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There is an increasing urge to make the transition toward biobased materials. Lignin, originating from lignocellulosic biomass, can be potentially valorized as humic acid (HA) adsorbents via lignin-based mesoporous carbon (MC). In this work, these materials were synthesized for the first time starting from modified lignin as the carbon precursor, using the soft-template methodology. The use of a novel synthetic approach, Claisen rearrangement of propargylated lignin, and a variety of surfactant templates (Pluronic, Kraton, and Solsperse) have been demonstrated to tune the properties of the resulting MCs. The obtained materials showed tunable properties (BET surface area: 95-367 m(2)/g, pore size: 3.3-36.6 nm V-BJH pore volume: 0.05-0.33 m(3)/g, and carbon land oxygen content: 55.5-91.1 and 3.0-12.2%, respectively) and good performance in terms of one of the highest HA adsorption capacities reported for carbon adsorbents (up to 175 mg/g).

Lab-scale continuous operation of self forming MF and UF dynamic membranes were investigated simultaneously by applying iron oxide as an alternative treatment option in those waters having natural organic matter (NOM), iron and manganese. Both dynamic membranes gave high removal rates and effluent concentrations of pollutants were below the limit values in synthetic water. 60-62% of DOC and 75-78% of UV254 were removed in low DOC synthetic water (LS) by MF and UF dynamic membranes, respectively. Although only 42-49% of DOC and 48-53% of UV254 could be removed by MF and UF dynamic membranes, remarkable effect on fouling alleviation was observed in high DOC synthetic water (HS). Iron oxide did not enhance the removal of organic matter in low DOC natural water (LN) as much as it did in synthetic water. Iron oxide led to the removal of high molecular weight organics, thus reversible fouling reduced almost 2 orders of magnitude through both types of dynamic membranes in high DOC natural water (HN). Reversible and ireversibe resistances were reduced by iron oxide to some extent in LN. Nevertheless the effect of iron oxide on fouling alleviation was much higher in HN than LN. Scientific Research Projects Coordination Unit of Istanbul University-Cerrahpasa [2810]; Memtek National Research Center on Membrane Technologies This work was supported by Scientific Research Projects Coordination Unit of Istanbul University-Cerrahpasa. Project number:2810. The authors appreciate the support and cooperation of Memtek National Research Center on Membrane Technologies during this research study.

Coagulation combined with ultrafiltration (UF) is an effective drinking water treatment process. However, inefficient removal of natural organic matter (NOM) and membrane fouling problems, especially those initiated by the adhesion of biopolymers, greatly restrict the practical application of the UF process. Here, we investigated a biologically enhanced coagulation–ultrafiltration (CUF) process treating samples of a natural surface water, which demonstrated a superior NOM removal and antifouling performance. The membrane flux (under 1.0 bar constant pressure) of the biologically enhanced CUF [using polyaluminum chloride (PACl)] process scheme was approximately 4.4 and 8.4 times higher than that of a conventional CUF and direct UF process, respectively, and PACl was found to perform better than AlCl3. Characterization of the NOM showed that the biological pretreatment combined with the coagulation process significantly contributed to the reduction of hydrophobicity, aromaticity, and molecular weight of the dissolved organics. Analyses of biopolymers showed that the combined process can remove over 99% of the biopolymers (represented by proteins and polysaccharides), which are considered to be the main cause of membrane fouling. Results of X-ray photoelectron spectroscopy and FTIR analyses further elucidated the transformation and reduction of biopolymers during the combined process. With respect to the disinfection byproduct formation potential (DBP-FP), the results showed that the conventional CUF process had a limited impact on the DBP-FP, while the biologically enhanced CUF process had a substantial impact consistent with meeting the current EPA DBP standards. Overall, this study has highlighted the potential advantages of using a biologically enhanced CUF process for producing higher quality drinking water with a simultaneous low membrane fouling propensity.

Graphical abstract, Highlights • Ultrasound degraded the molecular structure of humic acids. • Sonochemical effects (HO•) responsible for fluorescence reduction. • No TOC and colour removal with ultrasound pre-treatment. • O3 achieved a significant reduction in TOC and almost a complete colour removal. • Ultrasound pre-treatment may reduce subsequent O3 dosage for humic acid degradation., This paper presents an intensification study of an ozonation process through an ultrasonic pre-treatment for the elimination of humic substances in water and thus, improve the quality of water treatment systems for human consumption. Humic acids were used as representative of natural organic matter in real waters which present low biodegradability and a high potential for trihalomethane formation. Ultrasonic frequency (98 kHz, 300 kHz and 1 MHz), power (10–40 W) and sonicated volume (150–400 mL) was varied to assess the efficiency of the ultrasonic pre-treatment in the subsequent ozonation process. A direct link between hydroxyl radical (HO•) formation and fluorescence reduction was observed during sonication pre-treatment, peaking at 300 kHz and maximum power density. Ultrasound, however, did not reduce total organic carbon (TOC). Injected ozone (O3) dose and reaction time were also evaluated during the ozonation treatment. With 300 kHz and 40 W ultrasonic pre-treatment and the subsequent ozonation step (7.4 mg O3/Lgas), TOC was reduced from 21 mg/L to 13.5 mg/L (36% reduction). HO• attack seems to be the main degradation mechanism during ozonation. A strong reduction in colour (85%) and SUVA254 (70%) was also measured. Moreover, changes in the chemical structure of the macromolecule were observed that led to the formation of oxidation by-products of lower molecular weight.

