Biochar in the 21st century: A data-driven visualization of collaboration, frontier identification, and future trend

Research on drought stress in Medicago sativa L. from 1998 to 2023: a bibliometric analysis

Alfalfa (Medicago sativa L.) is one of the most important forage crops in the world. Drought is recognized as a major challenge limiting alfalfa production and threatening food security. Although some literature reviews have been conducted in this area, bibliometric reviews based on large amounts of published data are still lacking. In this paper, a bibliometric analysis of alfalfa drought stress from 1998-2023 was conducted using the Web of Science Core Collection database in order to assess global trends in alfalfa drought stress research and to provide new directions for future research. The results showed that the annual publication output maintained an increase in most years, with China and the United States contributing significantly to the field. Most of the journals published are specialized journals in botany, environmental science, soil science and crop science, as well as related agribusiness journals. "plant growth" and "yield" were the most frequently used keywords, reflecting the important purpose of research in this field. And two main research directions were identified: research on drought response mechanism of alfalfa and exploration of drought-resistant technology. In addition, physiological, biochemical, and molecular responses of drought tolerance and high yield in alfalfa, transgenics, and microbial fertilizer research have been hot research topics in recent years and may continue in the future. The ultimate goal of this paper is to provide a foundational reference for future research on alfalfa's drought resistance and yield optimization mechanisms, thereby enhancing the crop's application in agricultural production.

Activity and recyclability enhancement of pH-dependent Fe0@BC-mediated heterogeneous sodium percarbonate (SPC)-reducing agents (RA) system

Dyes pose great threats to the aquatic environment and human health. Fe0-based Fenton-like systems have been widely employed for the degradation of organic dyes. However, the regulation of degradability and recyclability was still unclear. In this study, Rhodamine B (RhB) was served as the model pollutant, hydroxylamine hydrochloride was selected as the RA, the natural photocatalysis system demonstrated stable operation. RA, as performance enhancement agent, was firstly reported in micro/nano-Zero-Valent Iron@Biochar (m/nZVI@BC) based SPC-RA system. Carrier size-fractionated m/nZVI@BC was fabricated by one-step carbothermal method. As a result, RA synergistically interacted with SPC, and the reaction time reduced from 15 min to 4 min. In the 0.010 g m/nZVI@BC-mediated SPC-RA system, over 95% of RhB (100 mg·L-1, 1041.667 mg·g-1) was successfully degraded. The maximum degradation ability could still exceed 1g·g-1 via 5 times repeated applications. Meanwhile, the loss of degradability, caused by halving SPC concentration could be compensated by RA dosage measurement. The entire degradation process was predominantly dominated by free radicals (•OH> 1O2> •O2-> •CO3-). Reactive oxidizing species (ROSs) were primarily excited by α-Fe0, Fe3C and N sites of biochar (BC). Light and BC carrier dedicated slight influence. These discoveries shed a light on the activity and recyclability regulation of catalytic material, aligning with the principles of green chemistry and cleaner production. This study demonstrates a novel approach to efficient management of solid waste disposal, reuse of waste biomass, advanced treatment of dye-containing wastewater, pollution control in aquatic environments.

Revealing the synergistic effect between radical and non-radical species of sulfur-doped carbon nitride for ciprofloxacin removal: Based on density functional theory study

The distinct characteristics of active species produced during the photocatalytic reaction can result in alterations in the degradation routes of organic pollutants with diverse chemical structures. The relationship between the active species and degradation pathways of organic pollutants lacks a direct experimental or characterization method, so in-depth research is still needed to understand the details of their interactions. In this study, sulfur-doped bulk carbon nitride (SBCN) was prepared based on bulk carbon nitride (BCN), and the process of S-doping enhancing the production of O21 was revealed. Through the degradation experiment, the degradation rate of CIP by SBCN reached 91 %, which was higher than that of BCN (66 %). The increase of degradation rate was mainly attributed to the increase of O21. Through the density functional theory (DFT) calculation of CIP and its degradation intermediate, due to the preferential oxidation of CIP by O21, O21 changes the initial degradation direction of CIP, releasing more attack sites for ˙O2-, thereby achieving more efficient degradation of CIP through the synergy of O21 and ˙O2-. In this study, the attack preferences of the active species and their synergistic promotion provide important insights for the efficient photocatalytic degradation of organic pollutants.

