Initial Concentration Research Articles

Decontamination of tetracycline from aqueous solution using activated carbon/Fe3O4/ZIF-8 nanocomposite adsorbent

The increase in the amount of antibiotics in water sources, especially after the spread of COVID-19, has caused serious environmental problems. Therefore, finding a suitable adsorbent for these pollutants is a new and serious challenge for researchers. In this study, magnetic activated carbon (AC/Fe3O4) was selected as a novel support to zeolitic imidazolate framework (ZIF-8)to create magnetic separation properties besides promoting its tetracycline (TC) removal efficiency. The successful formation of AC/Fe3O4/ZIF-8 nanocomposite was proved by FTIR, XRD, and SEM-EDX analysis. The surface area of AC/Fe3O4/ZIF-8 nanocomposite was computed at 996.38 m2/g using BET analysis. The maximum removal efficiency was obtained in the optimum condition of adsorption parameters, e.g., pH = 7, dose 1 g/L, initial concentration 20 mg/L, contact time 30 min, and temperature 25 °C. The maximum adsorption capacity (qmax) of AC, AC-H3PO4, AC/Fe3O4, ZIF-8, and AC/Fe3O4/ZIF-8 using Langmuir isotherm was obtained at 25.28, 30.03, 45.45, 51.2, and 57.47 mg/g, respectively revealing the effectiveness of AC/Fe3O4 in improving elimination performance of ZIF-8. Thermodynamically, the removal process of TC using AC/Fe3O4/ZIF-8 nanocomposite happened spontaneously and exothermally due to negative values of ΔG° (-6.94 kJ/mol) and ΔH° (-36.44 kJ/mol). The removal performance of AC/Fe3O4/ZIF-8 nanocomposite after four ad(de)sorption cycles is nearly constant (about 86 %) showing their stability in acidic and water media. Hydrogen bonding, electrostatic interaction, and π-π interactions are main mechanisms in TC removal by AC/Fe3O4/ZIF-8 nanocomposite. The results demonstrate that prepared adsorbents, mainly AC/Fe3O4/ZIF-8 nanocomposite, can be applied as recyclable and efficient adsorbents for TC elimination.

Eco-friendly nanoparticles: mechanisms and capacities for efficient removal of heavy metals and phosphate from water using definitive screening design approach.

Can nano-zero-valent iron, synthesized using oak leaf extract, be the key solution for water preservation, efficiently removing heavy metal ions and phosphate anions simultaneously? This research unveils how this technology not only promises high efficiency in the remediation of water resources, but also sets new standards for environmentally friendly processes. The high antioxidant capacity and high phenol content indicate suggest the possibility of oak-nZVI synthesis using oak leaf extract as a stable material with minimal agglomeration. The simultaneous removal of Cd and phosphates, as well as and Ni and phosphates was optimized by a statistically designed experiment with a definitive screening design approach. By defining the key factors with the most significant impact, a more efficient and faster method is achieved, improving the economic sustainability of the research by minimizing the number of experiments while maximizing precision. In terms of significance, four input parameters affecting process productivity were monitored: initial metal concentration (1-9mgL-1), initial ion concentration (1-9mgL-1), pH value (2-10), and oak-nZVI dosage (2-16mL). The process optimization resulted in the highest simultaneous removal efficiency of 98.99 and 87.30% for cadmium and phosphate ions, respectively. The highest efficiency for the simultaneous removal of nickel and phosphate ions was 93.44 and 96.75%, respectively. The optimization process fits within the confidence intervals, which confirms the assumption that the selected regression model well describes the process. In the context of e of the challenges and problems of environmental protection, this work has shown considerable potential and successful application for the simultaneous removal of Cd(II) and Ni(II) in the presence of phosphates from water.

Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.

