Interaction of Humic Substances with Organic Pollutants and its Influence on the Concentration of these Pollutants from Water

Abstract

The influence of fulvic acids (FAs) and humic acids (HAs) of different origin on liquid-liquid and solid-phase extraction of hydrophobic organic compounds (HOCs) with broadly varying values of octanol-water partition coefficients K_ow has been investigated. It is shown that the solubilization by dissolved FAs and HAs can lead to a significant decrease in recovery of some HOCs even from very dilute (10–20 mg/l) aqueous solutions of these acids. The results of these investigations and an analysis of the relevant literature data, demonstrate that the extent of solubilization of HOCs by humic substances is determined not only by K_ow, but also by the specific structure of the HOCs. The hypothesis of the formation of intramolecular micelles (IMMs) by unaggregated FAs and HAs, and the partition of HOCs between water and the IMMs is put forward to explain the solubilization of HOCs.     

腐植酸与环丙沙星结合机制的多维光谱学解析研究

本工作研究了水环境中残留喹诺酮类抗生素环丙沙星(ciprofloxacin, CIP)与溶解有机物(dissolved organic matter, DOM)腐植酸(humic acid, HA)的结合作用机理. 采用三维荧光、傅里叶红外光谱、二维相关光谱和液体核磁共振氢谱等技术进行表征分析. 结果表明, CIP和HA的结合作用会产生明显的荧光淬灭现象, 且在6 h后结合开始趋于平衡. 结合作用与HA表面的羟基、羧基以及酮基等官能团相关, 而CIP分子哌嗪环上的H质子是参与结合的主要位点. 此外, 影响因素实验表明, 离子强度(ionic strength, IS)对结合作用影响较小, 而pH对其影响较大, 且在pH=5时荧光淬灭率最高. 荧光淬灭率与金属离子价态呈现正相关. 通过研究水体中CIP和HA的相互作用, 对于监测研究天然水体中残留抗生素的迁移和转化提供理论依据.     

Attempts to Characterize the Degradation Products of a Humic Acid-Evidence for Glucides and Amino Acids

Abstract

We have succeeded in completely bleaching a humic acid, extracted from peats and carefully purified, by the action of the peroxoacids, followed by a chlorhydric or enzymic hydrolysis. The degradation products characterized by chromatographic analysis on paper, and by GLC after silylation, contain 3 reducing sugars (glucose, rhamnose, arabinose), a disaccharide and 8 amino acids among which are lysine, serine and tyrosine. The reducing sugar content of the mixture (expressed in glucose) corresponds to a yield of 65% relative to the initial product.     

氮缺陷石墨相氮化碳的制备及其光催化降解环境有机污染物性能

通过在三聚氰胺热分解过程中加入NaHCO₃制备出具有氮缺陷的石墨相氮化碳（g-C₃N₄）,利用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、N₂吸附-脱附、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征,并在可见光（λ> 420nm）照射下,以水相中罗丹明B（RhB）的降解为模型反应,研究了该氮缺陷g-C₃N₄对有机污染物降解的光催化活性。结果表明,引入氮缺陷可以提高g-C₃N₄对可见光的吸收以及电子-空穴对的分离效率,进而提高g-C₃N₄的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30min内对RhB的降解率分别为79.8%、100.0%和87.6%;而在相同条件下,没有氮缺陷的g-C₃N₄对RhB的降解率仅为59.8%。     

Efficient Fe/CuFeO2/rGO nanocomposite catalyst for electro‐Fenton degradation of organic pollutant: Preparation,characterization and optimization

The nanocomposite of zero‐valent iron and delafossite CuFeO₂ supported on reduced graphene oxide was synthesized for the first time to evaluate its performance as the heterogeneous catalyst toward electro‐Fenton (EF) removal of catechol. X‐ray diffraction, Fourier transform‐infrared, scanning electron microscopy and Brunauer–Emmett–Teller (BET) were used to characterize the nanocomposite. It was found that the rhombohedral structure of CuFeO₂ remained stable during the nanocomposite preparation. The BET surface area of the nanocomposite increased about 102 times in comparison with bare CuFeO₂. The influence of the operating parameters was investigated. The optimum operating conditions were pH 3, Fe/CuFeO₂/rGO: 1 g/l; catechol: 7.5 × 10^?4 mol/l; and I: 150 mA, which led to 99% and 78.4% catechol and chemical oxygen demand removal in 120 min, respectively. The stability of the catalyst by leaching measurements was studied. Only 2% and 3.1% of iron and copper, respectively, was leached in the solution. The obtained results introduced Fe/CuFeO₂/rGO as a stable and appropriate catalyst for removal of organic compounds by the EF process. It was inferred from the scavenger utilization that hydroxyl radical plays a major role in catechol elimination and EF reaction followed by the Haber–Weiss mechanism at optimum conditions. The gas chromatography–mass spectrometry analysis was performed to detect the intermediate products, and an acceptable degradation pathway was proposed. The EF degradation of catechol follows a pseudo‐first‐order kinetics model with a rate constant of 3.69 × 10^?2 min^?1 for the optimum operating conditions. The reusability of Fe/CuFeO₂/rGO was investigated for six cycles, and the catalytic efficiency almost remained.     

