Adsorption Of Organic Matter Research Articles

Reductive release of Fe mineral-associated organic matter accelerated by oxalic acid

The properties and composition of soil dissolved organic matter (DOM) are highly affected by the adsorption and desorption of organic matter (OM) on soil minerals and heterotrophic microbial respiration. Organic acids (e.g., oxalic acid), components of root exudates, have been revealed to liberate organic matter (OM) by the dissolution of protective mineral phases and stimulate microbial degradation of OM. However, the effects of organic acids on the properties and composition of soil DOM molecules and the related mechanisms are still poorly understood. In this study, we conducted microcosm incubation experiments with and without oxalic acid addition, and aimed to elucidate the variations of DOM properties and composition, employing a combination of Fourier transform ion cyclotron resonance mass spectrometry, optical spectroscopy, and bacterial community composition analysis. Our results indicated that the released OM from the direct dissolution of protective mineral phases by oxalic acid further stimulated the microbial reductive release of Fe mineral-associated OM under anoxic conditions. Furthermore, the addition of oxalic acid enhanced the degradation of aliphatic compounds and lignins with low O/C ratios, and increased the accumulation of lignins with high O/C ratios, tannins, and condensed aromatics. Linking the bacterial community composition to DOM molecular properties and composition further suggested that the enhanced reductive release of Fe mineral-associated OM was highly related to the increased abundances of Proteobacteria and Actinobacteria. Overall, oxalic acid induced long-lasting impacts on soil DOM properties and composition under anoxic soil conditions in our study. We expect that our results will contribute to understanding the dynamics of soil DOM molecules in the environment.

Adsorption of microplastic-derived organic matter onto minerals

Microplastic (MP) pollution is an increasing global problem due to the ubiquity of these particles in the environment and the uncertainty surrounding their fate. Most MPs undergo extensive weathering in the environment, which may result in the release of dissolved organic matter (DOM) into the aqueous phase. In this study, for the first time, we examined the adsorptive behavior of MP-derived DOM (MP-DOM) on minerals (kaolinite and goethite) using DOM samples leached from commercial plastics including polyvinylchloride (PVC) and polystyrene (PS) under dark and ultraviolet (UV) irradiation conditions. MP-DOM was characterized by a higher distribution of relatively smaller-sized molecules than natural organic matter (NOM). The PS-derived DOM (PS-DOM) leached under UV treatment exhibited more oxygen-containing groups than their counterparts in the dark. MP-DOM also exhibited net negative charges at neutral pH ranges. Adsorption isotherm experiments revealed that the mineral surfaces had high adsorption affinities for both types of MP-DOM, which is likely associated with both electrostatic attraction and ligand exchange. The extent of adsorption was greater for the UV-irradiated than the dark-treated DOM, and on goethite compared to kaolinite. The Fourier-transform infrared (FTIR) spectra of the residual PS-DOM after adsorption revealed differences in the adsorption affinities between its functional groups. Two-dimensional correlation spectroscopy for the irradiated PS-DOM showed that preferential adsorption occurred on minerals in the sequential order of oxidized structures → (PS monomers) → carboxylates in additives → carbonyl groups. The adsorption isotherm model parameters for MP-DOM were comparable to those obtained from aquatic/terrestrial NOM, which suggests that plastic-derived DOM can interact with minerals as strongly as NOM. This study highlights the overlooked role played by plastic-derived DOM in mineral-enriched environments, opening new opportunities for improving our understanding of the fate and environmental impacts of MPs.

Impact of different modes of adsorption of natural organic matter on the environmental fate of nanoplastics

Recently, the exposure of nanoplastics (NPs) in the environment has received extensive attention. Research concerning their fate and transport in the aquatic environment is very important and urgent. In this study, the influence of two sources of natural organic matter (NOM) on the behaviour of NPs were investigated in view of the complexity of NOM. Humic acid (HA), Suwannee River humic acid (SRHA) and Upper Mississippi River NOM (MRNOM) were chosen to represent pedogenic NOM, while bovine serum albumin (BSA) was on behalf of aquagenic NOM. The results showed that NOM could reduce the aggregation and sedimentation of NPs, exhibiting excellent stabilization effect. The stability effect was affected by the concentrations and the sources of NOMs. For pedogenic NOMs, the stabilization effect was caused by adsorption modes with different microscopic morphologies through specific functional groups, while it was induced by the mode of steric stabilization in the presence of BSA. Spectroscopic method and micromorphology study further provided a new insight into exploring the possible mechanism of the interaction between NPs and NOMs.

