微塑料去除技术研究现状及进展

微塑料作为一种新型的污染物,由于其粒径小、化学性质稳定不易降解,对水体环境、水生动植物以及人体健康造成了严重威胁,目前尚未形成针对微塑料的标准去除或分离方法。本文通过对国内外与微塑料去除相关的最新技术综述,从物理分离、化学去除、生物去除以及近年新兴的去除技术四个方面进行了系统的分析,同时对各技术适合的工况及优缺点进行了较全面的阐述。传统的物理分离、化学去除和生物去除技术对粒径较大的微塑料具有较好的去除效果,然而对于粒径小于20μm的微塑料无法完全去除;针对改进的传统技术及新兴技术虽然能有效去除微塑料,然而具有较高的成本及研究空白,仍需进一步深入研究和可行性论证。通过本文综述,有助于研究人员了解各类微塑料分离方法的优缺点,在实际处理不同类型微塑料时,为选择合适的去除方法提供借鉴。     

Chromium removal from water using LTA zeolites: effect of pH

The effect of pH changes on the ability of the synthetic zeolite NaA to remove Cr(3+) from water by ion exchange was investigated. The exchange rate was improved by working near neutrality. Despite of the occurrence of simultaneous adsorption, precipitation or cation exchange phenomena, spectroscopic analyses of samples taken at different contact times suggested the presence of an unique chromium environment in the solid phase. The increase in pH observed during the ion exchange favored polymerization-precipitation of chromium species present in solution, which, in turn, improved the metal removal capacity of zeolite NaA above the values expected for a pure cationic exchange reaction.     

Development and optimization of magnetic technologies based processes for removal of some toxic heavy metals

In the developing countries where the cost is often a decisive factor, extensive studies were undertaken to test the most effective factors on the preparation, optimization and validation of the magnetic particles (or, more accurately, magnetizable particles) for removal of heavy metals from wastewaters. The objective of the proposed work was focused to provide promising solid-phase materials, which, are relatively in expensive and combine high surface capacity with fast efficient treatment. Four various metal oxides including hydrous ferric oxide (HFO), hydrous stannic oxide (HSO) and mixed ferric/stannic oxide (HMO), were prepared by precipitation with ammonia from metal chloride solutions. Two mixed oxides were prepared with different Sn/Fe ratios of 50% and 20%. Optimal conditions for the activation of these particles and the subsequent mixing of various metals oxides are tested together with the utility of the method to get a new composite material with developed chemical characteristics over their individual metal oxides. Factors affecting the sorption behavior of the prepared samples in basic and acid media were elucidated. The magnetic treatment procedure using the mixed oxide (50%) enables the equilibration step to be carried out rapidly mainly due to ferric oxide during the magnetization process and efficiently due to high capacity of the stannic oxide. A key factor in achieving very high uptake percentage is the reduction of non-specific binding of various heavy metals to the solid phase support. This is usually achieved by increasing the ion exchange capability, in addition to their adsorption process.     

Chromium(III) removal from water and wastewater using a carboxylate-functionalized cation exchanger prepared from a lignocellulosic residue

This study concerns with the development of a new cation exchanger (SDGPMASPCOOH) carrying spacer (SP) group [CONH(CH(2))(2)NHCO(CH(2))(2)] and carboxylate functional group at the chain end. The preparation process was carried out through graft copolymerization of methacrylic acid onto sawdust, SD (a lignocellulosic residue) using ceric ammonium nitrate as an initiator. The poly(methacrylic acid) grafted SD (SDGPMA) was subsequently treated with thionyl chloride followed by ethylenediamine (transmidation) and succinic anhydride (carboxyfunctionalization) treatments. Infrared spectroscopy and potentiometric titrations were used to confirm graft copolymer formation and carboxylate functionalization. The effectiveness of the SDGPMASPCOOH in removing Cr(III) from water and wastewater was evaluated by the batch technique. The influence of different experimental parameters such as solution pH, contact time, absorbent dose, Cr(III) concentration and temperature on removal process was evaluated. The maximum Cr(III) removal was observed at the initial pH of 7.0. The Cr(III) was removed by SDGPMASPCOOH up to 99.3 and 92.6% from an initial concentration of 10 and 25 mg/L, respectively, at pH 7.0. Equilibrium time was reached within 4 h. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and Elovich equations. The data fitted very well to the pseudo-second-order rate expression. The Langmuir, Freundlich and Temkin equations were applied to the experimental isotherm data and the Langmuir model was found to be in better correlation with the experimental data. The monolayer adsorption capacity for Cr(III) removal was found to be 36.63 mg/g. The adsorption efficiency towards Cr(III) removal was tested using simulated tannery wastewater. The adsorbed Cr(III) on SDGPMASPCOOH can be recovered by treating with 0.1 M HCl. Four adsorption/desorption cycles were performed without significant decrease in removal capacity. The results showed that SDGPMASPCOOH developed in this study exhibited considerable adsorption potential for application in removal of Cr(III) from water and wastewaters.     

