Journal of Water Chemistry and Technology最新文献

Fly ash is the primary residue produced in huge amounts by coal combustion in thermal power plants, which needs to be utilized appropriately. In this connection, an experimental study was conducted with fly ash alone and in combination with soil for the treatment of simulated dumpsite leachate in constructed wetland (CW) (vertical flow) systems containing Canna + Typha plants. The study revealed that the fly ash + soil mixture as a CW substrate showed better removal efficiency of chemical oxygen demand (COD), phosphate (({text{PO}}_{4}^{{3 - }})), total nitrogen (TN), and chloride (Cl^–) by 97.3, 99.4, 94.5, and 89.6%, respectively, in comparison to the fly ash alone which was shown to yield the corresponding values of 88.5, 94.1, 84, and 73.2% of the efficiency in the removal of these pollutants from simulated dumpsite leachate.

A self-floating amphiphilic biosorbent (SFAB) was prepared by dispersing the plasma-modified water hyacinth (WH) (Eichhornia crassipes) fibers on the beeswax support. The synthesis process takes advantage of the functionalising properties of plasma with polar groups (–OH, –CO, –COOH) and the binding effect of beeswax. The characteristics of the obtained biosorbent exhibited significant changes in surface chemistry and roughness confirmed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDX). The resulting functionalised material offers appropriate anchoring sites for pollutants leading to a biomaterial with hydrophilic and lipophilic properties. The removal performance of the SFAB outperforms the natural biomass fibers taking alone, with an uptake capacity of 20.83 mg/g for merbromin (MB) (50 mg/L) and 19.90 mg/g for Green Naphthol B (GNB) (50 mg/L), based on the successfully fitted general-order kinetic model. The effects of some key adsorption parameters were optimised, and the equilibrium data (298–323 K) were best fitted by the Liu isotherm reaching 47.20 and 36.40 mg/g of uptake amounts for MB and GNB, respectively at 298 K. The removal mechanism is governed by π–π interplay, hydrophobic interaction, and hydrogen bonding effects.

Domestic wastewaters have a significant concentration of nutrients that can be utilised as alternative sources of phosphorus and nitrogen for agriculture applications. Chemical precipitation is one of the processes found to be an efficient way for nutrient recovery from various wastewater feedstock. However, not all nutrients are in a form that can be readily recovered. Therefore, a pre-treatment process may be necessary for an efficient recovery of nitrogen and phosphorus. In this research, acid hydrolysis was performed as pre-treatment to release phosphorus from synthetic septage into soluble forms for the subsequent precipitation as struvite (MgNH₄PO₄·6H₂O) which is known as a slow-release fertiliser for application in agriculture. Results show that acid hydrolysis increases the phosphate concentration (PO₄-P) to 148.07 ± 1.78 from 61.50 ± 0.07 mg/L, showing the potential of hydrolysis as pre-treatment to efficiently recover nutrients in the form of struvite. The result can inform further research to develop efficient processes for the recovery of nutrients from domestic wastewater.

The study investigates the adsorption of heavy metals (HMs), specifically Cd(II) and Co(II), from aqueous solutions using synthesized iron oxides with layered structures and surface groups of a basic nature: goethite α-FeO(OH), lepidocrocite γ-FeO(OH), and ferrihydrite Fe(OH)₃. The results indicate that these crystalline materials are effective in adsorbing heavy metals within pH ranges typical of natural aquatic environments (7.5). We determined the conditions for extracting heavy metals, examining the effect of pH in aqueous solutions, ionic strength, adsorbent dosage, and major components of natural waters. The results show that the majority of HM ions are extracted within the first 30 min of contact between the aqueous solution and the solid phase of the adsorbents, with adsorption equilibrium being reached for iron-containing adsorbents in approximately 4 h. To account for the relative distribution of HM species in aqueous environments with varying pH values, we calculated the distribution of these species for the concentrations studied in model water solutions, enabling an evaluation of the extraction mechanism. The adsorption of Co(II) and Cd(II) is primarily driven by the interaction of their cationic forms with ferrinol surface groups of the studied iron-containing minerals through chemisorption from aqueous solutions within the investigated pH range. The adsorption limits for goethite and ferrihydrite are nearly identical, while those for lepidocrocite are significantly lower, which can be attributed to their structure and the availability of active adsorption sites. The shape of the adsorption isotherm curves is also quite similar across the entire concentration range. Based on the data obtained regarding the adsorption efficiency of Cd(II) and Co(II), which are among the most challenging cations to remove using adsorption methods, the synthesized goethite and ferrihydrite can be recommended as cost-effective and efficient materials for the purification of natural waters contaminated with heavy metals.

