Search Results (155)

The increasing accumulation of industrial solid waste and worsening groundwater pollution pose significant environmental challenges. This study introduces a Si-Ca-Fe-based ceramsite from solid wastes with exceptional Cd adsorption capacity. A comprehensive investigation was conducted on the phase evolution, adsorption properties, and underlying mechanisms of the synthesized ceramsite. The findings revealed that the optimum sintering temperature for the ceramsite, characterized by austenite and pyroxene, was 1140 °C, which balanced mechanical strength and Cd adsorption capacity. Remarkably, the ceramsite (6.0 g) was immersed in 5 L of a Cd(NO₃)₂ solution for 21 h under initial conditions (pH = 7 and temperature = 20 °C), and the ceramsite exhibited a notable Cd adsorption capacity of 5.47 mg/g (initial Cd concentration: 53.42 mg/L), with a maximum theoretical capacity of 9.32 mg/g according to the Langmuir isotherm. An in-depth analysis of adsorption kinetics, phase composition, and EDS data indicated that the primary adsorption mechanism was the zero-valent iron (ZVI) corrosion-driven reaction. This ZVI formed in situ under reducing conditions during the ceramsite’s preparation and subsequently aided in the precipitation of Cd(OH)₂. Additionally, the honeycomb structure of the ceramsite, containing fine pores (approximately 2–5 μm), enhanced physical adsorption via capillary action, further improving Cd removal. These insights offer a robust foundation for crafting efficient, solid waste-derived ceramsite tailored for heavy metal extraction from polluted water, presenting a compelling approach to concurrent waste recycling and environmental remediation. Full article

The large-scale accumulation of coal gangue has caused serious environmental problems, and converting it into ceramsite is an important pathway for resource utilization. Grinding is a key step in the preparation of coal gangue ceramsite, but the effect of particle size distribution on heat release and ceramsite performance remains unclear. In this study, coal gangue with a calorific value of 699.77 kcal/kg was ground for 1, 2, 3, and 4 h, respectively, followed by pelletizing and sintering. The different ground powders and sintering ceramsites were investigated using particle size analysis, TG-DSC, and XRD, as well as pore structure and strength tests. The results show that for the Datong coal gangue raw material, grinding parameters and sintering regime adopted in this work, the powder milled for 2 h presents a left-shifted particle size distribution curve with a narrow main peak, particle refinement and a concentrated particle size profile (D50 = 8.498 μm, D90 = 23.941 μm). Combined with TG-DSC, XRD, and pore property test results, the 2 h ground powder delivers the most concentrated heat release during low-temperature combustion. This concentrated heat release is inferred to promote high-temperature mineral phase reconstruction and liquid phase formation, thereby generating a dense ceramsite structure featuring low apparent porosity, high closed porosity and excellent mechanical performance (water absorption: 2.99 ± 0.44%; compressive strength: 15.12 ± 0.43 MPa). When the grinding time is extended to 3 h, the particle size distribution broadens, and both the particle size distribution curve and the DSC curve show shoulder peaks, indicating dispersed heat release. Extending grinding time from 3 h to 4 h appears to induce fine-particle agglomeration with heat release becoming more dispersed and decreasing reaction degree, leading to an uneven temperature distribution and deteriorated ceramsite performance. Full article

The prolonged outdoor storage of coal gangue leads to significant environmental issues, while the contamination of water by antibiotics poses a worldwide health concern. Conventional adsorbents are often hindered by their expense and fragility. Current studies on ceramsite derived from coal gangue have not successfully combined the repurposing of solid waste with the management of water pollution. This research utilized coal gangue and waste electric porcelain as primary materials, incorporating 2 wt.% calcium carbonate as a foaming agent, and produced ceramsite through a gradient-heating sintering process. The investigation thoroughly examined how sintering temperature and particle size distribution influenced the material’s performance. Findings indicated that mullite-based ceramsite, sintered at 1400 °C for 15 min, achieved an apparent porosity of 35.68% and a compressive strength of 10.03 MPa. A particle size distribution following a normal model resulted in a 7.9% removal efficiency of 20.00 mg/L tetracycline hydrochloride in just 30 min, with a minimal post-adsorption strength decrease of 3.7%. This study offers a theoretical framework and practical guidance for the effective utilization of coal gangue and the economical treatment of antibiotic-laden wastewater. Full article

