Removal of fluoride from water using titanium-based adsorbents

Three adsorbents including TiO₂, Ti-Ce, and Ti-La hybrid oxides were prepared to remove fluoride from aqueous solution. The Ti-Ce and Ti-La hybrid adsorbents obtained by the hydrolysis-precipitation method had much higher sorption capacity for fluoride than the TiO₂ adsorbent prepared through hydrolysis. Rare earth (Ce and La) oxides and TiO₂ exhibited a synergistic effect in the hybrid adsorbents for fluoride sorption. The sorption equilibrium of fluoride on the three adsorbents was achieved within 4 h, and the pseudo-second-order model described the sorption kinetics well. The sorption isotherms fitted the Langmuir model well, and the adsorption capacities of fluoride on the Ti-Ce and Ti-La adsorbents were about 9.6 and 15.1 mg·g^-1, respectively, at the equilibrium fluoride concentration of 1.0 mg·L^-1, much higher than the 1.7 mg·g^-1 on the TiO₂. The sorption capacities of fluoride on the three adsorbents decreased significantly when the solution pH increased from 3 to 9.5. The electrostatic interaction played an important role in fluoride removal by the three adsorbents, and Fourier transform infrared (FTIR) analysis indicated that the hydroxyl groups on the adsorbent surface were involved in fluoride adsorption.     

Fabrication of magnetic multi-template molecularly imprinted polymer composite for the selective and efficient removal of tetracyclines from water

• Magnetic multi-template molecularly imprinted polymer composite was synthesized. • MIP composite was used as the adsorbent for removal of tetracyclines from water. • MIP composite showed excellent adsorption selectivity toward tetracyclines. • MIP composite possessed good reusability. Antibiotic contamination of the water environment has attracted much attention from researchers because of their potential hazards to humans and ecosystems. In this study, a multi-template molecularly imprinted polymer (MIP) modified mesoporous silica coated magnetic graphene oxide (MGO@MS@MIP) was prepared by the surface imprinting method via a sol-gel process and was used for the selective, efficient and simultaneous removal of tetracyclines (TCs), including doxycycline (DC), tetracycline (TC), chlorotetracycline (CTC) and oxytetracycline (OTC) from water. The synthesized MIP composite was characterized by Fourier transform infrared spectroscopy, transmission electron microscope and thermogravimetric analysis. The adsorption properties of MGO@MS@MIP for these TCs were characterized through adsorption kinetics, isotherms and selectivity tests. The MIP composite revealed larger adsorption quantities, excellent selectivity and rapid kinetics for these four tetracyclines. The adsorption process was spontaneous and endothermic and followed the Freundlich isotherm model and the pseudo-second-order kinetic model. The MGO@MS@MIP could specifically recognize DC, TC, CTC and OTC in the presence of some chemical analogs. In addition, the sorption capacity of the MIP composite did not decrease significantly after repeated application for at least five cycles. Thus, the prepared magnetic MIP composite has great potential to contribute to the effective separation and removal of tetracyclines from water.     

全氟辛烷磺酸盐(PFOS)对其它有机污染物在沉积物上吸附的影响

采用平衡振荡实验方法,研究了不同浓度的全氟辛烷磺酸盐(PFOS)对两种有机污染物(硝基苯和菲)在沉积物上吸附的影响.结果表明,单组分PFOS在沉积物上是非线性吸附;与其它有机污染物共存时,随着PFOS浓度的升高,硝基苯的吸附量先减少后增加,而菲的吸附量则先增加后减少.PFOS对其它有机污染物吸附的影响规律与有机污染物的...     

