Journal of Water Chemistry and Technology最新文献

The plasma-chemical decomposition of Acid Violet 7 dye and simultaneous production of carbon micro- and nanomaterials were investigated. For the purification of wastewater contaminated with the dye, we used a plasma electrochemical setup with modified electrodes. The experiments were conducted in a galvanostatic mode with current intensities of 45 and 80 A and voltages ranging from 21 to 24 V. Two types of carbon-containing degradation products were formed. One type comprised fine-dispersed hydrophobic material, which, due to its low specific weight, hydrophobicity, and inclusion of gas bubbles, floated and concentrated at the interface between the solution and air phases. This material predominantly consisted of particles ranging in size from 1 to 5 µm, with some particles in the order of hundreds of nanometers present as well. Another type consisted of hydrophilic particles larger than 50 µm, which were deposited at the bottom of the cell. Plasma-chemical treatment leads to rapid degradation of the Acid Violet 7 molecule. Intensive discoloration of the dye solution occurs within the first 5–7 min. Exposure for 20 min resulted in an 8.4-fold decrease in chemical oxygen demand (COD).

The article discusses a new efficient technology for the preparation of additional water in heating networks. According to the technology, additional water is prepared through the process of cationization using polyfunctional sulfonated coal cationites regenerated with a stoichiometric amount of salt. The research was carried out according to a continuous flow scheme. To obtain accurate results, a laboratory setup was prepared by approximating the height of the cationite and the average diameter of its particles to the required values relative to the diameter of the filter (d : D < 1 : 20) by adjusting the operating regime of the filter closer to industrial conditions. The regeneration regime of the cationite is selected in such a way that the amount of salt in the filtrate during water treatment does not exceed 3–6% of the amount of salt absorbed by the cationite. The main goal of the newly developed technological regime is to reduce the specific consumption of salt during regeneration, increase the exchange capacity of the cationite, and improve both the economic and ecological indicators of the process. As a result of the research, it can be concluded that the exchange capacity of the cationite varies within the interval of 7–20% under the influence of selected factors, and when the specific consumption of salt is increased from 8 to 16 kg/m³, the exchange capacity of the cationite approximately doubles. It should be noted that when the carbonate index in the treated water increases due to the presence of carbonate and hydrogen ions, the degree of water softening increases. However, the rapid rise of the carbonation value in the filtrate increases the average value of the carbonate index and leads to fouling of the filter, which results in a lower exchange capacity of the cationite compared to the mentioned values. It should be emphasized that depending on the values of alkalinity and specific consumption of the regenerant during the process, the filtrate volume of the treated water exiting the filter becomes 2–12% of the total volume and is characterized by saltiness. The salinity in the filtrate is neutralized by the buffer filter.

In this study, magnetic Fe₃O₄@SiO₂-NH₂ (FSN) nanocomposite adsorbent was synthesized using a green and convenient method. The FSN adsorbent was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and vibrating-sample magnetometry (VSM). The FSN nanocomposites exhibit excellent Zn²⁺ adsorption capacity. In addition, adsorption kinetics, isotherms, and adsorption mechanism of Zn²⁺ on the FSN nanocomposites were also studied. The FSN nanocomposites show rapid adsorption rate, easy separation process, and environmental friendliness, which are suitable for water and wastewater purification.

