Journal of Water Chemistry and Technology最新文献

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).

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 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.

Herein, the cost-effective utilization of biosorption for toxic pollutant removal was investigated, with a specific emphasis on enhancing mushroom-based biosorbents for the decontamination of heavy metals-polluted aqueous environments. Firstly, Oyster mushrooms (Pleurotus ostreatus) collected from Bajaur, Khyber Pakhtunkhwa, Pakistan, underwent thorough cleaning, followed by air-drying for 2–3 weeks to produce a fine powder. The obtained powder was subjected to thermal modification through heating at 400°C/1 h, and a portion of it was additionally modified using potassium hydroxide (KOH). This process resulted in three distinct materials: untreated dried mushroom (AM), thermally modified mushroom (TMM), and chemically modified mushroom (CMM), and their chemical compositions were assessed using Fourier Transform Infrared (FTIR) spectroscopy. Subsequently, the resulting materials were employed as bioadsorbents for the elimination of toxic Fe(III) ions from aqueous media. Various experimental variables, including solution pH, temperature, contact time, pollutant concentration, and adsorbent amount were varied to investigate their impact on adsorption. Analysis using an atomic absorption spectrophotometer (AAS) demonstrated exceptional Fe(III) removal capacities of mushrooms, achieving a removal extent of 29.99 mg/g at 303 K, pH 6.0, and an adsorbent dosage of 0.1 g/L, resulting in a remarkable 99.97% removal efficiency. The type of adsorbent significantly affected the extent of adsorption. Furthermore, thermodynamic analysis revealed that adsorption was spontaneous and exothermic. The adsorption data were evaluated using Langmuir, Freundlich, and Temkin isotherms, with the pseudo-second-order reaction kinetics providing the best fit, suggesting that chemisorption predominates the surface adsorption of Fe(III). This study highlights the potential of mushroom-based biosorbents as eco-friendly and effective materials for purifying water contaminated with toxic pollutants.

In this present work, photocatalysts based on a new pyrochlore-type solid solution were prepared using the ceramic method at 1000°C. X-ray diffraction (XRD) analysis shows the existence of a solid solution with pyrochlore structure Bi_1.5Sb_1.5Zn_1–xCu_xO₇ (0 ≤ x ≤ 1). Scanning Electron Microscope (SEM) images exhibited a slight difference in the external morphology of the samples. The UV-diffuse measurement revealed a change in the absorbance from the UV part for the zinc-rich compound to the visible part for the copper-rich compound. The Energy band gap values were between 3.15 and 1.84 eV. The photocatalytic activity of these prepared mixed oxides was studied for the photo-degradation of the dye Orange II (ORII) as an organic pollutant, in the presence of hydrogen peroxide (H₂O₂) as an oxidising agent, under sunlight irradiation, by varying different parameters such as the catalysts mass, the oxidant volume, the concentration of the pollutant and the pH. The experimental results obtained by UV-visible spectroscopy revealed that the removal efficiency of ORII increased with increasing the irradiation time for all tested photocatalysts. The pseudo-first-order kinetic model gave the best fit, with the highest correlation coefficients (R² = 0.99). The results of this study revealed the potential and various advantages of these new efficient photocatalysts.

The production and application of activated biochar have demonstrated significant improvements in environmental conditions both locally and across Ukraine. Researchers have confirmed the viability of creating carbon adsorbents specialized for water purification from plant-based materials, streamlining the conversion of organic biopolymers into the final product. Enhancements to traditional pyrolysis technology included the implementation of wet cooling-activation, which facilitated the development of the porous structure in wood biochar. The study further compared the efficiency of various technological solutions by evaluating biochar samples across several criteria in water purification technology.

In this paper, a method is proposed for the complex treatment of technical waste water containing essential concentrations of organomineral impurities including 1 g/dm³ of copper ions. Plasma treatment decreases the chemical oxygen demand of a solution by 17 times, the content of salts by 34%, and the copper and iron concentration by 20%. Electrodialysis decreases the total salt content from 3 to 0.2 g/dm³ and brings the copper and iron content to 8 and 3 mg/dm³, respectively. The destruction of organic substances contained in the water under plasma treatment results in a carbon-containing precipitate studied by physicochemical methods to determine structural and sorption characteristics. The FTIR spectrum of the carbon-containing precipitate indicates the presence of hydrophilic groups and a great amount of uncompensated active sites and free radicals, which can be used in sorption processes. The prospects of using the carbon-containing precipitate as a filler for the desalination chambers of an electrodializer under electrical field application is shown.

A fixed-bed column study for the removal of malachite green (MG) from the aqueous phase was demonstrated using strategically dewaxed honeycomb powder (HCP). The removal efficiency was tested at several working parameters of the column, in particular, the column bed height, initial dye concentration, working pH, and the flow rate. Breakthrough curves have been plotted using the throughput volume versus concentration ratio for different parameters to identify the pathway of uptake. Thomas and bed depth service time (BDST) kinetic models have been applied to obtain the rate constants and the uptake capacity. The BDST model suggests an adsorption capacity of 196.28 mg L^–1. The column performance was seen to vary with solution pH and was found favourable at higher pH values. The adsorption rate decreases with increasing flow rate but increases with increasing concentration of the dye. Easy regeneration ensures multi-cycle operations. The mechanism of dye adsorption by HCP has been proposed as a blend of electrostatic attraction and weak forces. Henceforth, the use of HCP for the removal of MG in column mode may be extrapolated to serve as a promising agent in the treatment of dye-containing water and wastewater.

In this study, we aimed to fabricate a novel, completely natural antibacterial disinfectant material for environmental applications, such as treating drinking water. We created two different berberine−alginate (BerAlg) beads using the ionotropic gelation method, employing calcium and aluminium ions as cross-linkers. The materials were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), swelling, and release kinetic studies. Antibacterial activity was assessed through time-kill analysis. Among the four release kinetics models tested, the BerAlg bead formulation showed the best fit with the Korsmeyer−Peppas model, having the highest R2 value (0.9757). The longest release of berberine (Ber) was observed over a 4-h period. The time-kill assay results revealed that BerAlg beads were effective in killing for up to 7 h. In conclusion, these results demonstrate the promising potential of BerAlg beads as an antibacterial delivery system for disinfecting various liquid environments, such as drinking water.