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Showing 23 of 146 peer-reviewed papers with full Graphical Abstracts.

Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508092• Jan 15, 2026

Identification and Evolution Analysis of Research Hotspots on Per- and Polyfluoroalkyl Substances in Soil

Authors: SHENG Ding, CAI Kejie, LIU Yao, CAO Yaowu, WU Xiang

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants with high environmental stability and bioaccumulation potential, posing risks to soil ecosystems and human health. To systematically map research hotspots and evolutionary trends, a bibliometric analysis was conducted on 1,459 publications from the Web of Science Core Collection and CNKI (1985–2025) using VOSviewer and Python. Keyword clustering identified four primary research themes: (1) transport and transformation of PFAS in soil, (2) bioaccumulation and toxic effects, (3) environmental fate and risk assessment of novel PFAS, and (4) remediation strategies for legacy PFAS. Temporal trend analysis using a trend factor (T) revealed a shift from early toxicological studies to policy-driven growth post-2006, with recent emphasis on remediation technologies, migration mechanisms, and bioconcentration. Future research priorities include understanding the fate of novel substitutes in complex media, developing green and sustainable remediation technologies, and establishing robust validation frameworks. The study provides a comprehensive knowledge map to guide scientific prevention and efficient governance of PFAS contamination.

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Identification and Evolution Analysis of Research Hotspots on Per- and Polyfluoroalkyl Substances in Soil

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202507013• Jan 15, 2026

Hydrochemical Characteristics and Health Risk Assessment of Karst Underground River Water in Southwest China: A Case Study of the Pingjiang Underground River Basin, Guangxi

Authors: 覃佳肖, 郑焕君, 李金明, 冯俊海, 侯萍萍, 张勤军, 黄春阳, 贝为昶

Karst groundwater systems in Southwest China are vital for water supply and ecosystem health in traditional agricultural regions. This study investigated the hydrochemical characteristics and health risks of groundwater in the Pingjiang Underground River Basin, a typical karst agricultural area. Forty-two groundwater samples were collected during wet, normal, and dry seasons. Hydrochemical facies were analyzed using comprehensive hydrochemical methods, and water quality was assessed using the objective combined weight water quality index (OCWQI) and a health risk model. Results showed that groundwater was weakly alkaline and slightly hard, with HCO3− and Ca2+ as dominant ions. The chemical composition followed a seasonal order: dry > normal > wet season. All samples were of HCO3-Ca type. Hydrochemistry was primarily controlled by silicate and carbonate weathering, with significant anthropogenic influence indicated by elevated NO3− concentrations from agricultural activities. Health risk assessment revealed that in normal and dry seasons, 64% and 79% of samples for adults, and 64% and 86% for children, exceeded the natural NO3− threshold of 3 mg·L−1, corresponding to low non-carcinogenic risk levels (adults: 0.09<RHI<0.30; children: 0.06<RHI<0.20). Spatial distribution of risk increased from northwest to southeast, with children at higher risk than adults. These findings provide a scientific basis for groundwater management and protection in karst agricultural basins.

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Hydrochemical Characteristics and Health Risk Assessment of Karst Underground River Water in Southwest China: A Case Study of the Pingjiang Underground River Basin, Guangxi

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202505012• Jan 15, 2026

Risk Assessment of Heavy Metal Pollution Characteristics in Environmental Dredging Sediment from Dianchi Lake under Multi-Scenario Land Use

Authors: DUAN Huibo, XING Hao

Sediment risk assessment for lakes and rivers often neglects the distinction between in-situ ecological risks and ex-situ comprehensive utilization risks. This study proposes a multi-scenario risk assessment model incorporating both in-situ and ex-situ contexts. For the in-situ scenario, a dual-background-value potential ecological risk assessment was applied using national and Yunnan soil background values. For ex-situ scenarios, pollution risk assessment models were established for agricultural land (paddy and other) and construction land (Class I and II). Taking the Dianchi Lake dredging project as a case study, 92 sediment samples from polluted and transition layers at 46 grid points were analyzed for six heavy metals (As, Hg, Cd, Zn, Cu, Cr). Results showed: (1) Under different background values, ≥97.83% of samples exhibited moderate or higher ecological risk, with Hg and Cd as main contributors, Hg posing higher risk. (2) In agricultural scenarios (paddy/orchard and other), 95.65% of points had unacceptable risk, with comprehensive pollution intensity order Cd>Cu>Zn>As>Cr; for Class I construction land, As was the target pollutant with 93.48% of points unacceptable, while Class II land was acceptable. (3) Spatial heterogeneity was significant: horizontal risk was higher at the lake outlet than at the Cixiang River inlet; vertical risk was higher in the polluted layer than in the transition layer, with Hg and Cd potential ecological risk coefficients 11.58% and 24.19% higher, and comprehensive potential ecological risk index 43.27% higher. Pollution coefficients for Cd, Zn, Cu (agricultural) and As (Class I construction) increased by 123.02%, 6.3%, 4.1%, and 41.02% in the polluted layer. (4) Different evaluation methods yielded significantly different results, indicating that metals without potential ecological risk may still pose pollution risk in utilization scenarios, necessitating comprehensive consideration in remediation.