Iodine is a naturally-occurring halogen in natural waters generally present in concentrations between 0.5 and 100 mu g L-1. During oxidative drinking water treatment, iodine-containing disinfection by-products (I-DBPs) can be formed. The formation of I-DBPs was mostly associated to taste and odor issues in the produced tap water but has become a potential health problem more recently due to the generally more toxic character of I-DBPs compared to their chlorinated and brominated analogues., This paper is a systematic and critical review on the reactivity of iodide and on the most common intermediate reactive iodine species HOI. The first step of oxidation of I- to HOI is rapid for most oxidants (apparent second-order rate constant, k(app) > 10(3) M(-1)s(-1) at pH 7). The reactivity of hypoiodous acid with inorganic and organic compounds appears to be intermediate between chlorine and bromine. The life times of HOI during oxidative treatment determines the extent of the formation of I-DBPs. Based on this assessment, chloramine, chlorine dioxide and permanganate are of the highest concern when treating iodide-containing waters. The conditions for the formation of iodo-organic compounds are also critically reviewed., From an evaluation of I-DBPs in more than 650 drinking waters, it can be concluded that one third show low levels of I-THMs ( 10 mu g L-1. The most frequently detected I-THM is CHCl2I followed by CHBrClI. More polar I-DBPs, iodoacetic acid in particular, have been reviewed as well., Finally, the transformation of iodide to iodate, a safe iodine-derived end-product, has been proposed to mitigate the formation of I-DBPs in drinking water processes. For this purpose a pre-oxidation step with either ozone or ferrate(VI) to completely oxidize iodide to iodate is an efficient process. Activated carbon has also been shown to be efficient in reducing I-DBPs during drinking water oxidation.

Hypochlorous acid (HOCl) is typically assumed to be the primary reactive species in free available chlorine (FAC) solutions. Lately, it has been shown that less abundant chlorine species such as chlorine monoxide (Cl2O) and chlorine (Cl2) can also influence the kinetics of the abatement of certain compounds during chlorination. In this study, the chlorination as well as bromination kinetics and mechanisms of 12 selected olefins (including 3 aliphatic and 9 aromatic olefins) with different structures were explored. HOCl shows a low reactivity towards selected olefins with species-specific second-order rate constants 103 M−1s−1). The reactivities of chlorine and bromine species towards olefins follow the order of HOCl < HOBr < Br2O < Cl2O ≈ Cl2. Generally, electron-donating groups (e.g., CH2OH- and CH3-) enhances the reactivities of olefins towards chlorine and bromine species by a factor of 3-102, while electron-withdrawing groups (e.g., Cl-, Br-, NO2-, COOH-, CHO-, -COOR, and CN-) reduce the reactivities by a factor of 3-104. A reasonable linear free energy relationship (LFER) between the species-specific second-order rate constants of Br2O or Cl2O reactions with aromatic olefins and their Hammett σ + was established with a more negative ρ value for Br2O than for Cl2O, indicating that Br2O is more sensitive to substitution effects. Chlorinated products including HOCl-adducts and decarboxylated Cl-adduct were identified during chlorination of cinnamic acid by high-performance liquid chromatography/high resolution mass spectrometry (HPLC/HRMS)., Water Research, 187, ISSN:0043-1354, ISSN:1879-2448

The occurrence of nanoplastics in oceans' surface waters is no more a hypothesis and it could severely affect marine organisms from different trophic levels. Nanoscale particles interaction with dissolved natural organic matter (NOM) significantly influence their behaviour and consequently bioavailability and toxicity to marine species. Extracellular polymeric substances (EPS) are among the main components of the NOM pool in seawater yet have been so far little investigated for their effect in altering the physical-chemical properties of nanosized objects. Here we employed EPS from marine diatom Phaeodactylum tricornutum to study the evolution of an eco-corona formation upon incubation with 60 nm carboxylated polystyrene nanoparticles (PS-COOH NPs), as proxy for nanoplastics in seawater. EPS significantly reduced PS-COOH NPs aggregation rate compared to biomolecule free natural seawater (NSW) and caused the formation of complexes constituted by both carbohydrate and protein components. Size Exclusion Chromatography (SEC) revealed four main distinct groups of peaks, spanning from high (>100 kDa) to low molecular weight (20 kDa) molecules, characterized by a high chemical heterogeneity. The lowering of the chromatographic signals detected after EPS incubation with PS-COOH NPs, mainly in the eluates at high molecular weight, suggests that an important fraction of EPS remained adsorbed on PS-COOH NPs. In agreement, SDS-PAGE analysis of proteins adsorbed on PS-COOH showed the occurrence of an eco-corona formed by proteins in the range of molecular weight 30-100 kDa. No toxicity to diatoms was observed upon PS-COOH exposure (72 h, 1-100mg L-1) even by adding a further source of exogenous EPS during exposure. Moreover, the addition of EPS reduced ROS production, even when cells were incubated with PS-COOH NPs at 10 and 50 mg L-1, suggesting an antioxidant scavenging activity of EPS. (C) 2020 Elsevier B.V. All rights reserved.

Membrane fouling is the principal factor that currently limits the performance of gravity-driven membrane (GDM) filtration systems in drinking water treatment. In this study, the benefits of applying a low dose (approximately 0.1 mg⋅L− 1) of environmentally benign oxidants, both H2O2 and KMnO4, as a pretreatment to GDM filtration system has been evaluated in terms of reduced membrane fouling and treated water quality. While both oxidants improved permeate flux, the effect of KMnO4 was greater than H2O2. Both oxidants reduced the size of influent organic substances and those of large molecular weight (>20 kDa), such as biopolymers, disappeared. The thickness of the fouling layers was substantially reduced after oxidation, and the KMnO4 system had a markedly different physical structure of fouling layer, with an apparent sub-layer of δ-MnO2 nanosheets below a fouling sub-layer. The formation of the δ-MnO2 nanosheets sub-layer appeared to protect the underlying membrane pores from contamination by influent organics. Oxidation pretreatment reduced the presence of proteins and polysaccharides in the fouling layers and significantly altered the bacterial community structures (p < 0.01) and decreased biodiversity. The microbial species that secreted amounts of extracellular polymeric substances (EPS), such as Xanthobacter, were not eliminated in the H2O2 fouling layer, while for the KMnO4 system, the manganese oxidizing bacteria (MOB; e.g., Pseudoxanthomonas) and metal-resistant genus Acidovorax, dominated the community.

