Water-soluble Contaminants Research Articles

Fe-doped ZnO nanoparticles prepared by high energy ball milling with enhanced sonophotocatalytic performance

Zinc oxidenanostructures were synthesized using a thermal decomposition method and subsequently doped with Fe (III)in this study. Techniques such as X-ray diffraction, Field emission scanning electron microscopy, and Fourier transform infrared spectroscopy were used to investigate the structural and chemical composition of nanomaterials. Fe-doped ZnO was synthesized using a simple, low-cost planetary high-energy ball milling process. The sonophotocatalytic activity of Fe-doped ZnO under visible light and ultrasonic waves was then studied. Another aspect of this study is the utilization of visible light, which is far more accessible and cost-effective than UV light. Malachite green (MG) and phenol were applied as water-soluble contaminants. MG degraded about 87.65% after 1 h in the presence of a Fe-doped ZnO catalyst under visible light and ultrasonic waves simultaneously. Phenolwas degraded by approximately 64.50% under the same conditions.

Pollution assessment and index properties of Okpulor soils, Rivers State, Nigeria: geochemical characterization, geotechnical and geoenvironmental implications

This study assessed soil pollution and index properties in Okpulor through geochemical, geotechnical, and geoenvironmental analyses. Twenty samples, comprising 14 surface and 6 shallow subsurface ones, underwent geochemical analysis for heavy metals (Fe, Cr, Cu, Zn, Ni, and Pb). Five geochemical indices, including the Geoaccumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), Metal Pollution Index (MPI), and Potential Ecological Risk Index (PERI), were utilized. Simultaneously, six subsurface samples underwent geotechnical analysis for Natural Moisture, Grain Size, Specific Gravity, Bulk Density, and Atterberg Limits, following Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) guidelines. The Igeo highlighted significant heavy metal contamination in Okpulor soils, particularly Cd. EF values exceeding 1.5 underscored a strong anthropogenic influence, with CF indicating Cd's substantial contribution to overall contamination. PERI underscored the ecological risks associated with Cd contamination. Natural moisture content, ranging from 18.21% to 21.45%, indicated a notable presence of water in the soil during the dry season, potentially leading to increased leaching and migration of water-soluble contaminants. Bulk density values suggested moderate to lightly packed soils, impacting porosity and permeability, and influencing contaminant movement. Atterberg limits indicated low soil plasticity, impacting moisture retention and contaminant behaviour. Grain size analysis revealed poorly graded soils with a close sand-to-clay ratio, affecting water drainage. These geotechnical properties and heavy metal contamination reveal the intricate interplay between soil characteristics and contamination risks in the Okpulor area, emphasizing the need for targeted interventions to safeguard the environment.

Fabrication of TiO2/WO3 heterostructure mesh with hierarchical structures, a tool for oily wastewater treatment

To address water pollution caused by the water-soluble organic contaminants and oily wastewater, a multifunctional TiO2/WO3 heterostructure mesh exhibiting superhydrophilic/underwater superoleophobic behavior has been developed by a combination of hydrothermal and solvothermal methods followed by an annealing process. The formation of TiO2/WO3 heterostructure was established by the XPS and TEM analysis. Exhibiting exceptional water affinity and underwater oil-rejection behavior, the TiO2/WO3 mesh separates different mixtures of water with oil of varying densities achieving efficiency of ∼98% for lighter oils and 97% for heavier oils respectively. Moreover, the TiO2/WO3 mesh separates emulsified oil from water with an efficiency of ∼95% following the size-sieving effect. The corresponding separation flux was found to be ∼31,560 Lm−2hr−1, 15,759 Lm−2hr−1 and 523 Lm−2hr−1 for lighter oil-water, heavier oil-water and emulsions respectively. In addition to this, the TiO2/WO3 mesh demonstrated outstanding self-cleaning behavior and exceptional abrasion resistance ability. Furthermore, the filtrate's organic contaminants were effectively degraded by the Z-scheme TiO2/WO3 heterostructure mesh with exceptional efficiency (∼92%). Owing to the outstanding ability to separate light oil-water, heavy oil-water and emulsions along with powerful photocatalytic degradation capabilities, the TiO2/WO3 heterostructure mesh stands out as an innovative material in the practical field of oily wastewater remediation.

Pioneering the preparation of porous PIM-1 membranes for enhanced water vapor flow.