Efficient removal of Rhodamine B dye using biochar as an adsorbent: Study the performance, kinetics, thermodynamics, adsorption isotherms and its reusability

Removal of toxic dyes such as Rhodamine B is essential as it pollutes aqueous and soil streams as well. This comprehensive study explores the potential of Calophyllum inophyllum seed char as an efficient bio-adsorbent based on their characteristic properties and a comparative study between various carbon-based adsorbents on the adsorption capacity of Rhodamine B dye. In this study, the char was prepared from Calophyllum inophyllum seed using a slow pyrolysis process (298 K/min) at an optimum temperature of 823 K and used as an adsorbent for the removal of Rhodamine B from water. The resulting char was mesoporous and had 155.389 m2/g surface areas (BET) and 0.628 cc/g pore volume. The formation of pores was observed from the SEM analysis. The adsorption studies were tested and optimized through various parameters such as solution pH, adsorbent dosage, initial dye concentration, stirring speed, contact time, and solution temperature. Maximum 95.5 % removal of Rhodamine B was possible at the pH: 2, stirring speed: 100 rpm, time: 25 min, temperature 308 K, and dose: 1.2 g/L. The highest adsorption capacity at equilibrium was determined to be 169.5 (mg/g) through Langmuir adsorption isotherm studies and followed pseudo 2nd order kinetics. The thermodynamics study confirmed the adsorption processes were spontaneous (ΔG°=−0.735 kJ/mol) and endothermic (ΔH° = 4.1 kJ/mol) processes. The reusability study confirmed that the mesoporous char can be reused as an efficient adsorbent for up to 3 cycles for environmental remediation.

Exploring a new vanadophosphate Li(C4N2H12)2[(HPO4)(VO)3(PO4)3]: Synthesis, Characterization, and catalytic behavior

Li(C4N2H12)2[(HPO4)(VO)3(PO4)3], a new vanadophosphate (VPO) material we synthesized using a hydrothermal route, crystallizes in the orthorhombic system (S.G.: Pna21), with the cell parameters: a = 14.6207(7) Å, b = 8.7090(3) Å, c = 17.6208(7) Å, V = 2243.69(16) (Å3), Z = 4. The crystal structure consists of bc-parallel layers of alternating polyhedra VO5, VO6 combined with PO4 or HPO4 tetrahedra. The layers stack provides cavities hosting Li+ cations. Within the interlayer space, protonated organic molecules act as a template and create hydrogen bonding interactions with the inorganic network. To assess its properties, the hybrid material’s thermal stability and reactivity were investigated using the IR spectroscopy and thermal analysis (TG/DTA). The potential of the title compound was investigated on the adsorptive removal of methylene blue (MB) dye by studying various parameters like pH, temperature, initial dye concentrations and contact time. The kinetic study revealed a gradual process of the dyés adsorption, with a removal efficiency of 99 % for initial MB concentrations of 50 ppm at pH = 7. The degradation MB continues even after three hours of oxidative reaction.

Prolific application of green synthesised CdS nanoparticles for the sequestration of cationic dyes from aqueous solution

Synthesis of cadmium sulfide (CdS) nanoparticles using watermelon rind aqueous extract was explored for its effectiveness in eliminating Methylene Blue (MB) and Crystal Violet (CV) dyes from water. The synthesised CdS nanoparticles were characterised with XRD, TEM and EDX and found to be around 10 nm in size with spherical shape. A central composite design was developed to optimise independent variables such as pH, contact time and initial concentrations. The developed quadratic model was found to be significant with p-value <0.0001 and lack of fit >0.005 suggesting the reliability of the model. Isotherm modelling analysis revealed that Langmuir and Freundlich's isotherms provided better explanation for the equilibrium data. The loading capacities of the CdS nanoparticles were found be 227.3 and 185.1 mg g-1, respectively for MB and CV. The experimental data showed a good fit with the pseudo-second-order kinetic model, indicating that chemical reactions were the determining factor in controlling the rate-limiting step. Thermodynamic analyses indicated that the process was spontaneous and exothermic. Desorption and regeneration investigations demonstrated that CdS nanoparticles could be successfully regenerated up to 5 times and reused in the adsorption process. The results conclude that the CdS nanoparticles are capable of remediating water containing cationic dyes.
 KEY WORDS: Watermelon rind, CdS nanoparticles, Synthetic dyes, Adsorption, RSM
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 631-645. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.7