全氟化合物在阳离子表面活性剂改性碳纳米管上的吸附

采用两种阳离子表面活性剂,四丁基溴化铵(TBA)及聚乙烯亚胺(PEI)对碳纳米管进行改性,并研究了全氟辛酸(PFOA)、全氟辛烷磺酸盐(PFOS)、全氟己烷磺酸盐(PFHxS)在改性碳纳米管上的吸附行为.研究结果显示,除PFOS在TBA修饰的碳纳米管(TBA-MWCNTs)上的吸附等温线呈线性外,全氟化合物在原碳纳米管(Pri-MWCNTs)、TBA-MWCNTs及PEI修饰的碳纳米管(PEI-MWCNTs)上的吸附均为非线性.吸附等温线可以用Freundlich及Langmuir模型拟合.与Pri-MWCNTs相比,PEI-MWCNTs的零电荷点(pHzpc)增加了6.2个单位,全氟化合物的吸附系数Kd值增加2—3倍;而TBA-MWCNTs的pHzpc增加了1.0个单位,PFOS在高平衡浓度下的Kd值增加了两倍.随着溶液pH值的降低,全氟化合物在Pri-MWCNTs和PEI-MWCNTs上的吸附量有所增加,而在TBA-MWCNTs上的吸附受pH值的影响不大.这说明疏水作用及静电作用是全氟化合物在Pri-MWCNTs和PEI-MWCNTs上吸附的主要机制,而疏水作用则为TBA-MWCNTs上吸附的主要机制.与单溶质体系相比,PFOS与PFOA同时存在时二者在PEI-MWCNTs上吸附的Kd值均有所减小,且PFOA的减小程度大于PFOS.PFOS在TBA-MWCNTs上吸附的Kd值在高浓度下几乎不受PFOA的影响.     

水滑石及其焙烧产物对阴离子染料酸性蓝-80的吸附

研究了水滑石(HT)及其焙烧产物(HTC)对阴离子染料酸性蓝-80的吸附特征.结果表明,在常见染料废水浓度范围内,HTC的吸附量和吸附速率都明显大于HT,HTC的吸附等温线和动力学分别符合Langmuir等温方程和粒间扩散模型.HTC对阴离子染料的去除受无机阴离子(Cl-, SO2-4 和CO2-3)的影响较小,阴离子表面活性剂十二烷基硫酸钠(SDS)的存在能明显降低酸性蓝-80的吸附量.吸附量随温度的升高明显下降.     

Effect of co-existing organic compounds on adsorption of perfluorinated compounds onto carbon nanotubes

Co-existing organic compounds may affect the adsorption of perfluorinated compounds (PFCs) and carbon nanotubes in aquatic environments. Adsorption of perfluorooctane sulfonate (PFOS), perfluorooctane acid (PFOA), perfluorobutane sulfonate (PFBS), and perfluorohexane sulfonate (PFH_xS) on the pristine multi-walled carbon nanotubes (MWCNTs-Pri), carboxyl functionalized MWCNTs (MWCTNs-COOH), and hydroxyl functionalized MWCNTs (MWCNTs-OH) in the presence of humic acid, 1-naphthol, phenol, and benzoic acid was studied. Adsorption kinetics of PFOS was described well by the pseudo-second-order model and the sorption equilibrium was almost reached within 24 h. The effect of co-existing organic compounds on PFOS adsorption followed the decreasing order of humic acid>1-naphthol>benzoic acid>phenol. Adsorbed amounts of PFOS decreased significantly in the presence of co-existing or preloaded humic acid, and both adsorption energy and effective adsorption sites on the three MWCNTs decreased, resulting in the decrease of PFOS adsorption. With increasing pH, PFOS removal by three MWCNTs decreased in the presence of humic acid and phenol. The adsorbed amounts of different PFCs on the MWCNTs increased in the order of PFBSxS相似文献   

Characterization of interaction between different adsorbents and copper by simulation experiments using sediment-extracted organic matter from Taihu Lake,China