In order to improve the performance of the ultrafiltration (UF) membrane process in drinking water treatment, in terms of permeate flux and natural organic matter (NOM) removal, a new form of carbon nanofiber (CNF) layer derived from bacterial cellulose (BC) was prepared and applied as a pre-deposited coating on the UF membrane surface. Using bench-scale, dead-end filtration tests, both CNF and CNF modified by ethanol treatment (M-CNF), were evaluated for the treatment of two model NOM solutions, namely bovine serum albumin (BSA) and sodium alginate (SA). The results showed that both types of coating were effective in mitigating membrane fouling (lower flux decline), with the mitigation increasing with the coating quantity, and also enhanced the removal of BSA and SA. In particular, the M-CNF layer at the greater loading (24 g/m2) was able to reduce membrane fouling to a very substantial degree and achieve > 90% removal of BSA and SA. Characterization of the CNF and M-CNF layers showed significant differences in their morphological and structural properties which may explain the observed differences in their ability to reduce membrane fouling; protection of the UF membrane by the carbon nanofiber layers may be attributed to both physical separation and surface adsorption of the NOM biopolymers.

Mutagenicity formation by low pressure (LP)-UV/H2O2 treatment of nitrate-rich water containing natural organic matter (NOM) was investigated. Laboratory-grade water samples spiked with either Pony Lake NOM or Suwannee River NOM (4 mg L−1 in both cases) and nitrate (50 mg L−1) were irradiated with UV fluences of 0, 1500 and 2000 mJ cm−2 and a H2O2 dose of 15 mg L−1 and tested for mutagenicity with the Ames II assay. LP-UV photolysis of nitrate in the presence of Pony Lake NOM caused a significant increase in the Ames II assay response and low concentrations of nitrite (0.08–0.09 mg NO2− L−1) and nitrophenols (0.014–0.046 μg L−1) were detected. Suwannee River NOM produced the same nitrite levels but no significant responses in the Ames II assay were observed. Additionally, samples collected from a drinking water treatment plant in the UK using LP-UV/H2O2 treatment were analysed with the Ames II assay. LC-OCD fractionation and SUVA measurements were performed to observe any changes in the properties of NOM. Significant differences in the mutagenicity response were observed between the treatment steps as well as between the two sampling periods. However, with respect to standard thresholds, none of the samples were found to be mutagenic towards the Salmonella typhimurium strain TA98 used.

Nanoparticles, namely titanium dioxide (TiO2), are emerging contaminants widely used to commercial and industrial applications, are a potential hazard and can cause damage to environment and human health due to their toxicity. Therefore, their removal from the water is urgent to minimize or eliminate the adverse environmental and human effects. This work, investigates the efficiency of conventional coagulation/flocculation/sedimentation (C/F/S) from drinking water treatment to remove TiO2 nano particles (NPs) from surface waters, and pretends to understand if the removal of TiO2 NPs affects the ability of C/F/S to remove natural organic matter (NOM) and turbidity, and consequently affects the quality of the treated water. Results show that TiO2 NPs removal is high (>90%) for all the waters studied (hydrophobic and hydrophilic waters) and the treated water quality is not compromised (turbidity, Ti and Al concentrations, pH and conductivity are below the national and international guidelines). In addition, TiO2 initial concentrations, ranging between 0.2 and 10 mg/L, have not a significant impact on NPs removal by C/F/S. Therefore, the widely used polyaluminium based coagulants are effective in the removal of TiO2 NPs by conventional C/F/S treatment, but removal is strongly influenced by the water characteristics. Hydrophobic waters need a higher coagulant dose than hydrophilic waters to achieve the same TiO2 NPs removals, as well as water with higher UV254nm values. The principal mechanism involved in TiO2 NPs removal is charge neutralisation. (C) 2016 Elsevier Ltd. All rights reserved. Portuguese Foundation of Science and Technology [SFRH/BD/100402/2014]

With the growth in production and use of chemicals and the fact that many end up in the aquatic environment, there is an increasing need for advanced water treatment technologies that can remove chemicals of emerging concern (CECs) from water. The current lack of a homogenous approach for testing advanced water treatment technologies hampers the interpretation and evaluation of CEC removal efficiency data, and hinders informed decision making by stakeholders with regard to which treatment technology could satisfy their specific needs. Here a data evaluation framework is proposed to improve the use of current knowledge in the field of advanced water treatment technologies for drinking water and wastewater, consisting of a set of 9 relevance criteria and 51 reliability criteria. The two criteria sets underpin a thorough, unbiased and standardised method to select studies to evaluate and compare CEC removal efficiency of advanced water treatment technologies in a scientifically sound way. The relevance criteria set was applied to 244 papers on removal efficiency, of which only 20% fulfilled the criteria. The reliability criteria were applied to the remaining papers. In general these criteria were fulfilled with regards to information on the target compound, the water matrix and the treatment process conditions. However, there was a lack of information on data interpretation and statistics. In conclusion, a minority of the evaluated papers are suited for comparison across techniques, compounds and water matrixes. There is a clear need for more uniform reporting of water treatment studies for CEC removal. In the future this will benefit the selection of appropriate technologies., Water Research, 161, ISSN:0043-1354, ISSN:1879-2448

Disposal of waste generated by inland water treatment technologies is highly expensive. The introduction of vibratory shear enhanced processing (VSEP) to treat waste produced from magnetic ion exchange (MIEX) shows benefits in terms of performance and economics. A small VSEP unit fitted with a nanofiltration (NF) membrane is capable of treating up to 15 kL of MIEX waste per day, is able remove more than 97% of dissolved organic compounds as well as recover over 80% of waste in the form of permeate. The reuse of permeate to makeup brine has seen significant reductions in salt consumption and waste disposal at Wanneroo Groundwater Treatment Plant (GWTP). During the first year of VSEP operation, salt consumption reduced by 42% and waste disposal was projected to reduce by 23.9%. Further improvements in both cost categories were observed in the second year of operation and considering the same trend is followed, the payback period of the project will occur between the 6th and 7th year of operation for discounted analysis and has a positive net present value.