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Risk Assessment of Heavy Metal Pollution Characteristics in Environmental Dredging Sediment from Dianchi Lake under Multi-Scenario Land Use

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202507058• Jan 15, 2026

Research Progress on Recycling Technologies for Cathode Materials of Spent Lithium Iron Phosphate Batteries

Authors: CHEN Weiju, YU Xinyi, JIANG Yang

With the rapid development of China's lithium-ion power battery industry, the recycling of large-scale retired batteries has become a critical link for the sustainable development of the new energy vehicle industry. The recovery of cathode materials from spent lithium iron phosphate (LiFePO4) batteries is a current research hotspot, significant for resource recycling and environmental protection. This study systematically reviews recent progress in recycling technologies for spent LiFePO4 cathode materials, mainly including direct regeneration, pyrometallurgy, and hydrometallurgy. It focuses on analyzing the current research status of key steps in hydrometallurgy, such as leaching of valuable elements, deep removal of impurities, and product regeneration, and compares the advantages and limitations of various methods. Addressing core issues in current recovery processes, such as insufficient high-value utilization of iron and phosphorus resources and difficulty in deep impurity removal, this study proposes corresponding solutions and technical prospects, aiming to provide theoretical reference and engineering guidance for efficient, clean, and high-value recycling of spent LiFePO4 batteries.

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Research Progress on Recycling Technologies for Cathode Materials of Spent Lithium Iron Phosphate Batteries

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202507088• Jan 15, 2026

Rapid Granulation of Anaerobic Sludge in Methanol Wastewater Treatment Using Functional Additives

Authors: XIAO Yan, SONG Liuying, LIU Yang, CUI Bing, WU Bin, LI Yuyou

Methanol is highly biodegradable, yet its efficient and stable anaerobic treatment is constrained by prolonged microbial adaptation to toxic substances, narrow microbial community structure, and poor sludge granulation. This study applied two functional additives—sodium bicarbonate (NaHCO3) as an inorganic carbon source (IC) and an amino-acid-rich organic functional supplement (FS)—to accelerate the startup of two upflow anaerobic sludge blanket (UASB) reactors. UASB-A received 3,000 mg·L−1 NaHCO3 and 127 mg·L−1 FS, while UASB-B received only 3,000 mg·L−1 NaHCO3. Both additives enabled rapid startup and granulation by shortening hydraulic retention time (HRT) and increasing organic loading rates (4, 6, 9, 15, 20, and 30 g COD·L−1·d−1). Granulation was evidenced by increased total suspended solids (TSS), volatile suspended solids (VSS), and particle size distribution. Microbial community analysis at HRT 0.2 d revealed highest relative abundances of Acetobacterium at 30.2% (UASB-A) and 36.9% (UASB-B). NaHCO3 supplementation enhanced syntrophy between Acetobacterium and the acetoclastic methanogen Methanothrix, while FS significantly increased the abundance of Sporomusa, establishing a novel syntrophic relationship with Methanothrix. These interactions promoted sludge granulation. The study demonstrates that functional additives facilitate rapid startup and granulation in methanol anaerobic treatment, offering a strategy to overcome process bottlenecks.

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Rapid Granulation of Anaerobic Sludge in Methanol Wastewater Treatment Using Functional Additives

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508013• Jan 15, 2026

Water Quality Trend Analysis of the Sanshenggong Section of the Yellow River from 2011 to 2024 Based on Mann-Kendall Test and Fuzzy Comprehensive Evaluation

Authors: YU Yongkun, ZHANG Lieyu, DU Caili, GAO Shengwang, BAI Yangwei, WEI Yimei, TIAN Zhenjun, JU

The Sanshenggong section of the Yellow River is a critical hydrological monitoring and control point, whose water quality directly affects the ecological safety and sustainable water resource utilization of the middle and lower reaches. This study analyzed water quality monitoring data from 2011 to 2024 using the Mann-Kendall test to identify abrupt change years, combined with single-factor evaluation and a fuzzy comprehensive evaluation method improved by CRITIC-entropy weight combination to systematically assess water quality evolution. The Mann-Kendall test identified 2013 and 2019 as abrupt change points, with non-significant improvement from 2013 to 2015 and significant improvement after 2016. Single-factor evaluation indicated that total phosphorus (TP) was the primary exceeding factor in 2011–2012, and its declining concentration drove the water quality upgrade from Class III to Class II in 2013. The CRITIC-entropy weight combination assigned the highest weight (28.96%) to permanganate index, whose decline was the core driver of water quality improvement. The improved fuzzy evaluation showed that the membership degree of Class III water dropped to zero in 2013, indicating stable improvement, but periodic rebounds in Class II membership suggested potential degradation risks. This study provides scientific evidence for ecological protection and high-quality development of the Yellow River Basin.