The complex capacity of different types of organic matters （OMs） for Cu was quantitatively studied by simulation experiments using different adsorbents prepared from the sediment in Taihu Lake. The free Cu was measured with ion selective electrode （ISE） and complex capacity was calculated using a conditional formation constant model. The result indicated that the complex capacity was 0.048 mmol·g-1, 0.009 and 0.005 mmol.g-1for raw sediment, sediment without DOM, sediment without insoluble organic matters but with DOM and sediment without OM. Insoluble organic matter played a major role in the sorption of Cu in sediment and it can adsorb most Cu from water column. In the solution, Cu mainly existed as a complex with DOM and the DOM-Cu complexation capacity was 327.87 mg. g-1. The change of TOC and pH indicated ion-exchange in the interaction between free Cu and DOM. When the Cu concentration in the experiment reached the complex capacity of DOM, precipitation was the major mechanism to remove Cu from water phase, which was observed from UV absorbance change of DOM, that is, its aromaticity increased while molecular weight decreased. The desorption result indi- cated that DOM was more capable of desorbing Cu from adsorbents without OM than adsorbent with OM. The desorbed quantity with DOM was 1.65, 1.78 and 2.25 times higher than that with water for adsorbents without OM, raw adsorbents （sediment） and adsorbents without DOM.     

北京水源地鱼体全氟化合物的暴露水平及其健康风险

全氟化合物(PFASs)作为一类新型的有机污染物,因具有持久性、可长距离传输、生物蓄积性和生物毒性等POPs特性,近年来得到全世界的广泛关注。本文以北京市水源地(密云水库和官厅水库)为研究区域,采用固相萃取(SPE)前处理与高效液相色谱串联质谱联用(HPLC-MS/MS)相结合的方法,分析测定了鱼样品中包括全氟辛烷磺酸(PFOS)、全氟辛酸(PFOA)、全氟丁酸(PFBA)、全氟丁烷磺酸(PFBS)等在内的12种PFASs的含量。利用同位素法确定了不同种类鱼的营养级关系,研究不同营养级中的PFASs浓度及生物放大效应,重点对全氟辛烷磺酸(PFOS)与全氟辛酸(PFOA)的生态风险以及对人体的健康风险进行评价。结果表明:北京市水源地的鱼体中的PFASs存在不同程度的检出,其中,全氟辛烷磺酸(PFOS)、全氟辛酸(PFOA)、全氟壬酸(PFNA)、全氟癸酸(PFDA)、全氟十一酸(PFUdA)和全氟十二酸(PFDoA)的检出率均达到100%,PFASs总量浓度达1.70~14.32 ng·g~(-1) wet weight(w.w.),PFOS和长链全氟羧酸PFCAs是鱼体中的主要污染物。同位素鉴定水库鱼的营养级层次范围在2.11~4.10,且肉食性鱼类营养级大多高于杂食性鱼类,PFOS沿着食物链生物放大的过程与稳定碳氮同位素富集过程基本同步。此外,采用人均日摄入量法(average daily intake,ADI)评估得到PFOS与PFOA的风险值分别为1.16 ng·kg~(-1)·d~(-1)和0.31ng·kg~(-1)·d~(-1),整体低于人均每天可承受摄入量(tolerable daily intake,TDI),结果表明,北京水源地鱼体中PFOS和PFOA含量未达到对生态系统和人体健康具有风险的水平。     

A review of spatial and temporal assessment of PFOS and PFOA contamination in China

The current state of concentrations of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in China is presented. While products that are known to degrade to either PFOS or PFOA have been used in China, concentrations in environmental media have been reported to be relatively low across China. Greater concentrations of PFOS and PFOA were observed in southern and eastern China than in other areas of China. Concentrations of PFOS and PFOA were relatively great in the Huangpu River, with concentrations of 20.5 ng l^?1 and 1590 ng l^?1, respectively. Surface waters of Dongguan and Shanghai were more contaminated by PFOS and PFOA than that of other cities. Dongguan was the only city in China in which PFOS value in surface water exceeded the water quality criterion, while PFOA concentration in Shanghai was 152 ng l^?1. Similar to other contaminants, point-source pollution was also the common pattern of PFOS and PFOA contamination. Concentrations of PFOS in human blood in China were relatively greater in China than other countries, with drinking water contamination given as the most likely source. Concentrations of PFOS in human blood have increased from the 1980s to the 2000s, while such a trend was not observed for PFOA.     