In this study, the reactions of engineered nanoparticles (ENPs) in soils, with respect to their nanospecific properties, and observed effects of key soil properties (e.g. pH, ionic strength and natural colloids) on their stability in pore water are discussed. Key processes include aggregation and dissolution of ENPs, straining of ENPs in the solid matrix, stabilization of ENPs in pore water due to binding of molecules from dissolved organic matter (DOM) and inorganic colloids and the effect of artificial coatings. In view of these processes, this study provides guidance in the development of a framework to measure available and total soil contents of ENPs, via a set of extraction methods and advanced analytical tools. Particularly, the lack of effective extraction methods is thoroughly discussed regarding the identification of most relevant research gaps preventing an effective assessment of the availability, mobility and risks of exposure of sensitive receptors to ENPs in soils. (C) 2015 Elsevier B.V. All rights reserved.

When terrigenous dissolved organic carbon (tDOC) rich in chromophoric dissolved organic matter (tCDOM) enters the ocean, solar radiation mineralizes it partially into dissolved inorganic carbon (DIC). This study addresses the amount and the rates of DIC photoproduction from tDOC and the area of ocean required to photomineralize tDOC. We collected water samples from 10 major rivers, mixed them with artificial seawater, and irradiated them with simulated solar radiation to measure DIC photoproduction and the photobleaching of tCDOM. The linear relationship between DIC photoproduction and tCDOM photobleaching was used to estimate the amount of photoproduced DIC from the tCDOM fluxes of the study rivers. Solar radiation was estimated to mineralize 12.5 +/- 3.7 Tg C yr(-1) (10 rivers)(-1) or 18 +/- 8% of tDOC flux. The irradiation experiments also approximated typical apparent spectral quantum yields for DIC photoproduction (phi(lambda)) over the entire lifetime of the tCDOM. Based on phi(lambda)s and the local solar irradiances in river plumes, the annual areal DIC photoproduction rates from tDOC were calculated to range from 52 +/- 4 (Lena River) to 157 +/- 2 mmol C m(-2) yr(-1) (Mississippi River). When the amount of photoproduced DIC was divided by the areal rate, 9.6 +/- 2.5 x 10(6) km(2) of ocean was required for the photomineralization of tDOC from the study rivers. Extrapolation to the global tDOC flux yields 45 (31-58) Tg of photoproduced DIC per year in the river plumes that cover 34 (25-43) x 10(6) km(2) of the ocean.

Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV–vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10–90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV–vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used.

A major cause of ultrafiltration (UF) membrane fouling in surface water treatment is natural organic matter (NOM). Some studies have reported that heated aluminum oxide particles (HAOPs), prepared by boiling a suspension containing precipitates of the common coagulant alum, can remove substantial amounts of NOM and reduce fouling when they were pre-deposited on UF membranes. However, the influence of the size and structure of the HAOPs in mitigating NOM membrane fouling has not been fully explored so far. This work has investigated the change in microstructure of the HAOPs during the heating process and the subsequent effect on the performance of the membrane process, and especially on the mitigation of fouling. As the heating time increased, the structure of the HAOPs transformed gradually from an amorphous nature to a semi-crystal, and then to a microcrystalline phase. It was found that this micro-crystallization process played a key role in affecting the structural properties of the nano-scale particles and the membrane filtration performance. During the crystalline transition, a change of particle size distribution occurred and the average particle size was found to decrease gradually owing to a dehydration reaction. The smaller particle size of the HAOPs provides a denser pre-filtration layer for NOM separation, and their more rigid structure reduces layer compression and hydraulic resistance during operation. Optimization of the pre-heating condition and surface loading can effectively enhance the performance of the HAOPs layer in reducing NOM fouling in the UF membrane system.

As water shortages are increasing, the need for sustainable water treatment and the reuse of water is essential. Water reuse from wastewater can be accomplished in a membrane bioreactor (MBR) in the secondary activated sludge stage of a wastewater treatment plant. To remove viruses, dissolved organics and inorganics still present in the MBR permeate, nanofiltration (NF) can be applied. Nevertheless, the major drawback of nanofiltration membranes is the production of a concentrate stream that cannot be discharged to the environment. In this research we investigate the concept of a combined MBR and NF system with NF concentrate recirculation back to the MBR to produce reusable water in a sustainable way. Long-term continuous operation (1 year) shows that the NF permeate quality is riot impacted by the recirculation. Fouling on the NF membrane is mostly the result of inorganics, while organics (e.g. humic acids) do not have a major impact on NF fouling. In fact, the flux of the NF was enhanced by the presence of humic acids due to recirculation. However, the MBR showed increased fouling and consequently more frequent membrane cleaning. The results presented show that the continuous production of reusable water from wastewater in a combined MBR and NO process with NO concentrate recirculation can be successful. (C) 2013 Elsevier B.V. All rights reserved

This paper comprises a selection tool for water disinfection methods for fresh produce pre- and postharvest practices. A variety of water disinfection technologies is available on the market and no single technology is the best choice for all applications. It can be difficult for end users to choose the technology that is best fit for a specific application. Therefore, the different technologies were characterized in order to identify criteria that influence the suitability of a technology for pre- or postharvest applications. Introduced criteria were divided into three principal components: (i) criteria related to the technology and which relate to the disinfection efficiency, (ii) attention points for the management and proper operation, and (iii) necessities in order to sustain the operation with respect to the environment. The selection criteria may help the end user of the water disinfection technology to obtain a systematic insight into all relevant aspects to be considered for preliminary decision making on which technologies should be put to feasibility testing for water disinfection in pre- and postharvest practices of the fresh produce chain.