Utilization of biochar for remediation of heavy metals in aqueous environments: A review and bibliometric analysis

Biochar usage for removing heavy metals from aqueous environments has emerged as a promising research area with significant environmental and economic benefits. Using the PICO approach, the research question aimed to explore using biochar to remove heavy metals from aqueous media. We merged the data from Scopus and the Web of Science Core Collection databases to acquire a comprehensive perspective of the subject. The PRISMA guidelines were applied to establish the search parameters, identify the appropriate articles, and collect the bibliographic information from the publications between 2010 and 2022. The bibliometric analysis showed that biochar-based heavy metal remediation is a research field with increasing scholarly attention. The removal of Cr(VI), Pb(II), Cd(II), and Cu(II) was the most studied among the heavy metals. We identified five main clusters centered on adsorption, water treatment, adsorption models, analytical techniques, and hydrothermal carbonization by performing keyword co-occurrence analysis. Trending topics include biochar reusability, modification, acid mine drainage (AMD), wastewater treatment, and hydrochar. The reutilization of heavy metal-loaded spent biochar includes transforming it into electrodes for supercapacitors or stable catalyst materials. This study provides a comprehensive overview of biochar-based heavy metal remediation in aquatic environments and highlights knowledge gaps and future research directions.

Knowledge mapping on the sun-induced chlorophyll fluorescence technology research: a scientometric and visualization analysis

The sun-induced chlorophyll fluorescence (SIF) has received increasing attention over the past few years. This scientometric study analyzed the SIF research field, based on publications available in Web of Science Core Collection visualization, and cluster analysis enabled us to map the knowledge domain and intellectual landscape of this field and identify thematic trends, landmark articles, and emerging research themes. In this study, the software VOSviewer and CiteSpace were used to identify the intellectual base and research front using visualization and analysis. Then, we analyzed synthesized networks of co-authorship (author, institution, and country), co-citation (author, document, and journal), and co-occurring keywords. SIF has increased its publication output steadily since 2002. This study provided a visual knowledge map of the major research domains of SIF. Also, explanations and implications of the findings were explored, and the emerging trends were identified. This report provides a thorough overview of the current state and growth trends of SIF research, and it helps researchers and practitioners understand the major areas of attention in this area and provides insights into prospective areas for further study.

Study on the effects of carbon dioxide atmosphere on the production of biochar derived from slow pyrolysis of organic agro-urban waste

Slow pyrolysis, a widely recognized thermochemical technique, is employed to produce biochar usually under inert atmospheres. Recently, there is a growing interest in utilizing CO2 as a carrier gas during pyrolysis as an alternative to inert atmospheres, aiming to modify the resulting pyrolytic products and make them suitable for different applications. This study investigated and compared the impact of CO2 atmosphere with N2 on pyrolysis of food waste, rice husk, and grape tree branches waste via slow pyrolysis at temperatures of 400, 500, and 600 °C at 5 and 15 °C/min for 1 h, to evaluate biochar production and its properties. The results demonstrate that CO2 atmosphere increased the biochar yield for all feedstocks and significantly influenced the physicochemical properties of biochar. Compared to N2, CO2-derived biochar exhibited less volatile matter, higher carbon content, lower O/H and O/C molar ratios and enhanced textural properties. This study highlighted the potential of utilizing CO2 for biochar production and tailoring biochar properties for specific applications and the findings contribute to the establishment of sustainable and efficient waste management systems and the production of value-added biochar products.

Cyano-Regulated Organic Polymers for Highly Efficient Photocatalytic H2 O2 Production in Various Actual Water Bodies

Photocatalytic production of H2 O2 has drawn significant attention in recent years, but the yield rate of current photocatalytic systems is still unsatisfactory. Moreover, the presence of various components in actual water bodies will consume the photogenerated charges and deactivate the catalyst, severely limiting the real applications of photocatalytic H2 O2 production. Herein, a cyano-modified polymer photocatalyst is synthesized by Knoevenagel condensation with subsequent thermal polymerization. The introduction of cyano group and sulfer (S), oxygen (O) elements modulates the microstructure and energy band of the polymer catalyst, and the cyano group sites can effectively adsorb and activate O2 , realizing the generation of H2 O2 in the two-step single-electron oxygen reduction process. The reported system achieves high H2 O2 generation rate up to 1119.2 µmol g-1 h-1 in various water bodies including tap water, river water, seawater, and secondary effluent. This simple and readily available catalyst demonstrates good anti-interference performance and pH adaptability in photocatalytic H2 O2 production in actual water bodies, and its photodegradation and sterilization applications are also demonstrated. This study offers new insights in developing polymer catalysts for efficient photocatalytic production of H2 O2 in various water bodies for practical application.