稀土元素对铬酵母中铬含量影响的研究

研究了稀土化合物在铬酵母制备过程中对总铬和有机铬含量的影响作用。镧、铈、镨、钕等轻稀土化合物均能明显提高铬酵母中总铬和有机铬的含量 ,其中镧化合物对铬酵母中总铬和有机铬含量的提高作用最显著 ,总铬含量可达到 70 8.33μg·g- 1 ,有机铬含量可达到 6 39.0μg·g- 1 ,是未加稀土铬酵母样品的近 3倍 ;添加钕化合物的铬酵母中有机铬占总铬的比例最高 ,可达到 97.5 %。通过紫外光谱分析 ,发现有机铬在 2 6 0nm处有特征吸收峰 ,通过红外光谱分析 ,发现有机铬在 478cm- 1 处有特征吸收峰 ,而加稀土化合物的铬酵母样品在此两处的吸收峰值均高于未加稀土的铬酵母样品     

稀土铬酵母的制备及其铬含量研究

研究了稀土元素La、Nd、Sm、Er的添加浓度分别为50μg·g-1、75μg·g-1、100μg·g-1和125μg·g-1时对富铬酵母中铬含量的影响 研究结果表明,稀土元素能够提高富铬酵母中的总铬和有机铬含量,当添加100μg·g-1Nd时,富铬酵母中的总铬含量和有机铬含量最高,分别为784.24μg·g-1和755.85μg·g-1,是未加稀土的富铬酵母的3倍以上     

New Chromium Enolates

Three new (η²‐acrylate)(η⁶‐arene)dicarbonylchromium complexes are reported. They were obtained either by CO/acrylate exchange in [Cr(η⁶‐benzene)(CO)₃] ( 1 ) via the photolytically generated η²‐cyclooctene intermediate or by arene exchange in [Cr(η²‐methyl acrylate)(η⁶‐benzene)(CO)₂] ( 3 ) (Scheme 1). On crystallization, [Cr(η²‐methyl acrylate)(η⁶‐o‐xylene)(CO)₂] ( 5 ) underwent partial resolution. The degree of this resolution was analyzed via X‐ray crystal‐structure determination (Fig. 1) and was correlated to the CD spectra in solution (Fig. 6), thus allowing the assignment of the absolute configuration. The reaction of [Cr(η²‐acrylate)(η⁶‐benzene)(CO)₂] complexes with cyclopentad‐1,3‐diene or 1H‐indene afforded new (η⁶‐cyclopenta‐2,4‐dien‐1‐yl)‐ or (η⁶‐1H‐inden‐1‐yl)(η³‐oxaallyl)chromium complexes (Scheme 2). A mechanism is proposed that involves arene‐ligand substitution by the diene ligand, initiated by haptotropic rearrangement of the acrylate from a η²‐ to a η⁴‐coordination mode, followed by hydride migration from the diene to the acrylate (Scheme 3). An X‐ray crystal‐structure determination of [Cr(CO)₂(η⁵‐1H‐inden‐1‐yl){η³‐CH(CH₂CF₃)C(O)OEt}] ( 8 ) reveals a metal enolate that is best described as η³‐oxaallyl species (Fig. 2). A shorter, more‐efficient route to the [Cr(η⁵‐1H‐inden‐1‐yl)(η³‐oxaallyl)] complexes was devised via the reaction of [Cr(CO)₂(η²‐cyclooctene)(η⁶‐1H‐indene)] with methyl acrylate (Scheme 4).     