Removing relatively concentrated salicylic acid (SA) from pharmaceutical aqueous waste was performed using unmodified and modified commercial cationic exchange resin (Amberlite 200C). The modification of the resin involved grafting functional molecules onto the aromatic ring through classical organic reactions or by irreversible adsorption into the resin’s structure. The nitro group (({text{NO}}_{2}^{ + })) was synthesized by combining nitric and sulfuric acids and then attached to the resin matrix through nitration. Meanwhile, 2,4-dinitrophenyl hydrazine (DNPH), tributyl phosphate (TBP), and ammonium (({text{NH}}_{4}^{ + }) ) were irreversibly adsorbed onto the resin matrix via immersion. Consequently, the unmodified resin achieved a 21% elimination of the initial SA, whereas modified resins significantly increased the elimination yield. Specifically, ({text{NH}}_{4}^{ + }) and DNPH-modified resins achieved SA elimination rates of 51.94 and 41.5%, respectively. However, the use of TBP and ({text{NO}}_{2}^{ + }) modified resins resulted in negligible SA removal. The optimal conditions for operation were determined to be: pH 5.5, temperature 21°C, and a contact time of 20 min.

Small rivers and other surface and groundwater sources form the basis for the functioning of river basin systems, shaping streamflow, providing water supply for rural areas, and supporting biodiversity. Local surface and groundwater sources are extremely sensitive to anthropogenic impacts and climate change. Changes in the quality and quantity of water in these sources are a primary factor influencing their use for various purposes, objects, methods, and technical conditions. Therefore, the research aimed to assess the quality of natural waters in the southern part of the Mohyliv-Podilskyi district, within the basin of the small river Kotlubayevka (a right tributary of the Dniester River). The primary research methods were analytical and statistical. The analytical method was used to determine the chemical composition of water samples according to standardized procedures. The statistical method was used to find out the reliability of measurement results and to provide a generalized assessment of water quality. Experimental results were processed for water samples based on ecological and sanitary criteria from eight potential sources of economic use located along the slopes of the Dniester and Kotlubayevka river basins, ranging from elevations of 215–206 to 78–55 m a.s.l. According to the ecological classification of surface water quality, the studied sources are classified as fresh oligotrophic (class I), and based on ion composition criteria, they are categorized as bicarbonate waters of type I (({text{HCO}}_{3}^{ - }) > Ca²⁺ + Mg²⁺). The study identified a trend of water source contamination in the research area concerning copper, iron (Fe_total), and saprophytic bacteria Escherichia coli. A generalized ecological assessment of water was calculated using block indices for salinity composition, ecological-sanitary, and specific toxic indicators, which ranged from 2.33 to 3.00 along the slope above the river currents. The results indicate that the quality of the studied water sources ranges from “very good,” “clean,” to “good,” “fairly clean.” However, based on the block index for specific toxic indicators, the water quality tends to approach “fairly good” or “slightly polluted.” Among the water contaminants, elevated levels of Fe_total, Cu²⁺, and E. coli primarily contribute to the deterioration of water quality and safety. Iron and copper contamination should be regarded as a natural factor, while microbiological contamination by E. coli should be considered a result of anthropogenic impact. The obtained research results impose limitations on the economic use of certain water sources, particularly in agricultural production.

2,4,5-Trichlorophenoxyacetic acid was shown to form an ion associate (IA) with astrafloxin FF (AF), a polymethine dye. Based on mathematical modeling, the energy efficiency of the formation of an ion associate was substantiated. The molecular modeling of 2,4,5-T^– + AF⁺ systems and related calculations were carried out by the HyperChem 8.0 software for different initial mutual arrangements of counterions (“single point” procedure). The geometric optimization of ions was performed by the molecular mechanics method MM+. The formed ion associates were readily extractable by different aromatic hydrocarbons. The maximum IA extraction from the aqueous phase was attained at pH of 4.5–12.0. The effect of the dye concentration on the absorbance of the toluene extracts of 2,4,5-T^– + AF⁺ ion associates was studied. The IA extraction was maximal at a dye concentration of (1.5–3.0) × 10^–4 M. Extraction equilibrium was attained for 50–60 s. The stoichiometry of 2,4,5-T^– + AF⁺ ion associates was established by the spectrophotometric isomolar series and equilibrium shift methods; the ratio of components was 1 : 1. The scheme of the formation and extraction of ion associates was proposed. The conditional molar extinction coefficient of the ion associates was 1.2 × 10⁵. The calibration extract absorbance–2,4,5-T concentration curve was described by a linear equation А = 0.012 + 0.062c within a 2,4,5-T concentration range of 1.50–58.07 µg/cm³. The 2,4,5-T detection limit calculated from the 3s criterion (n = 5, Р = 0.95) was 0.8 µg/cm³. The intralaboratory discrepancy of the calibration curve for the determination of 2,4,5-trichlorophenoxyacetic acid was estimated by using the Cochrane test G. The calculated value of this test (n = 5, P = 0.95) was lower than the tabular value, i.e., G_calcd = 0.25 < G_tab = 0.64 to evidence variance homogeneity. A method of photometric extraction analysis for 2,4,5-trichlorophenoxyacetic acid in water and bottom sediments was developed.

