Mechanisms of efficient indoor formaldehyde removal via electro-Fenton: Synergy in ·OH generation and utilization through a modified carbon cathode.

Indoor formaldehyde poses a significant carcinogenic risk to human health, making its removal imperative. Electro-Fenton degradation has emerged as a promising technology for addressing this concern. In the electro-Fenton system, ·OH is identified as the primary active species responsible for formaldehyde removal. Hence, its generation and utilization are pivotal for the system's effectiveness and economy. Experimental and quantum chemical methods were employed to investigate the effects and mechanisms of nitrogen doping on various aspects influencing ·OH generation and utilization. Results indicate that nitrogen doping synergistically enhances the generation and utilization of ·OH, leading to an improved formaldehyde removal efficiency in nitrogen-doped cathodic systems. The dominant nitrogen type influencing ·OH generation and utilization varies across different stages. Pyridinic nitrogen facilitates H2O2 adsorption through hydrogen bonding, while pyrrolic and graphitic nitrogen contribute to formaldehyde adsorption and catalyze the conversion of H2O2 to ·OH. Both pyridinic nitrogen and pyrrolic nitrogen boost the degradation of formaldehyde by ·OH. In comparison to the unmodified system, the modified system with NAC-GF/700C as cathode exhibits remarkable improvements. The formaldehyde removal efficiency has increased twofold, and energy consumption reduced by 73.45%. Furthermore, the system demonstrates excellent cyclic stability. These advancements can be attributed to the activation temperature, which leads to the appropriate types and high content of nitrogen elements in NAC-GF/700C. The research represents an important step towards more economical and efficient electro-Fenton technology for indoor formaldehyde removal.

Vegetation restoration restrains rill erosion on slag heaps in high-altitude goldfields.

Soil erosion leads to soil degradation and depletion of land resources, posing a significant threat to industrial production and ecological sustainability. In high-altitude regions, rill erosion is the main form of soil erosion in mining areas, however, our understanding of morphology and developmental characteristics of rills and the mechanisms influencing them remains limited. In this study, data were collected from 96 rill plots across two gold mines in the eastern Tibetan Plateau according to vegetation restoration modes (natural restoration (CK) and planted with Elymus dahuricus (ED), Medicago sativa (MS), and multi-plant mixed (Avena fatua L. + Elymus dahuricus + Medicago sativa + Oxytropis coerulea, MM)) and restoration periods (1 year, 3 years, 4 years, and 6 years). We investigated the variations of 7 indicators that can reveal rill morphological and developmental characteristics across different restoration modes and restoration periods, and utilized a partial least squares structural equation model (PLS-SEM) to analyze the effects of 15 indicators from topography, soil, and vegetation on rill erosion modulus (REM). The results indicated that artificial vegetation restoration effectively restrained rill development, notably by decreasing the frequency of wider (>15 cm) and deeper (>10 cm) rills when compared to CK plots. Planting MM and ED exhibited greater efficacy in controlling rill erosion than planting MS. However, the effectiveness of planting ED in controlling rill erosion gradually weakened with time, while MM consistently maintained a strong inhibitory effect. Topographic features, soil texture, and vegetation significantly influenced the REM through direct or indirect effects. Plant root functional traits were the main driving factors in reducing REM, affecting not only REM directly but also influencing vegetation-induced soil properties to indirectly effect REM.

Strategies for promoting the degradation of phenol by electro-Fenton: Simultaneously promoting the generation and utilization of H2O2.

The use of the electro-Fenton process to continuously generate H2O2 and efficiently degrade organic pollutants is considered a promising technology. The ratio of generation of H2O2 is usually regarded as the critical step; however, how the H2O2 is utilized is also of particular importance. Herein, activated carbon was activated at different temperatures and used to explore the effect of nitrogen doping on the production and utilization of H2O2 in the electro-Fenton-based degradation of organic pollutants. The experimental results indicate that nitrogen-doped activated carbon simultaneously promotes the generation and utilization of H2O2, which is attributed to the regulation of the competition between phenol and O2 adsorption by the doped nitrogen. Nitrogen doping not only improves 2e-ORR selectivity but also aggregates phenol near the cathode to balance the concentrations of phenol and ·OH. Density functional theory (DFT) calculations further confirmed that pyrrole-N as a dopant promoted the adsorption of phenol, while pyridine-N was more favorable for O2 adsorption. The unique balance of nitrogen types possessed by modified activated carbon NAC-750 permits the efficient synergistic generation and utilization of H2O2 in a balanced manner during the degradation of phenol. This work provides a new direction for the rational nitrogen-doping modification of activated carbon for the electro-Fenton-based degradation of organic pollutants.