Focusing on the idea that multivalent cations affect SOM matrix and surface, we treated peat and soil samples by solutions of NaCl, CaCl2 or AlCl3. Water binding was characterized with low field 1H-NMR-relaxometry (20 MHz) and 1H wideline NMR spectroscopy (400 MHz) and compared to contact angles. From 1H wideline, we distinguished mobile water and water involved in water molecule bridges (WaMB). Large part of cation bridges (CaB) between SOM functional groups are associated with WaMB. Unexpectedly, 1H NMRrelaxometry relaxation rates suggest that cross-linking in the Al-containing peat is not stronger than that by Ca. The relation between percentage of mobile water and WaMB water in the context of wettability and 1H NMR relaxation times confirms that wettability controls the water film surrounding soil particles. Wettability is controlled by WaMB-CaB associations fixing hydrophilic functional groups in the SOM interior. This can lead to severe water repellency. Wettability decreases with increasing involvement of functional groups in CaB-WaMB associations. The results demonstrate the relevance of CaB and WaMB for the dynamics of biogeochemical and hydrological processes under field conditions, as only a few percent of organic matter can affect the physical, chemical, and biological functioning of the entire 3-phase ecosystem.

To date, sorption of organic compounds to nanomaterials has mainly been studied for the nanomaterial in its pristine state. However, sorption may be different when nanomaterials are buried in sediments. Here, we studied sorption of Perfluorooctane sulfonate (PFOS) to sediment and to sediment with 4% multiwalled carbon nanotubes (MWCNTs), as a function of factors affecting PFOS sorption; aqueous concentration, pH and Ca 2+ concentration. Sorption to MWCNT in the sediment–MWCNT mixtures was assessed by subtracting the contribution of PFOS sorption to sediment-only from PFOS sorption to the total sediment–MWCNT mixture. PFOS Log K D values ranged 0.52–1.62 L kg −1 for sediment and 1.91–2.90 L kg −1 for MWCNT present in the sediment. The latter values are relatively low, which is attributed to fouling of MWCNT by sediment organic matter. PFOS sorption was near-linear for sediment (Freundlich exponent of 0.92 ± 0.063) but non-linear for MWCNT (Freundlich exponent of 0.66 ± 0.03). Consequently, the impact of MWCNT on sorption in the mixture was larger at low PFOS aqueous concentration. Effects of pH and Ca 2+ on PFOS sorption to MWCNT were statistically significant. We conclude that MWCNT fouling and PFOS concentration dependency are important factors affecting PFOS–MWCNT interactions in sediments.

Proton binding to one soil fulvic acid (JGFA), two soil humic acids (JGHA, JLHA) and a lignite-based humic acid (PAHA) was investigated. The results were fitted to NICA-Donnan model and compared directly with the predictions using the generic parameters. NICA-Donnan model can describe proton binding satisfactorily when parameter fitting is allowed for humic substance (HS). However, predictions based on the generic parameter sets deviate for soil samples in a non-systematic way from the measured results. Replacing Qmax,H1 in generic parameter sets with material-specific values improves the predictions for soil HA significantly. For JGFA, the agreement between the model prediction and data is still not satisfactory after substitution. This is due to a very different pattern of site distribution of JGFA from that of generic FA. For two other soil FAs (FH-14, FH-22 of Milne's database) the generic predictions can be improved significantly with material-specific Qmax,H1. Adjusting also Qmax,H2 to HS material-specific value improves the prediction only slightly further. In practice, Qmax,H1 and Qmax,H2 of HS can be obtained in a relatively simple way by performing one acid–base titration at a given ionic strength and applying the procedure of Lenoir et al. to fit data to NICA equation. Introduction of thus obtained Qmax,H1 and Qmax,H2 into generic parameter sets improves the generic predictions significantly. The functional group contents as obtained by SG-method are not adequate for this purpose.

Binding of lead (Pb) to soil fulvic acid (JGFA), soil humic acids (JGHA, JLHA), and lignite-based humic acid (PAHA) was investigated through binding isotherms and XAFS. Pb binding to humic substances (HS) increased with increasing pH and decreasing ionic strength. The NICA-Donnan model described Pb binding to the HS satisfactorily. The comparison of the model parameters showed substantial differences in median Pb affinity constants among JGFA, PAHA, and the soil HAs. Milne's "generic" parameters did not provide an adequate prediction for the soil samples. The Pb binding prediction with generic parameters for the soil HAs was improved significantly by using the value n(Pb1) = 0.92 instead of the generic value n(Pb1) = 0.60. The n(Pb1)/n(H1) ratios obtained were relatively high, indicating monodentate Pb binding to the carboxylic-type groups. The nPb2/nH2 ratios depended somewhat on the method of optimization, but the values were distinctly lower than the n(Pb1)/nH1 ratios, especially when the optimization was based on Pb bound vs log [Pb(2+)]. These low values indicate bidentate binding to the phenolic-type groups at high Pb concentration. The NICA-Donnan model does not consider bidentate binding of Pb to a carboxylic- and a phenolic-type group. The EXAFS results at high Pb loading testified that Pb was bound in bidentate complexes of one carboxylic and one phenolic group (salicylate-type) or two phenolic groups (catechol-type) in ortho position.

Here we evaluate the performance and limitations of two frequently used model-types to predict trace element solubility in soils: regression based "partition-relations" and thermodynamically based "multisurface models", for a large set of elements. For this purpose partition-relations were derived for As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se, V, Zn. The multi-surface model included aqueous speciation, mineral equilibria, sorption to organic matter, Fe/Al-(hydr)oxides and clay. Both approaches were evaluated by their application to independent data for a wide variety of conditions. We conclude that Freundlich-based partition-relations are robust predictors for most cations and can be used for independent soils, but within the environmental conditions of the data used for their derivation. The multisurface model is shown to be able to successfully predict solution concentrations over a wide range of conditions. Predicted trends for oxy-anions agree well for both approaches but with larger (random) deviations than for cations.