Constructed wetlands operated in plateau habitats may experience constrained biological treatment because low temperature, low atmospheric pressure, and low-carbon wastewater can jointly limit microbial metabolism. This 80-day pilot screening study evaluated three nonreplicated modular constructed wetland configurations (MCW1-MCW3) containing different sequences of zeolite, ceramsite, and quartz sand and planted with Veronica anagallis-aquatica. Each configuration consisted of one independent treatment train; therefore, the comparisons were interpreted as configuration-specific and exploratory rather than as statistically generalizable treatment effects. Pollutant-removal performance and microbial community succession were evaluated through repeated water-quality monitoring and 16S rRNA gene sequencing. MCW1 showed the highest observed mean NH₄⁺-N removal efficiency (88.6%), whereas MCW3 showed the highest observed mean TP and COD removal efficiencies (79.56% and 47.40%, respectively) and an NH₄⁺-N removal efficiency of 85.51%. TN removal by MCW3 remained limited at 20.49%, consistent with carbon limitation of denitrification. Under the naturally low-temperature plateau laboratory conditions, the observed COD reduction indicated partial mineralization or retention of organic pollution loads, potentially supported by substrate biofilms and cold-adapted microbial assemblages. Apparent module-contribution analysis suggested that zeolite contributed substantially to NH₄⁺-N reduction, whereas ceramsite contributed to TP and COD removal under the tested sequences. Because plant biomass and tissue nutrient contents were not measured, nitrogen and phosphorus removal could not be attributed quantitatively to hydrophyte uptake. Overall, substrate sequence influenced pollutant-removal patterns and microbial community assembly, providing preliminary evidence for habitat-adapted optimization of modular constructed wetlands for plateau domestic wastewater. Full article

To explore the feasibility of using recycled glass pumice (microcellular glass pumice aggregate, MGPA) as a substitute for traditional lightweight aggregates and to compare its mechanical performance with that of expanded clay ceramsite, this study systematically investigated the effects of water–cement ratio (0.40–0.46), cement content (330–360 kg/m³), fine MGPA replacement ratio (0–100%), and coarse MGPA replacement ratio (0–100%) on the dry density and compressive strength of lightweight aggregate concrete through an orthogonal experimental design. The results show that the bulk density of coarse MGPA (312 kg/m³) is only 46% of that of ceramsite (678 kg/m³), while its cylinder compressive strength (3.36 MPa) is slightly lower. The range analysis indicates that the dry density of MGPA concrete is primarily influenced by the replacement ratio of coarse aggregate, followed by fine aggregate replacement, water–cement ratio and cement content; the lowest dry density (1445 kg/m³) was obtained with a water–cement ratio of 0.46, cement content of 330 kg/m³, 100% replacement of coarse MGPA, and partial replacement of fine MGPA (mixture S19). For the 28-day compressive strength, the influencing factors rank as coarse aggregate replacement > water–cement ratio ≈ cement content > fine aggregate replacement. In comparison with the ceramsite concrete reference under the respective mix designs tested in this study, the optimal MGPA concrete exhibited only 4.6% higher dry density but achieved a significantly higher compressive strength of 40.0 MPa, compared with 20.5 MPa for the ceramsite mixture. The specific strength (strength/density ratio) of MGPA concrete is about 1.87 times that of ceramsite concrete. Both types of lightweight aggregate concrete reached 77–80% of their 28-day strength at 7 days. Overall, recycled glass pumice is a promising alternative to ceramsite for lightweight concrete, especially when both high strength and low weight are required for precast components, provided that its long-term durability (particularly ASR resistance) is verified in future studies. Full article