In this study, porous polymers of intrinsic microporosity (PIM-1) membranes were prepared by non-solvent induced phase inversion (NIPS) and investigated for water vapor transport in view of their application in membrane distillation (MD). Due to the lack of high boiling point solvents for PIM-1 that are also water miscible, the mixture of tetrahydrofuran (THF) and N-methyl-2-pyrrolidone (NMP) was found to be optimal for the formation of a membrane with a developed porous system both on the membrane surface and in the bulk. PIM-1 was synthesized by using low and high temperature methods to observe how molecular weight effects the membrane structure. Low molecular weight PIM-1 was produced at low temperatures, while high molecular weight PIM-1 was obtained at high temperatures. Several membranes were prepared, including PM-6, PM-9, and PM-11 from low molecular weight PIM-1, and PM-13 from high molecular weight PIM-1. Scanning electron microscopy (SEM) was used to image the surface and cross-section of different porous PIM-1 membranes. Among all the PIM-1 membranes (PM) obtained, PM-6, PM-9, PM-11 and PM-13 showed the most developed porous structure, while PM-13 showed large voids in the bulk of the membrane. Contact angle measurements showed that all PIM-1 porous membranes are highly hydrophobic. Liquid water flux measurements showed that PM-6, PM-9 and PM-11 showed minimal water fluxes due to small surface pore size, while PM-13 showed a high water flux due to a large surface pore size. Water vapor transport measurements showed high permeance values for all membranes, demonstrating the applicability of the developed membranes for MD. In addition, a thin film composite (TFC) membrane with PIM-1 selective layer was prepared and investigated for water vapor transport to compare with porous PIM-1 membranes. The TFC membrane showed an approximately 4-fold lower vapor permeance than porous membranes. Based on these results, we postulated that the use of porous PIM-1 membranes could be promising for MD due to their hydrophobic nature and the fact that the porous membranes allow vapor permeability through the membrane but not liquid water. The TFC membrane can be used in cases where the transfer of water-soluble contaminants must be absolutely avoided.

Coal fly ash-supported ZnO-promoted TiO2 towards UV photocatalytic degradation of anthraquinone dye: Parametric optimization, kinetics and mechanism studies

Heterogeneous photocatalysis via combination of catalyst and UV irradiation is one of the most promising advanced oxidation processes for degradation of water-soluble organic contaminants. Herein, different photocatalysts (ZnO/CFA, TiO2/CFA, and TiO2-ZnO/CFA) were synthesized via sol-gel and impregnation techniques and applied for the degradation of acid blue 25 (AB25) dye in aqueous solution under UV light in a photoreactor. Various spectroscopic techniques (XRF, XRD, BET, FTIR, UV–vis DRS, TEM and EDS) were employed to evaluate the chemical structure, functional groups, textural, and optical properties of the binary and ternary composites. TiO2-ZnO/CFA displayed rapid degradation of AB25 as compared to ZnO/CFA and TiO2/CFA, owing to the dualistic photocatalytic sites. The prepared TiO2-ZnO/CFA composite was used in synergy with the photoreactor for photocatalytic degradation process optimization, and the optimum degradation conditions in relation to initial AB25 concentration (10 mg/L), UV light intensity (18 W/m2), flow rate (12.5 L/h), and irradiation time (150 min) as input parameters were determined using Taguchi design approach. The maximum photocatalytic degradation efficiency was 98.79±0.94% under those aforementioned conditions, indicating that the synergies between the photoreactor and the TiO2-ZnO/CFA photocatalyst resulted in the effective destruction of AB25 dye molecules. Furthermore, the spent photocatalyst was easily removed from the degraded solution and reused up to nine times. After 150 mins of UV irradiation with TiO2-ZnO/CFA photocatalyst, almost complete mineralization of AB25 solution was achieved.

Hydrophobic microenvironment mediated photo-Fenton beads confining free radicals in vicinity of water-soluble contaminants for enhancing water purification

Heterogeneous photo-Fenton process can produce reactive oxygen species (ROS) on the catalysts surface; however, it will decay quickly in bulk solution, resulting in low utilization rate. Herein, we design a hydrophobic microenvironment mediated polymer beads (HMPBs) as an alternative platform to immobilize Fenton-like catalysts for efficiently confining ROS in hydrophilic area and improving mass transfer. Molecular dynamics simulation predicted that diffusion of reactants will slow down on mixed hydrophilic/hydrophobic interface so that the short-lived ROS can oxidize contaminants efficiently. Consequently, the optimal HMPBs exhibits remarkably increased degradation kinetic constants, which is about 4.4 and 1.5-fold improvement in comparison with single hydrophilic and hydrophobic beads, respectively. The continuous flow degradation system with packed column type is further developed to expanded its application for Fenton-like oxidation. Altogether, this work revealed the wettability effects on the Fenton chemstrity, manifesting a deeper understanding of ROS-based reaction behaviors on special wettability interface.