Modelling photochemical transformation of emerging organic pollutants in surface waters: effect of water level fluctuations following outflow or evaporation,relevant to arid and semi-arid environments

Water bodies located in arid and semi-arid environments undergo important fluctuations of the water level, and water loss in the dry season may occur through phenomena such as outflow and evaporation. Water scarcity often exacerbates the impact of pollution, because harmful compounds can reach very high concentration values in the presence of relatively low water volumes. Among self-cleansing (depollution) processes of water bodies, photochemical reactions are expected to play an important role in pollutant attenuation, although sometimes they yield harmful intermediates. In this work, the effects of water-level fluctuations on photochemical reactions were studied by means of a modelling approach. The model applies to well-mixed water bodies, such as the shallow ones that are more likely to undergo fluctuations of the water level. We investigated how water outflow and evaporation (as well as a mixed scenario) might modify the steady-state concentrations of the most important photoreactive transients (^?OH, CO₃^–?, ¹O₂ and triplet states of chromophoric dissolved organic matter, ³CDOM*). Under the same conditions, the possible phototransformation of emerging pollutants such as carbamazepine, ibuprofen, 2,4-dichloro-6-nitrophenol and 2,4-dinitrophenol was also assessed. It is shown that water loss would generally enhance photochemical reactions, but to a variable extent depending on the actual pathway. Outflow would favour all photoprocesses, and particularly those involving ^?OH and CO₃^–?. Conversely, evaporation would enhance reaction with ¹O₂ and ³CDOM* while having practically no effect on ^?OH, CO₃^–? and direct photolysis. Enhancement of photochemical self-cleansing of water bodies would partially reduce the pollution impact, but in some cases harmful compounds may be generated.     

水热pH值对溴氧化铋组成、形貌及光催化性能的影响

通过调节pH值一步水热法制备溴氧化铋光催化剂,并利用X射线衍射（XRD）、扫描电镜（SEM）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征。在可见光（γ>420 nm）照射下,通过对水溶液中罗丹明B,甲基橙和苯酚的降解效果来评价溴氧化铋的光催化活性。结果表明,由于B9提高了对可见光的吸收以及电子-空穴对的分离效率,B9具有最好的光催化活性,同时探索水热pH值对制备溴氧化铋的形貌和组成的影响,并说明了不同水热pH值下溴氧化铋的合成过程。     

Photodegradation of C‐PCPDTBT and Si‐PCPDTBT: Influence of the Bridging Atom on the Stability of a Low‐Band‐Gap Polymer for Solar Cell Application

The kinetics of photodegradation and the reactivity of different sites of the low‐band‐gap polymers poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (C‐PCPDTBT) and poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (Si‐PCPDTBT) are investigated as thin films and are compared to those of poly(3‐hexylthiophene) (P3HT). The decay kinetics are monitored with UV/Vis spectroscopy and the reactivity and product evolution are investigated with X‐ray photoelectron spectroscopy (XPS). Both polymers exhibit higher stability than P3HT. The bridging atom in the cyclopentadithiophene (CPDT) subunit has a significant influence on the stability. Varying oxidation rates for the different elements were observed. In the case of Si‐PCPDTBT, the silicon atom is oxidized primarily, whereas the photooxidation rates of the other elements are reduced relative to C‐PCPDTBT. Additionally, XPS experiments with varying excitation energies reveal a significant reaction gradient within a few nanometers of the surface of degraded thin films of C‐PCPDTBT.     

Porous Aerogels and Adsorption of Pollutants from Water and Air: A Review

Aerogels are open, three-dimensional, porous materials characterized by outstanding properties, such as low density, high porosity, and high surface area. They have been used in various fields as adsorbents, catalysts, materials for thermal insulation, or matrices for drug delivery. Aerogels have been successfully used for environmental applications to eliminate toxic and harmful substances—such as metal ions or organic dyes—contained in wastewater, and pollutants—including aromatic or oxygenated volatile organic compounds (VOCs)—contained in the air. This updated review on the use of different aerogels—for instance, graphene oxide-, cellulose-, chitosan-, and silica-based aerogels—provides information on their various applications in removing pollutants, the results obtained, and potential future developments.     