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Water Quality Trend Analysis of the Sanshenggong Section of the Yellow River from 2011 to 2024 Based on Mann-Kendall Test and Fuzzy Comprehensive Evaluation

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202507081• Jan 15, 2026

Analysis of Treatment and Resource Utilization of Coal Chemical Waste Salt: Current Status and Prospects

Authors: YANG Jun, HE Yi, XU Jie, LIU Yanping, LIU Guoliang, LIU Haibing

Coal chemical waste salt, a solid residue from evaporative crystallization of high-salinity wastewater, poses significant environmental risks and challenges for resource utilization due to its complex composition. This study systematically analyzes its composition and environmental hazards, highlighting its typical "mixed salt" nature and the potential threats of organic pollutants and heavy metals to soil, water, and ecosystems. It reviews mainstream treatment pathways, including organic degradation, inorganic impurity removal, and salt separation, with a focus on the resource utilization of sodium chloride and sodium sulfate and their industrial prospects. The current pollution control technical specifications and product quality standards are examined, comparing the scope and technical points of relevant standards such as the "Technical Specification for Pollution Control of Chemical Waste Salt." Finally, countermeasures are proposed to address challenges including difficult treatment of mixed salts, insufficient resource utilization incentives, and incomplete standard systems, emphasizing technological innovation, policy guidance, and standard improvement.

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Analysis of Treatment and Resource Utilization of Coal Chemical Waste Salt: Current Status and Prospects

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202510089• Jan 15, 2026

Removal Mechanisms of Fe3O4@MIL-100(Fe) for Microplastics in Water

Authors: TENG Xueyan, YANG Yuesuo, YANG Zhaofei, YANG Wenyue, SONG Xiaoming

Microplastics (MPs) are frequently detected in various water bodies, posing increasing environmental risks. This study synthesized magnetic Fe3O4@MIL-100(Fe) microspheres via an in-situ one-step hydrothermal method and investigated their adsorption removal mechanisms for polystyrene (PS) and polylactic acid (PLA) microplastics. The composite exhibited a core-shell structure with a high specific surface area of 848.6 m2·g−1. Adsorption kinetics showed that PLA followed a pseudo-second-order model, while PS fitted both pseudo-first-order and pseudo-second-order models. Equilibrium data for both MPs were well described by the Freundlich isotherm. Removal efficiencies for PLA and PS increased from 58.18% and 49.66% to 98.90% and 98.58%, respectively, as pH decreased, and from 64.24% and 21.58% to 97.05% and 94.63% with increasing ionic strength. The removal mechanism involved synergistic physical-chemical interactions: hydrogen bonding dominated for PLA, with some complexation, while π–π interactions and hydrogen bonding were primary for PS. The material demonstrated excellent reusability over multiple cycles. These findings highlight the potential of Fe3O4@MIL-100(Fe) for efficient removal of MPs from water, offering a novel approach for controlling emerging contaminants.

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Removal Mechanisms of Fe3O4@MIL-100(Fe) for Microplastics in Water

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202509035• Jan 15, 2026

A Novel Continuous-Flow Self-Circulating Upflow Granular Sludge Bed Process for Treating Real Domestic Wastewater

Authors: HU Rui, SUN Yuge, ZHANG Jingyu, QI Weikang, JU (Corresponding author: QI Weikang)

Aerobic granular sludge (AGS) is an economical and efficient technology, yet its application has been largely confined to sequencing batch reactors (SBRs). This study introduces a novel continuous-flow self-circulating upflow granular sludge bed (Zier) process with separate aeration for treating real domestic wastewater. By regulating operational parameters, the nitrogen removal performance and granular sludge stability were investigated. Under hydraulic retention time of 10 h, self-circulation times of 29–58, and upflow velocity of 11–18 m·h−1, effluent NH4+-N and TN averaged (5±3.4) mg·L−1 and (10±2.8) mg·L−1, respectively, with COD at (30±6.2) mg·L−1. The process maintained sludge stability: mixed liquor suspended solids increased from 5,080 to 6,650 mg·L−1, mean particle size was 209.6 μm, and sludge volume index (SVI) remained at 50–60 mL·g−1. Extracellular polymeric substances (EPS) increased from 26.05 to 68.27 mg·g−1, with proteins (PN) rising from 21.26 to 59.44 mg·g−1 and polysaccharides (PS) from 4.79 to 8.82 mg·g−1, elevating the PN/PS ratio from 4.4 to 6.7. These results confirm that the Zier process preserves granular structure and function in continuous flow. The process demonstrates robust nitrogen removal and offers a novel approach for continuous-flow AGS applications in real wastewater treatment.