Efficient adsorption of organic matters and ions by porous biochar aerogel as pre-treatment of ultrafiltration for shale gas wastewater reuse

The large amounts of flowback and produced water (FPW) generated from the shale gas extraction process have characteristics of high salinity and complicated organic matters. It is challenging to treat and reuse it economically. We have verified the reliability of powdered activated carbon (PAC)-ultrafiltration (UF) pre-treatment in treating FPW for reuse in our previous work. To further enhance adsorption efficiency, we employed porous biochar aerogel (PBA) adsorbent to the field of shale gas wastewater treatment for the first time. The PBA synthesized from carbonized chitosan in alkaline solution exhibited three-dimensional porous structure and abundant functional groups. The adsorption of dissolved organic carbon (DOC) in FPW adsorption onto PBA followed the Freundlich isotherm model and pseudo-second-order kinetic model. The PBA adsorbed 52.5% DOC from FPW in just 30 min, which was 2.1 times that of the PAC. Meanwhile, the PBA showed stronger selective adsorption for monovalent ions such as Li+ Na+, Cl−, Br−, and F− than PAC. Besides, the UF membrane fouling caused by pollutants from FPW was reduced owing to PBA adsorption pre-treatment. PBA can reduce UF membrane fouling by 46.8%. Because of its fast and efficient adsorption performance, PBA has tremendous potential in improving the efficiency of FPW treatment.

Adsorption and molecular weight fractionation of dissolved organic matters with different origins on colloidal surface

Dissolved organic matter (DOM) adsorption on colloid surface occurred ubiquitously in aquatic ecosystems, while variations in molecular weight (MW) distribution during adsorption remained poorly understood. In this study, the adsorption and MW fractionation of aquatic DOMs with different origins (e.g., macrophyte- and algae-derived, MDOM and ADOM, respectively) on colloid surface were examined using total organic carbon, absorption and fluorescence spectroscopy, and flow field flow fractionation (FlFFF) analysis. Both the total organic carbon and spectroscopic results showed the predominant adsorption of DOMs within the first 45 min, which behaved not synchronously with MW fractionation. Quantitative FlFFF analysis further indicated that the organic ligands with different MWs exhibited different adsorption affinities on colloid surface. It was found that 5–15 kDa and 50 kDã0.45 μm were preferential adsorption fraction for humic- and protein-like MDOM, respectively, while 0.3–2 kDa and 0.3–50 kDa were preferential adsorption fraction for humic- and protein-like ADOM, respectively. Therefore, the MW fractionation of DOMs upon adsorption was highly dependent on DOM origins as well as specific components. Results obtained herein can enlarge our insights into adsorption and the resultant behavior and fate of DOMs that were highly related with the MW fractionation in aquatic environments.

Organics removal and in-situ granule activated carbon regeneration in FBR-Fenton/GAC process for reverse osmosis concentrate treatment

Fluidized bed reactor Fenton (FBR-Fenton) process was adopted for reverse osmosis concentrate (ROC) treatment with three types of carriers, including sand, zeolite and granular activated carbon (GAC). Adsorption studies demonstrated that GAC achieved the best adsorption performance (maximum COD removal of 78% in 15 h) among the three carriers, and the adsorption of ROC organic matters followed a two-stage adsorption model. Fenton oxidations were carried out in three fluidized beds after column saturation, and FBR-Fenton/GAC process achieved highest COD removal (72%) and most BOD5/COD ratio enhancement (from 0.03 to 0.3) in ROC. Long-term operation data demonstrated good performance stability of GAC as the carrier. In addition, GAC fluidized bed obtained highest total iron removal rate via iron crystallization process. Continuous in-situ GAC regeneration with more than 90% recoveries of surface area, pore volume and adsorption capacity were observed along the ROC treatment with FBR-Fenton/GAC process. Mechanism studies revealed that better COD removal performance in FBR-Fenton/GAC process was attributed to the combining effects of homogenous Fenton reaction, GAC adsorption and GAC/H2O2 catalytic reaction.