Exploring recyclable alginate-enhanced GCN-LDO sponge for U(VI) and Cd(II) removal: Insights from batch and column studies

Developing effective water treatment materials, particularly through proven adsorption methods, is crucial for removing heavy metal contaminants. This study synthesizes a cost-effective three-dimensional material encapsulating graphitic carbon nitride-layered double oxide (GCN-LDO) in sodium alginate (SA) through the freeze-drying method. The material is applied to remove uranium (U(VI)) and cadmium (Cd(II)) in real water systems. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analyses conclusively verified the elemental composition and successful encapsulation of GCN-LDO within the SA matrix. Removal effectiveness was tested under various conditions, including adsorbent dose, ionic strength, contact time, temperature, different initial pollutant concentrations, and the impact of co-existing ions. The adsorption of U(VI) and Cd(II) conformed to the pseudo-second-order (PSO) kinetic model, signifying a chemical interaction between the sodium alginate-graphitic carbon nitride-layered double oxide (SA-GCN-LDO) sponge and the metal ions. The Langmuir isotherm indicated monolayer, homogeneous adsorption for U(VI) and Cd(II) with capacities of 158.25 and 165.00 mg/g. SA-GCN-LDO recyclability was found in up to seven adsorption cycles with a removal efficacy of 70%. The temperature effect study depicts the exothermic nature of the U(VI) and Cd(II) ion removal process. Various mechanisms involved in U(VI) and Cd(II) removal were proposed. Further, continuous fixed bed column studies were performed, and Thomas and the Yoon-Nelson model were studied. These insights from this investigation contribute to advancing our knowledge of the material's performance within the context of U(VI) and Cd(II) adsorption, paving the way for optimized and sustainable water treatment solutions.

Magnetic graphene derivates for efficient herbicide removal from aqueous solution through adsorption.

2,4-Dichlorophenoxyacetic acid (2,4-D) is an herbicide and is among the most widely distributed pollutant in the environment and wastewater. Herein is presented a complete comparison of adsorption performance between two different magnetic carbon nanomaterials: graphene oxide (GO) and its reduced form (rGO). Magnetic functionalization was performed employing a coprecipitation method, using only one source of Fe2+, requiring low energy, and potentially allowing the control of the amount of incorporated magnetite. For the first time in literature, a green reduction approach for GO with and without Fe3O4, maintaining the magnetic behavior after the reaction, and an adsorption performance comparison between both carbon nanomaterials are demonstrated. The nanoadsorbents were characterized by FTIR, XRD, Raman, VSM, XPS, and SEM analyses, which demonstrates the successful synthesis of graphene derivate, with different amounts of incorporate magnetite, resulting in distinct magnetization values. The reduction was confirmed by XPS and FTIR techniques. The type of adsorbent reveals that the amount of magnetite on nanomaterial surfaces has significant influence on adsorption capacity and removal efficiency. The procedure demonstrated that the best performance, for magnetic nanocomposites, was obtained by GO∙Fe3O4 1:1 and rGO∙Fe3O4 1:1, presenting values of removal percentage of 70.49 and 91.19%, respectively. The highest adsorption capacity was reached at pH 2.0 for GO∙Fe3O4 1:1 (69.98mgg-1) and rGO∙Fe3O4 1:1 (89.27mgg-1), through different interactions: π-π, cation-π, and hydrogen bonds. The adsorption phenomenon exhibited a high dependence on pH, initial concentration of adsorbate, and coexisting ions. Sips and PSO models demonstrate the best adjustment for experimental data, suggesting a heterogeneous surface and different energy sites, respectively. The thermodynamic parameters showed that the process was spontaneous and exothermic. Finally, the nanoadsorbents demonstrated a high efficiency in 2,4-D adsorption even after five adsorption/desorption cycles.