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A Novel Continuous-Flow Self-Circulating Upflow Granular Sludge Bed Process for Treating Real Domestic Wastewater

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508036• Jan 15, 2026

Optimization of Preparation Conditions for a Novel Composite Slow-Release Carbon Source and Its Denitrification Performance

Authors: CHEN Xiaonan, GU Jiayan, HE Guofu, JU, GUO Linrui, ZHANG Ruirui

To address the issues of insufficient carbon sources and low denitrification efficiency in rural domestic wastewater, this study developed and optimized a composite slow-release carbon source using corncob, rice husk, reed straw, polyvinyl alcohol (PVA), and sodium alginate (SA). The preparation conditions and raw material ratios were systematically optimized using Plackett-Burman (PB) design, response surface methodology (Box-Behnken design, BBD), and mixture-optimal design (MOD). The denitrification performance was evaluated through carbon release characteristics and denitrification experiments. The optimal preparation conditions were determined as PVA 8.64 g, SA 2.41 g, rice husk 3.82 g, corncob 4.47 g, reed straw 6.06 g, freezing time 19.11 h, and crosslinking time 12 h. The 7-day cumulative carbon release was (43.38 ± 1.3) mg·(g·h)−1. The release process followed first-order kinetics, Higuchi, Ritger-Peppas, and Weibull models, indicating that carbon release is controlled by multiple mechanisms including diffusion and skeleton erosion, ensuring stable slow-release characteristics. In denitrification experiments with influent NO3−-N concentration of 50 mg·L−1, the composite carbon source (RCR-PVA-SA) achieved a maximum NO3−-N removal rate of 90.8% after 10 days of operation, with a removal rate of 0.079 mg·(g·h)−1. Under dynamic conditions with hydraulic retention time (HRT) of 3 h, the average removal rate remained at 87.9%, demonstrating efficient and stable denitrification performance under both static and dynamic conditions. This research provides a reference for the preparation of natural slow-release carbon sources and the resource utilization of agricultural waste.

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Optimization of Preparation Conditions for a Novel Composite Slow-Release Carbon Source and Its Denitrification Performance

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202410085• Jan 15, 2026

Removal of Pollutants from Urban Surface Runoff by a Straw-Based Composite Bioretention System

Authors: HE Lin, ZHU Zheng, MA Shun, HE Hua, LIANG Wenyan, JU ...

Surface runoff pollution has become a significant source of water contamination. This study constructed an integrated composite bioretention system comprising straw, aquatic plant, and biochar zones for purifying urban surface runoff, aiming to meet the standards for reuse as landscaping water. The system's performance in removing conventional pollutants and polycyclic aromatic hydrocarbons (PAHs) was investigated, along with microbial community structure analysis. Results showed removal efficiencies of 81.1% for COD, 98.1% for TN, 79.1% for TP, and 90.3% for TSS, with effluent meeting the 'Water Quality for Scenic and Recreational Use' (GB/T 18921-2019) standard. The system exhibited robust resistance to pollutant and hydraulic loading. The alkali-modified straw zone was the primary pollutant removal region, facilitating physical adsorption and capture of suspended solids, while released carbon sources enhanced total nitrogen removal. This zone exhibited the highest microbial richness, with relative abundances of Proteobacteria and Firmicutes at 54.3% and 21.9%, respectively. The system effectively removed all 16 priority PAHs, reducing effluent toxicity equivalent by 86.5%. The straw zone completely removed four high-molecular-weight PAHs (BaP, DahA, BghiP, IcdP), while aquatic plants and biochar effectively removed medium- and low-molecular-weight PAHs.

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Removal of Pollutants from Urban Surface Runoff by a Straw-Based Composite Bioretention System

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202506084• Jan 15, 2026

Multidimensional Groundwater Quality Assessment and Source Apportionment in the Guyuan Region, Ningxia

Authors: LIU Yuxi, HUANG Yong, LIU Hong, SU Yue, LIU Hui, MA Yuxue, ZHANG Jinghua, YUAN Jianfei, YI Chengtai