Hydrophobic interpenetrating polyamide-PDMS membranes for desalination, pesticides removal and enhanced chlorine tolerance

Hydrophobic membranes for desalination and toxic organic pollutant removal have been fabricated using polyamide - PDMS (polydimethylsiloxane) chemistries in a one-step protocol. The curing of polyamide and PDMS are orthogonal and co-curing both networks imparts hydrophobicity to the thin film composite membranes. The membranes exhibit increased adsorption of pesticides from the feed water along with maintaining excellent salt rejection capability (97% NaCl rejection), thus giving the membranes a multifunctional character. Three toxic pesticides have been used in this study to demonstrate the viability of combining osmosis desalination technology with organic matter adsorption. The membranes also show excellent resistance to fouling by toxic pesticides (85% salt rejection vs 67% for commercial membranes in the presence of pesticides) and significantly improved chlorine tolerance (93.8% salt rejection vs 86.5% for commercial membranes after 20h of exposure to sodium hypochlorite solution).

The relationship of structure and organic matter adsorption characteristics by magnetic cattle manure biochar prepared at different pyrolysis temperatures

Abstract The preparation of magnetic biochar from cattle manure is an effective way for resource utilization. Fe3+-impregnated magnetic biochar for organic matter adsorption was synthesized by pyrolysis at 200, 400, and 600 °C respectively to investigate the influence of pyrolysis temperature on the structure and adsorption properties of magnetic biochar and their interrelationship. Congo red (CR) and Methylene blue (MB) were chosen to a representative of acidic and alkaline organics. The analyses showed that the number of functional groups decreased, and the specific surface area and iron oxides content increased with the increase of pyrolysis temperature. Fe3+ was loaded on biochar in form of γ-Fe2O3 and converted into Fe3O4 when the pyrolysis temperature rose from 400 to 600 °C. As the pyrolysis temperature increased from 200 to 600 °C, the adsorption capacities of magnetic biochar to MB first decreased and then increased, whereas that to CR increased gradually. There are three main structural factors affecting the adsorption properties of magnetic biochar: surface area, functional groups, and iron oxides content. The adsorption of magnetic biochar to MB is mainly related to the competitive mechanism of surface area and functional groups. The main factor affecting the adsorption of MB by MCMB200 (magnetic biochar prepared at 200 °C) and MCMB600 (magnetic biochar prepared at 600 °C) is functional groups and surface area, respectively. The adsorption of CR by magnetic biochar is mainly related to the synergistic mechanism of surface area and iron oxides content.

Dissolved organic matter adsorption from surface waters by granular composites versus granular activated carbon columns: An applicable approach

Many new sorbents have been introduced as an alternative for granular activated carbon (GAC), the most common sorbent for dissolved organic matter (DOM) removal. In the current study, we developed an applicable granular composite based on a flocculant commonly employed for drinking water treatment adsorbed to montmorillonite. DOM adsorption from surface waters, Lake Kinneret and Suwannee River, with low and high specific ultraviolet absorption (SUVA), respectively, by composite and GAC columns, was studied. Adsorption of DOM from Suwannee River was significantly higher by the composite column, in comparison to the GAC column, while an opposite trend was obtained for the adsorption of DOM from Lake Kinneret. In-situ regeneration of the columns with a brine solution was extremely efficient and inefficient for the composite and GAC columns, respectively. Adsorption, of both waters, post-regeneration by the composite column was not compromised, while GAC effectiveness decreased. The opposite trend in DOM adsorption from Suwannee River and Lake Kinneret was explained by the different affinities of the sorbents towards various DOM molecules. Distinguishing between different DOM components adsorbed by GAC and the composite was supported by 13C NMR and direct pyrolysis-GC-MS measurements. Furthermore, we demonstrated that the kinetics and adsorption at the equilibrium of five organic molecules to the composite and GAC can be correlated to their chemical-physical properties. Indeed, combining the properties of both sorbents, by integrating them into a single column, yielded higher DOM removal than by the individual columns. Furthermore, since DOM removal by GAC and by the composite, increases, and decreases with temperature, respectively, the integrated column, mitigates the changes in removal, stabilizing the adsorption performance. Such an integrated filter may minimize additional seasonal and water quality fluctuations.

