UV/ozone induced physicochemical transformations of polystyrene nanoparticles and their aggregation tendency and kinetics with natural organic matter in aqueous systems

Ferrate(VI) decomposition in water in the absence and presence of natural organic matter (NOM)

Stability studies for titanium dioxide nanoparticles upon adsorption of Suwannee River humic and fulvic acids and natural organic matter

Effect of UV/ClO2 pretreatment on controlling ultrafiltration membrane fouling of different natural organic matter (NOM) fractions

Effects of pre-ozonation on the ultrafiltration of different natural organic matter (NOM) fractions: Membrane fouling mitigation, prediction and mechanism

Effect of natural organic matter on the adsorption and fractionation of thorium and protactinium on nanoparticles in seawater

Sorption of hydrophobic organic compounds (HOCs) to natural organic matter (NOM) is an important process that affects the transport, transformation, bioavailability, and fate of HOCs in the environment. Manufactured nanoparticles (NPs) such as nano-oxides will inevitably enter the environment in the processes of their production, transfer, and use and could be coated by the ubiquitous NOM. Thus, sorption of HOCs to NOM in the environment could be affected by the NP interactions with NOM. Furthermore, the toxicity of nano-oxides could be increased due to the adsorbed HOCs. Therefore, sorption of phenanthrene by nano-Al(2)O(3) coated with humic acid (HA) was examined in this study to explore the possible effect of nanoparticles (NPs) on the environmental behavior of HOCs and the potential environmental and health risks of NPs. Four HAs were sequentially extracted with 0.1 mol/L NaOH from a peat soil. HAs, nano-Al(2)O(3), and HA-coated nano-Al(2)O(3) were characterized by techniques such as elemental analysis, solid-state (13)C NMR, N(2) surface area analysis, and zeta potential measurement. Adsorption isotherms of HAs by nano-Al(2)O(3) and phenanthrene by HAs and HA-coated nano-Al(2)O(3) were obtained using a batch equilibration technique at 25 +/- 1 degrees C. HA concentrations were measured by total organic carbon analysis. Phenanthrene concentrations were measured by liquid scintillation counting. The adsorption maxima of HAs by nano-Al(2)O(3) was one order of magnitude higher than that by soil inorganic minerals. Phenanthrene isotherms of HA-coated nano-Al(2)O(3) were more nonlinear than that of their respective bulk HAs. Concentration-dependent organic carbon-normalized sorption coefficients (K' (oc)) of phenanthrene by HA-coated nano-Al(2)O(3) were lower than those for their respective bulk HAs, especially at relatively high concentrations. Isotherm nonlinearity of phenanthrene could be interpreted by a combination of partitioning accompanied by linear isotherm with adsorption accompanied by nonlinear isotherm. HA conformation changes during their adsorption on nano-Al(2)O(3) could play an important role in phenanthrene sorption and were responsible for higher nonlinearity of phenanthrene isotherms and lower phenanthrene K' (oc) on the adsorbed HAs than their respective bulk HAs. Adsorption of HA on nano-Al(2)O(3) would form a more condensed HA state with higher pi-polarity/polarizability and lower partitioning affinity than the respective bulk HA, leading to an increase of relative contribution of adsorption to the total sorption and more nonlinear phenanthrene isotherms in the adsorbed HA due to the increase in phenanthrene adsorption affinity and decrease in phenanthrene partitioning affinity. Adsorption of HA on nano-Al(2)O(3) was much higher than that on soil oxide minerals and could form a more condensed HA state with higher pi-polarity/polarizability and lower partitioning affinity than the bulk HA, causing the significant difference in phenanthrene sorption between the adsorbed HA and the respective bulk HA. Therefore, once released in the environment, NPs such as nano-Al(2)O(3) will strongly alter the environmental transport, fate, and bioavailability of HOCs and could be potentially more toxic due to the adsorbed toxic chemicals. Due to the high adsorption of HA on nano-Al(2)O(3) and its significant effect on phenanthrene sorption, interactions of NOM with nano-oxides and their mechanistic relations with NOM conformation changes and HOC sorption merit further research. In addition, due to the higher sorption of phenanthrene on the HA-coated nano-Al(2)O(3) than the pure counterpart, the effect of NOM and HOCs on the ecotoxicity of NPs should be addressed in the future.