Lightweight aggregates have a porous structure and high water absorption, which may lead to underestimation of the powder content in conventional mix design methods for lightweight ultra-high-performance concrete (LUHPC). To address this issue, this study used ceramsite sand as the lightweight aggregate and combined the excess paste theory with the particle packing method to design and evaluate ceramsite-sand-based LUHPC mixtures based on the modified Andreasen packing model (APM) and the compressible packing model (CPM). By optimizing the particle size distribution of ceramsite sand and the binder composition, a mix design method suitable for ceramsite-sand-based LUHPC was developed. The workability, apparent density, mechanical properties, elastic modulus, and shrinkage behavior of the material with different steel fiber contents were systematically investigated. The results showed that the total binder content, water-to-binder ratio, and paste volume of the mixtures designed using the two models differed only slightly. However, the aggregate skeleton formed by CPM was denser, and its skeleton packing volume was approximately 3.5% lower than that obtained using APM. At the same steel fiber content, the main mechanical properties of the CPM-designed LUHPC were generally superior to those of the APM-designed mixtures. Specifically, the 28-day cube compressive strength increased by 5.0–7.6%, the axial compressive strength by 8.8–12.2%, the axial tensile strength by 6.4–25.8%, the flexural strength by 14.1–17.2%, and the shear strength by 3.1–6.5%. The elastic modulus was also slightly higher, while the shrinkage remained consistently lower. The CPM-2.0 LUHPC mixture achieved a 28-day cube compressive strength of 124.6 MPa and an apparent density of approximately 1982 kg/m³, realizing a compressive strength above 120 MPa at a density below 2000 kg/m³. The 28-day cube compressive strength of the CPM-3.0 mixture further increased to 131.7 MPa. As the steel fiber content increased from 1.5% to 3.0%, the workability of LUHPC decreased, whereas its compressive, tensile, flexural, and shear properties generally improved, and the elastic modulus increased slightly. Steel fibers effectively restrained shrinkage deformation, but the improvement showed diminishing marginal benefits with increasing fiber content. Considering the mechanical performance, shrinkage control, and material economy, a steel fiber content of approximately 2.0% is recommended as a reference range for ceramsite-sand-based LUHPC. Overall, CPM is more suitable than APM for the mix design of ceramsite-sand-based LUHPC and can provide guidance for mix optimization and performance regulation of lightweight ultra-high-performance concrete. Full article

The variation law and mechanism of the permeability characteristics of coal gangue ceramsite lightweight aggregate concrete (CLAC) remain unclear. Therefore, in this study, the effect of the ceramsite size and replacement ratio on the pore structure characteristics of the CLAC was analyzed by mercury pressure test. Moreover, based on a fractal approach, the relationship between permeability characteristics and pore structure of the CLAC was established. The results indicate that incorporating coal gangue ceramsite effectively decreases the maximum pore size. The fractal dimension increases as the replacement ratio of 20–30 mm and 10–20 mm ceramsite rises, whereas an opposite trend is observed when the content of 5–10 mm ceramsite increases. At moderate replacement levels, the introduction of ceramsite aggregates can reduce the fraction of detrimental pores and promote the formation of harmless and slightly harmful pores; however, at high replacement levels, the fraction of harmful and macropores may increase. Moreover, the fractal dimension is negatively correlated with the permeability grade and residual strength, but positively correlated with the strength degradation rate. Full article

Vanadium tailings-based ceramsite (VT-Ceramsite), a type of porous ceramsite synthesized from vanadium tailings, was employed for the adsorption of fluoride ions from high-fluoride wastewater. This approach not only mitigates environmental pollution caused by industrial solid waste but also effectively removes fluoride contaminants from wastewater. The effects of vanadium tailings content, sintering temperature, and sintering time on the adsorption performance of the VT-Ceramsite were systematically investigated. Comprehensive characterizations via XRD, SEM, BET, and adsorption modeling reveal that fluoride sequestration by VT-Ceramsite is governed by the synergy between physical diffusion and chemical interactions. While the porous architecture provides essential transport pathways, the chemically active sites facilitate stable bonding. Future research will prioritize surface functionalization and tailoring strategies to augment the density of these active sites, thereby maximizing the adsorption potential for treating complex industrial effluents. The optimal preparation conditions were determined to be a ratio of 6.5:2.5:1 for vanadium tailings, fly ash, and kaolin, with a preheating temperature of 300 °C for 20 min and a sintering temperature of 900 °C for 20 min. In these conditions, the adsorption capacity for fluorine ions can reach 43.59 mg/g. VT-Ceramsite exhibited a specific surface area of 3.61 m²/g, hydrochloric acid solubility of 1.2%, and a void fraction of 48.68%, all parameters met national industrial standards. In addition, the leaching concentrations of heavy metals were found to be well below the limits specified in CJ/T 299-2008, indicating that the material poses no risk of secondary pollution. The study provides an economical, safe, and environmentally friendly route for the utilization of solid waste, and it offers a promising adsorbent for treating high-fluoride wastewater. Full article

