Water Treatment Research Articles

Intensification of flocculation efficiency in multi-stage reactors by optimizing the multi-cone segment configuration

Flocculation is widely used in water treatment, and creating an optimal environment for floc growth is essential to enhancing flocculation efficiency. In this paper, we developed a multi-stage flocculation reactor (MFR) with strong, moderate, and weak mixing zones. Specifically, multi-cone structures with varying diameter ratios (DR) were incorporated in the moderate zone to promote floc growth. Computational simulations revealed that an MFR with a DR of 0.5 generated a uniform and symmetric flow field, reducing zero-velocity zones and forming distinct vortices within cones. This environment facilitated gradual floc growth while minimizing breakage. When applied to treating fracturing flowback fluid, a complex and challenging wastewater, the MFR produced larger and denser flocs, with an average chord length of 180 μm and a fractal dimension of 1.7170. These flocs exhibited high viscoelasticity, with a strength factor of 68.22 and a recovery factor of 47.77, indicating superior shear resistance and recovery ability after breakage. Consequently, the MFR achieved COD and turbidity removal rates of 92.05% and 93.61%, respectively, outperforming a stirred flocculation reactor, which achieved rates of 72.29% and 83.53% for the same parameters. Additionally, the MFR demonstrated excellent pollutant removal efficiency for both mineral processing wastewater and dyeing wastewater. With gradually decreasing energy along the flow direction, the MFR provided appropriate mixing intensities for different stages of floc growth, promoting efficient formation. These findings underscore the MFR’s potential as a highly effective solution for wastewater treatment applications.

Sodium titanate (Na2Ti4O9) nanoribbons for effective removal of organic dyes from water: Experimental and computational studies

In this work, Na2Ti4O9 nanoribbons (NTRs) were synthesized using the hydrothermal method for its potential application in water treatment. The NTRs were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, zeta potential, Fourier Transform infrared spectroscopy, and surface area analyzer. The adsorption of organic dyes, including cationic methyl green (MeG) and methylene blue (MB) model pollutants, onto the NTRs was explored for the first time. Various parameters such as pH, adsorbent dose, initial dye concentration, regeneration, contact time, the effect of temperature, and thermodynamics were studied to determine the efficiency of NTRs for removing both dyes from water. A variety of isotherm and kinetic models were applied to fit the dye adsorption data at pH 7.0, providing insights into the adsorption mechanism and process kinetics. Kinetic data for both dyes fit well with pseudo-second-order and mixed 1,2-order models. The isotherm data agreed well with Langmuir-Freundlich and Sips models. At the studied temperatures of 298.2, 318.2, and 328.2 K, the maximum adsorption capacities for MeG (353.2, 367.7, and 443.2 mg·g−1) are significantly higher than for MB (29.3, 52.6, and 67.2 mg·g−1), indicating a stronger affinity for MeG, with adsorption efficiency improving as temperature increases. The MeG samples at 328.2 K exhibited interesting behavior. After adsorption, the samples became colorless, with a final pH near 7.0, indicating effective dye removal. However, the color faintly reappeared at pH 4.0, suggesting pH-dependent behavior and incomplete dye removal. The adsorption mechanism on the NTRs surface was investigated using Monte Carlo and molecular dynamics simulations.

Machine Learning-Based Prediction of the Adsorption Characteristics of Biochar from Waste Wood by Chemical Activation.

This study employs machine learning models to predict the adsorption characteristics of biochar-activated carbon derived from waste wood. Activated carbon is a high-performance adsorbent utilized in various fields such as air purification, water treatment, energy production, and storage. However, its characteristics vary depending on the activation conditions or raw materials, making explaining or predicting them challenging using physicochemical or mathematical methods. Therefore, using machine learning techniques to determine the adsorption characteristics of activated carbon in advance will provide economic and time benefits for activated carbon production. Datasets, consisting of 108 points, were used to predict the adsorption characteristics of biochar-activated carbon derived from waste wood. The input variables were the activation conditions, and the iodine number of activated carbon was used as the output variable. The datasets were randomly split into 75% for training and 25% for model validation and normalized by the min-max function. Four models, including artificial neural networks, random forests, extreme gradient boosting, and support vector machines, were used to predict the adsorption properties of biochar-activated carbon. After optimization, the artificial neural network model was identified as the best model, with the highest coefficient determination (0.96) and the lowest mean squared error (0.004017). As a result of the SHAP analysis, activation time was the most crucial variable influencing the adsorption properties. The machine learning model precisely predicts the adsorption characteristics of biochar-activated carbon and can optimize the activated carbon production process.