Study on Uranium Occurrence State of Sandstone-Type Uranium Deposits in Qianjiadian Region, Songliao Basin, China

The Qianjiadian uranium deposit is located in the southwest margin of Songliao basin. In this paper, electron probe, energy spectrum, back scattering analysis, scanning electron microscopy and other experimental methods are used to study uranium occurrence form and uranium mineral type in Qiandaidian uranium deposit. The results are shown as follows. (1) The occurrence forms of uranium in Qiandaidian uranium mining area include uranium minerals, adsorption uranium. The uranium in low-grade ore is mainly in the form of dispersive adsorption, which is clay mineral and organic matter adsorption. The high-grade ore mainly exists in the form of uranium mineral, the type of uranium mineral is mainly pitchblende, followed by coffinite, a small amount of uranium mineral containing titanium. (2) Uranium minerals are often closely symbiotic with pyrite, carbonate and so on, most of them develop in the pyrite, carbonate margin and fractures in the form of colloidal, there are also granular, pellet independent distribution. (3) Uranium minerals are rich in Phosphorus, and there is an obvious positive correlation between Phosphorus and Silicon. It has been found that some samples contain phosphorus-rich uranium aggregates in microspheres, which is considered as a strong evidence that microorganisms are involved in uranium mineralization at low temperature.

Humification in extracellular polymeric substances (EPS) dominates methane release and EPS reconstruction during the sludge stabilization of high-solid anaerobic digestion

High-solid anaerobic digestion (HAD) can directly treat dewatered sewage sludge (total solid content ≥15%) with superior volume efficiency. Sludge stabilization during HAD is expected to achieve by throughout organic degradation and conversion towards methane-rich biogas release and humic formation. Sewage sludge is the combination of microbial zoogleas and theirs adsorption of organic and inorganic matter, in which the extracellular polymeric substances (EPS) account 60-80% of total sludge organic matter, inevitably participating most extracellular metabolic pathways. The interactions between EPS transformation and genetically annotated metabolic pathways were found in this research. In brief, noticing the highly cross-linked structures in EPS with major active components of humic substances (HS) and protein (PN), as PN hydrolysis and decomposition in EPS were enhanced in the high-solid anaerobic condition, the exposure of aromatic groups and sites in HS were considerable. HS release was the main factor shifting the electron exchange capacity and activity, which aided in energy metabolism of sludge microorganisms involved in redox reactions, especially the methanogenesis, thus in turn facilitating the PN degradation; Then, the screened humic groups and active protein derives might act as the beneficial precursors to regenerate neo-humic structures, whose significant bridging effect and signal role on stimulating amino acid biosynthesis, member transport and metallic complexation could further contribute to proteolytic condensation and EPS reconstruction. Hence, the in-depth sludge stabilization mechanism during HAD process was established for developing enlightening strategies.

Crystalline phase and surface coating of Al2O3 nanoparticles and their influence on the integrity and fluidity of model cell membranes

Aluminium oxide nanoparticles (Al2O3 NPs) potentially cause health hazards after their release into the environment. The crystalline phase of Al2O3 NPs determines their surface structure and the number of functional groups. The adsorption of natural organic matter (NOM) or biomolecules on the surface Al2O3 NPs also alters their surface properties and subsequent interactions with organisms. In this study, the roles of the Al2O3 crystalline phase and the surface coating of the nanoparticles on the membrane integrity and fluidity were investigated. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes to detect membrane disruption after exposure to Al2O3 NPs. Due to amorphous structure and high surface activity of γ-Al2O3 NPs, they had a stronger affinity with the membrane and caused more serious membrane rupture than that of α-Al2O3 NPs. The deposition of Al2O3 NPs on the membrane and the induced membrane disruption were monitored by a quartz crystal microbalance with dissipation (QCM-D) method. HA-coated Al2O3 NPs disrupted the SUV layer on the QCM-D sensor, while BSA-coated Al2O3 NPs only adhered to the membrane and induced unremarkable vesicle disruption. In addition, untreated γ-Al2O3 NPs induced remarkable gelation of a negatively charged membrane, but other types of Al2O3 NPs caused negligible membrane phase changes. The outcomes of this study demonstrate that the crystalline phase of the Al2O3 NPs affects the integrity and fluidity of cell membranes. The protein coatings on the NPs weaken the NP-membrane interaction, while HA coatings increase the damage of the NP-induced interaction.