Coal gasification slag (CGS) is rich in Si-Al-Ca components and thus has potential for ceramic utilization, but associated heavy metals may pose environmental risks. In this study, CGS from Yili (Xinjiang, China) was used as the major raw material (80 wt%), with clay and waste glass as additives, to prepare ceramsite by firing green pellets (8–12 mm) at 1000–1200 °C. The phase evolution, microstructure, and heavy-metal migration were characterized, and the leaching safety was evaluated. Increasing temperature leads to progressive quartz consumption, enrichment of feldspar-type crystalline phases, and liquid-phase sintering, which together enhance densification. The apparent density and single-particle compressive strength exhibit an “increase-then-decrease” trend with temperature and reach maxima at 1150 °C, where the compressive strength is 15.38 MPa. Heavy-metal behavior is element-specific: As and Zn show stronger volatilization, whereas Mn, Ba, Ni, and Cu are largely retained in the solid phase; Cr shows intermediate, temperature-dependent volatilization. After firing at ≥1150 °C, the leached concentrations of Cr, Mn, Ni, Cu, Zn, As, and Ba under the sulfuric acid–nitric acid test (HJ/T 299-2007) are below the Class III limits of the Chinese Groundwater Quality Standard (GB/T 14848-2017). Considering phase/structure evolution, mechanical performance, and short-term heavy-metal leaching, 1150 °C is identified as the preferred firing temperature in this work. Full article

In order to reduce the environmental pollution caused by waste white mud from the papermaking process, this paper proposes a new method of preparing lightweight concrete using waste white mud and shale ceramsite, aiming to provide a new approach for the recycling of papermaking waste. The main objective of this study is to investigate the feasibility of utilizing paper-making white clay as a cement replacement in lightweight concrete and to systematically evaluate the influence of key parameters, such as white clay content, on its fundamental mechanical properties. Based on lightweight ceramsite concrete, paper-making white clay was used to replace cement in preparing white clay lightweight concrete. Through orthogonal tests, mix proportion design and optimization were carried out, and the effects of factors like water–binder ratio and white clay content on the compressive strength, splitting tensile strength, and early-age cracking resistance of the concrete were studied. The results show that with the increase in white clay content, the cube compressive strength of concrete first increases and then decreases. When the white clay content is 5%, the splitting tensile strength of the concrete is the highest at all ages, and when the white clay content is 15%, the internal structural compactness of the concrete is optimal. Full article

Stormwater runoff represents a significant vector for the transport of organic pollutants and pathogens into aquatic ecosystems, posing serious environmental and public health risks. Although extensively employed for bank stabilization, traditional gabion structures demonstrate constrained efficacy in pollutant removal. In this study, an enhanced ecological gabion (EG) system was developed by integrating a stratified configuration of functional fillers (ceramsite, maifanite, and biochar) with vegetation (Iris germanica). This design leverages synergistic effects to enhance the concurrent removal of dissolved organic matter (DOM), particulate organic matter (POM), and fecal indicator bacteria (FIB) from simulated stormwater. The system was evaluated in continuous flow experiments through comparison with a traditional gravel gabion (TG). Results showed that, compared with the TG, the EG exhibited markedly enhanced removal performance, with chemical oxygen demand (COD), NH₄⁺–N, and TN removal efficiencies being approximately 2.48, 3.68, and 3.56 times those of the TG, respectively. In addition, the EG exhibited significantly higher removal efficiencies for both particulate organic carbon (POC) and dissolved organic carbon (DOC) than the TG, with increases of 329% and 137%, respectively. Fluorescence spectroscopy and particle size distribution analyses revealed that the EG effectively transformed and removed diverse DOM components and fine particulates. The stratified filler media synergistically enhanced pollutant retention, with biochar serving as the primary agent for nutrient and pathogen adsorption. These findings demonstrate the viability of the EG as an integrated, eco-friendly solution for enhanced stormwater purification in riparian zones, providing a compact and multifunctional alternative to conventional end-of-pipe systems. Full article

To address the dual challenges of aqueous phosphate pollution and the resource utilization of petrochemical solid wastes, this study proposes a novel closed-loop “waste-to-waste” strategy. This approach innovatively integrates multiple solid wastes (including oily sludge and petroleum hydrocarbon-contaminated soil) into a porous ceramic matrix and utilizes lanthanum recovered from spent catalysts for surface modification, successfully fabricating an optimized adsorbent—lanthanum-modified ceramsite (BC@La). Under the conditions of pH 6, an adsorbent dosage of 1 g/L, and a temperature of 318 K, BC@La achieved a maximum phosphate adsorption capacity of 2.56 mg/g, corresponding to 128.0 mg of phosphorus per gram of La. Kinetic and isotherm analyses revealed that the adsorption process followed the pseudo-second-order model and fitted well with the Langmuir isotherm, consistent with monolayer chemisorption. Thermodynamic studies further indicated that the adsorption was spontaneous and endothermic. The primary adsorption mechanism was attributed to the precipitation of lanthanum phosphate (LaPO₄). This study not only demonstrates a high-performance adsorbent but also provides a sustainable strategy for the synergistic utilization of industrial solid wastes. Full article