An important issue in chlorine drinking water disinfection is the generation from natural organic matter (NOM) of disinfection by-products (DBPs), especially trihalomethanes (THMs). The THMs generation can be limited by reducing the levels of NOM prior to the chlorination step. Herein, photo-Fenton system under solar simulator degraded humic acid solutions (as NOM model compounds), as well as NOM contained in river water (Pance River, Cali-Colombia), and dramatically reduced THMs formation during the subsequent chlorination step. In both cases the initial pH of treated water was near to 7.In no pre-treated river water 100-160 mu g/L of THMs are formed during chlorination while values of 20-60 mu g/L were reached in water previously treated for 4 h by neutral photo-Fenton under solar simulator. The decrease in the generated THMs/total organic carbon ratio suggests that mainly the NOM fraction sensitive to THMs formation was photo-degraded. Therefore, the neutral photo-Fenton reagent could be implemented as a technological option for NOM removal for limiting THMs formation during a subsequent chlorination step. (C) 2011 Elsevier B.V. All rights reserved.

The assessment of surface water nanofiltration (NF) for the removal of endocrine disruptors (EDs) – Nonylphenol Ethoxylate (IGEPAL), 4-Nonylphenol (NP) and 4-Octylphenol (OP) – was carried out with three commercial NF membranes – NF90, NF200, NF270. The permeation experiments were conducted in laboratory flat-cell units of 13.2 × 10−4 m2 of surface area and in a DSS Lab-unit M20 with a membrane surface area of 0.036 m2. The membranes hydraulic permeabilities ranged from 3.7 to 15.6 kg/h/m2/bar and the rejection coefficients to NaCl, Na2SO4 and Glucose are for NF90: 97%, 99% and 97%, respectively; for NF200: 66%, 98% and 90%, respectively and for NF270: 48%, 94% and 84%, respectively. Three sets of nanofiltration experiments were carried out: i) NF of aqueous model solutions of NP, IGEPAL and OP running in total recirculation mode; ii) NF of surface water from Rio Sado (Setubal, Portugal) running in concentration mode; iii) NF of surface water from Rio Sado inoculated with NP, IGEPAL and OP running in conc...

The anionic charge of humic substances (HS) plays a major role in the interaction of HS with other components. Therefore, the potential of the polyelectrolyte titration technique to obtain the charge density of HS in simple 1–1 electrolyte solutions has been investigated. Titrations are carried out with an automatic titrator combined with the “Mutek particle charge detector” which allows determination of the Mutek potential and the pH as a function of the added amount of titrant which is a solution of poly-diallyldimethylammonium chloride (polyDADMAC), a cationic strong polyelectrolyte. When the Mutek potential reverses its sign the iso-electric point (IEP) of the polyDADMAC–HS complex is reached. The polyDADMAC/HS mass ratio at the IEP gives information on the HS charge density and from the pH changes in solution an estimate of the charge regulation in the HS–polyDADMAC complex can be obtained. In general, for polyDADMAC–HS complexes an increase in the dissociation of the acid groups of HS is found (charge regulation). The charge regulation decreases with increasing concentration of 1–1 background electrolyte. Cation incorporation can be neglected at 1–1 electrolyte concentrations ⩽ 1 mmol L−1 and a 1–1 stoichiometry exists between the polyDADMAC and HS charge. However, at these low salt concentrations the charge regulation is substantial. A detailed analysis of purified Aldrich humic acid (PAHA) at pH 5 and a range of KCl concentrations reveals that the anionic charge of PAHA in the complex increases at 5 mmol L−1 KCl by 30% and at 150 mmol L−1 KCl by 12%. On the other hand, increasing amounts of K+ become incorporated in the complex: at 5 mmol L−1 KCl 5% and at 150 mmol L−1 KCl 24% of the PAHA charge is balanced by K+. By comparing at pH 5 the mass ratios polyDADMAC/PAHA in the complex at the IEP with the theoretical mass ratios of polyDADMAC/PAHA required to neutralize PAHA in the absence of charge regulation and K+ incorporation, it is found that at 50 mmol L−1 KCl the extra negative charge due to the interaction between polyDADMAC and PAHA is just compensated by K+ incorporation in the complex. Therefore, a pseudo 1–1 stoichiometry exists at about 50 mmol L−1 1–1 electrolyte concentration and only at this salt concentration polyDADMAC titrations and conventional proton titrations give identical results. Most likely this is also true for other HA samples and other pH values. For FA further study is required to reveal the conditions for which polyDADMAC and proton titrations give identical results.

The humic substances (HS) have a high reactivity with other components in the natural environment. An important factor for the reactivity of HS is their negative charge. Cationic surfactants bind strongly to HS by electrostatic and specific interaction. Therefore, a surfactant binding model is developed that takes both the specific and electrostatic interactions explicitly into account. The model is analogous to that of ion binding to HS with the NICA-Donnan model, but competition for the binding sites is not taken into account and the NICA-Donnan model reduces to the Langmuir–Freundlich–Hill–Donnan (LFH-D) model. The parameters of the LFH equation are the maximum binding, the affinity constant and the non-ideality constant. The non-ideality parameter accounts for both the site heterogeneity and the cooperativity due to hydrophobic interaction between surfactant molecules. The affinity constant incorporates the specific (e.g., hydrophobic) interactions between surfactant and HS. The Donnan part of the model accounts in a simple way for the electrostatic interactions by assuming that for a given set of conditions there is only one electrostatic potential that governs the behavior in the Donnan phase. The separation between the specific interactions (LHF) and the electrostatic interactions (D) is based on the so-called master curve (MC) procedure in which the binding is replotted as a function of the “free” surfactant concentration in the Donnan phase. The MC depends only on the specific interactions. Once the MC is obtained it can be fitted to the LFH equation to obtain the model parameters. Subsequently, the surfactant isotherms can be calculated with the LFH-D model. The model is tested using previously obtained data on dodecyl pyridinium chloride (DPC) and cetyl pyridinium chloride (CPC) binding to some purified humic and fulvic acids at pH about 5. The LFH-D model is well suited to describe the surfactant binding to HAs from very low concentrations up to the iso-electric point (IEP). The affinity of DPC for the different HAs allows ranking of the HAs according to their hydrophobicity. Prediction of DPC binding at other pH values also leads to good results for HA. For FAs the model can only describe the surfactant binding up to an adsorbed amount of 0.5 mol/kg. For higher binding values the LFH-D model underestimates the binding.