A Gradient Photothermal Hydrogel with Carbon-Dots Deposited Molybdenum Disulfide Nanoflowers as Photothermal Centers for Efficient Solar-Driven Water Evaporation and Treatment

Given the urgency of water pollution and freshwater scarcity, the pursuit of efficient and clean desalination techniques has gained prominence. In this study, a multi-defective molybdenum disulfide nanoflower was synthesized within a carbon-dots solution environment, named CDs/MoS2, exhibiting exceptional photothermal and catalytic properties. Relying on the excellent photothermal properties, antibacterial rates of up to 94% and 99% against Staphylococcus aureus and Escherichia coli. Additionally, the CDs/MoS2 nanoflowers exhibited a remarkable removal efficiency of 91% for high concentrations of methylene blue (MB) through photodegradation. A gradient photothermal composite hydrogel (CDs/MoS2@PVA Hydrogel) was designed to serve as a solar-driven clean water generator to isolate drinking water from various non-potable water. The gradient hydrogel effectively enhanced solar energy absorption through light trapping, creating dispersed hot spots to capture and activate water molecules. As a result, it achieved a high evaporation rate of 1.49 kg m-2 h-1 at a solar radiation of 1 kW m-2, with an impressive solar-to-vapor conversion efficiency of 92.5%. The hydrogel was successfully employed in diverse water treatment applications, including desalination, anti-bacteria and removal of organic contaminants from water. This study presents an innovative approach to developing novel solar vapor materials for water purification purposes.

Preparation of high performance CoCuAl@SiC catalytic ceramic membrane for nonradical degradation of sulfamethoxazole

Catalytic ceramic membranes (CCM) featuring catalytic and separating functions, show huge potential in water treatment. Nevertheless, the inability of catalytic ceramic membrane with high catalytic performance to be produced by current fabrication method are the bottleneck preventing their applications. Herein, the high performance CoCuAl@SiC CCM were successfully prepared by coating Al gel interlayer, hydrothermal reaction and annealing in reductive atmosphere. Annealing in reductive atmosphere play key role in enhancing the catalytic property of CoCuAl@SiC CCM. 99.3 % sulfamethoxazole (10 mg·L−1) degraded by CoCuAl@SiC CCM annealing at 300 °C and 0.5 mM PMS in 1 min under a wide pH range of 3.5–11.0 and in the presence of anions. Quenching tests confirmed the dominant role of singlet oxygen (1O2) in SMX degradation. The abundant oxygen vacancies and redox cycles of Co3+/Co2+ and Co2+/Co0 on CoCuAl@SiC CCM are crucial for PMS activation. In addition, the SMX degradation pathways were found to comprise deamination, hydroxylation, and ring open according to the degradation intermediates of SMX. This study not only provides an approach for the preparation of catalytic membranes with excellent catalytic activity, but also sheds a novel insight into the indispensable role of oxygen vacancy.

A New Tropical Wild Fern for the Green Synthesis of Gold Nanoparticles: Comprehensive Characterization and Application in Water Treatment