Methods to prepare biosorbents and magnetic sorbents for water treatment: a review

Access to drinkable water is becoming more and more challenging due to worldwide pollution and the cost of water treatments. Water and wastewater treatment by adsorption on solid materials is usually cheap and effective in removing contaminants, yet classical adsorbents are not sustainable because they are derived from fossil fuels, and they can induce secondary pollution. Therefore, biological sorbents made of modern biomass are increasingly studied as promising alternatives. Indeed, such biosorbents utilize biological waste that would otherwise pollute water systems, and they promote the circular economy. Here we review biosorbents, magnetic sorbents, and other cost-effective sorbents with emphasis on preparation methods, adsorbents types, adsorption mechanisms, and regeneration of spent adsorbents. Biosorbents are prepared from a wide range of materials, including wood, bacteria, algae, herbaceous materials, agricultural waste, and animal waste. Commonly removed contaminants comprise dyes, heavy metals, radionuclides, pharmaceuticals, and personal care products. Preparation methods include coprecipitation, thermal decomposition, microwave irradiation, chemical reduction, micro-emulsion, and arc discharge. Adsorbents can be classified into activated carbon, biochar, lignocellulosic waste, clays, zeolites, peat, and humic soils. We detail adsorption isotherms and kinetics. Regeneration methods comprise thermal and chemical regeneration and supercritical fluid desorption. We also discuss exhausted adsorbent management and disposal. We found that agro-waste biosorbents can remove up to 68–100% of dyes, while wooden, herbaceous, bacterial, and marine-based biosorbents can remove up to 55–99% of heavy metals. Animal waste-based biosorbents can remove 1–99% of heavy metals. The average removal efficiency of modified biosorbents is around 90–95%, but some treatments, such as cross-linked beads, may negatively affect their efficiency.

     

Optimisation of bisphenol A removal from water using chemically modified pine bark and almond shell

The ability of pine bark and almond shells to remove bisphenol A (BPA) from aqueous solutions was evaluated. Samples of these traditional agro-forestry by-products were milled, sieved into different particle size fractions (0.10–0.15 and 1.5–2.0 mm) and submitted to two different types of treatment. Sorption experiments were conducted in a batch system at room temperature and natural pH. Sorption equilibrium was attained after 48 h for all systems under study. Bisphenol A was adsorbed more effectively on the smaller particles of the sorbents. Pine bark and almond shell pretreated with formaldehyde presented higher sorption efficiency (95%), followed by almond shell (87%) and pine bark (82%) washed with hot water. All the sorption isotherms were found to fit a Freundlich equation, with correlation coefficients (R ²) between 0.823 and 0.989. The sorption coefficient (K _F) ranged from 0.06 to 0.74 (mg^1?1/n ·L ^1/n ·g ^?1). These results indicate that utilisation of both materials as an alternative sorbent for the removal of bisphenol A from contaminated waters is promising because they are available in large amounts and have an acceptable cost–efficiency ratio when compared with traditional adsorbents.     

Kinetic and mechanism studies of the adsorption of lead onto waste cow bone powder (WCBP) surfaces

This study examines the adsorption isotherms, kinetics and mechanisms of Pb2(+) sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb2(+) in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb2(+) with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca2(+) and PO?3? concentrations during the metal sorption processes. The Pb2(+) sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb(+). The sorption isotherm results indicated that Pb2(+) sorption onto the Langmuir and Freundlich constant q(max) and K( F ) is 9.52 and 8.18 mg g?1, respectively. Sorption kinetics results indicated that Pb2(+) sorption onto WCBP was pseudo-second-order rate constants K? was 1.12 g mg?1 h?1. The main mechanism is adsorption or surface complexation (≡POPb(+): 61.6%), co-precipitation or ion exchange [Ca?(.)?? Pb?(.)?? (PO?)? (OH): 21.4%] and other precipitation [Pb 50 mg L?1 and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb2(+) removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb2(+) indicates its potential as another promising way to remediate Pb2(+)-contaminated media.     