Groundwater is a vital drinking and irrigation source in the loess regions of northwestern China. In Guyuan, a densely populated area in southern Ningxia, systematic assessments of groundwater pollution risks are lacking. This study collected 60 groundwater samples and employed the Nemerow index, heavy metal pollution index (HPI), and health risk assessment models to evaluate pollution levels and health risks of eight elements including Cr, As, and Hg. Results show that the groundwater is generally Class IV quality, with a mean TDS of 1350.9 mg·L−1. Average concentrations of As, Cr, and Mn are 4.39, 29.87, and 45.77 μg·L−1, respectively. The Nemerow index indicates moderate pollution. The mean HPI is 10.56, but a local sample (PS1-51-下) reaches 36.15, indicating severe pollution. Health risk assessment reveals that carcinogenic risks from Cr and As for adults and children are 8.037×10−6 a−1 and 3.863×10−6 a−1, respectively, below US EPA limits but above recommended levels by Swedish and Dutch agencies, with children at higher risk. Hydrogen and oxygen isotopes and principal component analysis suggest that groundwater is primarily recharged by atmospheric precipitation. Cr, Zn, and Mn mainly originate from regional copper ore belts, coal mining, and agricultural activities. This study fills a gap in multidimensional groundwater assessment in populated loess areas, identifies pollution characteristics distinct from typical loess regions, and provides a scientific basis for regional water resource risk management and sustainable development.

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Multidimensional Groundwater Quality Assessment and Source Apportionment in the Guyuan Region, Ningxia

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508053• Jan 15, 2026

Biosurfactant-Enhanced Electrokinetic-Biobarrier Remediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soil from an Industrial Site

Authors: HAN Yana, LI Jingming, LI Bingni, TONG Menghan, XI Kailu, LI Fengmei

Polycyclic aromatic hydrocarbons (PAHs) in industrial soils pose significant risks due to their hydrophobicity and low bioavailability, limiting the efficacy of bioremediation. This study investigated the enhancement of an in-situ electrokinetic-biological barrier (EK-BB) system for PAH-contaminated soil using biosurfactants. Three biosurfactants—rhamnolipid (RL), alkyl polyglycoside (APG), and saponin (SAP)—were applied individually and in combinations at 10× critical micelle concentration (CMC), and the optimal RL+APG mixture was further tested at 2.5, 5.0, 7.5, and 10× CMC. Results showed that biosurfactant application improved soil electrical current, moisture retention, and PAH removal. Combined surfactants outperformed single ones, with the 10× CMC RL+APG treatment (Exp IV) achieving the highest average current intensity and moisture content, 1.31 and 1.12 times that of the control (CK), respectively, and a PAH removal of 106.02 mg·kg⁻¹. Biosurfactants also promoted bacterial growth in both contaminated soil and the biobarrier layer; the 10× CMC RL+APG treatment increased bacterial counts by 6.24-fold and 44.8%, respectively. However, excessive surfactant concentrations led to PAH accumulation in the biobarrier and clean soil. The 5× CMC RL+APG treatment provided optimal balance, maximizing PAH removal while maintaining barrier effectiveness. These findings confirm that appropriate biosurfactant concentrations can enhance EK-BB remediation, offering technical support for PAH-contaminated site remediation and safe reuse.

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Biosurfactant-Enhanced Electrokinetic-Biobarrier Remediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soil from an Industrial Site

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202507095• Jan 15, 2026

Mechanical Properties and Microstructural Evolution of CO2-Mineralized Cured Steel Slag-Fly Ash Composite Cementitious Materials

Authors: REN Bin, JU, WANG Wei, FENG Xihao, SHI Junjie, ZHANG Changqing

This study investigates the optimization of CO2 mineralization curing on the performance of a ternary cementitious system comprising steel slag, fly ash, and Portland cement. Specimens were fabricated with varying residual water-to-cement ratios (r/w), steel slag and fly ash contents, curing pressures, and durations, then subjected to standard curing and CO2 mineralization curing. Compressive strength and carbon sequestration rate were measured, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze mineral composition and microstructural evolution. Results indicate that compressive strength first increases then rapidly decreases with increasing residual water-to-cement ratio, with an optimal r/w below 0.15. Both compressive strength and carbon sequestration rate increase with higher steel slag content; the 50% steel slag + 10% fly ash formulation exhibited the highest values. Microstructural analyses revealed that CO2 mineralization primarily consumes hydration products such as Ca(OH)2, C-S(Al)-H, and AFt, generating abundant calcium carbonate that densifies the pore structure, thereby enhancing mechanical properties. Lower residual water-to-cement ratios, higher steel slag content, or extended curing durations increase the content and crystallinity of calcium carbonate. SEM observations confirmed the presence of densely packed, well-crystallized rhombohedral calcite in specimens with lower water-to-cement ratios and higher steel slag content. These findings provide a mechanistic basis for the engineering application of CO2 mineralization curing in ternary solid-waste cementitious materials.