Autoimmune diseases and gut microbiota: a bibliometric and visual analysis from 2004 to 2022

Many studies have shown that gut microbiota is closely related to autoimmune diseases (ADs). Studies on gut microbiota and ADs have also increased significantly, but no bibliometric analysis has summarized the association between gut microbiota and ADs. This study aimed to conduct a bibliometric and visual analysis of published studies on gut microbiota and ADs. Based on the Web of Science Core Collection SCI-expanded database, we utilize Excel 2019 and visualization analysis tools VOSviewer and co-occurrence13.2 (COOC13.2) for analysis. A total of 2516 related kinds of literature were included, and the number of papers presented an overall increasing trend. The country/region with the most publications is the USA, the institution is the Harvard Medical School, and the author is Mikael Knip from the USA. Hot research areas include intestinal regulation (such as dysbiosis, short chain fatty acids, and probiotics), multisystem ADs (such as multiple sclerosis, rheumatoid arthritis, and inflammatory bowel disease), and immune-related cells (such as T cells, and dendritic cells). Psoriasis, dysbiosis, autoimmune liver disease, and fecal microbiota transplantation may be the future research direction. Our research results can help researchers grasp the current status of ADs and gut microbiota research and find new research directions in the future.

Out-of-hospital cardiac arrest: A data-driven visualization of collaboration, frontier identification, and future trends

One of the main causes of death is out-of-hospital cardiac arrest (OHCA), which has a poor prognosis and poor neurological outcomes. This phenomenon has attracted increasing attention. However, there is still no published bibliometric analysis of OHCA. This bibliometric analysis of publications on OHCA aimed to visualize the current status of research, determine the frontiers of research, and identify future trends. Publications on OHCA were downloaded from the web of science database. The data elements included year, countries/territories, institutions, authors, journals, research areas, citations of publications, etc. Joinpoint regression and exponential models were used to identify and predict the trend of publications, respectively. Knowledge domain maps were applied to conduct contribution and collaboration, cooccurrence, cocitation, and coupled analyses. Timeline and burst detection analysis were used to identify the frontiers in the field. A total of 3 219 publications on OHCA were found from 1998 to 2022 (average annual percentage change = 16.7; 95% CI 14.4, 19.1). It was estimated that 859 articles and reviews would be published in 2025. The following research hotpots were identified: statement, epidemiology, clinical care, factors influencing prognosis and emergency medical services. The research frontier identification revealed that 7 categories were classified, including therapeutic hypothermia, emergency medical services, airway management, myocardial infarction, extracorporeal cardiopulmonary resuscitation, stroke foundation and trial. The burst detection analysis revealed that percutaneous coronary intervention, neurologic outcome, COVID-19 and extracorporeal cardiopulmonary resuscitation are issues that should be given continual attention in the future. This bibliometric analysis may reflect the current status and future frontiers of OHCA research.

Current Status and Future Direction of Albumin-Bilirubin in Hepatocellular Carcinoma: A Bibliometric Analysis

INTRODUCTION

Hepatocellular carcinoma (HCC) is a common malignant tumor, so we need a convenient and objective way to diagnose and treat HCC. We discuss the current situation, progress, hotspots, and existing problems of Albumin-Bilirubin (ALBI) in HCC, which can provide new ideas for the prevention, diagnosis, and treatment of HCC.

METHODS

We adopt Excel 2019 software and visual analysis tools based on Web of Science database search. This manuscript uses VOSviewer, Co-Occurrence13.3 (COOC13.3) software to conduct overall trend analysis, synonym merging, frequency of countries, journals, institutions, funds, dissimilarity matrices, co-occurrence matrices, bimodal matrices, coupling matrices, cluster analysis of topic evolution time zone graphs.