Synergistic mechanism of formaldehyde adsorption by intrinsic defects and carboxyl groups on the surface of carbon materials.

The adsorption of formaldehyde on the original carbon material is limited. Determining the synergistic adsorption of formaldehyde by different defects on the carbon material is necessary for comprehensively understanding the mechanism of formaldehyde adsorption on the surface of the carbon material. The synergistic effect of intrinsic defects and oxygen-containing functional groups on formaldehyde adsorption on the surface of carbon materials was simulated and verified by experiments. Based on the density functional theory, the adsorption of formaldehyde on different carbon materials was simulated by quantum chemistry. The synergistic adsorption mechanism was studied by energy decomposition analysis, IGMH, QTAIM, and charge transfer, and the binding energy of hydrogen bonds was estimated. The results showed that the energy for the adsorption of formaldehyde adsorbed by the carboxyl group on the vacancy defect was the highest, at -11.86 kcal/mol, the hydrogen bond binding energy was -9.05 kcal/mol, and a larger charge transfer was recorded. The mechanism of synergy was studied comprehensively, and the simulation results were verified at multiple scales. This study provides valuable insights into the effect of carboxyl groups on the adsorption of formaldehyde by activated carbon.

Effect of oxygen functional groups on competitive adsorption of benzene and water on carbon materials: Density functional theory study.

It is important to study the effect of oxygen-containing functional groups on the competitive adsorption mechanism of benzene and water on the surface of carbon materials, and to directional modification of activated carbon to improve its selective adsorption of benzene in air. In this study, the adsorption characteristics of benzene and water on original and linked ester, carboxyl, hydroxyl, carbon materials linked by ether groups were calculated by quantum chemical simulation based on density functional theory. The types and proportions of weak interactions in the adsorption process were calculated by energy decomposition analysis, and the adsorption mechanism of carbon materials for water and benzene was described. The influence and contribution of oxygen-containing functional groups on the adsorption of benzene and water were further analyzed by van der Waals potential and electrostatic potential, respectively, so as to determine the difference in the adsorption effect of different types of oxygen-containing functional groups on the two molecules. It was found that the carboxyl group has a great influence on the hydrophilicity of carbon materials, and the electrostatic potential distribution before and after linking the carboxyl group changed significantly. Therefore, they can attract each other with water through hydrogen bonds and occupy the surface adsorption sites of carbon materials, thereby inhibiting the adsorption of benzene on carbon materials. On the contrary, due to its hydrophobic properties, the ether group will free up adsorption space for the adsorption of benzene on the surface of the carbon material, which is beneficial to the adsorption of benzene. The adsorption experiments were carried out, and the results were consistent with the simulation. This study provides an idea for preparing efficient carbonaceous adsorbent of benzene and reducing benzene pollution in industry.

Promotion of formaldehyde degradation by electro-Fenton: Controlling the distribution of ·OH and formaldehyde near cathode to increase the reaction probability.