Surface modification of membranes is thought to be equally important to the membrane industry as membrane material and process development; surface functionalization has already become a key technology, the major aims being performance improvement (flux and selectivity) by reduction of unwanted protein fouling (often considered the first step for biofouling). Poly(arylsulfone) [ i.e. , Polysulfone (PSf) and poly(ethersulfone) (PES)] membranes have been widely used for separation and purification purposes. However, in many cases, nonspecific (protein) adsorption takes place on the membrane surface and in the membrane pores due to the inherent hydrophobic characteristics of poly(arylsulfone). Therefore several (surface) modification techniques for poly(arylsulfone) membranes have been developed. Given the importance of modification methods for these membranes and their operation, we decided to dedicate this mini-review solely to this topic. The modification methods can be divided into the following main groups: (1) coating, (2) blending, (3) composite, (4) chemical, (5) grafting, or (6) a combination of methods. With all these methods, interesting results were obtained concerning reduction of protein adsorption (see respective sections), although the quantification of improved performance is not straightforward. In the Section 4, all techniques are compared on various aspects such as flux after modification, simplicity, reproducibility, environmental aspects, and cost effectiveness.

† Background and Aims Plant nutrition models do not properly account for the effects of root-induced chemical changes in the rhizosphere, e.g. pH changes, on the availability of nutrients such as phosphorus (P). As a result, they underestimate the actual P uptake, i.e. P bioavailability to the plant, in low-P soils. The present study aims at simulating root-induced chemical mechanisms controlling P nutrition in a P-limited soil. † Methods In this work a mechanistic description for the adsorption of cations and anions by soil constituents (1pK-Triple Plane Model, ion-exchange and Nica–Donnan) was used to simulate changes induced by durum wheat (Triticum durum turgidum) in the P availability of the soil, as measured by water and CaCl2 extraction. Calcium (Ca) availability was also measured and simulated. † Key Results The simulations were found to be in close agreement with experimental data. In the rhizosphere, the goodness-of-fit required to account for the measured uptake of Ca by plants, in addition to the measured uptake of P and root-induced alkalization, were satisfactory. Calcium uptake significantly increased P availability, as assessed through water extraction, by decreasing the promoting effect of Ca adsorption on P adsorption. The study thus enabled P and Ca availability to be related to their bioavailability for durum wheat under experimental conditions. It was also shown that P was primarily adsorbed onto Fe oxides and clay minerals (kaolinite and illite) depending on soil pH. The major source of P for durum wheat nutrition was P desorbed from goethite and kaolinite. † Conclusions In addition to confirming the validity of our approach to model P availability, the present investigation suggested that in the studied soil, a novel root-induced chemical process was controlling P nutrition under P-deficient conditions, namely the uptake of Ca.

In this work we will introduce a hierarchical framework that can be used to optimize an ultrafiltration process that is used for the purification of surface water. Within the suggested framework modelling and optimization of chemical cleaning of membranes were performed. This paper will discuss the proposed model, the quantitative criteria that can be used to select a proper cleaning agent and lastly the optimization procedure on the basis of the dynamic model. Systematic optimization showed that two optimal scenarios for cleaning can be formulated, one in which cleaning time is reduced significantly with respect to a conventional cleaning procedure, and a second one where cleaning time and cleaning agent consumption as well are reduced significantly. These reductions show that the ultrafiltration process can be made sustainable and greener, by systematic optimization of the cleaning process. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved.

Data for interactions between arsenate (AsO4(3-) and fulvic acids (FA) or humic acids (HA) at the surface of goethite are presented (pH 3-7, ionic strength 2 mM and 10 mM). Adsorption of FA and HA leads to desorption of arsenate and a correspondingly strong increase of arsenic concentration in solution. Adsorption of both FA and HA is mutually decreased by the competition with arsenate. The competition between FA and arsenate is much stronger than that between HA and arsenate. Using an advanced model, the LCD model (Ligand and Charge Distribution), arsenate adsorption to goethite in the presence of both adsorbed FA and HA can be predicted reasonably well. The stronger effects of FA on arsenate adsorption are caused, according to the model, by its spatial location which is closer to the oxide surface, and as a consequence, the electrostatic interactions between adsorbed FA particles and arsenate ions are much stronger than those for HA particles. The results show that site and electrostatic competition are the major mechanisms explaining the effects of natural organic matter on the arsenic speciation, whereas other possible mechanisms, such as a chemical reduction of arsenate to arsenite and formation of ternary organic arsenic complexes, are of minor significance.

Interactions of purified Aldrich humic acid (PAHA) with the protein lysozyme (LSZ) are studied with dynamic light scattering and isothermal titration calorimetry by mixing LSZ and PAHA at various mass ratios. In solution LSZ is positive and PAHA is negative at the investigated pH values. Up to moderate KCl concentrations no aggregation occurs for LSZ and for PAHA aggregated particles with an average radius of 80 nm are present Complexation of PAHA with LSZ starts as soon as PAHA is added to LSZ and is followed by aggregation when the isoelectric-point (IEP) of the complexes is approached. Aggregation is gradual for 50 mM KCl and sudden for low KCl concentrations. The aggregate size is at its maximum at the IEP of the complexes. At mass ratios beyond the IEP the aggregates partially disaggregate. Positively charged complexes of PAHA and LSZ, formed in the absence of salt, strongly aggregate upon salt addition. Mixing of LSZ and PAHA is initially enthalpically driven. Near the IEP complexation and aggregation are due to hydrophobic forces (structural reorganization) and counterion release. The observations are relevant for other HA-protein systems when the protein is positively charged.