RESULTS

A total of 610 papers were included, and the number of papers output showed an overall upward trend. ALBI has been valued by the industry in HCC and plays an important role in diagnosing and treating HCC, even better than the classic Child-Pugh (C-P) grade. At the same time, hot spots in the treatment of HCC and other applications of ALBI were discovered.

CONCLUSION

ALBI score is a convenient and objective liver function evaluation index, which plays an important role in the prediction of patient survival rate and prognosis. Promoting the ALBI score in HCC can help doctors judge the patient's condition and improve the diagnosis and precise treatment effect.

Unveiling the Effects of Carbon-Based Nanomaterials on Crop Growth: From Benefits to Detriments

To systematically assess the impact of typical CNMs on the growth effects of cereal crops, we conducted a meta-analysis of 48 independent studies worldwide. The pooled results showed that shoot weight (13.39%) and antioxidant metabolite content (SOD: 106.32%, POD: 32.29%, CAT: 22.63%) of cereal crops exposed to the presence of CNMs were significantly increased, but phytohormones secretion (17.84%) was inhibited. The results of subgroup analysis showed that there were differences in the results of different CNM types with the same exposure concentration on growth effects. Short-term exposure adversely affected the root and photosynthetic capacity of the crop, but prolonged exposure instead showed a promoting effect. Multiple linear regression analysis showed that the concentration of CNMs and cereal variety variables were significantly associated with changes in multiple growth effect values. This work could offer references and fresh perspectives for investigating how nanoparticles and crops interact.

Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review

Heavy metal contamination of water sources has emerged as a major global environmental concern, threatening both aquatic ecosystems and human health. Heavy metal pollution in the aquatic environment is on the rise due to industrialization, climate change, and urbanization. Sources of pollution include mining waste, landfill leachates, municipal and industrial wastewater, urban runoff, and natural phenomena such as volcanic eruptions, weathering, and rock abrasion. Heavy metal ions are toxic, potentially carcinogenic, and can bioaccumulate in biological systems. Heavy metals can cause harm to various organs, including the neurological system, liver, lungs, kidneys, stomach, skin, and reproductive systems, even at low exposure levels. Efforts to find efficient methods to remove heavy metals from wastewater have increased in recent years. Although some approaches can effectively remove heavy metal contaminants, their high preparation and usage costs may limit their practical applications. Many review articles have been published on the toxicity and treatment methods for removing heavy metals from wastewater. This review focuses on the main sources of heavy metal pollution, their biological and chemical transformation, toxicological impacts on the environment, and harmful effects on the ecosystem. It also examines recent advances in cost-effective and efficient techniques for removing heavy metals from wastewater, such as physicochemical adsorption using biochar and natural zeolite ion exchangers, as well as decomposition of heavy metal complexes through advanced oxidation processes (AOPs). Finally, the advantages, practical applications, and future potential of these techniques are discussed, along with any challenges and limitations that must be considered.

Artificial intelligence in wastewater treatment: A data-driven analysis of status and trends

Wastewater treatment is a complex process that involves many uncertainties, leading to fluctuations in effluent quality and costs, and environmental risks. Artificial intelligence (AI) can handle complex nonlinear problems and has become a powerful tool for exploring and managing wastewater treatment systems. This study provides a summary of the current status and trends in AI research as applied to wastewater treatment, based on published papers and patents. Our results indicate that, at present, AI is primarily used to evaluate removal of pollutants (conventional, typical, and emerging contaminants), optimize models and process parameters, and control membrane fouling. Future research will likely continue to focus on removal of phosphorus, organic pollutants, and emerging contaminants. Moreover, analyzing microbial community dynamics and achieving multi-objective optimization are promising directions of research. The knowledge map shows that there may be future technological innovation related to predicting water quality under specific conditions, integrating AI with other information technologies and utilizing image-based AI and other algorithms in wastewater treatment. In addition, we briefly review development of artificial neural networks (ANNs) and explore the evolutionary path of AI in wastewater treatment. Our findings provide valuable insights into potential opportunities and challenges for researchers applying AI to wastewater treatment.

