Competitive kinetics of adsorption onto activated carbon for emerging contaminants with contrasting physicochemical properties

Environmental Science and Pollution Research - Activated carbon (AC) can be used for the removal of emerging contaminants (e.g., drugs) in water and wastewater treatment plants. In the present...     

Photocatalytic oxidation of soot by P25 TiO2 films

The photomineralisation of soot by P25 titania films is studied using FT-IR and the process shown to involve the oxidation of carbon to CO2 exclusively. The efficiency of this process is low, however, with a formal quantum efficiency of 1.1 x 10(-4) molecules of carbon oxidized per incident photon of UVA light. The cause of this low efficiency is attributed largely to the less than intimate contact between the fibrous soot layer and the surface of the photocatalyst.     

Studies on the adsorption and kinetics of photodegradation of a model compound for heterogeneous photocatalysis onto TiO(2)

An investigation was made on the adsorption and kinetics of photodegradation of potassium hydrogenphthalate in an aqueous suspension of TiO(2). Two models, Langmuir and Freundlich, were used to describe the adsorption process and the model proposed by Langmuir-Hinshelwood (L-H) was employed to describe the kinetics of the photodecomposition reactions of hydrogenphthalate. The results of the adsorptions were fitted to the models proposed by Langmuir and Freundlich. Adsorption was found to be a function of the temperature, with adsorption capacity increasing from 2.4 to 4.5 mg/g when the temperature rose from 20 to 30 degrees C. The kinetic model indicates that the rate constant, k, of the first order reaction, is high in the 10.0 to 100 mg/l interval, which is coherent with the low value of the adsorption constant, K. The results fitted to the L-H model led to an equation that, within the range of concentrations studied here, theoretically allows one to evaluate the photodegradation rate.     

Differential sensitivity of marine algae Dunaliella salina and Chlorella sp. to P25 TiO2 NPs

Environmental Science and Pollution Research - The use of P25 TiO2 NPs in consumer products, their release, and environmental accumulation will have harmful effects on the coastal ecosystems. The...     

Photocatalytic degradation of contaminants of concern with composite NF-TiO2 films under visible and solar light

This study reports the synthesis and characterization of composite nitrogen and fluorine co-doped titanium dioxide (NF-TiO₂) for the removal of contaminants of concern in wastewater under visible and solar light. Monodisperse anatase TiO₂ nanoparticles of different sizes and Evonik P25 were assembled to immobilized NF-TiO₂ by direct incorporation into the sol–gel or by the layer-by-layer technique. The composite films were characterized with X-ray diffraction, high-resolution transmission electron microscopy, environmental scanning electron microscopy, and porosimetry analysis. The photocatalytic degradation of atrazine, carbamazepine, and caffeine was evaluated in a synthetic water solution and in an effluent from a hybrid biological concentrator reactor (BCR). Minor aggregation and improved distribution of monodisperse titania particles was obtained with NF-TiO₂-monodisperse (10 and 50 nm) from the layer-by-layer technique than with NF-TiO₂?+?monodisperse TiO₂ (300 nm) directly incorporated into the sol. The photocatalysts synthesized with the layer-by-layer method achieved significantly higher degradation rates in contrast with NF-TiO₂-monodisperse titania (300 nm) and slightly faster values when compared with NF-TiO₂-P25. Using NF-TiO₂ layer-by-layer with monodisperse TiO₂ (50 nm) under solar light irradiation, the respective degradation rates in synthetic water and BCR effluent were 14.6 and 9.5?×?10^?3?min^?1 for caffeine, 12.5 and 9.0?×?10^?3?min^?1 for carbamazepine, and 10.9 and 5.8?×?10^?3?min^?1 for atrazine. These results suggest that the layer-by-layer technique is a promising method for the synthesis of composite TiO₂-based films compared to the direct addition of nanoparticles into the sol.     