Removal of fluoride and natural organic matter from natural tropical brackish waters by nanofiltration/reverse osmosis with varying water chemistry

Natural organic matter (NOM) in water contains organic compounds that are both hydrophobic and hydrophilic with a wide range of molecular weights. It is composed of non-homogeneous organic compounds such as humic substances, amino acids, sugars, aliphatic and aromatic acids, and other chemical synthetic organic matters. NOM in water is a major concern not only because of its contribution to the formation of disinfection by-products (DBPs) and taste and odor, but also its influence on the demand for coagulants and disinfectants, the removal efficiency of water treatment processes, etc. This research aims at identifying the influence of NOM in coagulation and flocculation processes in order to optimize the coagulation and flocculation conditions. In this study, pretreated pond water was used as the source water. It was observed from the experimental results that:The optimum pH for coagulation to remove NOM is around 7.The optimum alum dose at this pH can vary from 125-1,225 mgl-1 when the TOC is increased from 4 to 25 mgl-1.The presence of secondary compounds such as Ca2+, Mg2+ divalent cations had no significant effect on the removal of organic matter.The presence of clay increased the organic removal by 15%.The organic compound with higher molecular weight has higher removal affinity in coagulation process.Floc size and settling velocity of floc and sludge production all increased with the increase in NOM concentration. From the results of Capillary Suction Time (CST) tests, the floc formed with lower TOC readily released the water to make the dewatering process easier.The organic removal efficiency was significantly different for natural water containing non-homogeneous organic compounds compared to the synthetic water containing humic acid only (homogeneous organic matter). For example, the NOM removal efficiency was 80% for the synthetic water containing humic acid with TOC of 7 mgl-1 at pH 7; but the NOM removal for the pretreated pond water was 60%.

The foundation of separation science is the division or deconvolution of a mixture into constituent parts. To do so greatly informs our understanding of complex systems. Equally important is consideration of the behavior of a mixture as a whole—to consider if the whole is the sum of the parts or if individual components interact synergistically or antagonistically when combined. Application of separation science has seldom assumed greater importance than in consideration of the controversy surrounding the traditional and emergent views of the complex chemical system of natural organic matter (NOM). Analyses of simulated and actual environmental water samples using noninvasive separation techniques including flow field‐flow fractionation (flow FFF), excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analyses, and dynamic light scattering (DLS) are discussed. The data are used to explore whether a distinct chemical category of humic (diagenetic) substances exists in NOM; whether separation of organic matter into fulvic and humic extracts has relevant meaning translatable to actual environmental water samples; whether extraction procedures alter the chemistry of NOM extracts; and, if humic and fulvic acids exist, what physicochemical property or properties make humic substances unique among other forms of NOM. A fluorescence‐based nonoperational definition of humic substances is introduced. The underexplored role of supramolecular, self‐assembled aggregation is presented as a NOM conceptual model. Responses are provided to questions raised in the great NOM debate within a supramolecular context.Core Ideas A new supramolecular conceptual model invokes strong near‐covalent hydrogen bonding. A nonoperational definition of diagenetic (humic) substances is proposed. Alkali extracts are valid, though imperfect, organic matter proxies. A mechanism for intrinsic chemical recalcitrance of natural organic matter exists. Protection is a “function” of the supramolecular “form.”

Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH

The presence of natural organic matter (NOM) in drinking water can increase the levels of copper released from copper pipes to water and inhibit the formation of protective deposits such as malachite. Since adsorption of NOM on copper pipes surfaces is believed to be one of mechanisms that explains this phenomenom, the objective of this study was to determine kinetics and the adsorption equilibrium of main components of NOM, humic acid (HA) and fulvic acid (FA), onto copper surfaces. The kinetics and equilibrium adsorption of HA and FA on copper foils were examined using batch experiments at 22°C. HA and FA followed pseudo second-order kinetics adsorption. Rate constants measured were 2.59 × 10−1 (mgTOC cm−2 h−1) for HA and 3.13 × 10−1 (mgTOC cm−2 h−1) for FA. The adsorption behavior of HA and FA on the copper surface is in accordance with the Langmuir adsorption isotherm. Langmuir adsorption constants measured were 5.98 × 10−2 L mg−1 for HA and 4.78 × 10−2 L mg−1 for FA. The copper foils exposed during five months to FA formed malachite deposits, whereas those exposed to HA did not and just cuprite was found. The results of this study showed that both HA as well as FA adsorption on copper surfaces is favored and no significant differences were found in the adsorption parameters calculated for both compounds. However, the inhibition of the malachite precipitation could be attributed to the HA adsorption.

Relative importance of humic and fulvic acid on ROS generation, dissolution, and toxicity of sulfide nanoparticles