The application of machine learning to air pollution research: A bibliometric analysis

Machine learning (ML) is an advanced computer algorithm that simulates the human learning process to solve problems. With an explosion of monitoring data and the increasing demand for fast and accurate prediction, ML models have been rapidly developed and applied in air pollution research. In order to explore the status of ML applications in air pollution research, a bibliometric analysis was made based on 2962 articles published from 1990 to 2021. The number of publications increased sharply after 2017, comprising approximately 75% of the total. Institutions in China and United States contributed half of all publications with most research being conducted by individual groups rather than global collaborations. Cluster analysis revealed four main research topics for the application of ML: chemical characterization of pollutants, short-term forecasting, detection improvement and optimizing emission control. The rapid development of ML algorithms has increased the capability to explore the chemical characteristics of multiple pollutants, analyze chemical reactions and their driving factors, and simulate scenarios. Combined with multi-field data, ML models are a powerful tool for analyzing atmospheric chemical processes and evaluating the management of air quality and deserve greater attention in future.

Hotspots and trends of biological water treatment based on bibliometric review and patents analysis

In order to reveal the hotspots and trends of biological water treatment from the perspectives of scientific and technological innovation, both of the bibliometric review and patents analysis were performed in this study. The Web of Science Core Collection database and Derwent Innovation Index database recorded 30023 SCI papers and 50326 patents, respectively were analyzed via information visualization technology. The results showed that China ranked the first in both papers and patents, while the United States and Japan had advantages in papers and patents, respectively. It was concluded through literature metrology analysis that microbial population characteristics, biodegradation mechanism, toxicity analysis, nitrogen and phosphorus removal and biological treatment of micro-polluted wastewater were the research hotspots of SCI papers. Activated sludge process and anaerobic-aerobic combined process were the two mainstream technologies on the basis of patent technology classification analysis. Technology evolution path of biological water treatment was also elucidated in three stages based on the citation network analysis. Furthermore, the future directions including research on the law of interaction and regulation of biological phases and pollutants and the technology innovations towards the targeted biotransformation or selective biodegradation of pollutants and resource reuse of wastewater were prospected.

Efficient degradation of sulfamethoxazole in various waters with peroxymonosulfate activated by magnetic-modified sludge biochar: Surface-bound radical mechanism

First time, this study synthesized a magnetic-modified sludge biochar (MSBC) as an activator of peroxymonosulfate (PMS) to eliminate sulfamethoxazole (SMX). The removal efficiency of SMX reached 96.1% at t = 60 min by PMS/MSBC system. The larger surface area and magnetic Fe₃O₄ of MSBC surface enhanced its activation performance for PMS. The PMS decomposition, premixing and reactive oxygen species (ROS) identification experiments combined with Raman spectra analysis demonstrated that the degradation process was dominated by surface-bound radicals. The transformed products (TPs) of SMX and the main degradation pathways were identified and proposed. The ecotoxicity of all TPs was lower than that of SMX. The magnetic performance was beneficial for its reuse and the removal efficiency of SMX was 83.3% even after five reuse cycles. Solution pH, HCO₃^- and CO₃^2- were the critical environmental factors affecting the degradation process. MSBC exhibited environmental safety for its low heavy metal leaching. PMS/MSBC system also performed excellent removal performance for SMX in real waters including drinking water (88.1%), lake water (84.3%), Yangtze River water (83.0%) and sewage effluent (70.2%). This study developed an efficient PMS activator for SMX degradation in various waters and provided a workable way to reuse and recycle municipal sludge.

Biological filtration for wastewater treatment in the 21st century: A data-driven analysis of hotspots, challenges and prospects