Utilizing natural plant extracts to synthesize of gold nanoparticles (AuNPs) has emerged as a sustainable and eco-friendly alternative to conventional methods. Nephrolepis biserrata (NB), a tropical perennial fern, is rich in bioactive phytochemicals such as alkaloids, tannins, and flavonoids, which can effectively serve as reducing and stabilizing agents in the green synthesis of AuNPs. UV-visual spectrophotometry was employed to optimize synthesis parameters, including the reactant ratio of chloroauric acid (HAuCl₄) to NB, HAuCl₄ concentration, and reaction temperature. Optimal AuNP synthesis was achieved at a 1:0.25 HAuCl₄ ratio, a concentration of 0.25 mM HAuCl₄, and a reaction temperature of 70 °C, yielding nanoparticles with an absorbance of 1.449 ± 0.039 at a λmax of 531 nm. The synthesized AuNPs were characterized using FTIR, Zeta potential, FESEM/EDX, and XRD analyses. FTIR results indicated that the hydroxyl (O–H) and carbonyl (C=O) groups in NB facilitated the reduction of Au³⁺ ions. Zeta potential measurements confirmed AuNPs’ stability at -15.1 mV. The FE-SEM images and EDX analysis verified that the AuNPs were predominantly spherical, with minimal variation in shape. The average particle size was measured to be 28.184 ± 7.87 nm. The EDX spectrum showed strong signals for atomic gold at 2.12 and 2.14 keV, indicating that gold constituted approximately 48.49% of the sample by weight, which can be attributed to the bio-reductants in the plant extracts.The peaks in the X-ray diffractogram that correspond to Bragg’s reflection values of 38°, 44°, 64°, and 77° at 2θ indicate the formation of the face-centered cubic crystalline structure of AuNPs. These nanoparticles demonstrated high catalytic efficiency in the degradation of methylene blue (MB) dye, following a pseudo-first-order reaction in the presence of NaBH₄. These findings suggest that NB-mediated AuNPs offer a promising and eco-friendly approach for catalytic applications in wastewater treatment.

Microenvironment modulation of Fe single atoms in porous g-C3N4 by introducing −SOx groups for enhanced photo-Fenton reactions

Heterogeneous photo-Fenton reactions based on hydrogen peroxide (H2O2) activation exhibit great potential in the treatment of organic wastewater. For developing efficient photo-Fenton catalysts, a fundamental investigation into the specific catalytic sites and the reaction mechanism is highly desired. Herein, a novel photo-Fenton catalyst (Fe1/CN-SOx) was constructed by synchronously anchoring Fe single atoms (SAs) and oxidized sulfur (−SOx) groups into porous graphitic carbon nitride (g-C3N4). The presence of trace −SOx groups altered the local configuration of g-C3N4 and optimized the coordination microenvironment of Fe SAs, thereby modulating the electronic structures of catalytic sites in favor of H2O2 activation. The cooperation between Fe SAs and the neighboring C atoms bonded with −SOx (C-SOx) enhanced the adsorption and cleavage of H2O2. The photoinduced charge carriers further accelerated Fe2+/Fe3+ redox cycles and hydroxyl radical (•OH) production, achieving an efficient photo-Fenton synergistic catalysis for continuous degradation of organic contaminants. The Fe1/CN-SOx catalyst also exhibited excellent anti-interference performance in diverse aquatic systems and good long-term stability, indicating its great potential for applications in water treatment. This study provides an in-depth insight into the optimal fabrication of single-atom active sites by modulating the local structures of support materials, aiming to enhance photo-Fenton reactions.

Demonstration scale treatment of drainage canal water in the Nile Delta through a combination of facultative lagoons and hybrid constructed wetlands

Drainage canal water (DCW), a mixture of Nile water, drainage water and municipal wastewater, is largely used for irrigation in the Nile Delta. Facultative lagoons (FL) and constructed wetlands (CWs) represent interesting options for DCW treatment before its agricultural re-use, but very few studies investigated their implementation in Egypt. This work aimed at developing at demonstration scale (250 m3 d-1) a FL+CW treatment train capable to turn DCW into an effluent reusable in agriculture. Three types of hybrid CWs were tested in parallel for 530 days. The combination of FL with a cascade hybrid CW, operated at a 200 L d-1 m-2 surface loading rate, led to medium-to-high removal efficiencies (suspended solids 90%, total nitrogen 84%, phosphate 80%, COD 67%, faecal coliforms 2.2 Log) and surface removal rates (COD 47.5 t y-1 ha-1, total nitrogen 10.9 t y-1 ha-1, faecal coliforms 1.5 1011 MPN y-1 ha-1). The effluent, compliant with class C of EU 2020/741 regulation, is potentially reusable to irrigate numerous Egyptian crops. The results show that the combination of FLs with cascade hybrid CWs has a great potential for the treatment of DCW and low-strength municipal wastewater, with near-zero energy consumption, null consumption of chemicals and a land requirement varying between 1.1% and 1.5% of the agricultural land irrigated with the treated DCW.