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Mechanical Properties and Microstructural Evolution of CO2-Mineralized Cured Steel Slag-Fly Ash Composite Cementitious Materials

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508041• Jan 15, 2026

Stress Responses and Accumulation Characteristics of Duckweed (Landoltia punctata) to Lead Oxide Nanoparticles

Authors: LAN Yan, GENG Heyan, YANG Guili

Lead oxide nanoparticles (PbO NPs) are increasingly released into aquatic environments from industrial processes, posing ecological risks. Duckweed (Landoltia punctata) is a known lead hyperaccumulator, but its physiological and biochemical responses to PbO NPs remain unexplored. This study synthesized PbO NPs via a plant-mediated biosynthesis method and exposed L. punctata to concentrations of 0 (control), 10, 20, 30, and 40 mg·L−1 in hydroponic culture for 7 days. Results showed concentration-dependent effects: low concentrations (10–20 mg·L−1) stimulated growth, while high concentrations (≥30 mg·L−1) inhibited fresh weight, growth rate, and root length. Chlorophyll b content decreased significantly at ≥20 mg·L−1 (by 14.09%, 10.79%, and 18.48% at 20, 30, and 40 mg·L−1, respectively), while carotenoid content increased. Malondialdehyde content and activities of superoxide dismutase, peroxidase, and catalase increased with PbO NPs concentration, indicating oxidative stress. Lead accumulation reached 1265.65 mg·kg−1 at 30 mg·L−1 and 2030.01 mg·kg−1 at 40 mg·L−1, with bioconcentration factors >1 and lead removal rates above 68.94%. Subcellular distribution showed lead predominantly in the cell wall fraction, followed by soluble components and organelles. These findings demonstrate that L. punctata exhibits strong PbO NPs accumulation and stress tolerance, supporting its use in phytoremediation of metal nanoparticle-contaminated waters.

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Stress Responses and Accumulation Characteristics of Duckweed (Landoltia punctata) to Lead Oxide Nanoparticles

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508021• Jan 15, 2026

Characterization of Pollutants in Coal Chemical Industry Waste Salt and Its Resource Utilization Potential: A Case Study of a Coal Chemical Industrial Park in Northwest China

Authors: YANG Jun, HE Yi, LIU Yanping, WANG Nianxi, ZHOU Tianlai, LIU Guoliang, ZHENG Yang

Coal chemical industry waste salt, generated from high-salinity wastewater treatment, poses a bottleneck for green transformation under the 'dual carbon' strategy due to its low value and high complexity. This study investigated a typical coal chemical industrial park in Northwest China, using principal component analysis (PCA) on actual waste salt samples to identify pollutant characteristics and assess resource utilization potential. Results showed total organic carbon (TOC) ranged from 707.9 to 7,737.9 mg·kg⁻¹, with benzo(a)pyrene concentrations frequently exceeding the limits of the 'Identification Standards for Hazardous Wastes' (GB 5085.3). Hardness ions and metal ions also surpassed relevant product standards. PCA classified the waste salts into three types: sodium sulfate type, sodium chloride type, and high-complexity mixed salt, each corresponding to distinct resource utilization pathways. The study proposes differentiated technical routes based on PCA classification, providing a feasible reference for classified management and technology selection. This research supports the national policy of 'harmless pretreatment + resource utilization' for waste salt, contributing to green and high-quality development of the coal chemical industry.

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Characterization of Pollutants in Coal Chemical Industry Waste Salt and Its Resource Utilization Potential: A Case Study of a Coal Chemical Industrial Park in Northwest China

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508050• Jan 15, 2026

Spatial Differentiation of Heavy Metals in a Landfill Site in a High-Altitude Cold Region Driven by Freeze-Thaw Cycles

Authors: ZHOU Zhongzhu, ZHOU Peng, ZHAO Yuzhu, HU Han, DENG Guochang, ZENG Mengyuan, CHEN Guanyi, DAN Zeng

This study investigated the spatial distribution and ecological risk of heavy metals (As, Cd, Cr, Cu, Ni, Pb, Zn) in soil beneath an informal waste dump in a pastoral area of Baingoin County, Nagqu City, Tibet, a high-altitude cold region with frequent freeze-thaw cycles. A total of 55 soil samples were collected from surface (0 cm), middle (10-30 cm), and deep (50 cm) layers. Single-factor index (Pi), geo-accumulation index (Igeo), Nemerow index (PN), and risk assessment code (RAC) were employed to evaluate contamination levels and potential ecological risks, while Kriging interpolation was used to map spatial distribution. Results showed that average concentrations of all seven heavy metals exceeded local background values. Horizontally, high-concentration zones were mainly located at five points within the dump. Vertically, Cd, Cu, Pb, and Zn were significantly enriched in the surface layer, whereas Ni exhibited higher concentrations in deeper layers, indicating downward migration driven by freeze-thaw processes. All evaluation methods identified Cd as the primary pollutant. Speciation analysis revealed that heavy metals were predominantly in the residual fraction, with Ni having the highest weak-acid-extractable fraction (5.55%), indicating strong mobility and potential biological toxicity. This study fills a gap in systematic research on informal waste dumps in high-altitude ecologically fragile areas and provides a case reference for environmental management and remediation of such sites in cold regions.