This study investigated the effects of varying water–binder (w/b) ratios and internal curing materials—superabsorbent polymer (SAP) and ceramsite—on the shrinkage behavior and crack resistance of ultra-high-performance concrete (UHPC). Although internal curing has been extensively studied, the comparative effectiveness of different internal curing materials on early-age shrinkage and restrained cracking behavior of UHPC under consistent mixture proportions remains unclear. To address this gap, a systematic experimental comparison of SAP and ceramsite was conducted. The influences of w/b ratio and different amounts and addition methods (dry and pre-absorbed addition) of SAP and ceramsite on the flowability, mechanical properties, early autogenous shrinkage, drying shrinkage, and early crack resistance of UHPC were discussed. Findings indicate that increasing the w/b ratio reduces autogenous shrinkage but compromises mechanical properties, altering the cracking mode from primary microcracks to a few wider cracks. Pre-saturated ceramsite (less than 10% volume) and SAP effectively mitigate autogenous and drying shrinkage, enhancing crack resistance without significantly reducing mechanical properties. However, exceeding a ceramsite volume dosage of 10% or using the dry addition method increased the flowability of UHPC, while decreasing crack resistance. Microstructural analysis reveals that internal curing materials facilitate hydration and enhance structural density through the formation of ettringite and calcium silicate hydrate. To optimize shrinkage reduction while maintaining mechanical properties, SAP should be incorporated in a dry state, with a dosage limited to 0.4% of the mass of the cementitious material; ceramsite needs to be pre-saturated and limited to 5% of the total volume. Full article

The sustainable management of typical petrochemical hazardous wastes, such as oil sludge (OS), spent fluid catalytic cracking catalysts (SFCCs), and petrochemical-contaminated soil (PCS), poses a significant challenge. This study developed a synergistic sintering strategy that utilizes the complementary properties of these materials, with OS serving as an organic source, SFCCs and PCS providing an aluminosilicate framework, and waste glass powder (GP) acting as a fluxing agent to produce an environmentally friendly, high-strength ceramsite (OSPG-Opt). Single-factor experiments were first conducted to investigate the effects of OS content, sintering temperature, and duration. Subsequently, the Box–Behnken design was employed to optimize the process for maximizing aggregate strength. The optimal conditions were determined to be 30.5% OS content, a sintering temperature of 1142 °C, and a sintering time of 32 min. Under these conditions, the resulting ceramsite demonstrated a compressive strength of 23.12 MPa, along with a bulk density of 1012.50 kg/m³ and low water absorption of 1.61%, meeting the requirements of the Chinese standard T/CSTM 00548-2022 for structural materials. Microstructural analysis identified the presence of quartz, anorthite solid solution, hematite, and albite. The remarkable mechanical strength is attributed to an interlocking structure of anorthite solid solution within a glassy matrix, which also contributes to effective heavy metal immobilization, ensuring the excellent environmental performance of the final product. Full article

Coalbed methane (CBM) reservoirs are characterized by low permeability and poor methane desorption, which limit recovery rates. To address this, a novel graphite composite thermally conductive proppant is proposed, offering enhanced thermal conductivity and mechanical performance. The composite consists of porous ceramsite as a mechanical scaffold, epoxy resin as an interfacial binder, and graphite as a thermally conductive reinforcement. The effects of graphite content and resin dosage on the composite’s structure, thermal conductivity, suspension stability, surface wettability, and interfacial adhesion are systematically investigated. The results show that an optimized formulation with 20 wt% graphite and 1.0 g epoxy resin achieves a thermal conductivity of 3.8 W/(m·K)—6.3 times that of pure ceramsite—along with an improved thermal response under simulated stimulation, good suspension stability (suspension ratio of 0.53 in 0.2 wt% guar gum solution), a hydrophobic surface (contact angle 74.9°) to mitigate water lockup, and strong interfacial adhesion (125 nN under 2500 nN load) for durable proppant performance. Microscopic analysis confirms the formation of a continuous “resin–graphite–ceramsite” three-phase interface and a percolative thermal conductive network. This study provides a feasible design strategy for high-performance thermally conductive proppants and demonstrates their potential for application in the hydraulic fracturing of unconventional oil and gas reservoirs. Full article