The multilayer model of soil mineral–organic interfaces—a review

AbstractAssociation of organic matter (OM) with minerals is an important pathway in the formation of stable OM in soil. While the importance of mineral–organic associations (MOA) in regulating soil carbon cycling has been rigorously demonstrated by empirical evidence, knowledge about the molecular‐scale arrangement of OM at mineral surfaces is still lacking. Such knowledge is urgently needed to disentangle the mechanisms of long‐term storage of soil OM. Based on indirect observations regarding the formation, composition, and structure of MOA, a conceptual multilayer model was proposed by Kleber et al. in 2007 to foster debate and help elucidating the structure and reactivity of MOA. According to this model, the associated OM at mineral surfaces is discrete and self‐organized into a multilayer structure. In this review, we aim to collect and evaluate existing studies that used this model to explain biogeochemical processes at mineral–organic interfaces, and based on this, assess the applicability of the model. The multilayer model has seen extensive adoption within soil science and related fields. In general, existing studies either support the concept of a patchy distribution of adsorbed OM on mineral surfaces or advocate that OM can be coprecipitated with nanosized poorly crystalline minerals or hydrolysable metals. However, the evidence for the patchy distribution of adsorbed OM cannot support the multilayer model on its own. There is little consensus about the role of N‐rich OM in forming the contact zone according to the multilayer model but surface conditioning by different classes of organic compounds appears to be an essential factor for the overall adsorption of OM. Nevertheless, large uncertainty still remains with respect to multilayer‐like organization of MOA. By taking advantage of recent developments in surface analytical sciences and computational chemistry, a rigid experimental testing of the multilayer model at the molecular level is still required and awaits to be integrated into improved concepts of MOA formation and OM stabilization.

Adsorption and coadsorption of single and multiple natural organic matter on Ag (1 1 1) surface: A DFT-D study

The nature of the interaction of low molecular weight natural organic matter (NOM) with the Ag (1 1 1) surface is of crucial importance in the environment. The low molecular weight organics used in this study are formic acid (FA), acetic acid (AA1) and ascorbic acid (AA2). In this study, we think of a realistic environment where single, multiple or even a mixture of NOM’s can attach on one Ag (1 1 1) surface. Such critical information is relevant in order to understand the behaviour of engineered nanoparticles (ENPs) when they get into the environment. To bridge this gap, we investigate the adsorption and co-adsorption properties of NOM’s on Ag (1 1 1) surface using dispersion-corrected density functional theory (DFT-D) in the gas phase and water as a solvent. Throughout this paper, the number behind the letter represents the number of molecules i.e. nFA, nAA1, nAA2 (n = 1, 2, 3, 4). The results of the calculated adsorption energy suggest that the interaction of 4FA, 2AA1 and 2AA2 molecules with Ag (1 1 1) surface is the strongest with the most negative values (−6.54 and −3.84 eV) in both gas phase and COSMO respectively which reveals that is the most stable system. The global reactivity descriptors in the gas phase and water as a solvent were calculated.

Mechanistic understanding of the adsorption of natural organic matter by heated aluminum oxide particles (HAOPs) via molecular dynamics simulation

Membrane fouling caused by natural organic matter (NOM) in water is a pressing problem. To address this, heated aluminum oxide particles (HAOPs) have been used as dynamic membranes pre-deposited onto the primary membrane to effectively remove NOM and thereby significantly diminish the fouling potential. An in-depth understanding of the mechanisms underlying the superior performance of HAOPs remains amiss, which motivated this study. Molecular dynamics (MD) simulations were conducted to systematically compare the performance of HAOPs, which have been reported to be particularly effective for high molecular weight (HMW) NOM, with the conventional powdered activated carbon (PAC) adsorbent. Six NOM constituents, three of which have HMW and three have low molecular weight (LMW), were studied. Results indicate that the mechanisms underlying the effective removal of HMW NOM by HAOPs include: (1) higher foulant-HAOPs interaction energy; (2) greater hydration of the HMW NOM, which thereby increases the affinity to the more hydrophilic HAOPs; (3) diminished mobility of the foulant once adsorbed, which deters desorption; and (4) higher peak intensities in the radial distribution functions for multiple functional groups on the HMW NOM foulants. These results are expected to be valuable towards the better design of such materials for mitigating membrane fouling.