2D hollow leaf shaped mesoporous carbon derived from ZIF-L for efficient capacitive deionization

Electrochemical treatment of saline or brackish water by capacitive deionization (CDI) is a novel resource-saving solution to ensure the availability of freshwater resources in the environment. MOF (metal–organic framework) derived carbon as a novel carbonaceous material in CDI has received considerable research attention. Among them, ZIF-L-derived carbon (ZC) suffers from problems such as self-aggregation, poor mesoporous structure, and low electrical conductivity, which lead to poor CDI performance. In this paper, a strategy of ZIF-L coated with polydopamine (PDA) is proposed to solve the above problems. When the amount of PDA was 0.5 g, ZIF-L@PDA0.5-derived carbon composite (ZPC0.5) is obtained for efficient capacitive deionization. The ZPC0.5 composite not only maintains the 2D leaf shaped structure consistent with ZIF-L, exposing more active sites, but also has an elevated mesopore occupancy ratio to promote solution diffusion. Meanwhile, the interaction between PDA and ZIF-L makes the ZPC0.5 have a cavity structure, which improves the mass transfer capacity. The resulting ZPC0.5 composite has a specific capacitance (165.8F g−1) that is 3.86 times higher than that of ZC (42.9F g−1). Consequently, in 1.2 V, 500 mg/L NaCl solution, the symmetric CDI cell ZPC0.5//ZPC0.5 exhibits an excellent desalination capacity (29.6 mg/g), which is 2.69 times that of the ZC//ZC.

Enhanced removal of tetracycline using three-dimensional electrochemical system with Fe/N/S co-doped coffee grounds biochar particle electrodes: Performance and mechanism

In this study, Fe/N/S co-doped biochar was prepared from coffee grounds for using as particle electrodes (PE) to construct a three-dimensional electrochemical system (3DES). Tetracycline (TC) was selected as the simulated contaminant to evaluate the performance of 3DES in removing trace organic contaminates form water. First, characteristics analysis revealed that the PE was the micron-level carbon-based solid material with good electric conductivity, excellent catalytic performance and stability. Then, the performance of the 3DES was evaluated. About 92% of TC and 76% of total organic carbon (TOC) was removed under optimal operation conditions of potassium peroxydisulfate (PDS) addition of 3mM, current density of 100mA·cm−2, PE dosage of 0.5g·L−1 and solution initial pH of 7. The 3DES exhibited satisfactory stability and application prospect for trace organic contaminates treatment in real water. Furthermore, analysis of the reactive oxidized species (ROS) revealed that the 1O2 and O2•− contributed much more to the TC removal than •OH and SO4•−. In addition, three possible pathways of TC removal in 3EDS was proposed. TC was degraded to organics with simple structures through functional group removal, ring-opening, and C=O bond rupturing, and finally mineralized into CO2, H2O, and NO3-, etc. Finally, toxicity evaluation of the intermediate products indicated that the ecological risks of TC was effectively reduced through 3DES. This study provided a new strategy for resource utilization of carbon-based solid waste and efficient treatment of refractory wastewater.

Assessment of Cerium Adsorption Potential of Phosphoric acid Activated Biochar in Aqueous System: Modelling and Mechanistic Insights