There is growing concern about the accumulation of metals in tropical agricultural soils. In this study, experimental results from batch studies were used to test whether multi-surface geochemical models could describe metal binding in selected Vietnamese soils. The multi-surface models considered metal binding to iron hydroxides (using the diffuse layer model), organic matter (Stockholm Humic model and NICA-Donnan model), and phyllosilicate clay (Gaines-Thomas equation) as well as complexation to dissolved organic and inorganic ligands in the solution phase. We found that for total dissolved Cd, Cu and Zn the two multi-surface models being tested provided very good model fits for all soils, as evidenced by low root-mean square errors between model predictions and observations. These results suggest that organic matter is an important sorbent for many metals in these soils. However, poor fits were obtained for Cr(III), Mn and Pb for all soils. The study also suggests that the pH is the main factor that controls the solubility of metals in tropical Fluvisols and Acrisols subjected to application of biosolids and wastewater, and that advanced multi-surface models can be used to simulate the binding and release of many trace metals. QC 20100525

Adsorption of randomly branched polyelectrolytes, "hairy" particles and internally structured macromolecules, collectively denoted as heterogeneously charged nanoparticles, on charged surfaces is important in many technological and natural processes. In this paper, we will focus on (1) the charge regulation of both the nanoparticle and the surface and (2) the surface complexation between the particle functional groups and the surface sites and will theoretically study the adsorption using the extended surface complexation approach. The model explicitly considers the electrochemical potential of a nanoparticle with an average (smeared-out) structure and charge both in bulk solution and on the surface to obtain the equilibrium adsorption. The chemical heterogeneity of the particle is described by a distribution of the protonation constant. Detailed analysis of the chemical potential of the adsorbed nanoparticle reveals that the pH and salt dependence of the adsorption can be largely explained by the balance between an energy gain resulting from the particle and surface charge regulation and the surface complexation and an energy loss from the unfavorable interparticle electrostatic repulsion close to the surface. This conclusion is also supported by the strong impacts that the chemical heterogeneity of the particle functional groups, the magnitude of the surface complexation, the number of the functional groups, and the size of the particle have on the adsorption.

The development of speciation and surface complexation models to calculate partitioning of metals between the soil solid phase and soil solution has made a large progress. We evaluated the use and practical applicability of an assemblage of complexation models to predict sorption of Cd, Cu, Ni, Pb and Zn. We used 353 samples which cover a wide range of soil properties and metal contents. For sorption of cations to solid and dissolved organic matter the NICA-Donnan model was used, to clay minerals a non-specific Donnan type exchange model, and to metal(hydr)oxides a two-site DDL model. Calculated solution concentrations agree well with measurements, except for Pb where calculations overestimate concentrations by one order of magnitude on average. Some highly Zn contaminated samples show relatively large deviations between measured and calculated concentrations. This is most likely caused by Zn containing minerals which are included in the total amount of reactive metals in the soil as determined by acid extraction. Hence, such models can be used for practical applications if one is aware of the possible complications. When the “total reactive metal content” includes a substantial amount of precipitated metals, which may occur for heavily contaminated soils, the model tends to overestimate concentrations in solution.

This paper reviews the published literature on potential membrane fouling components, available cleaning agents and possible interactions between cleaning agents and fouling components. It also lists the cleaning models available in the literature, and evaluates the advantages and disadvantages of these models. Based on this outcome, a new cleaning model is proposed to capture cleaning dynamics for 10 different cleaning agents, varying from acidic, alkali and oxidizing to sequestering agents and detergents that were used to clean dead-end ultra filtration membranes fouled by surface water. The model is effectively fitted to the experimental data of the different cleanings. Two criteria are subsequently introduced to quantify the overall cleaning effect of a cleaning agent in terms of cleaning rate and cleaning effectiveness. For membranes fouled by surface water with high organic content it was found that caustic-and oxidizing cleaning agents give the best overall cleaning results. (c) 2007 Elsevier B.V. All rights reserved.

Dichloroacetamide (DCAcAm), a disinfection byproduct, has been detected in drinking water. Previous research showed that amino acids may be DCAcAm precursors. However, other precursors may be present. This study explored the contribution of the antibiotic chloramphenicol (CAP) and two of its analogues (thiamphenicol, TAP; florfenicol, FF) (referred to collectively as CAPs), which occur in wastewater-impacted source waters, to the formation of DCAcAm. Their formation yields were compared to free and combined amino acids, and they were investigated in filtered waters from drinking-water-treatment plants, heavily wastewater-impacted natural waters, and secondary effluents from wastewater treatment plants. CAPs had greater DCAcAm formation potential than two representative amino acid precursors. However, in drinking waters with ng/L levels of CAPs, they will not contribute as much to DCAcAm formation as the μg/L levels of amino acids. Also, the effect of advanced oxidation processes (AOPs) on DCAcAm formation from CAPs in real water samples during subsequent chlorination was evaluated. Preoxidation of CAPs with AOPs reduced the formation of DCAcAm during postchlorination. The results of this study suggest that CAPs should be considered as possible precursors of DCAcAm, especially in heavily wastewater-impacted waters.

A coagulation (FeCl3)-ultrafiltration process was used to treat two different raw waters with/without the presence of Fe3O4 nanoparticle contaminants. The existence of Fe3O4 nanoparticles in the raw water was found to increase both irreversible and reversible membrane fouling. The trans-membrane pressure (TMP) increase was similar in the early stages of the membrane runs for both raw waters, while it increased rapidly after about 15 days in the raw water with Fe3O4 nanoparticles, suggesting the involvement of biological effects. Enhanced microbial activity with the presence of Fe3O4 nanoparticles was evident from the measured concentrations of extracellular polymeric substances (EPS) and deoxyribonucleic acid (DNA) and fluorescence intensities. It is speculated that Fe3O4 nanoparticles accumulated in the cake layer and increased bacterial growth. Associated with the bacterial growth is the production of EPS which enhances the bonding with and between, the coagulant flocs; EPS together with smaller sizes of the nano-scale primary particles of the Fe3O4-CUF cake layer, led to the formation of a lower porosity, more resilient cake layer and membrane pore blockage.