Occurrence,impact, and elimination of contaminants of emerging concern (CECs) in soil,water, and air streams: advances and challenges in Ibero-American countries

Environmental Science and Pollution Research -     

乙萘酚和甲萘胺在超高交联树脂上的竞争吸附

通过氯甲基化的苯乙烯-二乙烯苯共聚物的后交联反应制备了超高交联吸附树脂(NDA150),通过红外光谱和比表面孔径分析对NDA150和XAD-4树脂的结构和表面参数进行表征。通过等温吸附实验研究了水溶液中乙萘酚和甲萘胺在NDA150和XAD-4上的竞争吸附行为。结果表明,NDA150树脂具有较高的比表面积为1 144 m2/g和较丰富的微孔,而XAD-4树脂的比表面积为904 m2/g,且以中孔为主。通过等温线吸附实验可知,在单组分水体系中NDA150和XAD-4树脂对乙萘酚和甲萘胺都具有较好的吸附性能,303 K时,NDA150和XAD-4对乙萘酚的吸附量分别可达1.97和1.24 mmol/g;对甲萘胺的吸附量分别为2.33和1.45 mmol/g;吸附质在树脂上的吸附等温线符合Langmuir模型。在双组分水体系中乙萘酚和甲萘胺的物质的量之比为1:1(C0=2.0 mmol/L),树脂对两种吸附质的吸附量均减少,但是树脂对吸附剂的吸附总量大于相同平衡浓度下对单组分水溶液中乙萘酚和甲萘胺的吸附量。在303 K时,建立LCA模型来预测吸附质的竞争吸附,并对模型进行修正,用LCA修正模型的拟合效果较好。     

ClO2氧化/TiO2复合吸附剂协同体系处理印染废水的实验研究

利用ClO2 氧化/TiO2 复合吸附剂协同体系对处理实际印染废水进行了实验研究.结果表明,对于COD为750 mg/L、色度为250倍、SS为100 mg/L的1 000 mL印染废水,当溶液pH为4.0、ClO2 用量20 mg/L、TiO2 复合吸附剂用量2.5 g、反应时间和吸附时间分别为2、8 min时,处理后的废水COD＜100 mg/L、色度＜40倍、SS＜70 mg/L,达到了《纺织染整工业水污染物排放标准》(GB 4287-92)排放要求.并对两者的协同机理进行了理论上的探讨.     

Performance comparison of commercial TiO2: separation and reuse for bacterial photo-inactivation and emerging pollutants photo-degradation

This research aims to compare the disinfection and degradation effectiveness in water of a commercial suspension of nano-TiO₂ (TiO₂Levenger) with the standard TiO₂Degussa P25. Photo-inactivation and photo-degradation experiments were conducted with UVA-vis light. Concerning the disinfection, the effects of TiO₂ dose (0–2 g/l), water matrix, bacterium type (Gram-positive or Gram-negative), and bacterial regrowth after the photo-treatments were studied for each catalyst. The experimental results show that Enterococcus sp. (Gram-positive) was more resistant to the photo-treatments than Escherichia coli (Gram-negative) for both catalyst; however, postirradiation trends showed similar behavior for both bacteria, favoring regrowth for short-treated cells and decay for longer-treated ones. Caffeine was selected as a model substance of pharmaceuticals and personal care products. In terms of caffeine removal, the effects of TiO₂ dose (0–2 g/l) and water matrix were analyzed. Besides, the comparison between mechanical coagulation-flocculation-decantation and simple decantation of TiO₂ was carried out. The results show that simple decantation allowed the recovery of 97.5% of TiO₂ Degussa P25 and TiO₂ Levenger within 1 day of simple decantation, while applying the proposed mechanical coagulation-flocculation decantation 99.7% of recovery of both catalysts was achieved in 2 hours. Finally, the subsequent reuse of both catalysts was proved with little loss of efficiency in terms of photo-disinfection during the four cycles. Nevertheless, the standard TiO₂ Degussa P25 photo-degradation efficiency of caffeine decreases considerably as compared to commercial suspension of TiO₂ Levenger concerning the reutilization.

     

State-of-the-art and current challenges for TiO2/UV-LED photocatalytic degradation of emerging organic micropollutants

Environmental Science and Pollution Research - The development of ultraviolet light-emitting diodes (UV-LED) opens new possibilities for water treatment and photoreactor design. TiO2...     

白云石矿物对水溶液中Cu2+、Pb2+吸附的动力学和热力学

采用静态实验方法研究了白云石对水溶液中Cu2+、Pb2+的吸附特性,通过批实验考察了反应时间、溶液初始浓度、pH值、离子强度、温度以及固液比等因素对吸附的影响,探讨了白云石对Cu2+、Pb2+的吸附动力学、热力学规律及其反应机制。实验结果显示:白云石对Cu2+、Pb2+的吸附在24 h达到平衡,对Pb2+的吸附量大于Cu2+,伪二级和双常数动力学方程分别能较好地拟合白云石对Cu2+、Pb2+的吸附;在一定条件下,白云石对Cu2+、Pb2+的去除率与溶液初始浓度呈反比,与固液比呈正比;吸附等温方程符合Langmuir模型,为单分子层吸附;溶液pH值对吸附行为影响显著,在溶液pH=6~7时,吸附效果最好,离子强度对吸附影响甚微;白云石对Cu2+、Pb2+的吸附属于吸热反应,反应自发进行,高温促进白云石的吸附行为。     