The magnetic fabric of the Wolfcamp shale, Midland Basin, west Texas: Understanding petrofabric variability, hydrocarbon associations, and iron enrichment

Rock fabrics have long been recognized as a key variable influencing unconventional reservoir properties, and yet, petrofabric analysis is rarely incorporated in reservoir characterization in a quantitative and scalable manner. This work introduces anisotropy of magnetic susceptibility (AMS) coupled with handheld x-ray fluorescence to define the origin of petrofabrics in the Wolfcamp shale and examine their relationship with total organic carbon (TOC) and oil saturation indices (OSI). Standard paleomagnetic plugs were drilled from three vertical cores spanning the entire Wolfcamp shale in the Midland Basin, west Texas. Low-temperature magnetic experiments suggest paramagnetic minerals contribute between 93.4% and 98.6% to the low-field bulk magnetic susceptibility (klf) across all lithotypes. Scanning electron microscopy revealed frequent occurrences of paramagnetic minerals such as chlorite, illite, ferroan dolomite, marcasite, and pyrite. The Fe-rich clays such as chlorite carry the AMS signal in mudrocks with a minor contribution from ferroan dolomite. Conversely, ferroan dolomite carries the AMS signal in most carbonate facies with a minor influence from Fe-rich clays. The degree of magnetic anisotropy (Pj) and shape factor (T) in mudrocks are compositionally dependent and respond to changes in both clay and framework grain concentration. For carbonate facies, Pj and T vary widely because of changes in depositional facies and the concentration of ferroan dolomite. The TOC correlates well with Pj and strongly oblate magnetic fabrics. This relationship likely stems from the adsorption of organic matter (OM) to clays during deposition and may indicate that organoclay composites were responsible for delivering OM to the Midland Basin. Elevated OSI are fabric selective, favoring low Pj and T fabrics, suggesting that such fabrics facilitate hydrocarbon migration more so than high Pj and T fabrics. Fuzzy c-means clustering provides a framework to describe AMS and geochemical transitions at the core scale and could serve as a tool to map barriers and pathways to hydrocarbon migration. Finally, Ti–Nb and klf data point to a mafic provenance lithotype and suggest layered intrusive complexes in the Central Basin uplift were exposed and eroded during deposition of the Wolfcamp shale. Mafic source rocks probably increased supply of micronutrients such as dissolved iron and may have enhanced productivity in the Midland Basin.

A novel process of adsorption cum enhanced coagulation-flocculation spiked with magnetic nanoadsorbents for the removal of aromatic and hydrophobic fraction of natural organic matter along with turbidity from drinking water

Abstract The present study developed a novel conjugate process for the removal of aromatic, hydrophobic fraction of natural organic matter and turbidity from drinking water supplies. Magnetic nanoadsorbents were synthesized under laboratory conditions and their surface properties were enhanced by surface modifiers followed by their characterization. The synthesized magnetic nanoadsorbents was then used in combination with conventional aluminum and iron coagulants for the removal of both natural organic matter and turbidity from drinking water. Adsorption cum enhanced coagulation-flocculation study was conducted in two different stages i.e. adsorption of natural organic matter by magnetic nanoadsorbents (stage 1) followed by coagulation-flocculation experiments using conventional coagulants like alum and ferric chloride (stage 2). Study indicated that magnetic nanoadsorbents-alum conjugate process is efficient in removing trihalomethane precursors. Significant removal of dissolved organic matter (98.7%), ultra violet absorbance at 254 nm (99.7%) and trihalomethane formation potential (91%) was achieved. The overall study showed that the developed magnetic nanoadsorbents-alum conjugate process is highly efficient in removing the trihalomethane precursors with a marked reduction in the overall cost for its large scale application.

