II), Cd(II), La(III), and Gd(III) ions from aqueous solutions. It was found that the ligand has the best removal ability for Cd(II) metal of 98.66% at a concentration of 0.03 mg/L.     

Asphaltene precipitation from latin american heavy crude oils. Effects of solvent aromaticity and agitation on particle size reduction

Asphaltenes from three crudes were precipitated with a mixture of n-heptane and toluene, the size of the particles formed under different solvent mixtures and different agitation regimes were studied. The kinetic size reduction of aggregates formed with an excess of precipitant agent is followed, contrary to other published studies where the kinetic followed is of growing particles. It was found that the particle size of precipitated asphaltenes decreases as precipitant aromaticity increases and agitation energy rises, which indicates the formation of aggregates bonded by weak forces, since the agitation applied was not of high energy, except for the ultrasonic device.     

Characterization of Magnetic Nanoiron Oxides for the Removal of Metal Ions from Aqueous Solution

ABSTRACT

Two nanostructured hybrid materials are reported that include uncoated magnetic nanoiron oxides and magnetic nanoiron oxides treated with rose leaf extract. Atomic and molecular absorption spectrometry were used to evaluate the sensitivity of these materials for the isolation of Cr(VI), Zn(II), Pb(II), and Ca(II) from aqueous solution. The structure and physicochemical properties of the resulting nanohybrids were characterized by scanning electron microscopy coupled with energy-dispersive spectroscopy, atomic force microscopy, and X-ray diffraction. The results show that following 15?min of contact in acidic solution, the uncoated magnetic nanoiron oxides removed approximately 90% of Cr(VI), while the magnetic nanoiron oxides coated with rose leaf extract removed 92% of the analyte. These correspond to most industrial wastewater conditions. For the removal of Ca(II) and Zn(II), it was necessary to adjust the pH to neutral to maximize the efficiency. Pb(II) showed maximum removal efficiency when the solution is basic. The simple rose extract suspension was also used for metal removal with high capacity. The results demonstrate that the magnetic nanoiron oxides were uniformly distributed in the rose leaf extract. The extract served as a capping agent due to the presence of polyphenolics.     

Crosslinking network structure governing particle shape and size distribution by one-step emulsion polymerization in the presence of particle coagulation

In this study, sub-200?nm, crosslinked latex particles with a narrow particle size distribution were prepared by one-step emulsion polymerization in the presence of particle coagulation. The relationship between the particle shape and particle coagulation was investigated by varying the time of crosslinking network structure formation and particle coagulation. Particles with irregular shapes such as doublet, triplet, and ellipsoid were obtained using divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agents, because the crosslinking network structure of particles was formed before the particle coagulation. In contrast, latex particles with a uniform spherical shape were also prepared using triallyl isocyanurate (TAIC) or dihydrodicyclopentadienyl acrylate (DCPA) as the crosslinking agents by delaying the time of crosslinking network structure formation. Alternatively, uniform spherical latex particles were prepared by bringing forward the particle coagulation time using cationic initiator, 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). This study presents a new idea that would further broaden the application of particle coagulation in emulsion polymerization.     

Heavy metal distribution in the sediment profiles of the Sauípe River Estuary, north seashore of the Bahia State, Brazil

The distribution of the elements Al, Fe and selected heavy metals (Pb, Zn, Cd, Cu and Cr) plus the organic matter in the sedimentary substratum of the mangrove ecosystem that surrounds the estuary of the Sauípe River (Bahia, Brazil) is presented. Mangrove sediments were collected from six stations from where each sample was collected from the interface water-sediment till the depth of 50 cm and its location was in accordance to the inter-tidal transection in order to characterize the three mangrove stands (proximal, intermediate and distal spatial position in relation to the main river channel). The results are important to subsidize any further studies in this region that require local geochemical references. The substratum of the Sauípe River's mangrove is in accordance with the other mangroves that occur in the Bahia State where there is no evidence of anthropic source of pollution.     

Recent applications of atomic spectroscopy coupled with magnetic solid-phase extraction techniques for heavy metal determination in environmental samples: A review

Atomic spectroscopy is the most popular approach to determine the presence of heavy metals in the environment. Heavy metals are potentially toxic and have various negative effects on many living organisms, including humans. With the rapid increase in the variety of industries and human activities, large amounts of heavy metals are released into the atmosphere, water, and soil. Heavy metal analysis of environmental samples is very important for determining the exposure limits. Environmental samples are highly complex matrices, and various sample preparation techniques have been developed for the extraction of heavy metals from them, including magnetic solid-phase extraction (MSPE). The use of MSPE in heavy metal analysis has recently gained significant attention owing to a number of advantages. MSPE technique overcomes main issues such as phase separation, handling, and column packing. The use of magnetic adsorbents in sample preparation has grown over the past few years, making MSPE a promising technique for sample preparation. The objective of this review article is to provide the latest applications of MSPE coupled with atomic spectroscopy for heavy metal determination in environmental samples. In addition, new magnetic adsorbents and their analytical merits are emphasized.     