Cerium pollution in waterbodies by improper industrial waste disposal is a major concern due to its detrimental impacts on the environment. Therefore, treatment of cerium-contaminated water is inevitable. Hence, this study is focused on the remediation of cerium pollution using phosphoric acid-activated biochar (PPMB) as an adsorbent, synthesized upon pyrolytic activation of palmyra palm male flower-based pristine biochar (PMFB) with H3PO4 at 500°C. The physico-chemical surface properties of PMFB and PPMB were evaluated through various microscopic and spectroscopic analyses. The key parameters such as biochar dosage, pH, temperature, contact time and initial cerium concentration were optimized as 0.5 g/L, 5.0, 303 K, 180 min and 50 mg/L respectively via batch adsorption. Pseudo-second order kinetic and Toth isotherm are the best-fitted models. The thermodynamic parameters including ΔG◦ (-30.4707±0.7618 kJ/mol at 303 K), ΔH◦ (16.1499±0.78 kJ/mol), and ΔS◦ (153.617±3.8404 J/mol/K) conveying that cerium adsorption onto PPMB was spontaneous, endothermic, and highly disordered at PPMB-bulk adsorption medium interface. Precipitation, electrostatic attraction, and surface complexation are predicted to be the predominant mechanisms for the chosen PPMB-cerium adsorption system. Moreover, cerium phytotoxicity on Vigna radiata explains the real-time applicability and feasibility of cerium adsorption using PPMB. Thus, the key findings of this study specified that the higher adsorption capacity of PPMB (141.3484±6.9856 mg/g) contributed by the incorporated phosphate groups, predominant mesoporosity, SSABET of 230.559 m2/g and anionic surface at a wider pH range (pH>3.08) make PPMB as efficient, economically feasible and environmentally friendly adsorbent for cerium adsorption in aqueous system.

Nano-Fe3O4/FeCO3 modified red soil-based biofilter for simultaneous removal of nitrate, phosphate and heavy metals: Optimization, microbial community and possible mechanism

The pollution of nitrogen, phosphorus and heavy metals in surface water is becoming more and more serious, affecting the safety of water quality. In this study, three biofilters were constructed using iron-modified red soil-based filler carriers (RSC, nano-Fe3O4@RSC, and FeCO3@RSC) combined with strain Zoogloea sp. ZP7 to simultaneously remove nitrate (NO3--N), phosphate (PO43--P), copper (Cu2+), and zinc (Zn2+). The long-term operation results showed that the three groups of biofilters could remove 85.0, 90.0, and 89.8% of NO3--N, respectively. Furthermore, the addition of iron compounds enhanced the removal of PO43--P and the resistance to the stress of Cu2+ and Zn2+ in the biofilter. The analysis illustrated that iron modification improved the redox activity and zeta potential of RSC surface. The secondary structure analysis of the protein showed that the microbial secreted proteins were more compact on the surface of the iron-modified RSC, which facilitated the formation of biofilm on the carrier surface. In addition, the iron-modified RSC-based biofilter also showed excellent NO3--N and PO43--P removal efficiency in the treatment of actual surface water. The microbial community analysis results showed that Zoogloea became the dominant species in the biofilter. On the other hand, the presence of iron-reducing bacteria and the expression iron cycle-related genes may contribute to denitrification under low nutrient conditions.

Synthesis and Characterization of CaO nanoparticles from Periwinkle shell for the Treatment of Tetracycline-contaminated Water by Adsorption and Photocatalyzed Degradation

Due to the ever-increasing discharge of antibiotic residues into different water bodies, there is a significant need to improve existing water treatment methods. In this study, we synthesized calcium oxide nanoparticles from periwinkle shells using the sol-gel method for applications in the adsorption and photodegradation of tetracycline from wastewater. The nanoparticles were characterized using FTIR, UV-Visble spectroscopy, XRD, SEM-EDX, TEM, BET and TGA/DTA. The nanostructure produced showed strong crystalline, optical, structural and surface properties. With an average crystallite size of 25 nm, particle size of 2.09 nm, BET surface area of 582.68 m2/g, specific surface area of 90.08 m2/g, bandgap of 4.8 eV and other properties that supported their functionality as adsorbent and photocatalyst for the removal of tetracycline residue from water. The adsorption experiment gave a maximum efficiency of about 80% while the photodegradation catalysed by the nanoparticles indicated efficiency up to 97%. Both adsorption and photodegradation showed strong dependency on pH, tetracycline concentration, catalyst load and concentration of KI. Response surface analysis and subsequent experimental validation indicated that degradation approaching 100% for tetracycline is feasible under optimum conditions involving concentration = 500 ppm, time = 50 min, catalyst load = 1.25 g and KI concentration = 0.25 M. Computational calculations gave results that are in good match with experimental data and further proved that the degradation is limited by adsorption and is majorly controlled by oxidation facilitated by O2*.