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Spatial Differentiation of Heavy Metals in a Landfill Site in a High-Altitude Cold Region Driven by Freeze-Thaw Cycles

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202507094• Jan 15, 2026

Strength and Microstructural Characteristics of Sludge Solidified by Loess-Based Composite Solidifying Agent

Authors: MA Xiaolei, BAI Xuemei, LI Jian, SHI Xujun, YE Shuaihua, JU, SHEN Zhiyuan, SHI Hongzhuang

To address land waste and poor bearing capacity from sludge landfill, this study developed a composite solidifying agent using loess, fly ash, desulfurized gypsum, and cement. Orthogonal experiments combined strength testing, SEM/XRD microanalysis, permeability and heavy metal leaching tests, and cost accounting. Results show that cement significantly enhances early and mid-term strength, while loess dominates later strength development. Optimal fly ash and desulfurized gypsum content is 12% each. The optimal mix ratio (loess:fly ash:desulfurized gypsum:cement:sludge) is 0.1:0.12:0.12:0.08:1. The solidified matrix forms dense structures via C-S-H gel and ettringite (Aft), effectively controlling heavy metal leaching at low cost. This work enables solid waste resource utilization and provides robust support for sludge solidification engineering.

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Strength and Microstructural Characteristics of Sludge Solidified by Loess-Based Composite Solidifying Agent

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508047• Jan 15, 2026

Multi-stage Activation of Fly Ash for Al(OH)3 Extraction: Process Optimization and Mechanistic Insights

Authors: ZHOU Yan, WEI Cong, SHI Haoyang, YAN Xinyi, QU Jihu, LIN Jing

Selective recovery of aluminum compounds from fly ash is a key route for its high-value utilization. This study developed a multi-stage activation process for extracting Al(OH)3 from fly ash, comprising mechanical activation, calcination activation, chemical separation, and carbonation precipitation. Fly ash was mixed with carbide slag and CaF2, then calcined; the resulting clinker was leached with Na2CO3 solution to extract Al. The CaO generated from high-temperature calcination of carbide slag facilitated the separation of Si and Al. After solid-liquid separation, CO2 was introduced into the Al-rich leachate to precipitate Al(OH)3. The process promoted the formation of Ca12Al14O32F2 and inert Ca2SiO4, achieving efficient Si-Al separation during calcination. Under optimal conditions (mechanical activation for 60 min, 4% CaF2, calcination at 1000°C for 2 h, leaching with 40 g/L Na2CO3), the Al extraction rate reached 91.8%, and the product purity was 98.9%. The alumina extraction residue exhibited porous and highly reactive characteristics, suitable for producing flame-retardant materials or high-value silicon-based products (e.g., white carbon black, molecular sieve adsorbents). The process offers a promising industrial route for fly ash valorization, with potential integration with cement production lines for synergistic CO2 capture and utilization.

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Multi-stage Activation of Fly Ash for Al(OH)3 Extraction: Process Optimization and Mechanistic Insights

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508084• Jan 15, 2026

Mechanical Properties and Pore-Forming Mechanism of Porous Ceramsite Prepared from Multi-Source Granite Solid Waste

Authors: JIN Jiaxu, JU, QIU Xiaolei, WANG Ping, LIU Lei, WU Pengfei

Granite mining areas generate large quantities of abandoned soil and rock powder, posing environmental challenges and resource waste. This study investigates the synergistic preparation of porous ceramsite from two typical granite solid wastes—weathered granite soil (high Al2O3) and granite waste rock powder (high SiO2)—with waste glass powder as a fluxing agent. Single-factor experiments and response surface methodology (Box-Behnken) were employed to optimize the process and elucidate the pore-forming mechanism. The optimal conditions were a mass ratio of weathered granite soil:granite waste rock powder:waste glass powder of 5.6:2.4:2, a preheating temperature of 480 °C, a sintering time of 32 min, and a sintering temperature of 1140 °C. Under these conditions, the resulting porous ceramsite achieved a compressive strength of 1.74 MPa. The ceramsite effectively immobilized heavy metals, ensuring environmental safety. This research demonstrates that multi-component complementarity and multi-factor coupling optimization can produce porous ceramsite with favorable mechanical properties and stable pore structure, providing a theoretical basis and technical support for high-value utilization of granite solid waste.

