Journal of Water Chemistry and Technology最新文献

Magnetically recyclable nanoparticle catalysts, in particular, Fe₃O₄, TiO₂@Fe₃O₄, SiO₂@Fe₃O₄, TiO₂–SiO₂@Fe₃O₄ and silver doped TiO₂–SiO₂@Fe₃O₄ (Ag–TiO₂–SiO₂@Fe₃O₄) were synthesized by sol-gel and modified sol-gel synthesis methods. These nanoparticle catalysts were prepared from metal salts and alkoxide precursor salts. Photocatalytic activity of these catalysts was studied in the degradation of organophosphorus pesticides Glyphosate, and Malathion in water. A detailed study of photodegradation of these organic compounds under UV radiation was performed. The physicochemical characterization of the synthesized nanoparticles was performed using TEM (Transmission electron microscopy), EDX (energy dispersive X-ray), ICP-AES (inductively coupled plasma−atomic emission spectroscopy), XRD (X-ray diffraction) and BET surface area measurement techniques. The degradation reactions of organic pesticides were performed in a specially designed photo-batch reactor. The use of H₂O₂ as an oxidant in the reaction was found to enhance the catalytic performance towards degradation and subsequent mineralization of the organophosphorus pesticides. Silver-doped nanocatalyst exhibits high recycling efficiency and stability over several subsequent runs. The course of the reactions was studied using COD (chemical oxygen demand) removal and HPLC (high-performance liquid chromatography) methods of water before and after the photodegradation reactions. More than 95% reduction in the COD was observed in the treated water sample using Ag–TiO₂–SiO₂@Fe₃O₄.

The method of isotherm simulation by approximating mathematical expressions that are valid for a small experimental section of the isotherm over the entire range of equilibrium concentrations is an important and useful tool in adsorption practice. Nine adsorption equilibrium systems of activated carbon (AC)–derivatives of aniline and phenol were examined. The adsorbent used was activated carbon obtained from fruit pits. The results of isothermal adsorption of aromatic substances with relatively small molecules on a microporous carbon adsorbent indicate the simultaneous adequacy of the Freundlich and Langmuir models to the experimental data in moderate concentration ranges ((0.1–100)n mg/dm³, where n = 1, 2, 3, 4, 5). Thus, the results of adsorption from the aqueous phase do not demonstrate the energy differences of the AC surface that are incorporated into the theoretical classical model isotherms. The isotherm reflects the adsorption process on both homogeneous and heterogeneous surfaces simultaneously. This may be due to the displacement nature of adsorption from the aqueous phase, where initial surface screening by water molecules occurs during adsorbent wetting, leading to the leveling of its energetic heterogeneity. In the next stage—displacement of some water molecules by the organic adsorbate—the energetic differences of the adsorption sites are not as clearly manifested as in gas-phase adsorption. Therefore, theorizing the nature of the AC surface based on the best model simulation of experimental isotherms using classical equations becomes questionable. Three-parameter equations (Langmuir–Freundlich, Redlich–Peterson) demonstrated a finer simulation of the experiment compared to the classical two-parameter models. The study emphasizes that the mathematical description of the isotherm is a convenient method for the efficient storage and use of information about the adsorption properties of the system. It serves to compare the effectiveness of new materials with commercial analogs and to predict the performance of real purification systems under dynamic conditions.

Industrialization has caused serious heavy metal pollution in water resources, which is harmful to human health. It is of great significance to use heavy metal removal technology to ensure water safety. In this study, a new kaolin/chitosan composite (TGL-CS) was prepared for the adsorption of lead-containing wastewater based on the mercapto-alkenyl base reaction strategy. The effects of pH, adsorbent dosage and ionic strength on the adsorption performance of TGL-CS were investigated. The adsorption process of Pb(II) on TGL-CS is consistent with the Langmuir isotherm and pseudo-second-order kinetic model. The maximum adsorption capacity of TGL-CS for Pb(II) was 87.72 mg/g. The adsorption mechanism of TGL-CS is mainly the coordination between Pb(II) and hydroxyl, amino and sulfur-containing groups. In particular, the click chemical reaction does not consume the amino group in chitosan but also introduces the sulfur-containing group to improve the adsorption capacity of heavy metals. In addition, the ionic strength in the environment system has little effect on the adsorption of Pb(II) by TGL-CS, and the reusability of TGL-CS is high. In summary, TGL-CS has the advantages of low cost, simple preparation, and broad application prospects in the treatment of heavy metal-polluted water bodies.