Managing Acidic Mine Water Pollution in Karst Regions Based on Hydrogeological Structures

Acidic mine drainage (AMD) is one of the primary pollutants from abandoned mines. This type of pollution is characterized by its extensive area, prolonged duration, and challenging detection process, especially in karst region with intricate hydrological systems, thereby posing a significant threat to the sustainable development of the economy. This paper focuses on the pollution of acidic mine water in the karst region of Southwest China and adopts a comprehensive watershed pollution management strategy. Considering the unique hydrogeological structure of the karst mines, the active water cycle, and the sensitivity and fragility of the ecological environment, this study proposes a set of acid mine drainage pollution control methods based on hydrogeological structures. These include “zonal management, one policy per mine; source control, pollution reduction; and end-of-pipe treatment, standard discharge.” This study applies coal mine water prevention and control techniques to environmental management, developing a series of source control methods including “filling, isolating, blocking, intercepting, draining, and controlling”. It also integrates physical, chemical, and biological methods for the end-of-pipe treatment of acidic mine water. This approach has been successfully applied to the management of acidic mine drainage in the Yudong River basin in Kaili, Guizhou. Long-term monitoring of the "three-fields and four-water” revealed that rainfall significantly influences mine water quality. The study identified a “U-tube effect” whereby mine water exacerbates the pollution of karst water, leading to the development of a comprehensive prevention and control strategy termed the “three blocking (obstruction) and one guarantee” project. A comparative analysis of total iron content in the basin before and after treatment demonstrated a marked reduction, from 97.8mg/L to less than 0.3mg/L. This study provides a typical example for the prevention, control, and management of acid water pollution in karst areas across the watershed, and can serve as a reference for similar pollution management efforts.

Xylopia parviflora (A. rich.) benth. Mitigates anxiety behavior and chronic mild stress-induced depression-like behavior in mice: The involvement of biogenic amine neurotransmitters, cyclooxygenase-2 and stress biomarkers in its antidepressant activity

BackgroundXylopia parviflora is a novel botanical in Modern Chinese Medicine that contains bioactive constituents including alkaloids, flavonoids, and terpenoids, which are the pharmacologically active components in various Chinese herbal formulations such as Coptis chinensis (alkaloid-rich herbs), Ginkgo biloba (flavonoid-rich herbs) and Artemisia annua (terpenoid-rich herbs). ObjectiveThis investigation sought to evaluate the anxiolytic and antidepressant-like effects of the hydroethanol leaf extract of Xylopia parviflora using mouse models. We elucidated the roles of noradrenaline, serotonin, cyclooxygenase-2, and reactive oxidative species in mediating its antidepressant effects, providing a fresh perspective on the pharmacological activity of Xylopia parviflora. MethodsThe acute toxicity of XPE was assessed following OECD guideline 420. Established behavioral tests were used to evaluate the anxiolytic (including the hole-board, open field, elevated plus maze, and light/dark exploration assessments) and antidepressant (encompassing the forced swim and tail suspension tests) effects of the extract. Mice received treatments of distilled water (10 mL/kg, serving as the negative control), fluoxetine (20 mg/kg, acting as the reference medication), and XPE (at doses of 50, 100, and 200 mg/kg). The concentrations of noradrenaline, serotonin, and COX-2 within the brain tissue were quantified using ELISA kits. The levels of antioxidant biomarkers were evaluated using standardized commercial assay kits. ResultsThe oral/intraperitoneal LD50 for the extract was established at 2000 mg/kg. In the behavioral assessments designed to measure anxiolytic effects, XPE significantly mitigated anxiety levels in mice, as evidenced by an increase in exploratory behaviors (including head dips, sectional crossings, general square crossings, rearing, and assisted rearing) and an increased time spent in the brightly illuminated compartments. Concerning the antidepressant evaluations, XPE significantly reduced depression-like behaviors in mice, which was indicated by an increased latency to immobility and a decrease in the duration of immobility. XPE was found to modulate noradrenaline and serotonin transmissions, attenuate oxidative species, and inhibit COX-2 activity. ConclusionThe findings above demonstrate that Xylopia parviflora possesses anxiolytic and antidepressant-like activities. The antidepressant property of XPE, as revealed in this study, may be attributable to the enhancement of biogenic amines (specifically noradrenaline and serotonin), the suppression of oxidative species, and the inhibition of COX-2 activity.