Developmental bisphenol S toxicity in two freshwater animal models

Freshwater animals are exposed to anthropogenic contaminants and are biomonitors of water quality and models of the deleterious impacts of exposure. Sponges, such as Ephydatia muelleri, constantly pump water and are effective indicators of water-soluble contaminants. Zebrafish (Danio rerio), native to Southeast Asia, live in the water column and feed at the water-sediment interface and are exposed to both water-soluble and insoluble contaminants. While sponges and zebrafish diverged ∼700 million years ago, they share common genetic elements, and their response to contaminants can be predictive to a wide-range of animals. An emerging contaminant, bisphenol S, was tested to evaluate its toxicity during development. The toxicity and mechanism(s) of action of BPS is not well known. Water-borne exposures to BPS caused differing hatching rates, morphological changes, and shared gene expression changes of toxicologically-relevant genes. This study shows that BPS causes similarly adverse developmental impacts pointing to some overlapping mechanisms of action.

Super-amphiphobic arabic gum-based coatings on textile for on-demand oily and dye wastewater treatment

Different membrane materials have broadly been constructed for oil-containing water separation, but most of preparation routes involve corrosive or toxic chemicals and especially many materials have only single superwetting property. Herein, a novel and eco-friendly cellulose-based textile membrane is developed by incorporating the composite coating consisting of arabic gum (AG), attapulgite (APT), and iron (Fe) onto cellulose textiles. The functionalized textile is superoleophobic underwater and superhydrophobic underoil. As a result, the textile prewetted with water or oil can be employed to separate light oil layer/water and heavy oil layer/water mixtures, respectively, and the separation efficiency to the two types of mixtures is larger than 98.3 %. Results also reveal that the decorated textile possesses superior stability and recyclability in purifying oily wastewater. More importantly, such coated textile is capable of filtrating water-soluble contaminants (dyes) from polluted water. Due to the versatility and environmental compatibility of product as well as the accessibility as agricultural and forestry product as raw materials, the advanced textiles may offer effective solutions to oily wastewater purification and water-soluble contaminant removal.

Sonochemical synthesis and characterization of Sm2CuO4 nanostructures and their application as visible-light photocatalyst for degradation of water-soluble organic pollutants

In recent years, water contamination has become a significant crisis, and it is crucial to find new materials that can efficiently eliminate these contaminants. The current work presents the Sm2CuO4 nanophotocatalyst for the decolorization of different water-soluble organic contaminants. The fabrication of Sm2CuO4 nanostructures was achieved using a simple and rapid sonochemical pathway, resulting in an optical bandgap of 1.62 eV as determined by diffuse reflectance spectroscopy. Several factors, including different organic contaminants, organic contaminant concentrations, Sm2CuO4 dosages, and the pH of the media, were scrutinized to achieve the best efficiency. The results manifested that Sm2CuO4 was highly effective in removing different organic contaminants from water. For example, when 30 mg of Sm2CuO4 was used with 20 mg L−1 methyl orange under visible irradiation for 100 min, 91.4% of the methyl orange was destroyed. Further investigation revealed that holes (h+) were primarily responsible for pollutant photodegradation when using Sm2CuO4 as a photocatalyst. This finding suggests that Sm2CuO4 could be an excellent candidate for developing new materials to effectively remove water contaminants.

Dual-functional superwetting CuCo2O4 coated stainless steel mesh for wastewater treatment: Highly efficient oil/water emulsion separation and photocatalytic degradation

Oily water and soluble contaminants from marine oil spills, industrial wastewater and domestic sewage has caused serious water pollution. Although advanced membranes with super-wettability have been used in oil/water separation, most of them lack the capacity to separate oil/water emulsions and remove water-soluble contaminants. Herein, a dual-functional CuCo2O4 nanoneedle array coated stainless steel mesh is successfully fabricated for water purification. The as-prepared mesh shows excellent superhydrophilicity-underwater superoleophobicity and superior anti-oil-fouling capability. The as-prepared mesh can efficiently separate oil/water emulsion and photodegrade soluble organic dyes under UV light irradiation. The as-prepared mesh exhibits the superior oil/water separation emulsion performance with separation efficiency > 99.5% and high flux (172 L m−2 h−1). In addition, the as-prepared mesh possesses excellent photodegradation performance toward organic dyes with a degradation efficiency of more than 96.95%. More importantly, the as-prepared mesh shows durability and stability. The as-prepared mesh has great potential for multi-functional water purification.