Biological filtration has been widely used in wastewater treatment around the world, yet achieving satisfactory removal of pollutants remains a challenge due to the complexity of water pollution. In order to reveal the hotspots and trends of biological filtration from the perspective of research innovation, 5454 SCI papers and 14,287 patents collected from the Web of Science Core Collection and Derwent Innovation Index database were analyzed by visualization techniques. The results showed that China ranked first in the number of both papers and patents, while the USA and Japan contributed significantly in papers and patents, respectively. Co-occurrence analysis obtained the mapping knowledge domains and demonstrated distinct associations between contaminants ("nitrogen", "pharmaceuticals", "personal care products"), chemicals ("carbon", "activated carbon", "media"), process ("biodegradation", "adsorption" or "ozonation") and characteristics ("kinetics", "performance", "diversity"). Moreover, this review summarized the recent advances of biological filtration media, microorganism and combined process being applied. It was concluded that environmentally friendly biological filtration ("phytoremedi", "microalga", "recirculating aquaculture system"), bio-enhanced biological filtration ("bioaugment", "fungi", "low augment") and emerging pollutants ("emerging contamin", "antibiotic resistance gen", "organic micropollut", "trace organic chem") were the hotspots through data-driven analyses. Technology evolution path of biological filtration generally indicated the transition from conventional biological filtration for nitrogen and phosphorus removal to Fenton-biofiltration combined technology and finally to ozone-biological filtration. Furthermore, the technical innovation direction of the collaborative control of multi-media pollution, the low-carbon biological filtration and short-process technology was prospected. This work can serve as a quick reference for early-career researchers and industries working in the area of biological filtration.

An overview and trend analysis of research on the relationship between urban streets and residents' health in China pre- and post COVID-19 pandemic

Introduction

After the outbreak of COVID-19, the international community has been faced with various problems it has brought to cities. A large number of research projects and corresponding management measures were launched globally, trying to reduce the impact of COVID-19 on society. Among them, exploring how to maintain the health of residents by managing and updating the design of urban streets is one of the important issues regarding urban sustainability in the post-epidemic era.

Methods

This study uses bibliometric analysis techniques to obtain an overview of the knowledge structure of 898 Chinese urban streets and residents' health relationship studies from the China National Knowledge Infrastructure (CNKI) database for two periods (1999-2019 and 2020-2022). Five aspects were analyzed in terms of the keyword domain co-occurrence network, topic evolution path, emergent terms, hierarchical clustering, and confusion matrix.

Results and discussion

The findings revealed that studies focused on six broad themes: community residents, health surveys, health education, COVID-19, healthy city, and public health. Based on these findings, the paper compares and discusses research priorities before and after the outbreak and highlights areas for further research and attention.

Predicting the speciation of ionizable antibiotic ciprofloxacin by biochars with varying carbonization degrees†

Sorption mechanisms of ionizable organic pollutants by biochars and approaches for the prediction of sorption are still unclear. In this study, batch experiments were conducted to explore the sorption mechanisms of woodchip-derived biochars prepared at 200–700 °C (referred as WC200–WC700) for cationic, zwitterionic and anionic species of ciprofloxacin (referred as CIP⁺, CIP^± and CIP⁻, respectively). The results revealed that the sorption affinity of WC200 for different CIP species was in the order of CIP^± > CIP⁺ > CIP⁻, while that of WC300–WC700 remained the order of CIP⁺ > CIP^± > CIP⁻. WC200 exhibited a strong sorption ability, which could be attributed to hydrogen bonding and electrostatic attraction with CIP⁺, electrostatic attraction with CIP^±, and charge-assisted hydrogen bonding with CIP⁻. Pore filling and π–π interactions contributed to the sorption of WC300–WC700 for CIP⁺, CIP^± and CIP⁻. Rising temperature facilitated CIP sorption to WC400 as verified by site energy distribution analysis. Proposed models including the proportion of the three CIP species and sorbent aromaticity index (H/C) can quantitatively predict CIP sorption to biochars with varying carbonization degrees. These findings are vital to elucidating the sorption behaviors of ionizable antibiotics to biochars and exploring potential sorbents for environmental remediation.

This study revealed the evolution of sorption mechanisms with pyrolysis temperature of biochar and CIP speciation, and provided a novel approach for the sorption prediction of ionizable antibiotics.

Coassisted carbonization with HCOOK/(HCOO)2Ca for the fabrication of bamboo-derived oxygen-doped porous carbons exhibiting high-performance sorption of diethyl phthalate from aqueous solutions

Porous carbons are excellent sorbents for removing organic pollutants. Green conversion of biowaste into advanced porous carbons is crucial for industrialized production and practical applications, which, however, have rarely been investigated. This study develops a coassisted carbonization method for the preparation of porous carbons with the environmentally friendly agents HCOOK and (HCOO)₂Ca for the first time. The bamboo waste-derived hydrochar was transformed into oxygen-doped porous carbons, which displayed a large surface area and pore volume, abundant oxygen content, graphene structure and many surface functional groups. These properties contributed to the extremely high sorption of large quantities of diethyl phthalate, which reached 761 mg g^-1. Surface adsorption, including pore filling, hydrogen bonding, and π-π stacking, rather than partitioning, was the main sorption process. Therefore, this study provides a sustainable and promising route for the preparation of porous carbons that can be applied in the efficient removal of organic pollutants.