Electrocatalytic conversion of nitrate to ammonia on the oxygen vacancy engineering of zinc oxide for nitrogen recovery from nitrate-polluted surface water.

Nitrate pollution in surface water poses a significant threat to drinking water safety. The integration of electrocatalytic reduction reaction of nitrate (NO3RR) to ammonia with ammonia collection processes offers a sustainable approach to nitrogen recovery from nitrate-polluted surface water. However, the low catalytic activity of existing catalysts has resulted in excessive energy consumption for NO3RR. Herein, we developed a facile approach of electrochemical reduction to generate oxygen vacancy (Ov) on zinc oxide nanoparticles (ZnO1-x NPs) to enhance catalytic activity. The ZnO1-x NPs achieved a high NH3-N selectivity of 92.4% and NH3-N production rate of 1007.9 h-1 m-2 at -0.65 V vs. RHE in 22.5 mg L-1, surpassing both pristine ZnO and the majority of catalysts reported in the literature. DFT calculations with in-situ Raman spectroscopy and ESR analysis revealed that the presence of Ov significantly increased the affinity for the (nitrate) and key intermediate of (nitrite). The strong adsorption of on Ov decreased the energy barrier of potential determining step ( →*NO3) from 0.49 to 0.1 eV, boosting the reaction rate. Furthermore, the strong adsorption of on Ov prevented its escape from the active sites, thereby minimizing by-product formation and enhancing ammonia selectivity. Moreover, the NO3RR, when coupled with a membrane separation process, achieved a 100% nitrogen recycling efficiency with low energy consumption of 0.55 kWh at a flow rate below 112 mL min-1 for the treatment of nitrate-polluted lake water. These results demonstrate that ZnO1-x NPs are a reliable catalytic material for NO₃RR, enabling the development of a sustainable technology for nitrogen recovery from nitrate-polluted surface water.

Chemical characterization of activated carbon derived from Napier grass, rubber wood, bamboo, and hemp

This study examines the process and analysis of activated carbons that use H2SO4, H2O2, and NaOH as activating agents. The distinct chemical methods employed by each activator impacted the ash and carbon content, surface properties, and functional groups of the activated carbons, exhibiting notable disparities. The ash level varied from 6.86% to 37.08%. H2SO4-activated carbons had the lowest ash content, suggesting better elimination of inorganic contaminants. The iodine number, which serves as a measure of adsorption capacity, was consistent among all samples, with values ranging from 800 to 950 mg g-1. This indicates that the three activating agents effectively increased the surface area and porosity. The BET surface areas varied between 9.14 and 167.42 m2 g-1, whereas the BJH adsorption surface areas ranged from 9.68 to 28.89 m2 g-1. The pore volumes ranged from 0.0071 to 0.0595 cm2 g-1, while the sizes ranged from 0.51 to 8.2 nm. These measurements suggest the presence of both micropores and mesopores. The FTIR spectra exhibited comparable functional groups among all samples, such as OH, CH, C=C, and C-O. The SEM-EDX and XPS tests showed that there was a lot of carbon. The carbon content was highest in H2O2-activated carbons because they were exposed to less severe oxidative conditions. These activated carbons comply with the requirements set by IUPAC and ASTM. They are suitable for catalytic processes and liquid adsorption, such as water and wastewater treatment. Subsequent research should aim to improve activation conditions to get the highest possible carbon content and optimise surface characteristics.