Encapsulation of zero valent iron nanoparticles in biodegradable amphiphilic janus particles for groundwater remediation

Reactive Zero Valent Iron (ZVI) nanoparticles have been widely explored for in situ ground water remediation to degrade both non-aqueous phase liquid (NAPL) and water-soluble contaminants. However, they usually suffer from rapid oxidation and severe agglomerations restricting their delivery at NAPL/water interface. Aim of this study was to encapsulate the ZVI nanoparticles (50 nm) in amphiphilic bicompartmental Janus particles (711 ± 11 nm) fabricated by EHDC (electrohydrodynamic co-jetting). The dual compartments were composed of PLA (polylactic acid) and a blend of PLA, PE (poly (hexamethylene 2,3-O-isopropylidenetartarate) and PAG (photo acid generator). Upon UV irradiation, PAG releases acid to unmask hydroxyl groups present in PE to make only PE compartment hydrophilic. The entrapped ZVI nanoparticles (20 w/w%; ∼99 % encapsulation efficiency) were observed to degrade both hydrophilic (methyl orange dye) and hydrophobic (trichloro ethylene) contaminants. UV treated Janus particles provided stable dispersion (dispersed up to 3 weeks in water), prolonged reactivity (∼24 days in contaminated water), and recyclability (recyclable up to 9 times) as compared to non-treated ones. In addition, the amphiphilic Janus particles demonstrated high transportability (>95%) through porous media (sand column) with very low attachment efficiency (0.07), making them a promising candidate to target contaminants at NAPL/water interface prevailed in groundwater.

Evaluating the effectiveness of a geostatistical approach with groundwater flow modeling for three-dimensional estimation of a contaminant plume

When assessing the risk from an underground environment that is contaminated by radioactive nuclides and hazardous chemicals and planning for remediation, the contaminant plume distribution and the associated uncertainty from measured data should be estimated accurately. While the release history of the contaminant plume may be unknown, the extent of the plume caused by a known source and the associated uncertainty can be calculated inversely from the concentration data using a geostatistical method that accounts for the temporal correlation of its release history and groundwater flow modeling. However, the preceding geostatistical approaches have three drawbacks: (1) no applications of the three-dimensional plume estimation using concentration data from multiple depths in real situations, (2) no constraints for the estimation of the plume distribution, which can yield negative concentration and large uncertainties, and (3) few applications to actual cases with multiple contaminants. To address these problems, the non-negativity constraint using Gibbs sampling was incorporated into the geostatistical method with groundwater flow modeling for contaminant plume estimation. This method was then tested on groundwater contamination in the Gloucester landfill in Ontario, Canada, using three-dimensional contaminant transport model and concentration data from multiple depths. The method was applied to three water soluble organic contaminants: 1,4-dioxane, tetrahydrofuran, and diethyl ether. The effectiveness of the proposed method was verified by the general agreement of the calculated plume distributions of the three contaminants with concentration data from 66 points in 1982 (linear correlation coefficient of about 0.7). In particular, the reproduced peak of 1,4-dioxane corresponding to the large disposal in 1978 was more accurate than the result of preceding minimum relative entropy-based studies. The same peak also appeared in the tetrahydrofuran and diethyl ether distributions approximately within the range of the retardation factor derived from the fraction of organic carbon.