One-pot synthesis of a novel magnetic activated carbon/clay composite for removal of heavy metals from aqueous solution

Abstract

In the present work, a novel composite consisting of magnetite, activated carbon from spent coffee grounds and natural clay (MACCC) was prepared by a one-pot synthesis method via a simultaneous activation and magnetization processes. Various techniques (XRD, FTIR, SEM, TEM, EDX, BET) were utilized to characterize the synthesized composite before utilizing it as an adsorbent for removal of Cu(II), Ni(II) and Pb(II) ions from aqueous solutions. Conditions for removal of heavy metals were thoroughly optimized as 25?°C, pH of 5.5, adsorbent dosage of 2?g L^?1, and a contact time of 60?min. Three models of pseudo first-, second-order and intraparticle diffusion as well as three models of Langmuir, Freundlich, and Temkin were used to analyze kinetics and isotherms of the adsorption process. Thermodynamics was discussed completely. Regeneration and recyclability of the adsorbent were also evaluated. Based on the analysis of experimental results, a possible adsorption mechanism of heavy metals onto the synthesized composite was proposed. The maximum capacities caculated from Langmuir model followed the order of Pb(II) > Cu(II) > Ni(II) as 143.56, 96.16 and 84.86?mg·g^?1, respectively. The overall results indicated that MACCC is a potential adsorbent for removal of toxic Pb(II), Cu(II) and Ni(II) ions from wastewater due to simple preparation, high removal efficiency and good recyclability.     

Spatial distribution and accumulation of heavy metals in tidal flat sediments of Shanghai coastal zone

Surface and core sediments from the high, middle and low tidal flats of Shanghai coastal zone were analyzed for heavy metal (e.g. Cu, Pb, Zn, Cr, Cd, Fe, Mn) concentrations. Besides Cd, the concentrations of Cu, Zn, Cr and Pb are 2-5 times higher than their background values and show serious pollution trend due to the direct discharge of industrial and municipal sewage along the Shanghai tidal flat, as well as the wet and dry depositions of industrial dusts. It seems that heavy metals prefer to accumulate and be enriched in the sediments near large sewage outlets, high flats, and the subsurface layer at the depth of 10-30 cm. Several main factors, which include the direct sewage discharge along the tidal flat, tidal hydrodynamic action, large engineering activity, early diagenesis and windstorm tide, are considered to be responsible for influencing spatial distribution patterns of heavy metals in the Shanghai tidal flat.     

Conductance study of the thermodynamics of some transition and heavy metal cryptates in binary acetonitrile-dimethylsulfoxide mixtures

A conductance study of the interaction between Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺, Zn²⁺ and Pb²⁺ ions with cryptands C211, C221 and C222 in different acetonitrile-dimethylsulfoxide mixtures has been carried out at various temperatures. The formation constants of the resulting metal cryptates were determined from the molar conductance-mole ratio data. It was found that the stability of Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ cryptates vary in the order C211>C221>C222, while for Cd²⁺ cryptates the stability order is C221>C222>C211. A linear relationship is observed between logK _f of different metal cryptates and the mole fraction of acetonitrile in the solvent mixture. The enthalpy and entropy of cryptate formation reactions were determined from the temperature dependence of the formation constants. The enthalpy and entropy changes are quite sensitive to the solvent composition and the resultingTS ⁰–H ⁰ plot shows a fairly good linear correlation, indicating the existence of an entropy-enthalpy compensation in the cryptate formation reactions. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82181 (30 pages).     

Seasonal, neap-spring variation of sediment concentration in the joint area between Yangtze Estuary and Hangzhou Bay

An analysis of variations in suspended sediment concentration (SSC) over one year is presented for the joint area between the Yangtze Estuary and the Hangzhou Bay. Results suggest that daily SSC presents periodic variations, which correspond with seasonal and neap-spring tidal cycle. SSCs are higher during the winter season and during spring tides when compared with summer and neap-tide conditions. Furthermore, data indicate that wave and tidal currents are the two dominant factors affecting SSC. Although the Yangtze River discharges abundant sediments to the study area, it does not directly affect concentration variations. But the changing path of the Yangtze River plume plays a certain role in the seasonal variations of SSC. Finally, the calculation of bottom stresses suggests that SSC is a function of both wave and tide-induced resuspension.     

新型重金属离子捕集剂的合成及其对废水中铜离子的捕集作用

以活化硅胶为载体,γ-氯丙基三甲氧基硅烷为偶联剂,由乙二胺和二硫化碳合成了新型的具有螫合功能的氨基硫代甲酸聚合物(EPCR).研究了EPCR用量、pH值、反应时间、温度等对乙二胺四乙酸(EDTA)配合Cu2+溶液中Cu2+去除率的影响,确定了最佳去除条件.结果表明,EPCR对Cu2+的最大吸附量为34.10mmol/g...     