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Mechanical Properties and Pore-Forming Mechanism of Porous Ceramsite Prepared from Multi-Source Granite Solid Waste

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202509009• Jan 15, 2026

Two-Phase Flow Characteristics of a Jet Aerator with Built-in Porous Thin Plates

Authors: WU Yao, HAN Leng, LI Aoqi, XI Wenjun, ZHANG Shinan, ZHANG Anlong

Air-supplied jet aerators, combining hydraulic jet and gas induction principles, are critical equipment in aerobic biological wastewater treatment. However, low energy conversion efficiency and insufficient local gas-liquid mixing are core bottlenecks limiting their competitiveness. A three-dimensional flow field analysis method for jet aerators was developed based on the k-ε turbulence model and Euler-Euler multiphase flow model. The effects of different orifice plate distributions, shapes, sizes, hole numbers, and installation positions on average pressure, turbulent kinetic energy, and turbulent dissipation rate were systematically studied. Results show that the asterisk-shaped orifice plate yields the highest gas-liquid two-phase turbulent mixing intensity, followed by the annular shape, while the parallel arrangement yields the lowest. With increasing hole number and single-hole size, average pressure, velocity, turbulent kinetic energy, and turbulent dissipation rate for different plate shapes initially fluctuate downward and then stabilize. When the number of triangular holes is 9, mass transfer efficiency is significantly enhanced, and overall aerator performance is excellent. When the triangular hole diameter is 7 mm, the device achieves an optimal match between energy utilization and mixing efficiency across pressure distribution, velocity field, turbulent kinetic energy, and dissipation rate. The farther the porous thin plate is installed from the sewage nozzle, the further gas-liquid two-phase turbulence is enhanced. Experiments confirm that the boundary layer is fully developed, liquid and air are thoroughly mixed, and the orifice plate promotes bubble breakup and refinement through throttling and collision, significantly improving oxygen transfer efficiency. This research provides a theoretical basis and technical support for the transformation and upgrading of aeration technology towards high efficiency and low carbon, and for extending equipment service life.

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Two-Phase Flow Characteristics of a Jet Aerator with Built-in Porous Thin Plates

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202508052• Jan 15, 2026

Numerical Simulation of the Performance of a Channel-Steel Baffle-Type Pre-Dust Collector for Biomass Boiler Flue Gas

Authors: YE Xinglian, ZHANG Chucheng, SU Yinbiao, LAI Huicai, AN Xizhong, LIN Chunyuan

To improve the performance of pre-dust collectors in biomass boiler flue gas purification systems, a novel channel-steel baffle-type pre-dust collector was proposed to address the low collection efficiency of conventional designs. A gas-solid two-phase flow model was developed within the MP-PIC (multiphase particle-in-cell) framework and validated against physical experiments. The model simulated gas-particle motion inside the collector, systematically investigating the effects of structural modifications, flue gas conditions, and dust properties on collection efficiency and pressure drop. Results indicate that adding a flow baffle in the ash hopper and adopting an upper-inlet flue duct enhance collection efficiency with negligible impact on pressure drop. Flue gas velocity significantly influences performance: increasing velocity reduces efficiency while raising pressure drop; an optimal design velocity of 1.0–2.0 m·s−1 is recommended. Elevated flue gas temperature slightly decreases both efficiency and pressure drop, with minimal impact over a range of tens of degrees Celsius. Higher dust density and larger particle size improve collection efficiency and reduce pressure drop, whereas higher dust concentration increases both efficiency and pressure drop. The study elucidates the mechanisms by which structural and operational parameters affect pre-dust collector performance, providing theoretical guidance for designing low-resistance, high-efficiency collectors for biomass boilers.

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Numerical Simulation of the Performance of a Channel-Steel Baffle-Type Pre-Dust Collector for Biomass Boiler Flue Gas

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Original ResearchVol. 20, Issue 4 • pp. 100-112DOI: 10.12030/j.cjee.202510028• Jan 15, 2026

Aging Mechanism of Microplastics in UV/Persulfate System and Its Effect on Norfloxacin Adsorption Behavior

Authors: ZHOU Fuya, WANG Yanan, XIE Jincheng, DENG Qiheng, LI Hao

This study investigates the aging mechanism of polystyrene microplastics (PS MPs) induced by ultraviolet (UV)-activated potassium persulfate (KPS) and its influence on the adsorption of norfloxacin (NOR). Results show that aged PS exhibited yellowing, increased surface roughness and specific surface area, enhanced oxygen-containing functional groups, and elevated negative surface charge, along with the generation of environmentally persistent free radicals (EPFRs). Compared with UV alone, UV+KPS induced more pronounced aging due to the generation of reactive oxygen species (ROS) including hydroxyl radicals (·OH) and superoxide radicals (O2·−). Adsorption kinetics and isotherm data revealed that UV+KPS-aged PS significantly enhanced NOR adsorption, with a maximum adsorption capacity of (2.539±0.032) mg·g−1, which was 4.20 times higher than that of pristine PS. The adsorption mechanism was governed by hydrogen bonding, electrostatic interactions, and pore filling. Solution pH modulated the electrostatic interactions by affecting NOR speciation and PS surface charge, thereby influencing NOR adsorption. This study systematically reveals the accelerated aging of coexisting MPs and EPFRs generation during UV+KPS treatment, contributing to a comprehensive understanding of MPs environmental behavior and potential ecological risks.

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