Determining Toxic Potencies of Water-Soluble Contaminants in Wastewater Influents and Effluent Using Gene Expression Profiling in C. elegans as a Bioanalytical Tool

With chemical analysis, it is impossible to qualify and quantify the toxic potency of especially hydrophilic bioactive contaminants. In this study, we applied the nematode C. elegans as a model organism for detecting the toxic potency of whole influent wastewater samples. Gene expression in the nematode was used as bioanalytical tool to reveal the presence, type and potency of molecular pathways induced by 24-h exposure to wastewater from a hospital (H), nursing home (N), community (C), and influent (I) and treated effluent (E) from a local wastewater treatment plant. Exposure to influent water significantly altered expression of 464 genes, while only two genes were differentially expressed in nematodes treated with effluent. This indicates a significant decrease in bioactive pollutant-load after wastewater treatment. Surface water receiving the effluent did not induce any genes in exposed nematodes. A subset of 209 genes was differentially expressed in all untreated wastewaters, including cytochromes P450 and C-type lectins related to the nematode’s xenobiotic metabolism and immune response, respectively. Different subsets of genes responded to particular waste streams making them candidates to fingerprint-specific wastewater sources. This study shows that gene expression profiling in C. elegans can be used for mechanism-based identification of hydrophilic bioactive compounds and fingerprinting of specific wastewaters. More comprehensive than with chemical analysis, it can demonstrate the effective overall removal of bioactive compounds through wastewater treatment. This bioanalytical tool can also be applied in the process of identification of the bioactive compounds via a process of toxicity identification evaluation.Graphical abstract

Anaerobic degradation of benzene and other aromatic hydrocarbons in a tar-derived plume: Nitrate versus iron reducing conditions

The anaerobic degradation of aromatic hydrocarbons in a plume originating from a Pintsch gas tar-DNAPL zone was investigated using molecular, isotopic- and microbial analyses. Benzene concentrations diminished at the relatively small meter scale dimensions of the nitrate reducing plume fringe. The ratio of benzene to toluene, ethylbenzene, xylenes and naphthalene (BTEXN) in the fringe zone compared to the plume zone, indicated relatively more loss of benzene in the fringe zone than TEXN. This was substantiated by changes in relative concentrations of BTEXN, and multi-element compound specific isotope analysis for δ2H and δ13C. This was supported by the presence of (abcA) genes, indicating the presumed benzene carboxylase enzyme in the nitrate-reducing plume fringe. Biodegradation of most hydrocarbon contaminants at iron reducing conditions in the plume core, appears to be quantitatively of greater significance due to the large volume of the plume core, rather than relatively faster biodegradation under nitrate reducing conditions at the smaller volume of the plume fringe. Contaminant concentration reductions by biodegradation processes were shown to vary distinctively between the source, plume (both iron-reducing) and fringe (nitrate-reducing) zones of the plume. High anaerobic microbial activity was detected in the plume zone as well as in the dense non aqueous phase liquid (DNAPL) containing source zone. Biodegradation of most, if not all, other water-soluble Pintsch gas tar aromatic hydrocarbon contaminants occur at the relatively large dimensions of the anoxic plume core. The highest diversity and concentrations of metabolites were detected in the iron-reducing plume core, where the sum of parent compounds of aromatic hydrocarbons was greater than 10 mg/L. The relatively high concentrations of metabolites suggest a hot spot for anaerobic degradation in the core of the plume downgradient but relatively close to the DNAPL containing source zone.

The joint effects of salt and 6PPD contamination on a freshwater herbivore

Using sodium chloride (NaCl) for de-icing roads is known to have severe consequences on freshwater organisms when washed into water bodies. N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, also known as 6PPD, is an antiozonant mainly found in automobile tire rubber to prevent ozone mediated cracking or wear-out. Especially the ozonated derivate, 6PPD-quinone, which is washed into streams after storm events, has been found to be toxic for coho salmon. Studies on other freshwater organisms could not confirm those findings, pointing towards distinct species-specific differences. Storm events result in greater run-offs from all water-soluble contaminants into freshwater bodies, potentially enhancing the concentrations of both chloride and 6PPD during winter. Here we show that these two contaminants have synergistic negative effects on the population growth of the rotifer Brachionus calyciflorus, a common freshwater herbivore. Hence, while only high concentrations of 6PPD and even higher concentrations of 6PPD-quinone, beyond environmentally relevant concentrations, had lethal effects on rotifers, the addition of NaCl enhanced the sensitivity of the rotifers towards the application of 6PPD so that their negative effects were more pronounced at lower concentrations. Similarly, 6PPD increased the lethal effect of NaCl. Our results support the species-specific toxicity of 6PPD and demonstrate a synergistic effect of the antiozonant on the toxicity of other environmentally relevant stressors, such as road salt contamination.