On the evolution of particle size average and size distribution in suspension polymerization processes

The dispersion of methyl methacrylate (MMA) and its suspension polymerization were used as models to elaborate the evolution of particle size average and size distribution in the course of suspension polymerization. The underlying mechanisms for the occurrence of the dynamic and static steady states in the population of drops were defined and their effects on the evolution of drop/particle size average and size distributions were examined. The characteristic intervals of suspension polymerizations (transition, steady-state, growth, and identification) were elaborated. The formation of satellite droplets and their evolution in the course of polymerization were also discussed.     

Effect of particle size in the hydrogenation of crotonaldehyde on supported Pt and Pt-Sn catalysts

The present work reports the effect of metal particle size on the selectivity to crotyl alcohol (S_UOL) in the liquid phase hydrogenation of crotonaldehyde over SiO₂ and a-Al₂O₃-supported Pt and Pt-Sn catalysts. It was demonstrated that, for the monometallic catalysts, a higher particle size led to a higher S_UOL, while for the bimetallic catalysts, this effect was not so important.     

Variations of mercury distribution in the water column during the course of a tidal cycle in the Yangtze Estuarine intertidal zone, China

Tidally induced resuspension processes play an important role in the release of mercury (Hg) into the water column, which increases the risk of Hg exposure to estuarine eco-systems. In order to further understand the geochemical activities of Hg in the intertidal area, the temporal variations of dissolved Hg (Hg D ) and particulate Hg (Hg P ) in the water column during the course of a tidal cycle and its geochemical processes were studied in the southern intertidal zone of the Yangtze Estuary, China. The concentrations of Hg D and Hg P varied between 37-612 ng/L and 51-638 ng/L respectively during the tidal cycle. The increase of Hg D was distinguished at the early flood tide and late ebb tide when the water flow rates were higher. The Hg D concentrations were negatively correlated with Hg P (r = 0.523, p < 0.05) and positively correlated with dissolved organic carbon (DOC) (r = 0.605, p < 0.05) in the bottom water, indicating that the Hg D released from the sediments into the overlying water was associated with the simultaneously released colloidal material in the bottom water. The main pathways for the translocation of Hg from the sediments to the overlying water include the processes of desorption from resuspended particles, advection or diffusion from sediments, and the oxidation of resuspended sulfide. The results of principal components analysis (PCA) and Pearson correlation analysis showed that the combined effects of the total suspended substrate (TSS), DOC, pH and dissolved oxygen (DO) influenced the geochemical activities of Hg in the water column during the course of a tidal cycle.     

Combining multivariate analysis and geochemical approaches for assessing heavy metal level in sediments from Sudanese harbors along the Red Sea coast

Multivariate statistical analysis and geochemical approaches were exploited for the assessment of the level of some heavy metals (Mn, Fe, Ni, Cu, Zn and Pb) in sediments from Sudanese harbors along the Red Sea coast. Principal component analysis, as a multivariate statistical analysis approach, was applied to identify contribution sources by heavy metals in sediments. While a single source (crustal) was recorded in the bulk sediments and coarse sediment grains (grain-size 1000-500 µm), two sources (crustal and anthropogenic) were recorded in fine sediment grains (grain-size < 500 µm). Furthermore, enrichment factor (EF), as a geochemical approach, appointed polluted sites by heavy metals in the study area. Based upon a previous study addressed the interpretation of EF values, minor to moderate anthropogenic enrichment were recorded in sediments from some sites in the study area. The main anthropogenic activities that believed to be the major sources of pollution by heavy metals in the study area are discharges from oil refinery, industry, shipping activity and domestic waste. Hierarchical cluster analysis (HCA), as another multivariate statistical analysis approach, was applied for the concentrations of heavy metals in bulk sediments to group sediments according to their mineralogical composition. The output of HCA is that sediments from the Port-Sudan harbor can be divided mainly into three areas — east, west and south. For the Sawakin harbor, no apparent trend for the spatial distribution of heavy metals in sediments was recorded.     

Influence of particle size on the crystallization process and the bioactive behavior of a bioactive glass system

Bioactive glasses have attracted considerable interest in recent years, due to their technological application, especially in biomaterials research. Differential scanning calorimetry (DSC) has been used in the study of the crystallization mechanism in the SiO₂–Na₂O–CaO–P₂O₅ glass system, as a function of particle size. The curve of the bulk glass presents a slightly asymmetric crystallization peak that could be deconvoluted into two separate peaks, their separation being followed in the form of powder glasses. Also, a shift of the crystallization peaks to lower temperatures was observed with the decrease of the particle size. FTIR studies – that are confirmed by XRD measurements – proved that the different peaks could be attributed to different crystallization mechanisms. Moreover, it is presented the bioactive behavior of the specific glass as a function of particle size. The study of bioactivity is performed through the process of its immersion in simulated human blood plasma (simulated body fluid, SBF) and the subsequent examination of the development of carbonate-containing hydroxyapatite layer on the surface of the particles. The bioactive response is improved with the increase of the particle size of powders up to 80 μm and remains almost unchanged for further increase, following the specific surface to volume ratio decrease.