Sonodegradation of Sulfamethoxazole in Water Using Red Mud and Rice Husk Biochar Catalysis

This research evaluated the effectiveness of sulfamethoxazole (SMX) antibiotic degradation in aqueous solution using red mud and rice husk biochar (RMC) as catalytic material for ultrasound-supported degradation process. Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDX) were applied to study the characteristics of the catalytic material. The results demonstrated that the main components of RMC catalytic material are C, O, Si, and Fe elements with high weight percentage of 26.56%, 50.89%, 1.86% and 10.26%, respectively, and with high crystallized mix ratio. These are beneficial for SMX degradation reactions in water under the effect of ultrasound irradiation. The SMX degradation products were analyzed using High-performance liquid chromatography (HPLC). The effect of pH, contact time, initial concentration, and catalyst weight on degradation effectiveness were also investigated. The highest degradation efficiency of 75% at the treated rate of 15 mg SMX/g RMC was observed at pH = 3, contact time of 180 minutes, initial concentration of 20 mg SMX/L. This suggested a new solution to utilize the waste resources for waste treatment.

Integrated photocatalysis adsorption processes for oxytetracycline removal: using volborthite and its composite with g-C3N4.

The photocatalytic-adsorption performance of the composites of volborthite (CuVA) and graphitic carbon nitride (g-C3N4) was studied in this work using oxytetracycline (OTC) as model pollutant under LED light irradiation. CuVA at different weight percentages (10, 30, 50), namely, C10, C30, and C50, were loaded onto graphitic carbon nitride using wet chemical method. The physical, chemical, and optical properties were evaluated via various analytical techniques. Through integrated adsorption-photocatalytic process, no significant photocatalytic reaction occurred in g-C3N4 and the composite even after 4h of irradiation. The setup was modified such that each run was conducted in the presence and absence of light. Aside from photolysis and g-C3N4, all composites performed better under the presence of light in which CuVA improved the most from ~ 50% down to ~ 20% of initial concentration. CuVA performed almost identically (80% removal of OTC) under the presence of light irradiation at ambient temperature (22°C) and in the dark at 32°C, confirming that temperature was the contributing factor to the improvement instead of light. CuVA exhibited excellent adsorption capacity of 171mg/g and adsorption rate of 90% towards the removal of highly concentrated OTC (100mg/L) under optimized parameters of pH 5.0 and at 42°C after 3h of adsorption process. Life cycle assessment revealed that close to 50% of fresh 100ppm OTC could be removed after five cycles without any desorption process.

Polymerization of Thermo-Responsive Poly(N-vinylcaprolactam): Effects of Temperature, Initiator and Monomer Concentration on Percent Conversion

Poly(N-vinyl caprolactam) (PNVCL) is a thermally responsive polymer. Its temperature-responsive properties make it an attractive candidate for various applications. A series of temperature-sensitive PNVCL were synthesized through free radical polymerization, using various of amount of Azobisisobutyronitrile (AIBN) as initiator agent and with reaction temperatures set at 60oC, 70oC, 80oC. The percent conversion of polymerization was determined using the Hubl method to investigate the effects of three factors: initiator agent concentration, monomer concentration and reaction temperature. Furthermore, the chemical structure and the responsiveness of the PNVCL polymer were analyzed using Fourier transform infrared spectroscopy (FTIR) and UV-vis spectrometer, respectively. The study revealed that increasing the reaction temperature, initiator concentration, and monomer concentration resulted in higher percent conversion of polymerization. Finally, the obtained polymer demonstrated thermal sensitivity within the range of 32oC to 38oC, which is close to human body temperature, suitable for biomedical applications.

Exploration on the Mildew Conditions of Cladosporium asperulatum CY-H1, a Pathogenic Fungus on Tobacco Leaves