The mismatch of pollutant concentration and ·OH concentration is the key reason for the inefficient degradation of formaldehyde in the electro-Fenton system. Therefore, formaldehyde and ·OH are adsorbed near the cathode, and the high concentration reaction region is constructed to increase the reaction probability, which is called control of the reaction region. Through nitrogen doping modification of the activated carbon cathode, the adsorption capacity of the modified cathode for formaldehyde and active species, and the selectivity of the two-electron oxygen reduction reaction were deeply analyzed. The results show that the suitable nitrogen doping form of the modified cathode significantly promotes the adsorption capacity of formaldehyde and H2O2, which is beneficial to realizing the promotion of formaldehyde degradation by nitrogen doped cathodes in the electro-Fenton system through control of the reaction region. Graphite nitrogen and pyrrolic nitrogen improve formaldehyde adsorption by enhancing the van der Waals force (8.897 mg g-1), and pyridinic nitrogen improve H2O2 adsorption (1.841 mg g-1) by enhancing the effect of hydrogen bonding interaction. Nitrogen doping enhances Fe2+ regeneration, which contributes to the generation of ·OH at the cathode, and promotes formaldehyde degradation. The control of the reaction region through modification of the electro-Fenton cathode achieved formaldehyde degradation of 35.1 mg L-1 (48.51% higher than that of the unmodified cathode), which provides a promising process for formaldehyde treatment.

Size-changeable nanoprobes for the combined radiotherapy and photodynamic therapy of tumor.

PURPOSE: Radiation therapy (RT) and photodynamic therapy (PDT) are promising while challenging in treating tumors. The potential radiation resistance of tumor cells and side effects to healthy tissues restrict their clinical treatment efficacy. Effective delivery of therapeutic agents to the deep tumor tissues would be available for tumor-accurate therapy and promising for the tumor therapy. Thus, developing nanoprobes with effectively delivering radiotherapy sensitizers and photosensitizers to the interior of tumors is needed for the accurate combined RT and PDT of tumor. METHODS: The size-changeable nanoprobes of Gd2O3@BSA-BSA-Ce6 (BGBC) were synthesized with a crosslinking method. Magnetic resonance imaging (MRI) and in vivo near-infrared (NIR) imaging were measured to evaluate the nanoprobes' tumor accumulation and intratumor penetration effect. The tumor suppression effect of combined RT and PDT with these nanoprobes was also studied for the 4T1 bearing Balb/c mice. RESULTS: The nanoprobes BGBC showed high tumor accumulation and disintegrated into small particles responding to the photo-irradiation-produced reactive oxygen species (ROS), allowing for tumor penetration. Abundant radiotherapy sensitizers and photosensitizers were delivered to the deep tumor tissues, which is available for the accurate therapy of tumor. In addition, the BGBC displayed outstanding MRI and fluorescence imaging effects for evaluating the biodistribution and tumor suppression effect of nanoprobes. Consequently, significant tumor suppression effect was obtained based on the accurate tumor treatment with the combined RT and PDT. CONCLUSION: The designed size-changeable nanoprobes BGBC showed excellent tumor accumulation and deep tumor penetration, resulting in a significant tumor suppression effect based on the combined RT and PDT. This study provides a novel strategy for dual delivery of radiotherapy sensitizers and photosensitizers into the deep tumor tissues and is promising for the accurate theranostics of tumor.

Ethambutol-induced optic neuropathy: a nationwide population-based study from Taiwan.

AIM: To investigate the risk factors and comorbidities associated with ethambutol-induced optic neuropathy (EON). METHOD: Using the Taiwan Longitudinal Health Insurance Database, we conducted a study within a nationwide representative cohort of patients treated with EMB. We identified 231 patients newly diagnosed with EON between 2000 and 2008, and 924 control subjects. Adjusted OR by estimating the risk of EON in relation to comorbidities and EMB prescription protocol was determined. RESULTS: Compared with the control group, EON patients were at risk with older age, hypertension (adjusted OR=1.62, 95% CI 1.16 to 2.26) and renal diseases (without end-stage renal diseases (ESRD), adjusted OR=2.11, 95% CI 1.02 to 4.35; with ESRD, adjusted OR=3.73, 95% CI 1.79 to 7.74). Patients with an EMB prescription duration longer than 3 months were not at elevated risk compared with those whose prescription less than 3 months (OR=1.35, 95% CI 0.99 to 1.83, adjusted for age, sex, hypertension and renal diseases). Patients whose average daily dose was greater than 1200 mg, compared with the other two groups (800~1199 mg, less than 800 mg) were not at increased risk for EON. CONCLUSIONS: Age, hypertension and renal diseases are risk factors for EON in the Taiwanese population.