Determination of Phenols,Inorganic Anions,and Carboxylic Acids in Kraft Black Liquors by Capillary Electrophoresis

Two methods are presented for the quantitative capillary electrophoretic (CE) determination of phenolic lignin degradation compounds as well as of inorganic anions and organic acids in Kraft black liquors. Important phenolic lignin degradation compounds can be rapidly separated by co-electroosmotic CE after acidification of the liquors and subsequent extraction of the compounds with chloroform. A capillary electrophoretic separation of phenolic compounds is performed by using a phosphate/borate electrolyte system and UV detection at 214 nm. In addition, a HPLC method using a gradient with water, methanol, and acetic acid is also developed. Inorganic ions which are of importance to the pulping process can be determined by simply diluting the black liquors after sampling and subsequent analysis with a chromate electrolyte system and indirect UV detection at 185 nm. In addition, the concentration of low molecular aliphatic carboxylic acids can be determined simultaneously within the same run. By method optimization it is possible to separate the anions within one minute and, at the same time, to increase the resolution of the solutes. The electrolyte systems for the CE separations were optimized by varying the pH value and by adding organic solvents. Short separation times are obtained by adding a polycationic EOF modifier (hexadimethrine bromide) to the electrolyte which reverses the electroosmotic flow. A migration of the anionic analytes in the same direction as the electroosmotic flow is thus established.     

Enhanced Recyclability,Stability, and Selectivity of CdS/C@Fe3O4 Nanoreactors for Orientation Photodegradation of Ciprofloxacin

A unique CdS/C@Fe₃O₄ nanoreactor was fabricated by the surface‐imprinting technique, which effectively enhances the recyclability, stability, and selectivity for orientation recognition and photodegradation of ciprofloxacin in the binary mixed solution under visible‐light irradiation. This work not only puts forward a novel design idea that develops the potential application value of CdS, but also provides a new approach for inhibiting its secondary pollution.     

Synthesis of methyl sulfomycinate, sulfomycinic amide and sulfomycinine, degradation products of the sulfomycin thiopeptide antibiotics

The convergent synthesis of methyl sulfomycinate and sulfomycinic amide, two acidic methanolysis products of the sulfomycin thiopeptide antibiotics, is achieved starting from diethoxyacetonitrile. Further confirmation of structure is obtained by heating methyl sulfomycinate at 110 °C in hydrochloric acid to give (±)-sulfomycinine hydrochloride, the acid hydrolysate of sulfomycin I.     

还原-氧化协同降解全/多卤代有机污染物

全/多卤代有机污染物大多具有生态毒性、生物蓄积性、环境持久性及长距离迁移性,不仅危害环境与生态安全,而且可经食物链传递威胁人类健康。由于卤原子是吸电子基团且取代数目多,这类物质的最高占据分子轨道能较低,难于被氧化降解,相反较易被还原法脱卤降解。随卤原子取代数减少,脱卤产物难被进一步还原,而其毒性甚至高于母体污染物。注意到低卤代有机物更容易发生氧化降解,一些研究构建了还原-氧化接力降解体系,即先利用还原法将全/多卤代有机污染物还原为低卤代产物,再利用氧化法降解这些中间产物,从而实现深度/完全脱卤和矿化。本文根据催化反应类型对还原-氧化联用法进行了归纳,分类介绍了基于传统化学催化、光催化、电化学、光电化学及机械化学等构建还原-氧化协同降解体系的原理及应用,以期为开发高效的处置技术提供思路和建议。     

Spatiotemporal Distribution and Analysis of Organophosphate Flame Retardants in the Environmental Systems: A Review

In recent times, there has been a cumulative apprehension regarding organophosphate flame retardants (OPFRs) owing to their high manufacturing and usage after brominated flame retardants were strictly regulated and banned from being distributed and used in many countries. OPFRs are known as the main organic pollutants in the terrestrial and aquatic environment. They are very dangerous to humans, plants and animals. They are also carcinogenic and some have been implicated in neurodevelopmental and fertility challenges. OPFRs are distributed into the environment through a number of processes, including the usage, improper disposal and production of materials. The solid phase extraction (SPE) method is suggested for the extraction of OPFRs from water samples since it provides high quality recoveries ranging from 67% to 105% and relative standard deviations (RSDs) below 20%. In the same vein, microwave-assisted extraction (MAE) is highly advocated for the extraction of OPFRs from sediment/soil. Recoveries in the range of 78% to 105% and RSDs ranging from 3% to 8% have been reported. Hence, it is a faster method of extraction for solid samples and only demands a reduced amount of solvent, unlike other methods. The extract of OPFRs from various matrices is then followed by a clean-up of the extract using a silica gel packed column followed by the quantification of compounds by gas chromatography coupled with a mass spectrometer (GC–MS) or a flame ionization detector (GC-FID). In this paper, different analytical methods for the evaluation of OPFRs in different environmental samples are reviewed. The effects and toxicities of these contaminants on humans and other organisms are also discussed.     

铁基金属-有机骨架及其复合物高级氧化降解水中新兴有机污染物

新兴有机污染物(Emerging organic contaminants,EOCs)是对人体健康及生态环境具有潜在或实质威胁的新型化学污染物.由于其被频繁使用且能在水生生态系统中持久性存在而对水生生物健康和安全造成严重威胁,故引起大众越来越多的关注.以活性污泥法为代表的传统水处理工艺通常不足以消除这些新兴有机污染物....