Aims: Mildew poses a significant threat to tobacco industry. This study focuses on a strain of Cladosporium asperulatum isolated from moldy tobacco leaves to investigate its growth under different temperature and humidity conditions, aiming to provide a theoretical basis for local prevention and control strategies against this fungus.
 Methodology: Potential fungal strains were obtained from moldy tobacco leaves utilizing isolation techniques and individual colonies were cultured on PDA medium subsequently. Microscopic examination and molecular identification were employed to determine the species of the isolated strains. Isolated strain was initially inoculated with varying spore powder concentrations at water activities of 0.99, 0.95, 0.90, 0.87, 0.83, and 0.77, combined with diverse culture temperatures of 15°C, 20°C, 25°C, 30°C, and 35°C on PDA. The growth of colony area was daily measured by ImageJ software, and spore powder yield was observed after a 7-day incubation period under these specified culture conditions.
 Results: (1) colony area of isolated C. asperulatum CY-H1 has a rising trend with increasing culture time at consistent temperatures. Sporulation exhibited an initial increase followed by a decrease, yet overall demonstrated an upward trajectory. The maximum value was attained at a water activity of 0.95. Under identical water activity, escalating temperatures initially augmented colony area until reaching a maximum at 25°C. Similarly, spore production displayed an initial increase followed by a decrease, with the highest production occurring at 25°C. (2) Varied concentrations of initial spore suspension influenced colony growth differently. A high concentration (initially 106 spores/mL) exhibited an earlier growth trend compared to medium (105 spores/mL) and low concentrations (104 spores/mL). (3) C. asperulatum CY-H1 did not thrive under the culture conditions of 35°C, irrespective of the initial inoculation concentration and water activity.
 Conclusion: C. asperulatum assumes a crucial role as a predominant mold in tobacco storage environments. Effective prevention of fungal mildew in stored tobacco leaves is achieved by maintaining temperatures exceeding 35°C and sustaining water activity below 0.77. These findings highlight the significance of environmental conditions in controlling mold growth during tobacco storage.

Research on column adsorption of Zn<sup>2+</sup> by hydroxyapatite granules

Hydroxyapatite (HAp) granules were fabricated successfully from HAp powder and polyvinyl alcohol (PVA) additive by sintering method. The characterization of material was analyzed by color, durability in the water, XRD, EDX, SEM and BET. The obtained HAp granules were white, single phase of HAp, with specific surface area of 73 m2/g, size of granule about (2 × 10) mm. HAp granules were used for the removal of Zn2+ ions from aqueous solution. The effect of factors on the Zn2+ adsorption property was investigated. The adsorption efficiency and capacity obtained 77.15 % and 2.57 mg/g, respectively at suitable batch adsorption condition: HAp granule mass of 0.5 g/ 50mL solution, initial concentration of 20 mg/L Zn2+, contact time 40 minutes and pH0 5.7 at 30 oC. The adsorption efficiency reached about 99.55 % at suitable column adsorption condition: contact time of 3,5 min, flow rate of 14 mL/min, adsorption zone height of 4Ф (Ф = 2.5 cm), initial concentration of 20 mg/L Zn2+, HAp granule mass of 11.9 g/ 2L solution, pH0 5.7 at 30 oC.

Adsorption properties of nanotube type halloysite clay mineral for La<sup>3+</sup> ions

This paper presents the results of research on the adsorption capacity of La3+ ions from aqueous solution of nanotube-type halloysite. The influence of operational conditions such as contact time, initial concentration of La3+, initial pH of solution, halloysite mass and temperature on the adsorption of La3+ had also been examined. The results show that the optimal efficiency and adsorption capacity of La3+ reached 90.19% and 3.76 mg/g in the suitable conditions: haloysite mass 0.6 g/50 mL solution, initial La3+ ion concentration 50 mg/L, pH 5.8, contact time 60 minutes at room temperature (25oC). The adsorption isotherm was studied based on both Langmuir and Freundlich models. The adsorption kinetics were studied by both pseudo-first-order and pseudo-second-order kinetic models. These results open up prospects for the application of haloysite clay minerals to remove and recover La in polluted water.

Manipulation of Bowl-Shaped Nanoparticles Self-Assembled from a Bipyridine Pendant Containing Homopolymer.