The evolution of research on depression during COVID-19: A visual analysis using Co-Occurrence and VOSviewer

Background

The COVID-19 pandemic has led to public health problems, including depression. There has been a significant increase in research on depression during the COVID-19 pandemic. However, little attention has been paid to the overall trend in this field based on bibliometric analyses.

Methods

Co-Occurrence (COOC) and VOSviewer bibliometric methods were utilized to analyze depression in COVID-19 literature in the core collection of the Web of Science (WOS). The overall characteristics of depression during COVID-19 were summarized by analyzing the number of published studies, keywords, institutions, and countries.

Results

A total of 9,694 English original research articles and reviews on depression during COVID-19 were included in this study. The United States, China, and the United Kingdom were the countries with the largest number of publications and had close cooperation with each other. Research institutions in each country were dominated by universities, with the University of Toronto being the most productive institution in the world. The most frequently published author was Ligang Zhang. Visualization analysis showed that influencing factors, adverse effects, and coping strategies were hotspots for research.

Conclusion

The results shed light on the burgeoning research on depression during COVID-19, particularly the relationship between depression and public health. In addition, future research on depression during COVID-19 should focus more on special groups and those at potential risk of depression in the general population, use more quantitative and qualitative studies combined with more attention to scale updates, and conduct longitudinal follow-ups of the outcomes of interventions. In conclusion, this study contributes to a more comprehensive view of the development of depression during COVID-19 and suggests a theoretical basis for future research on public health.

Effects of activated carbon, biochar, and carbon nanotubes on the heterogeneous Fenton oxidation catalyzed by pyrite for ciprofloxacin degradation

Pyrite and engineering carbon materials have received increasing attention for their catalytic potential in Fenton reactions due to their extensive sources and low cost. However, effects of carbon materials on the degradation of pollutants by pyrite-catalyzed heterogeneous Fenton oxidation have not been fully understood. In this study, the performance of pyrite-catalyzed heterogeneous Fenton system on the degradation of ciprofloxacin (CIP) was investigated in the presence of activated carbon (AC), biochar (BC), and carbon nanotubes (CNTs). Synchronous and asynchronous experiments (adsorption and catalysis) were conducted to elucidate the roles of the carbon materials in pyrite-catalyzed Fenton reactions. The results demonstrated that all the three carbon materials accelerated the pyrite-catalyzed Fenton oxidation of CIP. Under the experimental conditions, the reaction rates, which were obtained by fitting the synchronous experimental results with the pseudo-first-order kinetic model, of pyrite/AC, pyrite/BC and pyrite/CNTs with H₂O₂ for the removal of CIP were 8.28, 3.40 and 3.37 times faster than that of pyrite alone. Adsorption experiments and characterization analysis showed that AC had a higher adsorption capacity than BC and CNTs for CIP, which enabled it to distinguish itself in assisting the pyrite-catalyzed Fenton oxidation. In the presence of the carbon materials, the adsorption effect should not be neglected when studying the catalytic performance of pyrite. Free radical quenching experiments and electron spin-resonance spectroscopy (ESR) were used to detect and identify free radical species in the reactions. The results showed that hydroxyl radicals (•OH) contributed significantly to the degradation of CIP. The addition of carbon materials promoted the production of •OH, which favored the degradation of CIP. The results of this study suggested that the synergistic effect of oxidation and adsorption promoted the removal of CIP in pyrite/carbon materials/H₂O₂ systems, and coupling pyrite and carbon materials shows great potential in treating antibiotic wastewater.