Modeling transport and deposition of contaminants to ecosystems of concern: a case study for the Laurentian Great Lakes

Transfer efficiency (TE) is introduced as a model output that can be used to characterize the relative ability of chemicals to be transported in the environment and deposited to specific target ecosystems. We illustrate this concept by applying the Berkeley-Trent North American contaminant fate model (BETR North America) to identify organic chemicals with properties that result in efficient atmospheric transport and deposition to the Laurentian Great Lakes. By systematically applying the model to hypothetical organic chemicals that span a wide range of environmental partitioning properties, we identify combinations of properties that favor efficient transport and deposition to the Lakes. Five classes of chemicals are identified based on dominant transport and deposition pathways, and specific examples of chemicals in each class are identified and discussed. The role of vegetation in scavenging chemicals from the atmosphere is assessed, and found to have a negligible influence on transfer efficiency to the Great Lakes. Results indicate chemicals with octanol-water (K(ow)) and air-water (K(aw)) partition coefficients in the range of 10(5)-10(7) and 10(-4)-10(-1) combine efficient transport and deposition to the Great Lakes with potential for biaccumulation in the aquatic food web once they are deposited. A method of estimating the time scale for atmospheric transport and deposition process is suggested, and the effects of degrading reactions in the atmosphere and meteorological conditions on transport efficiency of different classes of chemicals are discussed. In total, this approach provides a method of identifying chemicals that are subject to long-range transport and deposition to specific target ecosystems as a result of their partitioning and persistence characteristics. Supported by an appropriate contaminant fate model, the approach can be applied to any target ecosystem of concern.     

The adsorption of benzene and methylethylketone onto activated carbon: thermodynamic aspects.

The adsorption of volatile organic compounds (VOCs), exemplified by benzene and methylethylketone (MEK), onto seven different types of activated carbon was investigated. Results show that for benzene adsorption the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 17.12-36.86, -20.8 to -44.7, -11.89 to -16.22 kJ/mole and -29.4 to -85.3 J/mole/K, respectively. For the adsorption of MEK, the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 14.47-32.34, -18.3 to -40.8, -10.78 to -15.56 kJ/mole and -24.8 to approximately -60.3 J/mole/K, respectively. The adsorption enthalpy can be calculated indirectly from statistical thermodynamic method and directly from the immersion enthalpy method. The adsorption characteristic energy is calculated by the Dubinin-Astokhov equation. The free energy is calculated by the measured equilibrium adsorption constant.     

Sorption of ionic liquids onto soils: experimental and chemometric studies

Chemometric analyses are a great tool to support typical experimental studies of the interactions of xenobiotics with natural environment. Such interpretations are able to determine statistically significant correlations and finally lead to identification of the major sorption factors. However, to effectively use chemometrics a bigger data set is required. Even though the ionic liquids are intensively studied, their complete fate or prediction of their behavior in the natural environment is still unclear. Therefore, to evaluate and distinguish the patterns of interactions of ILs in soil environment by chemometrics, sorption of nine ionic liquids (imidazolium and pyridinium chlorides) on 11 types of various soils was tested. Experimental studies indicated that compounds with longer alkyl side chains were sorbed far more strongly than weakly lipophilic ones. Moreover, salts with short and/or hydroxylated derivatives were more mobile in soils/sediments and thus, might cause a danger of contamination of surface or ground waters. Cluster analysis revealed that ionic liquids form two major clusters according to interaction with soil surface - one grouping compounds with short and hydroxylated alkyl side chains and the second with the rest of compounds. Pairwise scatterplots for correlations between soil variables and sorption coefficients indicated that the main soil parameter responsible for the sorption was cation exchange capacity. Correlation of sorption coefficients, K(d), with pH indicated the existence of lower sorption potency in lower pH values.     

Evaluation of kinetics and mechanism properties of CO2 adsorption onto the palm kernel shell activated carbon

Environmental Science and Pollution Research - The volumetric adsorption kinetics of carbon dioxide (CO2) onto the synthesized palm kernel shell activated carbon via single-stage CO2 activation and...     