The morphological control and transformation of soft nanomaterials are critical for their physical and chemical properties, which can be achieved by dynamically regulating the hydrophilicity of amphiphilic polymers during self-assembly. Herein, an amphiphilic homopolymer poly(N-(2,2'-bipyridine)-4-acrylamide) (PBPyAA) with bipyridine pendants is synthesized, and the effect of various parameters including initial concentration, temperature, pH, and metal ion coordination on the self-assembly behavior and morphology of the assemblies is investigated. Upon changing the initial concentration of PBPyAA, bowl-shaped nanoparticles (BNPs) with precisely controlled diameter, opening size, and thickness are obtained. With the decrease of pH of the solution, the negatively charged surface of BNPs transforms to a positively charged state. Furthermore, the addition of divalent metal ions (Co2+, Mn2+, and Zn2+) induces the transformation of BNPs to vesicles and giant vesicles. The effect of the above factors on the morphology of the assemblies is essential to change the hydrophilicity of PBPyAA dynamically, leading to variation of the local viscosity during self-assembly. Overall, manipulation of the structural parameters of BNPs and transformation of BNPs to vesicles are achieved, providing fresh insights for the precise control of the morphologies of soft nanomaterials.

Fine-tuning the use of moss transplants to map pollution by Potentially Toxic Elements (PTEs) in urban areas

Mosspheres are a kind of moss transplants which offer a novel approach for detecting atmospheric pollution using devitalized mosses, as they reflect the atmospheric deposition of certain elements and polycyclic hydrocarbons. However, due to the unique features of the mosspheres such as the low elemental concentrations in the cultured material, the data treatment needs to be different from that of conventional biomonitoring studies. In this article, our objectives are to identify the best parameter for expressing the levels of chemical elements accumulated by mosspheres, and to apply a recently developed method to assess the probability of pollution of each sample and of the study area. To do this, we used data from a study in which 81 mosspheres were exposed in a medium-sized city in southwestern Europe.Comparing different pollution indices, we selected the enrichment rate (ER) as the most useful, as it is resilient to fluctuations in the initial concentrations and takes into account the time factor, allowing for greater comparability among studies. Then, we determined that the statistical distribution of the ERs of most elements fitted a normal distribution, showing that most samples did not differ significantly from the background concentrations for these elements. On the other hand, for Ni, Pb and Zn there was a subpopulation of samples above background values. In these cases, we determined the probability of pollution of each sample. Finally, we used indicator kriging to calculate the probability of pollution across the study area, identifying the polluted areas, which for some elements match the distribution of the main industries and highways, indicating that this is a suitable protocol to map elemental pollution in urban areas.

Static Robust Design Optimization Using the Stochastic Frontier Method: A Case Study of Pulsed EPD Process on TiO2 Films

This paper aims to optimize a pulsed electrophoretic deposition (EPD) process for TiO2 films. This is accomplished by determining the optimal configuration of the coating parameters from a robust optimization perspective. The experimental study uses a composite central design (CCD) with four control factors, i.e., the initial concentration (x1 in g/L), the deposition time (x2 in s), the duty cycle (x3 in %), and the voltage (x4 in V). The process responses that should all be maximized are the photocatalytic efficiency of the thin film (De) and three critical charges, which characterize the adhesion failure, i.e., LC1: the load at which the first cracks occurred; LC2: the load at which the film starts to delaminate at the edge level of the scratch track; and LC3: the load when the damage of the film exceeds 50%. This paper compares the robust optimization design of the EPD process using two methods: the robust design of processes and products using the stochastic frontier (RDPP-SF) and the surface response and desirability function methods. The findings show that the RDPP-SF method is superior to the response surface–desirability method for the process responses De and LC2 because of non-natural sources of variation; however, both methods perform comparably well while analyzing the LC1 and LC3 responses, which are subjected to pure random variability. The parameters setting for the process robust optimization are met in run 25 (x1 = 14 g/L, x2 = 150 s, x3 = 50%, and x4 40 V).