4种短链全氟化合物替代物在城市污水处理厂的污染特征研究

全氟辛烷羧酸(perfluorooctanoic acid,PFOA)和全氟辛烷磺酸(perfluorooctyl sulfonate,PFOS)等长链全氟化合物(perfluorinated compounds,PFCs)具有持久性、生物累积性和毒性,近年来发现一些短链PFCs具有相对较短的半衰期,可以成为PFOA和PFOS的替代品,这些物质包括C4和C6结构的PFCs,如全氟丁烷羧酸(perfluorobutanoic acid,PFBA)、全氟己烷羧酸(perfluorohexanoic acid,PFHx A)、全氟丁烷磺酸(perfluorobutyl sulfonate,PFBS)和全氟己烷磺酸(perfluorohexyl sulfonate,PFHx S)。为解析我国城市污水厂短链PFCs污染水平和地域分布特征,本研究调查了我国不同地区17座城市污水处理厂的进水、二沉出水和污泥中4种短链PFCs的分布和浓度水平。结果表明4种短链PFCs、PFOA和PFOS在17座污水厂进水中检出率均为100%(6种目标物单体浓度范围:0.19~274.72 ng·L-1);污泥中PFOS和PFOA检出率为100%(PFOS:2.08~72.31 ng·g-1,PFOA:1.03~24.81 ng·g-1),PFBA、PFHx A检出率为100%(0.60~3.33 ng·g-1),PFBS和PFHx S的检出率分别为42.11%和63.16%。在污水厂进水中,将PFOA和PFOS与其同类的短链PFCs浓度进行比较,发现短链PFCs分别相对于PFOA和PFOS的比例最高可达93.47%和94.57%。4种短链PFCs、PFOA和PFOS的地域分布差异明显,总浓度呈现出华东、华南地区高于西北、东北、华北地区的趋势,其中华东地区调查的污水处理厂浓度最高。污水厂4种短链替代物主要通过污水排放,不同污水厂的日排放总量(污泥和出水)为0.25~273.07 g·d-1,万吨水排放量范围为0.04~1.37 g。研究将为我国全氟化合物替代物污染和控制提供数据基础和科学依据。     

全氟辛烷磺酸（PFOS）急性暴露对斑马鱼鳃显微结构的影响

采用光镜和电镜的方法,探讨了高浓度全氟辛烷磺酸(PFOS)急性暴露对斑马鱼(Danio rerio)鳃显微结构的影响.暴露组PFOS浓度分别为0.5、1、2mg·L-1,同时设对照组,连续暴露7d,取鳃制备石蜡切片,进行光镜和扫描电镜观察.结果表明,7d后PFOS暴露组斑马鱼鳃部均有不同程度的损伤,石蜡切片上可观察到暴露组鱼鳃上皮细胞坏死脱落,鳃小片断裂或融合,并伴有鳃丝充血,且病变程度随PFOS浓度的升高而加重;扫描电镜下可观察到暴露组鱼鳃鳃丝表面分泌物增多,鳃丝细胞脱落或水肿,鳃小片前端细胞破损.高浓度PFOS急性暴露可在短期内对斑马鱼鳃组织造成严重损伤,且损伤程度存在剂量依赖效应.     

我国削减并逐步替代全氟辛烷磺酸盐(PFOS)的策略与建议

全氟辛烷磺酸盐(PFOS)具有低表面张力、良好的热稳定性和化学稳定性等特性,作为含氟表面活性剂被广泛应用于卫生、消防与电镀等工业领域。但是,PFOS具有高持久稳定性,会在环境、人体与动物组织中富集,因此2009年《斯德哥尔摩公约》将PFOS列为新增POPs受控物质。目前,我国还在生产和使用PFOS,如何对其进行有效控制,削减并逐渐替代PFOS及其衍生物,是我国面临的巨大挑战。在介绍了PFOS的生产与应用现状基础上,结合其替代技术,提出了削减和逐步替代PFOS的策略。     

Sorption of pyrene from water by oil shale ash and mineral particles

The aim of this work was to estimate the sorption of pyrene from water solutions on mineral substrates, e.g., alumina, silica, and oil shale ash, from the Estonian thermal plant. Results obtained from this study indicate that the sorption of pyrene on mineral oxides and oil shale ash particles from water can be described with a linear equation. The sorptive capacity per weight of oil shale ash in aqueous systems was significantly lower compared with mineral adsorbents. The distribution coefficient (K_d) for pyrene in the system with particles of oil shale ash was 10–12 times lower as than for mineral adsorbents.     