In this work, the Washingtonia palm stems were used as a novel precursor to product biochar (BCW) and activated carbon (CAW). The resulting CAW and BCW samples were characterized by N₂ adsorption−desorption, scanning electron microscopy (SEM) and pH of zero-charge point (pH_PZC). The results show a very large specific surface area and pore volume for CAW (S_BET = 1032 m²/g, V = 1.1 cm³/g) compared to BCW (S_BET = 357 m²/g, V = 0.27 cm³/g). The SEM images show a more or less regular porous shape for both samples. The obtained values of pH_PZC were 5.2 and 6 for CAW and BCW samples, respectively. The ionic strength from 0 to 1.0 M greatly affects the adsorption capacity of Crystal Violet (CV) on BCW unlike that for CAW. The adsorption process occurred quickly and the kinetic data were well described by the pseudo first order (PFO), pseudo second order (PSO), Elovich and Avrami models. The maximum adsorption capacity of CV on CAW and BCW calculated from the Langmuir model was 328 and 93 mg/g respectively at 35°C. The values of the average free energy determined by the Dubinin–Radushkevich model are less than 8 kJ/mol, indicative of physisorption. The thermodynamic study at different solution temperatures (15, 25, and 35°C) shows that the adsorption process occurred spontaneously (∆G° < 0) and was exothermic for CAW and BCW (∆H° = –28.66 and –38.46 kJ/mol, respectively).

In this study, a pullulan hydrogel is grafted by poly(N-vinylimidazole) (PNVI) in a heterogeneous acidic medium under a nitrogen atmosphere for Methyl Orange (MO) and Acid Green 25 (AG25) dye removal application. The effect of monomer concentration as a significant parameter for grafting yield is investigated thoroughly, and it is demonstrated that 189% grafting yield of PNVI grafted onto epichlorohydrin crosslinked pullulan (pullulan-ECH-graft-PNVI) can be obtained under proper conditions. Equilibrium water absorption capacity values reveal the pH-responsivity of pullulan-ECH-graft-PNVI hydrogels (6000%) as compared to the epichlorohydrin crosslinked pullulan (pullulan-ECH) hydrogel (1000%) counterpart. Further characterization of the samples was performed by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Adsorption of MO and AG25 on pullulan-ECH-graft-PNVI samples was studied at various pH, dye concentration, and time. The optimal adsorption pH value was measured at pH 3.0 with an adsorption capacity of 36.6 mg MO/g adsorbent and 5.72 mg AG25/g adsorbent. Isotherms and kinetic studies describe the adsorption profiles of the samples. The adsorption trends of the samples best fit the Freundlich model, which supports heterolayer dye adsorption and surface heterogeneity. Adsorption kinetic results indicate a pseudo-second-order kinetic model, which shows chemisorption.

The country’s first tubular microfiltration membranes for water purification from various contaminants, made from an alternative natural material—wood,—was developed at the Dumansky Institute of Colloid and Water Chemistry of the National Academy of Sciences of Ukraine. The proposed procedure cuts significantly the costs of manufacturing membranes. They studied the main patterns of the defluoridation process of water using these lignocellulosic (wooden) membranes, which were modified with a dynamic layer of hydrophilic A-300 aerosil. The modification of the lignocellulosic membranes involved the preliminary formation of an additional retentive layer on their surface, due to the steric mechanism, in the form of a dynamic membrane. The research demonstrated the high efficiency of the water defluoridation process using a dynamic membrane made of SiO₂ particles, which retained fluoride ions (F^–) ions due to the electrostatic mechanism of their interaction. Specific conditions for forming the dynamic membrane included concentrations of modifying and membrane-supporting aerosil additives at 500 and 100 mg/dm³, respectively, with an operating pressure of 1.0 MPa and a formation duration of 120 min. The concentration of suspended SiO₂ particles in the permeate (turbidity) did not exceed the maximum permissible concentration (0.3 mg/dm³) in water. The modified lignocellulosic membrane could decrease the fluoride concentration in water to the permissible level for drinking water (0.7–1.5 mg/dm³) from an initial concentration of up to 7.5 mg/dm³ and a neutral pH at an operating pressure of 1.0 MPa. The membrane’s specific productivity was 0.024 m³/(m² h), due to significant pore blockage by SiO₂ particles.