Brewer’s Spent Grain Biochar: Grinding Method Matters

The present work is based on the principle of biomass waste valorization. Brewer’s spent grains (BSG) come from breweries as by-products. Their huge amount of production on an industrial scale should focus our attention on their valorization, which creates challenges as well as opportunities. One way to valorize BSG by-products is to convert them into biochar, a functional material with multiple potential applications. With an emphasis on sustainable development and the circular economy, in this work, we focused on a comparative study of the different mechanical processes of BSG grinding and their effect on the resulting biochar formed after pyrolysis. Home appliances such as blenders, coffee mills, and mortar and pestles were used for this purpose. FESEM images confirmed the successful creation of five different morphologies from the same BSG under the same pyrolysis conditions. Interestingly, a novel Chinese tea leaf egg-like biochar was also formed. It was found that a series of physical pretreatments of the biomass resulted in the reduced roughness of the biochar surface, i.e., they became smoother, thus negatively affecting the quality of the biochar. XRD revealed that the biomass physical treatments were also reflected in the crystallinity of some biochar. Via a Raman study, we witnessed the effect of mechanical pressure on the biomass for affecting the biochar features through pressure-induced modifications of the biomass’s internal structure. This induced enhanced biochar graphitization. This is a good example of the role of mechanochemistry. DSC revealed the thermochemical transformation of the five samples to be exothermic reactions. This study opens up an interesting possibility for the synthesis of biochar with controlled morphology, crystallinity, degree of graphitization, and heat capacity.

The evolution of stable nanohybrids to complex heteroaggregates between nZVI and soil nanoparticles: The influence of ionic strength and soil components

The heteroaggregation mechanism of nZVI with four types of natural soil nanoparticles (SNPs) extracted from representative soils in northern and southern China was investigated. Heteroaggregation rates between nZVI and SNPs were quantified by dynamic light scattering and evaluated as a function of ionic strength at pH 7. The nZVI-SNPs heteroaggregates were stable with hydrodynamic diameters (D_h) ranging from 400 to 600 nm in 0.1 mM solution. Based on the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, nZVI underwent heteroaggregation with SNPs to form stable nZVI-SNPs nanohybrid due to the attachment of nZVI on the SNPs. However, with enhanced ionic strength, SNPs accelerated the aggregation of nZVI and formed large heteroaggregates with D_h in the range from 1200 to 2000 nm, owing to insignificant electrostatic repulsions and oppositely charged patches. In addition, the differences in the heteroaggregation rates of nZVI with four SNPs were negligible, caused by the negligible impacts of SNPs components such as soil organic matter and Fe/Al oxyhydroxides on the heteroaggregation of nZVI in the 10 mM NaCl solution. These findings are helpful for understanding the interaction between nZVI and SNPs and of significance to groundwater remediation using nZVI.

A Novel Low-Cost Bio-Sorbent Prepared from Crisp Persimmon Peel by Low-Temperature Pyrolysis for Adsorption of Organic Dyes

In order to properly reuse food waste and remove various contaminants from wastewater, the development of green, sustainable and clean technologies has demonstrated potential in the efficient inhibition of secondary pollution to the environment. In this study, an economical and green method was used to prepare biochar from crisp persimmon peel (CPP) using flash-vacuum pyrolysis at different temperatures (200–700 °C; referred to as CPP200–CPP700). CPP200 has high polarity, low aromaticity and high oxygen-containing functional groups that exhibit superior MB adsorption capabilities. CPP200 that was prepared at a relatively low temperature of 200 °C exhibited a high adsorption capacity of 59.72 mg/g toward methylene blue (MB), which was relatively higher than that for alizarin yellow R (4.05 mg/g) and neutral red (39.08 mg/g), indicating that CPP200 possesses a higher adsorption selectivity for cationic dyes. Kinetics investigation revealed that the kinetic data of CPP200 for the adsorption of MB was better fitted by a linear pseudo-second-order model. Isothermal studies indicated that the linear Langmuir model was more suitable for describing the adsorption process. The adsorption thermodynamics illustrated that the adsorption of MB onto CPP200 was spontaneous and endothermic. EDS and IR analyses of CPP200 for both pre- and post-adsorption of MB showed that electrostatic interactions between oxygen-containing groups on biochar and target MB dominated the adsorption procedure, in addition to hydrogen bonding interactions. Reusability tests confirmed the excellent regeneration characteristics of CPP200, indicating that CPP200 may be used as a green, sustainable, highly efficient and recyclable adsorbent for the selective removal of cationic organic dyes.