The possibility of extracting Cu compounds through adsorption using galvanic sludge modified with solutions of humic acids was investigated. The chemical and structural composition of rigid galvanic sludge from printed circuit board production was examined. The primary phase-forming element is Fe compounds in the form of β-FeOOH, constituting up to 45% of the sludge mass. X-ray phase analysis of the sludge revealed the presence of two main phases: akaganeite (β-FeOOH) and an atacamite-like crystalline phase of copper hydroxychloride (Cu(OH)₃Cl) in quantities exceeding 10%. The conditions for leaching Cu compounds from the sludge and the effect of thermal treatment on the sludge adsorption capacity were determined. Copper was leached from galvanic sludge using an H₂SO₄ solution within the pH range of the equilibrium solution of 3–5.5. This allowed for the leaching of up to 97% of copper, with minimal dissolution of Fe compounds. The Cu concentration in the leaching solution reached 10–15 g/dm³, while the concentration of Fe ions did not exceed 1 mg/dm³, enabling the subsequent utilization of these solutions for Cu electroextraction. The modification of the sludge with humic acid solutions increases its adsorption capacity for copper ions by more than threefold.

Selenium (Se) is an important nutritional element which exists at very low concentrations, easily accumulates via the food chain and creates adverse effects such as a deprived reproduction rate and diminutive growth in human and aquatic organisms. So, it has become a severe concern around the world. We explore electrocoagulation using Al and Fe electrodes and activated sludge process (ASP) in batch process and also in an integrated process to remove Se. The optimized parameters of the current density in the batch process were: 6.7 and 5.7 mA/cm² for Al and Fe, respectively. The mass transfer coefficient has been estimated through numerical modelling for batch and integrated processes using the equations K = ({text{0}}{text{.0146}}C_{{{text{Se}}}}^{{{text{0}}{text{.3651}}}}{{I}^{{{text{0}}{text{.8916}}}}}) and K = ({text{295}}{text{.387}}C_{{{text{Se}}}}^{{{text{6}}{text{.607}}}}{{I}^{{{text{3}}{text{.587}}}}}); the energy consumption and metal dissolution were 138240 and 384 MWh/m³, 60 and 3.58 g, respectively. The response surface methodology (RSM) was implemented in Box−Benken design to assess the parametric optimization, and the validation of experimental data was done using ANOVA and regression analysis. The obtained p-values and model F-values were 0.000 and 63.09 for Al and 0.000 and 79.98 for Fe, which indicated the significance of the model. The chemical oxygen demand (COD) reduction values estimated along with Se reduction in real effluent treatment were above 90 and 60% in electrolytic and 80% in an integrated ASP with very high-cost efficiency. The results assure that this proposed hybrid work will provide a higher reduction, improved energy and cost efficiency for the effluent with indeterminate influent Se and COD concentration. The proposed model also helps to make predictions of removal efficiency without requiring an extensive time and cost burden.

This paper discusses the results and observations of experiments that were performed to investigate the presence and implication of total petroleum hydrocarbons (TPH) in oil produced water (OPW) samples from an oil depot. An analytical method based on gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) was developed for the determination of TPH. The effect of the extracting organic solvent was studied, and n-hexane was found to be the best extraction solvent as it resulted in 96.28% extraction efficiency. The TPH were determined in both influent and effluent samples. Various TPH fractions were identified including n-alkanes, branched alkanes, alkenes, etc. The TPH determination was investigated on a seasonal basis and the winter period (June-August) registered many compounds especially from the influent compartments than they were found in autumn. This suggests that the physical treatment employed by the oil depot does remove the TPH to a certain degree which is above the limit thresholds set by the regulatory authorities which is not satisfactory and thus the effluents need to be subjected to secondary treatment. The TPH analysis and identification results presented are mainly qualitative except for 1-chloro-octadecane, the surrogate standard. The TPH compounds were identified based on similarity indices to the databases.