铬与健康

对铬与人体健康的关系进行了综述，主要内容包括：三价铬的作用、六价铬的作用和环境中的铬。     

Recent advance in microbial fuel cell reactor configuration and coupling technologies for removal of antibiotic pollutants

Microbial fuel cell (MFC) technology, as a biological treatment model that can convert antibiotic pollutants into electrical energy, has attracted extensive attention in recent years. Reactor configuration and coupling process play an important role in the treatment of antibiotic wastewater by the MFC, which will affect microbial activity, pollutant removal, and electricity generation. In this review, recent advances of reactor configuration (single chamber, double chamber, and cylinder) and coupling technology (wetland-MFC, sediment-MFC and membrane-MFC, and so on) of the MFC on treating of antibiotics are summarized, and their characteristics in the aspects of pollutant removal and power output are analyzed. Finally, through comparing removal quantity (mg antibiotics per day), the double chamber MFC as the individual treatment unit and the membrane-MFC exhibit better removal quantity.     

Chromium(III) and Chromium(IV) Tetraphenylporphine Complexes

Stable chromium complex (AcO)CrTPP was synthesized through the reaction of meso-tetraphenylporphine with chromium(III) acetate in boiling phenol. Coordination properties of chromium porphyrin in reaction with imidazole and pyridine in o-xylene were studied by electronic absorption spectroscopy and computer modeling. A single-electron oxidation of chromium(III) complex was found to be affected by peroxide compounds. The stability of an extra complex depends on the basic properties of the extra ligand and oxidation number of the central metal atom. The complex stability correlates with the calculated energy of formation of the metal–extra ligand bond. The geometrical structure and energy parameters of hexacoordinated chromium porphyrins were calculated using the quantum-chemical method. The effect of the cis and trans position of ligands in the composition of a macrocyclic compound was established to be significant only in the extra complexes (AcO)CrTPP.     

铬与人体健康研究

对铬与人体健康关系作了综述，包括：铬作为人体必需微量元素的生理功能，葡萄糖耐量因子定义和结构推测，以及与人体健康有关的生理临床作用研究进展状况，以引起更多的科技工作者对这一领域的关注和重视。     

Chromium carbides and cyclopropenylidenes

Carbon tetrabromide can be reduced with CrBr₂ in THF to form a dinuclear carbido complex, [CrBr₂(thf)₂)][CrBr₂(thf)₃](μ-C), along with formation of [CrBr₃(thf)₃]. An X-ray diffraction (XRD) study of the pyridine adduct displayed a dinuclear structure bridged by a carbido ligand between 5- and 6-coordinate chromium centers. The carbido complex reacted with two equivalents of aldehydes to form α,β-unsaturated ketones. Treatment of the carbido complex with alkenes resulted in a formal double-cyclopropanation of alkenes by the carbido moiety to afford spiropentanes. Isotope labeling studies using a ¹³C-enriched carbido complex, [CrBr₂(thf)₂)][CrBr₂(thf)₃](μ-¹³C), identified that the quaternary carbon in the spiropentane framework was delivered by carbide transfer from the carbido complex. Terminal and internal alkynes also reacted with the carbido complex to form cyclopropenylidene complexes. A solid-state structure of the diethylcyclopropenylidene complex, prepared from 3-hexyne, showed a mononuclear cyclopropenylidene chromium(iii) structure.

Carbon tetrabromide can be reduced with CrBr₂ in THF to form a dinuclear carbido complex, [CrBr₂(thf)₂)][CrBr₂(thf)₃](μ-C), along with formation of [CrBr₃(thf)₃].     

铬与人体健康

介绍了铬的生理功能,指出三价铬是人体必需的微量元素,六价铬则是严重危害人体健康的有害元素,必须适量补铬和严防六价铬的中毒,才能维持人体健康。     

铬和环境保护

重金属污染是当今世界必须解决的环境污染问题之一。重金属进入环境后不易除去,它们在环境中迁移、转化和长期累积,对生物和人体产生毒害作用。本文侧重谈一谈重金属铬的污染和环境保护问题。