A low-waste combined technology for water softening, desalination, and deionization is proposed. The low-waste nature of the method is achieved through H-cationization of water using carboxylic polyacrylic ion exchange resin, followed by its deionization via reverse osmosis. If the requirements for desalinated water are high, such as when purified liquid is used for feeding supercritical pressure once-through boilers (SPB), it is additionally treated using ion exchange. The preconcentrate from reverse osmosis is processed through electrodialysis or electrolysis to yield acidic and alkaline solutions. These solutions are then used in conjunction with spent regeneration solutions from deep deionization ion exchange filters to regenerate the filter containing carboxylic polyacrylic ion exchange resin. The paper outlines the advantages of carboxylic cation exchange resins compared to sulfonated cation exchangers. A two-chamber H⁺,Na⁺-cation exchange filter operation circuit is proposed. Recirculation of the acidic portion of the spent regeneration solution from the BC storage reservoir through the H⁺Na⁺-cation exchange filter is planned to maximize the recovery of the cation exchange resin’s working capacity. The specifics of regenerating carboxylic cation exchange resin with acid solution in a fluidized bed mode are presented. The acidic solution storage tank should be constructed as a reservoir with a conical bottom and a cylindrical upper part. Such tank design enables its use as a gypsum particle crystallizer and settler. This circuit of separate water H⁺,Na⁺-cationization with a decarbonizer significantly expands technological capabilities. Intermediate water decarbonization decreases the alkalinity of the Na⁺-cation exchange filter effluent, thereby hindering the hydrolysis of the salt form of the cation exchanger. Water obtained through magnesium ionization is advisable to be directed into the softened water stream. To prevent an increase in liquid pressure drop across the filter and a sharp decrease in filtration rate, it is proposed to pass the alkaline regeneration solution from bottom to top.

In this study ciprofloxacin-loaded carboxymethyl cellulose (CMC)/ polyvinyl alcohol (PVA) cryogel systems were prepared by using low molecular weight PVA. The high degree of segmental mobility of PVA molecules makes them more prone to form CMC/PVA cryogels via hydrogen bondings with CMC. Physically crosslinked gels were characterised by using Fourier-transform infrared spectroscopy (FTIR). Swelling results have shown that low molecular weight PVA had a fast-swelling rate and this can explain the fast release of ciprofloxacin within 30 min from CMC/PVA cryogels during release studies. Release of ciprofloxacin from the CMC/PVA cryogel system was the best fit to first-order release model with R² = 0.9980. It was found that the release exponent is lower than 0.45 and it is a good indication of quasi-Fickian diffusion, which means that ciprofloxacin can be released without swelling of the cryogel. Ciprofloxacin was found to have even better antimicrobial activity against E. coli than positive control as having a higher inhibition zone. In addition, CMC/PVA cryogels can be used for water treatment application to remove Methylene Blue (MB) dye from water and this was supported by adsorption kinetics and isotherm studies.

The present study proposes technological solutions to address the existing limitations by modifying the treatment system to enhance its oxidation potential. The case study focuses on the Magdacesti biological treatment plant, which has encountered a new source of pollution from the “Ocean Fish” factory. Under high loading conditions during the biological treatment stage, both the activated sludge and the biological film, composed of aerobic microorganism flakes, experience changes in their culture composition and lose their sedimentation properties. To overcome these challenges, implementing an anaerobic pre-treatment process and integrating the “Integrated Fixed-Film Activated Sludge” technology into the aerobic process are recommended for intensifying the biological treatment.

This study aims to determine the concentrations of fluoride, nitrite, nitrate, chloride, sulfate, phosphate, calcium, sodium, magnesium, ammonium, and potassium ions in different natural spring water brands available in the markets using ion chromatography. The ion chromatography technique is an accurate, sensitive, and reliable method for determining sample anion and cation concentrations. Measurement range, calibration, method detection level, repeatability, precision, recovery, and standard deviation were evaluated to assess the suitability of the method. The R² values of anion and cation calibration plots were good (greater than 0.994) in this method. The recovery values for low and high concentrations changed from 101 to 111% and from 97 to 104%, respectively. The concentration results were used for human health risk assessment, using Chronic Daily Intake of nitrate and fluoride. The potential adverse health effects of fluoride intake were less than 1 for adults, so there is no potential risk. Moreover, our results suggest that there is a risk for dental decay according to the fluoride limits in spring water recommended by the World Health Organization.