Assessment of sulfamethoxazole removal by three wetland plant species under hydroponic conditions: uptake, accumulation, and physiological responses

Plants play a crucial role as a removal pathway in constructed wetlands, demonstrating the ability to absorb and tolerate antibiotics from wastewater. However, the specific contribution of plants in this regard has not yet to be sufficiently established. To gain a more comprehensive insight into the associated processes, we selected three common wetland plant species, Canna indica L. (C. indica), Cyperus alternifolius L. (C. alternifolius), and Thalia dealbata Fraser (T. dealbata), to evaluate their capacity for uptake, accumulation, and physiological response in the removal of sulfamethoxazole (SMX) at varying initial concentrations (10, 30, 100, and 300 µg/L) under hydroponic conditions. The results showed that SMX removal was more efficient at lower concentrations (10 and 30 µg/L) than at higher concentrations (100 and 300 µg/L). Moreover, plant systems were found to consistently outperform unplanted systems in SMX removal. Among the assessed species, C. indica was identified as being relatively effective in the removal of SMX, whereas the performance of C. alternifolius was notably less pronounced. A positive correlation was observed between the concentration of SMX in the plant tissues and that in the external aqueous medium. However, plant tissue residues contributed only a minor fraction to the overall removal of SMX. Wetland plants absorb SMX through their roots, and we accordingly detected significantly higher concentrations in submerged plant tissues. Furthermore, we also detected reductions in net photosynthetic rates indicative of potential phytotoxicity, which is associated with the accumulation of antibiotic in the shoot tissues. Accumulation of SMX in the roots and rhizomes was also found to be associated with the development of shorter roots, with this effect becoming more pronounced with an increase in the concentration of exogenous SMX. However, despite these adverse effects, plants can detoxify antibiotics via the glutathione pathway. Of the assessed plant species, C. indica was identified as the most SMX tolerant, as indicated by K m and V max values, with C. alternifolius being the least tolerant. Our findings in this study reveal the potential value of wetland plants in the sequestration of antibiotics and provide evidence for the underlying mechanisms of action. These findings could make an important contribution to the implementation of phytoremediation in antibiotic-contaminated water.

Water disinfection using hydrogen peroxide with fixed bed hematite catalyst - kinetic and activity studies.

A lab-scale reactor with a fixed-bed hematite catalyst for the effective decomposition of H2O2 and bacteria inactivation was designed. The bactericidal effect is the largest at a low initial bacterial count of 2·103CFU/L, which is typical for natural surface waters. When using a 5mM H2O2 solution and a residence time of 104min, the reduction in the number of E. coli bacteria is about 3.5-log. At a higher initial bacterial count of 1-2·104CFU/L, a 5mM H2O2 solution reduces the bacteria number by about 4-log. The H2O2 decomposition follows the log-linear kinetics of a first-order reaction while the bacterial inactivation does not. The kinetics of bacterial inactivation was described using the Weibull model in the modified form: log10(N0/N) =b · tn. The values of the non-linearity parameter n were found to be lower than 1, indicating that bacterial inactivation slows down over time. With increasing initial H2O2 concentration, the rate parameter b increases while the non-linearity parameter n decreases. With increasing temperature, both parameters increase. The stability of the catalyst has been proved by XRD, FTIR, SEM, and ICP-OES. The concentration of iron leaching into water during disinfection is much lower than the limit declared by WHO for iron in drinking water. The results show that technical-grade hematite is a promising Fenton-like catalyst for water disinfection. The fixed-bed reactor can be the basis of the mobile installations for water purification in emergencies.

The AA7075–CS1018 Galvanic Couple under Evaporating Droplets

The galvanic corrosion behavior of the AA7075–CS1018 couple was examined in dynamic electrolytes using the ZRA technique. A modified electrochemical setup was developed to support the use of thin-film gel and liquid electrolytes on metallic surfaces. This allowed the collection of chemical information, left behind by the liquid electrolyte during evaporation, through a thin-film gel. The analysis of the gel electrolyte film confirmed the acidification on AA7075 and the alkalinization on CS1018 but also offered novel insights on their dependence on the galvanic current. The galvanic current was proportional to the initial NaCl concentration in the range of 0.01 to 0.06 M. However, due to continuous evaporation, the NaCl concentration increased, limiting oxygen diffusion and decreasing the galvanic current, especially for electrolytes exceeding 0.06 M. The galvanic current was determined by considering the dynamic evolution (caused by the evaporation of the electrolyte film) of both the thickness of the electrolyte and its concentration.