The oxidative degradation of an antibiotic, Ofloxacin (OFX), has been investigated using the electro-Fenton (EF) process with a constant current between 100 and 500 mA and a carbon-felt cathode. The kinetics of oxidative degradation and the efficiency of mineralization were examined about the applied current and catalyst (Fe²⁺) concentration. The absolute rate constant for the oxidation of OFX by hydroxyl radical was determined using the competition kinetic approach as 3.04 ± 0.19 × 10⁹ M^–1s^–1. For efficient degradation of OFX at the relevant operating conditions, the ideal current value is 400 mA at a concentration of the catalyst (Fe²⁺) at 0.10 mM. After 6 h of electrolysis, in the present study, it is demonstrated that several cathodes, including carbon felt (CF), carbon-graphite (CG) and stainless steel (SS), had an impact on the electrochemical oxidation of the organic contaminant, OFX. A high level of mineralization (>97%) was attained. The development of F⁻, ({text{NH}}_{{text{4}}}^{{text{ + }}}) and ({text{NO}}_{{text{3}}}^{ - }) ions was also monitored and their evolution during their release into the medium was discussed. Several intermediate products were identified using LC-MS/MS (liquid chromatography-mass spectrometry) and HPLC (High-performance liquid chromatography) analyses. Based on the identity of these products, a feasible route for the mineralization process is proposed. Finally, biodegradability was studied and the results indicated the following ratio of biological oxygen demand within 5 days to chemical oxygen demand BOD₅/COD through OFX mineralization by EF treatment for the possibility of evaluating the combination of electro-Fenton and biological treatment.

Quantum chemical analysis using the density functional theory (DFT) was used to characterize the adsorption mechanism of metronidazole on the surface of polypyrrole (PPy). Researchers have established the electrophilic character of metronidazole and the nucleophilicity of PPy, as well as the electrophilic and nucleophilic zones responsible for non-covalent interaction in the processes of physical sorption of metronidazole on PPy as part of the decontamination of water using a drug. The adsorption mechanism of metronidazole on PPy is mainly governed by physical interactions (water bonds) between the adsorbate and adsorbent, and also the energy and structure results indicate that physically the process is sorption. These structural and energetic procedures match well with experimental results. The changes in thermochemical enthalpy and entropy showed the non-negotiable and exothermic phenomenon of physical adsorption. Thus, PPy can be considered an environmentally friendly and effective adsorbent material for the removal of metronidazole and, possibly, other pharmaceutical pollutants from pharmaceutical and municipal wastewater.

Despite being a water-rich state in South Asia, more than 70% of Afghan communities currently lack access to safe and reliable drinking water. This deficiency is largely attributed to the presence of contaminants, e.g., arsenic, fluoride, nitrates, sulfate, boron, etc., in groundwater aquifers. This study aims to trace the concentration of arsenic in groundwater aquifers in major cities in Afghanistan. The findings suggest that among the tested water samples in Ghazni, Kabul and Logar—the last two provinces are characterized parts of Kabul River Basin—Herat and Bamyan provinces, 70, 7, 2, and 23% of the examined water samples, respectively, exceed the permissible arsenic limit set by the World Health Organization (10 μg/L) and the National Drinking Water Quality Standard of Afghanistan (NDWQSA) (50 μg/L). The elevated concentration of arsenic in these aquifers results from excessive agricultural pumping and industrial and urban waste discharge. Additionally, inadequate sanitation and hygiene practices coupled with the absence of waste disposal network systems contribute significantly to the heightened level of arsenic in these provinces. It is concluded that unless the government adopts sustainable strategies to reduce the elevated arsenic concentration in groundwater aquifers, environmental and human health crises will continue to escalate.

With the rapid growth of industrialization/urbanization, the discharge of industrial effluent into the environment is increasing day by day. Conventional technologies for wastewater treatment possess difficulties in meeting all the requirements of wastewater discharge standards, and therefore, the exploration and establishment of new procedures to treat wastewater is a need of hour. Advanced oxidation processes (AOPs) possess an ability of strong oxidation, complete destruction and mineralisation, and no secondary pollutants. It has been proved in the literature that the addition of the catalyst in AOPs can largely enhance the treatment efficiency. The current study mainly emphasizes the practical applications of AOPS towards textile wastewater treatment. The study includes the pros and cons of individual AOPs, fixed photocatalysis, the dual process of photocatalysis and photo-Fenton coupled photocatalysis/photo-Fenton and biological treatment process. This article summarizes the useful theoretical foundation of the scientists and discusses the key areas that need more investigation in the fields of AOPs for industrial wastewater treatment.