Preparation of a permanent magnetic hypercrosslinked resin and assessment of its ability to remove organic micropollutants from drinking water

A rapid and effective method based on a novel permanent magnetic hypercrosslinked resin W150 was proposed for the removal of organic micropollutants in drinking water. W150 was prepared by suspension and post-crosslinking reaction and found to possess a high specific surface area of 1149.7 m²·g^-1, a small particle size of 50 μm to 100 μm, and a saturation magnetization as high as 8 emu·g^-1. W150 was used to eliminate nitrofurazone (NFZ) and oxytetracycline (OTC) from drinking water compared with commercial adsorbents XAD-4 and F400D. The adsorption kinetics of NFZ and OTC onto the three adsorbents well fitted the pseudo-second-order equation (r>0.972), and the adsorption isotherms were all well described by the Freundlich equation (r>0.851). Results showed that the reduction in adsorbent size and the enlargement in sorbent pores both accelerated adsorption. Moreover, the effect of particle size on adsorption was more significant than that of pore width. Given that the smallest particle size and the highest specific surface area were possessed by W150, it had the fastest adsorption kinetics and largest adsorption capacity for NFZ (180 mg·g^-1) and OTC (200 mg·g^-1). For the adsorbents with dominant micropores, the sorption of large-sized adsorbates decreased because of the inaccessible micropores. The solution pH and ionic strength also influenced adsorption.     

Cerium dioxide and composites for the removal of toxic metal ions

The presence of contaminants in potable water is a cause of worldwide concern. In particular, the presence of metals such as arsenic, lead, cadmium, mercury, chromium can affect human health. There is thus a need for advanced techniques of water decontamination. Adsorbents based on cerium dioxide (CeO₂), also named ‘ceria,’ have been used to remove contaminants such as arsenic, fluoride, lead and cadmium. Ceria and composites display high surface area, controlled porosity and morphology, and abundance of functional groups. They have already found usage in many applications including optical, semiconductor and catalysis. Exploiting their attractive features for water treatment would unravel their potential. We review the potential of ceria and its composites for the removal of toxic metal ions from aqueous medium. The article discusses toxic contaminants in water and their impact on human health; the synthesis and adsorptive behavior of ceria-based materials including the role of morphology and surface area on the adsorption capacity, best fit adsorption isotherms, kinetic models, possible mechanisms, regeneration of adsorbents; and future perspectives of using metal oxides such as ceria. The focus of the report is the generation of cost-effective oxides of rare-earth metal, cerium, in their standalone and composite forms for contaminant removal.     

久效磷在海洋沉积物上的吸附行为

研究了久效磷在海洋沉积物上的吸附行为，发现其吸附行为主要受沉积物有机质的影响，沉积物有机质的分配作用对久效磷的吸附起主要作用，在实验浓度范围内，吸附行为很好地服从线性吸附等温式，因而其吸附行为较为简单，海水的离子强度对其吸附行为影响很大，海水中分配系数明显高于淡水，温度对其吸附行为也起一定的作用，分配系数随着温度的升高略微减小。     

Spatial distribution of perfluorooctane sulfonate (PFOS) in major rivers in southwest Nigeria

Concentrations of perfluorooctane sulfonate (PFOS) were measured for the first time in major rivers within southwest, Nigeria. PFOS was concentrated from water and sediment using solid-phase extraction, identified and quantified with high-performance liquid chromatography coupled with tandem mass spectrometry. Concentrations of PFOS ranged from 1.71 to 16.19 ng L^?1 in water, and from 1.64 to 10.29 ng g^?1 in sediments across all locations. Comparatively, the concentrations of PFOS observed in this study were within the range ever measured in the environment. Field-based sediment water distribution coefficients (log K_d, L kg^?1) ranged from 2.08 to 3.56. While no correlation was observed between K_d and organic carbon contents, there was significant positive correlation between K_d and salinity (r² = 0.7867), which suggested that activities capable of increasing salinity can enhance PFOS removal from the environment.