Distribution, Enrichment and Transport of Trace Metals in Sediments from the Dagu River Estuary in the Jiaozhou Bay, Qingdao, China

26 river bank sediments and 15 estuary seafloor sediments were sampled from the Dagu River and the estuary of Northwestern Jiaozhou Bay to determine contaminations of heavy metals and metalloids (Cu, Pb, Zn, Cr, Cd, Hg and As). The trace metal contents in sediment from the estuary area were much higher than those of the river. Correlation analysis showed that except for Pb, the metals were mainly controlled by the grain size, and enriched by adsorption of aluminosilicate minerals, Fe/Mn oxides and organic matter in river and estuary sediments. In addition to Cu in some stations, the metals met the requirements of the marine organism and humans for the quality of the marine environment. The concentrations of Cu, Pb, Cr, Hg and As were between the threshold effect level (TEL) and probable effect level (PEL), indicating those metals might have occasional adverse effects. Results of Enrichment Factor values revealed that the entire study area was enriched in Pb and Hg, at moderate environmental risk, but the estuary was more significant. Pb and Hg contaminations in this area were mainly from coal combustion and automobile emissions. River runoff and atmospheric deposition dominated the metals distribution and enrichment in the study area. Contaminants in sediments entering the estuary were further transported to the south and east under the river runoff and reciprocating current in the Jiaozhou Bay.

Reduction of organic matter from municipal wastewater at low cost using green synthesis nano iron extracted from black tea: Artificial intelligence with regression analysis

Nanotechnology especially green synthesis nanoparticles is the modern technology for the adsorption and degradation a wide range of wastewater contaminants. The prepared Green Synthesis nano Zero Valent Iron (GT-nZVI) extracted from soft black tea was characterized using XRD, SEM, and EDAX analysis. This study explores different nonlinear adsorption and kinetic models that can describe the adsorption mechanism of organic matter represented in COD and BOD onto GT-nZVI. The effect of GT-nZVI on COD and BOD removal were studied at different pH, adsorbent dose, contact time, stirring rate, and concentrations. The results indicated that GT-nZVI is effective in the removal of COD and BOD from wastewater, where the removal efficiencies of 87.9 and 100% were achieved for 600 ± 15.0 and 100 ± 11.8 mg/L COD, respectively, and 91.3 and 100% for 365 and 60 mg/L BOD, respectively. Also, GT-nZVI is a highly effective material for wastewater contaminants removal and pass the Egyptian Ministerial Resolution No. 92 of 2013 limits with Operating and Maintenance Cost 0.440 $ USD. The adsorption isotherm data of COD and BOD fitted well to Freundlich and khan, respectively, and Pseudo Second Order kinetic model. Artificial neural network importance data agree with the result of response surface methodology in simulating the adsorption of organic matter onto GT-nZVI indicating the most significant coverable is adsorbent dose. Finally, this study appropriates using GT-nZVI in highly salted municipal wastewater rather than traditionally activated sludge treatment techniques.

Modelling the adsorption of natural organic matter on Ag (111) surface: Insights from dispersion corrected density functional theory calculations

Understanding the nature of the interactions between natural organic matter (NOM) and engineered nanoparticles (ENPs) is of crucial importance in understanding the fate and behaviour of engineered nanoparticles in the environment. In the present study, dispersion-corrected density functional theory (DFT-D) has been used to elucidate the molecule-surface interactions of higher molecular weight (HMW) NOM ambiguously present in the aquatic systems, namely: humic acid (HA), fulvic acid (FA) and protein Cryptochrome (Cry) on Ag (111) surface. Investigations were done in the gas phase and to mimic real biological environment, water has been used as a solvent within the conductor-like screening model (COSMO) framework. The calculated adsorption energies for HA, FA and Cry on Ag (111) surface were −27.90 (−18.45) kcal/mol, −38.28 (−18.68) kcal/mol and −143.89 (−150.82) kcal/mol respectively in the gas (solvent) phase and the equilibrium distances between the surface and HA, FA and Cry molecules were 1.87 (2.18) Å, 2.31(2.31) Å and 1.91 (1.70) Å respectively in the gas (solvent) phase. In both gas and water phase Cry showed stronger adsorption which means it has a stronger interaction with Ag (111) surface compared to HA and FA. The results for adsorption energy, solvation energy, isosurface of charge deformation difference, total density of state and partial density of states indicated that indeed these chosen adsorbates do interact with the surface and are favourable on Ag (111) surface. In terms of charge transfer, one of many calculated descriptors in this study, electrophilicity (ω) concur that charge transfer will take place from the adsorbates to Ag (111) surface.