Molecular modeling and molecular dynamics (MD) simulations are capable of improving our molecular-level understanding of natural organic matter (NOM) by providing new alternatives such as virtual experiments that may be difficult (or even impossible) to perform in real tests. The fine control of molecular structure required in molecular simulations is highly valuable and significant due to the fact that neither the structure nor (often) detailed composition of real NOM is known. The control of molecular structure and its educated variation guided by experimental data on 13C NMR-derived composition may be performed using Vienna Soil Organic Matter Modeller (VSOMM) [1], which allows accounting for the simultaneous presence of multiple NOM molecules of different structures. This work exploring the VSOMM is focused on examining how and whether the humic substances (HS) models representing Leonardite humic acid (LHA) can maintain stable associates in water. In this approach, the stability of HS aggregates was elucidated in the 100 ns MD simulations by varying amounts of water in a broad range, from representing "water solution in NOM" to aqueous dissolved NOM, and modifying molecular size and extent of ionization of HS models, and the type of counter-ions (Na+ vs Ca2+). Multiple properties characterizing HS-water systems have been calculated, e.g., cumulative coordination numbers, numbers of HS-HS and HS-water contacts and H-bonds at short-range distances, number and size of formed clusters as well as energies of Coulomb and Lennard-Jones interactions of HS with ions (Na+ or Ca2+), HS and water. One outcome of this modeling work is that it shows how HS dilution leads to the decomposition of HS aggregates which occurs, in particular in the presence of the Na+ counter ion, gradually. The results of this work are placed into the context of experimental data and discussion on whether the detected large HS sizes can be assigned to the presence of large aggregates and the formation of supramolecular structures [2]. Although strong interactions between HS molecules may lead to small stable aggregates (e.g., dimers) persisting during dilution, the modeling suggests that the formation and decomposition of HS associates is "a step-wise" process, and, together with experimental data on LHA dialysis proposes that large-size HS molecules (aggregated or not) may need to be taken into account while examining HS properties in aqueous solutions.[1] Escalona, Y., Petrov, D., & Oostenbrink, C. (2021). Vienna soil organic matter modeler 2 (VSOMM2). Journal of Molecular Graphics and Modelling, 103, 107817.[2] Borisover, M., Petrov, D., Oostenbrink, C., & Galicia-Andrés, E. (2025). Diluting humic substances in water in molecular dynamics simulations: Are aggregates stable? Colloids and Surfaces A: Physicochemical and Engineering Aspects, 704, 135507.

Role of natural organic matter (NOM), colloidal particles, and solution chemistry on ultrafiltration performance

Objectives : The purpose of this study was to evaluate the effect of increasing the number of regeneration of granular activated carbon (GAC) on the adsorption capacity of natural organic matter (NOM), and to suggest the technical process options associated the limit number of regeneration and the efficient use of regenerated GAC.Methods : The physicochemical properties of virgin and thermally regenerated GAC were analyzed. To evaluate the NOM adsorption capacity of virgin- and regenerated-GAC, five laboratory-scale columns packed with virgin- and regenerated-GAC were used for treating effluent from pilot-scale drinking water treatment facility. The NOM concentration in the influent and the effluent treated by each column was analyzed by LC-OCD (liquid chromatography-organic carbon detector) to evaluate the adsorption capacity of each NOM fractions (humic substances (HS), building blocks (BB), low molecular weight organics (LMWs)).Results and Discussion : Due to the change in the pore structure of GAC by thermal regeneration, the volume of micropores (< 2 nm) decreased, while the volume of mesopores (> 2 nm) increased. The volume ratio of micropore in virgin-GAC was about 60%, but it gradually decreased as the number of regenerations increased, resulting that the volume ratio of micropore in the 5th-regenerated (5th-Re) GAC decreased to 23%. On the other hand, the volume ratio of mesopore increased in proportion to the number of regenerations from 40% of the virgin GAC to 77% of the 5th-Re-GAC. The DOC adsorption capacities of the regenerated GACs were higher than that of virgin GAC, and the DOC adsorption capacity increased as the number of regenerations increased. As a result of comparing the adsorption capacity of virgin- and regenerated-GAC by NOM fractions, the adsorption capacity of high molecular weight NOM, such as HS, increased by 1.5 to 1.7 times as the number of regenerations increased. In contrast, the adsorption capacity of low molecular weight NOM, such as BB and LMWs, decreased by 78% and 48% as the number of regeneration increased. The limit number of regeneration was evaluated based on that the adsorption capacity (qe) of each NOM fractions keep over than 70% relative to its virgin GAC. As a result, the adsorption capacity for low molecular weight NOM was greatly reduced in GAC regenerated over than 3rd time, so that the 2nd-Re-GAC was valid to keep 70% removal of whole NOM fractions. Low adsorption of low molecular weight NOM (BB and LMWs) by 3rd-Re-GAC could be complemented by using together with virgin-GAC, and low adsorption of high molecular NOMs (HS) could be compensated as well.Conclusions : Due to the change in the pore structure of GAC by thermal regeneration, the DOC adsorption capacity was higher in regenerated GAC than its virgin-GAC, and the adsorption capacity of DOC and high molecular weight NOM (HS) was enhanced as the number of regenerations increased. On the other hand, the pore volume of micropore was reduced by regenerations, and in more than 3rd times regenerations, the adsorption capacity of low molecular weight NOMs (BB and LMWs) was reduced by less than 70% compared to its virgin GAC, so that 2nd-Re-GAC was suggested for suitable GAC. When using a mixture of virgin- and 3rd-Re-GAC, low adsorption of low molecular weight NOM (BB and LMWs) by 3rd-Re-GAC could be complemented by using together with virgin-GAC, and low adsorption of high molecular NOMs (HS) could be compensated as well.