A review on electrocoagulation process for the removal of emerging contaminants: theory,fundamentals, and applications

Electrocoagulation (EC) is an excellent and promising technology in wastewater treatment, as it combines the benefits of coagulation, flotation, and electrochemistry. During the last decade, extensive researches have focused on removal of emerging contaminants by using electrocoagualtion, due to its several advantages like compactness, cost-effectiveness, efficiency, low sludge production, and eco-friendness. Emerging contaminants (ECs) are micropollutants found in trace amounts that discharging into conventional wastewater treatment (WWT) plants entering surface waters and imposing a high threat to human and aquatic life. Various studies reveal that about 90% of emerging contaminants are disposed unscientifically into water bodies, creating problems to public health and environment. The studies on removal of emerging contaminants from wastewater are by global researchers are critically reviewed. The core findings proved that still more research required into optimization of parameters, system design, and economic feasibility to explore the potential of EC combined systems. This review has introduced an innovative collection of current knowledge on electro-coagulation for the removal of emerging contaminants.

Graphical abstract

     

Statistical thermodynamics of adsorption of dye DR75 onto natural materials and its modifications: double-layer model with two adsorption energies

In this article, adsorption modelling was presented to describe the sorption of textile dye, Direct Red 75 (DR75), from coloured wastewater onto the natural and modified adsorbent, Posidonia oceanica. The formulation of the double-layer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics some physico-chemical parameters related to the adsorption process were introduced in the analytical model expression. Fitting results show that the dye molecules are adsorbed in parallel position to the adsorbent surface. The magnitudes of the calculated adsorption energies show that the DR75 dye is physisorbed onto Posidonia. Both Van der Waals and hydrogen interactions are implicated in the adsorption process. Despite its simplicity, the model fits a wide range of experimental data, thereby supporting the underlying data that the grafted groups facilitate the parallel anchorage of the anionic dye molecule. Thermodynamic parameters, such as adsorption energy, entropy, Gibbs free adsorption energy and internal energy were calculated according to the double-layer model. Results suggested that the DR75 adsorption onto Posidonia was a spontaneous and exothermic process.     

Application of molecularly imprinted and non-imprinted polymers for removal of emerging contaminants in water and wastewater treatment: a review

Over the past decade, several studies have reported trace levels of endocrine disrupting compounds, pharmaceuticals, and personal care products in surface waters, drinking water, and wastewater effluents. There has also been an increased concern about the ecological and human health impact of these contaminants, and their removal from water and wastewater has become a priority. Traditional treatment processes are limited in their ability to remove emerging contaminants from water, and there is a need for new technologies that are effective and feasible. This paper presents a review on recent research results on molecularly imprinted (MIP) and non-imprinted (NIP) polymers and evaluates their potential as a treatment method for the removal of emerging contaminants from water and wastewater. It also discusses the relative benefits and limitations of using MIP or NIP for water and wastewater treatment. MIP, and in particular NIP, offer promising applications for wastewater treatment, but their toxicity and possible health effects should be carefully studied before they are considered for drinking water treatment. More research is also required to determine how best to incorporate MIP and NIP in treatment plants.     

Adsorption of multi-heavy metals Zn and Cu onto surficial sediments: modeling and adsorption capacity analysis

Improved multiple regression adsorption models (IMRAMs) was developed to estimate the adsorption capacity of the components [Fe oxides (Fe), Mn oxides (Mn), organic materials (OMs), residuals] in surficial sediments for multi-heavy metal Zn and Cu. IMRAM is an improved version over MRAM, which introduces a computer program in the model developing process. As MRAM, Zn(Cu) IMRAM, and Cu(Zn) IMRAM again confirmed that there is significant interaction effects that control the adsorption of compounded Zn and Cu, which was neglected by additional adsorption model. The verification experiment shows that the relative deviation of the IMRAMs is less than 13 %. It is revealed by the IMRAMs that Mn, which has the greatest adsorption capability for compounded Zn and Cu (54.889 and 161.180 mg/l, respectively), follows by interference adsorption capacity of Fe/Mn (?1.072 and ?24.591 mg/l respectively). Zn and Cu influence each other through different mechanisms. When Zn is the adsorbate, compounded Cu mainly affects the adsorption capacities of Fe/Mn and Fe/Mn/OMs; while when Cu is the adsorbate, compounded Zn mainly exerts its effect on Mn, Fe/Mn, and Mn/OMs. It also shows that the compounded Zn or Cu weakened the interference adsorption of Fe/Mn, and meanwhile, strengthened the interference adsorption of Mn/OMs.