The efficiency of accumulating phenol by sorption on Fe₃O₄ magnetic nanoparticles in a static mode in the absence and presence of HCl is evaluated in a wide concentration range (0.0005–10 mmol/L). The most efficient extraction of phenol (53–63%) (4.5 × 10^–4 mol/L) in the absence and presence of HCl additives is observed for the concentrations of ≤0.018 mmol/L. It is established that the efficiency of phenol extraction vaguely depends on pH. Thus, there are concentration ranges for which the extraction efficiency of phenol is slightly higher in the presence of HCl, but there are concentrations (for example, 0.005 or 2–4 mmol/L) for which the degree of extraction and, accordingly, the adsorption values in the presence and absence of HCl are close. Based on the higher value of the correlation coefficient (0.932 versus 0.729), it is established that the kinetics of phenol adsorption on Fe₃O₄ magnetic nanoparticles is better described by the pseudosecond-order model. It is shown that the concentration dependences of the degree of phenol extraction and the adsorption isotherm show nonlinear stepwise behavior (or have well-defined extremes). It is proposed to adhere to systemic concepts when explaining the stepwise behavior of concentration dependences, according to which aqueous solutions are proposed to be considered as complex open nonequilibrium systems that have structural integrity and are characterized by the functional unity of structural components inclined to dynamic self-development due to self-organization and self-renewal. At the same time, it is the self-organization and self-renewal ability that explains the presence of stationary states and jumps (spontaneous transition to a new ordered state) on the concentration dependences of the physicochemical properties of aqueous phenol solutions. A correlation between the efficiency of phenol sorption and structural rearrangements in its aqueous solutions is established. The identified concentration areas are proposed to be associated with the effect of the penetration of phenol molecules into the cavity of the structural network of water molecules, the destruction of the structure of the latter, and the formation of mixed intermolecular associates of phenol with water molecules in different ratios.

The reasonability of using the redox potential to characterize the state of a certain water system was substantiated. Peat fulvic acids characteristic for the natural water of the Dnipro River were selected as a target compound for study before and after the adsorption processes. Fruitstone-derived activated carbon (FDAC), FDAC oxidized by hydrogen peroxide (FADC-O), and FDAC modified with iron oxides (FDAC-Fe) were used as adsorbents. All the systems with both distilled and tap water were shown to have an oxidative character for the period of study, especially after sodium azide and hydrogen peroxide were added. The introduction of fulvic acids into the system neutralized this effect due to their interaction. The redox potential was proposed to use for simplified measurement as an indicator of pollution in water of different types.

The irrigation of soil is an important measure for achieving the desired agricultural productivity, especially in regions with deficit of precipitations. The presence of sodium in the irrigation water can exert an adverse influence on the soil structure by reducing the rate at which water reaches the roots of plants. The Vakhsh river basin with more than 220 000 hectares of the irrigated land area is among the largest river basins in Tajikistan, which contains irrigation channels and a collector–drainage system with lengths of about 5000 to 6000 kilometers, respectively. The Vakhsh River merging with the Pyanj River to form the transboundary Amudarya River, which is the largest river in Central Asia, is the main river of the Republic of Tajikistan. The Vakhsh River Basin (VRB) is among the largest river basins (39 100 km²) in the highest part of Central Asia. In the VRB territory, 1213 million m³/year of the waste and collector–drainage waters are formed, of which 4 million m³/year are used for irrigation and 1209.1 million m³/year flow into natural surface water bodies. Therefore, the issue of water quality in the river basin is an urgent one. This study is aimed at analyzing the chemical composition of the Vakhsh River and its main tributaries and determining the degree of their applicability for irrigation of agricultural lands. It has been established that the Vakhsh River and its tributaries meet the requirements for irrigation water when regarding the main parameters, namely, the fractions of adsorbed, soluble, and exchangeable sodium and magnesium. It has been shown that the chemical composition of rivers is primarily formed because of weathering the rocks and washing out the skin of basins.