Application of hydrogen-rich water maintains red pitaya fruit quality through regulation of ROS and energy metabolism

Hydrogen-rich water (HRW) treatment has been shown to enhance the shelf life of fruit and vegetables. This study aimed to investigate the effects of HRW on improving the quality of red pitaya and its underlying regulatory mechanisms. The results revealed that applying HRW at a 70% concentration reduced decay and weight loss rates, slowed the respiratory rate, and delayed the decline in titratable acidity and total soluble solids. Additionally, HRW treatment mitigated the increase in superoxide anion production and hydrogen peroxide levels, while enhancing antioxidant enzyme activities and gene expression, including those of peroxidase, superoxide dismutase, glutathione peroxidase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, and glutathione reductase. Non-enzymatic antioxidant compounds such as ascorbate and glutathione also increased. Moreover, RT-qPCR analysis showed that HRW treatment upregulated HcMYB6 and downregulated HcR2R3MYB. Dual-luciferase reporter assays indicated that HcMYB6 activated the expression of HcSOD and HcCAT, whereas HcR2R3MYB repressed their expression. These findings suggest that HcMYB6 and HcR2R3MYB may be involved in reactive oxygen species metabolism, with HcMYB6 being induced and HcR2R3MYB inhibited by HRW treatment. Furthermore, HRW treatment led to increased adenosine triphosphate and adenosine diphosphate levels, a decrease in adenosine monophosphate content, and elevated gene expression and activity of Ca2⁺-ATPase, succinate hydrogenase, H⁺-ATPase, and cytochrome C. Collectively, these results demonstrate that HRW treatment effectively reduces oxidative damage and improves energy status, thereby preserving the quality of red pitaya fruit.

Aerobic granular sludge enhances start-up and granulation in single-stage partial nitritation anammox granular sludge systems: Performance, mechanism, and shifts in bacterial communities

The rapid start-up and granulation of a single-stage partial nitritation anammox granular sludge (PN/AnGS) system under limited seed sludge conditions is crucial for its practical application. This study proposed an aerobic granular sludge (AGS) − based strategy, enhanced the enrichment of anammox bacteria (AnAOB), and shortened the start-up time of PN/AnGS system by 20.5%. In addition, the inoculation of AGS can ensure the stable operation of the system during the selective sludge discharge to washout the flocs. Microbial community structure, particle size distribution, morphology results showed that niche shift was the key to promote the enrichment of AnAOB and AGS played a decisive role in the particle characteristics of PN/AnGS. Since AGS can be directly obtained from full-scale AGS wastewater treatment plants, integrating PN/AnGS with AGS processes can transition wastewater treatment from a “linear economy” to a “circular economy”, enhancing nitrogen removal efficiency and delivering significant economic and environmental benefits.

Consequential life cycle assessment of urban source-separating sanitation systems complementing centralized wastewater treatment in Lund, Sweden

This study examined various source-separating sanitation systems to evaluate their environmental performance, providing decision-makers with insights for selecting an appropriate system for a newly developed neighborhood in Sweden. A full consequential LCA was conducted to account for resource recovery and substitution. The local wastewater treatment plant WWTP was modeled as a reference. Secondly, a urine recycling system was introduced to treat 75% of the collected urine, with the remainder piped to the WWTP. Thirdly, a black and greywater (BW&GW) treatment system handling all generated wastewater was examined. Finally, a hybrid source-separating system combining urine, black, and greywater was investigated. The results indicated that the four scenarios exhibited global warming potentials (GWP) of 78, 62, 32, and 24 kg CO2-eq per PE/ y. Recycling urine as fertilizer led to a 20% reduction in the GWP of the reference. It also reduced other impact categories, with a 55%, 65%, and 45% reduction in eutrophication, ozone depletion, and acidification, respectively. The BW&GW system achieved a 60% reduction over the reference GWP, mainly due to fertilizer, biogas, and cleanwater recovery. Integrating urine, black, and greywater recycling in the final scenario achieved a 25% reduction compared to the BW&GW scenario, primarily due to lowering of the ammonia stripping GWP and the additional fertilizer recovery. Based on sensitivity analyses, switching citric acid for sulfuric acid reduced the GWP of the urine stabilization unit process by 101%, from 15.47 to -0.14 kg CO2-eq per PE/ y. Ultimately, the findings suggest that the fully decentralized source-separating sanitation system incorporating urine, blackwater, and greywater recycling, particularly when combined with 70% energy recovery at the urine concentrator, is most favorable.