Highly porous cryogels loaded with bimetallic nanoparticles as an efficient antimicrobial agent and catalyst for rapid reduction of water-soluble organic contaminants

The development of robust materials possessing simultaneously antibacterial and catalytic activities for the reduction and removal of organic pollutants from wastewater with enhanced efficacy has received unwavering interest. Herein, highly porous and thermo-responsive cryogels of poly(N-isopropylacrylamide-co-acryamido-2-methylpropane sulfonic acid) have been fabricated via redox-initiated cryo-polymerization. Silver/gold bimetallic nanoparticles were introduced into a bare cryogel through thermal reduction of metal salts. The fabricated bare cryogels and bimetallic integrated cryogel were confirmed with different techniques including fourier transform infrared spectroscopy. The crystallinity of bare cryogels and bimetallic nanoparticles inside cryogel was examined by using powder X-ray diffraction. Thermo-gravimetric analysis confirmed that bimetallic nanoparticle loaded cryogels were thermally more stable than bare cryogels. The macro-porosity of cryogels before and after loading bimetallic nanoparticles were studied by using scanning electron microscopy. Energy dispersive X-ray and X-ray photoelectron spectroscopy were implemented, confirming the presence of metal elements in the synthesized bimetallic hybrid cryogel. Furthermore, the uniform distribution of silver and gold nanoparticles in cryogel was examined with transmission electron microscopy. The fabricated bimetallic nanoparticle loaded cryogel exhibited high antibacterial activities against E. coli and S. aureus as well as the good catalytic capacity for the rapid reduction of p-nitrophenol and rhodamine B. Catalytic activity was also examined at various temperatures, different pH values and catalyst amounts. The activation energy (Ea = 34.41 kJ mol-1), enthalpy change (ΔH = - 31.92 kJ mol-1) and entropy change (ΔS = −145.19 J mol-1 k-1) of catalytic reduction activation were determined using Arrhenius and Eyring equations. The catalytic performance of bimetallic nanoparticle loaded cryogel was also examined in pure water and tap water. The fabricated bimetallic catalyst was highly stable up to five consecutive cycles without any change in their catalytic performance.

Research of the dynamics and level of watercourse pollution by paper and paperboard production processes

The use of waste paper as a fibrous semi-finished product in the production of paper and paperboard products makes it possible to somewhat reduce the consumption of cellulose. However, waste paper contains a number of water-polluting components of mineral and organic nature, which were introduced into its composition at the stage of production. One of the issues that may arise in the design of technological systems for the production of a given type of paper or cardboard or in the reconstruction of existing production to reduce losses of fibrous semi-finished products and ensure their optimal use or reduce fresh water consumption is to calculate the pollution and also to determine the impact of cardboard and paper production tanks and treatment plants on the dynamics and level of watercourse pollution. To study and analyze the paper and cardboard production processes, which belong to the class of complex technological systems, a methodology was developed that, using computer technology, allows assessing the state of a technological system until its implementation in action. However, from a practical point of view, methods still should be developed that will allow the designer to find solutions to problems that may arise at the design stage of the technological system for production of a given type of paper or cardboard or in the reconstruction of existing production. These problems are related to the calculation of the pollution level and the determination of impact from cardboard and paper production tanks and treatment facilities. The purpose of this article is to conduct research and forecast calculations based on mathematical models to determine the patterns of influence exerted by tanks on the dynamics and level of watercourse pollution in the production of paper and cardboard. The generalized technological system of cardboard production, which is presented in the form of a material flow graph, is taken as an object for research. Water-soluble contaminants of mineral and organic nature enter the production system together with fibrous raw materials, partly with fresh water, and with chemical additives used to impart certain qualities to the product at the stage of its production and at the stage of mechano-chemical water purification. In order to study their impact, it is necessary to conduct at least two stages of calculations on a personal computer using pre-designed models for the dynamics and level of watercourse pollution. At the first stage, the dynamic characteristics of each element of the technological system were equated to elements that do not have a dynamic delay and for which the passage of all watercourses is subject to the speed at which the cardboard web is cast on the mesh. The number of cycles before equilibrium is 99. In the second stage of calculations, it was taken into account that the four tanks in the technological system of production are characterized by a moment of delay and, therefore, the values ​​of delay factors were chosen based on water reserves that accumulate in these basins. The number of cycles before equilibrium in the second stage increased to 264. The main conclusion from the analysis of two options: the technological system in both cases goes to equilibrium at equal values ​​for all components of water-soluble mineral and organic components. However, there are often situations when, in the process of developing (designing) a complex technological system for the production of paper or cardboard, developers are interested in the weighted average concentration of water-soluble mineral components that most affect the state of water flows, and then the technological system can be simplified and presented as a single container linked to the environment. Analysis of the calculation formula of the time for the technological system to reach equilibrium shows that the time value is largely determined by the ratio of the water capacity (W) of the process system to the amount of water (BS) removed from the system. The greater the water capacity of the technological system and the smaller the BS, the longer the time the technological system reaches equilibrium. The next step of the study is to verify the results obtained on the basis of adequate mathematical models in actual production conditions.

Effective removal of water-soluble methylated arsenic contaminants with phosphorene oxide nanoflakes: A DFT study

This work explores by density functional theory the ability of oxidized phosphorene nanoflakes (PhosO) to simultaneously remove toxic water-soluble methylarsenicals from contaminated waters. We focused on the microscopic understanding of the PhosO-Methylarsenic complexes in solution, i.e., structure, stability, and intermolecular driving forces. In this way, adsorption energies and conformations, binding and energy decomposition analyses (ALMO-EDA), implicitly/explicitly solvated structures, and competitive adsorption with coexisting molecules in solution afford deep insights into the selectivity adsorption and interaction mechanisms. The PhosO nanoflakes form inner-sphere surface complexes with methylarsenicals in solution, even with enhanced adsorption stability compared to intrinsic phosphorene and without the competition of water molecules for adsorption sites. The inner-sphere surface adsorption of trivalent methylarsenicals is driven by electrostatic and charge-transfer (orbital) intermolecular forces. Surface complexation of pentavalent methylarsenicals occurs by a balanced contribution of orbital and long-range intermolecular forces, while anionic contaminants also show a high stabilization via extra polarization effects. PhosO nanoflakes turn convenient to recycle via simple treatment with alkaline eluents because of the increased affinity with hydroxide anions in solution compared with intrinsic phosphorene. Conceptually understanding the adsorption properties of phosphorene oxide towards hazardous methylarsenicals provides a valuable framework for new developments in future water and wastewater treatment technologies with adsorbents of large surface area, high adsorption capacity/selectivity, and easy recovery.

Synthesis of carboxyl-modified hyper-cross-linked polymers with conspicuous removal capability for various water-soluble contaminants

In this study, we employed hyper-cross-linked porous polymer (HCP-MAH) as precursor to prepare carboxyl-modified hyper-cross-linked polymer (HCP-COOH) through mild alkaline modification. The prepared HCP-COOH had excellent dispersity in water, high specific surface area and abundant pore structures, resulting in highly-efficient adsorption of tetracycline (TC). The TC adsorption capacity of HCP-MAH and HCP-COOH was calculated to be 273.22 mg·g−1 and 418.41 mg·g−1, respectively. Moreover, both of HCP-MAH and HCP-COOH showed excellent adsorption capacities towards dyes and phenols. The electrostatic attraction, pore filling, hydrogen bond, ions exchange and π-π interaction were responsible for TC adsorption. In addition, it was found that the dissolved organic matter (DOM) in the secondary wastewater could promote the removal of TC, which contributed to higher adsorption removal of TC by HCP-MAH and HCP-COOH compared to that in pure water system. This study not only provided a simple method to fabricate an eco-sufficient adsorbent with rich carboxyl groups for TC removal, but also evaluated the application of the adsorbents in the treatment of water-soluble organic pollutants in actual wastewater, which has a great potential in practical use.

Pollutants Sorbent Made of Cotton Fabric Modified with Chitosan-Glutaraldehyde and Zinc Oxide Particles

The paper reports on the preparation of composite materials by modifying cotton fabric with a layer of crosslinked glutaraldehyde chitosan containing zinc oxide particles. The ability of chitosan to form complexes with zinc ions has been used to control the size, structure, and distribution of the particles on the fiber surface. The three different obtained materials have been characterized by optical and scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and fluorescent analysis. It has been found that the interaction of the ZnO particles with the functional groups of chitosan affects its swelling ability in water and thus determines its sorption properties. The capacity of the materials to wipe water-soluble (textile reactive dye) and water-insoluble (crude oil and oil products) contaminants has been compared. The effect that the amount of zinc oxide has on the ability of the materials to remove contaminants has also been studied. The possibility for adsorption–desorption of the crude oil and reuse of the sorbent material has been investigated as well.