Search Results (1,382)

Phosphate tailings (PTs), a solid waste generated from phosphate flotation, are a low-grade phosphate resource rich in quartz and dolomite. Their long-term accumulation leads to both resource loss and environmental risks, making valorization increasingly important for the sustainable development of the phosphorus chemical industry. In this study, calcareous–magnesian PTs were used as raw materials, and selective hydrothermal leaching with weakly acidic AlCl₃ solution was employed to separate the dolomite phase and directly construct a Ca-Mg-Al precursor solution for layered double hydroxides (LDHs). The LDHs were subsequently synthesized by co-precipitation and evaluated for phosphate removal from wastewater. The results showed that the precipitation pH markedly affected the phase composition and platelet morphology of the LDHs, while appropriate aging conditions further improved their adsorption performance. Under the optimal conditions of pH 12, aging at 40 °C for 2 h, the obtained LDHs exhibited the best phosphate uptake. Adsorption kinetics followed the pseudo-second-order model, and the maximum adsorption capacity calculated from the Langmuir model reached 38.61 mg-P/g. Characterization by XRD, FTIR, TG-DTA, point of zero charge, and XPS indicated that phosphate removal was dominated by surface complexation, accompanied by anion exchange, ionic precipitation, and electrostatic attraction. Full article

Seasonal freeze–thaw cycling progressively rearranges pores and propagates microcracks in silty clay, reducing the reliability of cold-region earthworks. This study evaluated a bio–polymer stabilization strategy combining microbially induced carbonate precipitation (MICP) with anionic polyacrylamide (APAM) to improve mechanical performance and freeze–thaw durability. Six groups were prepared at identical moisture and compaction conditions: water, APAM, and four MICP–APAM groups with bacterial optical densities (OD600) of 0.8, 1.0, 1.2, and 1.4. Unconfined compressive strength, unconsolidated-undrained triaxial compression, ultrasonic pulse velocity, and SEM, TG/DTG, XRD, and FTIR analyses were conducted before and after freeze–thaw cycling. The M1.0-APAM group showed the best overall performance, with UCS values of 1.35 MPa before cycling and 0.89 MPa after nine cycles, together with high shear resistance and ultrasonic velocity. Lower bacterial concentration provided insufficient cementation, whereas higher concentrations promoted non-uniform carbonate deposition, pore heterogeneity, and local stress concentration. Microstructural evidence indicated that OD600 ≈ 1.0 produced a relatively homogeneous network of fine carbonate clusters and polymer-associated films, with calcite formation supported by TG/DTG and XRD. The results show that MICP–APAM treatment enhances silty clay primarily through coordinated mineralization uniformity, pore refinement, and polymer bridging, providing a sustainable stabilization option for seasonally frozen soils. Full article

Co-contamination of biphenyl and heavy metals is widespread in industrial environments, but systematic studies on the simultaneous treatment of both pollutants using a single microbial strategy remain limited. In this study, we characterized the biphenyl degradation performance, metabolic pathway, transcriptomic response, and Cr(VI) tolerance of Rhodococcus sp. TG-1, and developed an alkali-modified biochar immobilization system to enhance its degradation efficiency for biphenyl under Cr(VI) stress. Degradation experiments were carried out under optimal conditions (30 °C, pH 7.0), and it was found that strain TG-1 degraded 76.84% of 300 mg/L biphenyl within 3 days. Intermediate metabolites were identified by LC-MS, and five key intermediates were detected, confirming that TG-1 metabolizes biphenyl via the classical 2,3-dihydroxybiphenyl dioxygenase pathway, with subsequent entry into the tricarboxylic acid cycle. Transcriptomic analysis was performed to profile gene expression, revealing 845 differentially expressed genes under biphenyl stress, including 672 upregulated genes significantly enriched in aromatic degradation pathways. Seven complete bph gene clusters responsible for biphenyl catabolism were also identified. Strain TG-1 exhibited high tolerance to Cr(VI), with a minimum inhibitory concentration (MIC) of 500 mg/L. However, its biphenyl degradation efficiency dropped to 51.32% in the presence of 200 mg/L Cr(VI). After immobilization using alkali-modified straw biochar (JBC), heavy metal toxicity was alleviated, and the biphenyl removal rate increased to 99.30% under co-contamination conditions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses confirmed that TG-1 was stably loaded onto the biochar surface through hydrogen bonding and electrostatic interactions. Altogether, this study provides a promising bacterial strain and a green immobilization strategy for enhancing biphenyl removal in the presence of Cr(VI), offering a practical approach for the treatment of environments co-contaminated with aromatic compounds and heavy metals. Full article

This study aims to enhance the hydration performance and mechanical strength of steel slag-based cementitious materials via the synergistic activation of Na₂SiO₃ and triethanolamine (TEA), solving the early-age hydration and low reactivity of steel slag. The mix is 32% steel slag (SS), 43% blast furnace slag (BFS), 12% desulfurized gypsum (DG), and 13% ordinary Portland cement (OPC). The full factorial design uses Na₂SiO₃ (4–6%) and TEA (0.03–0.08%) as composite activators. Mortar specimens were tested for compressive and flexural strengths at 3d, 7d, 10d, and 28d. XRD, SEM, FTIR, and TG revealed the hydration mechanism and microstructure evolution. The results show an optimal dosage of 5% Na₂SiO₃ and 0.05% TEA increasing compressive strengths at 3d and 28d by 43.10% and 22.09%, respectively, compared with the control group. This synergy improves matrix compactness, supporting the high-value utilization of steel slag and development of steel slag-based cementitious materials. Full article

In the context of the circular bioeconomy and environmental protection trends, the efficient use of renewable resources has become a driving force for industry, and lignin represents precisely a renewable carbon resource, abundant in terrestrial biomass that could become a sustainable substitute for fossil resources, under conditions of full exploitation. This study systematically evaluates the biosorption of Manganese (Mn(II)) from aqueous media using unmodified Tripidium bengalense (Sarkanda grass) lignin. Under optimal operating conditions (adsorbent dosage of 5 g/L, pH 6.5, and 20 °C), a highly competitive experimental adsorption capacity of 12.52 mg/g was achieved. Kinetic studies revealed exceptionally rapid uptake rates, with thermodynamic equilibrium established within the first 30 min, fitting perfectly with the pseudo-second-order (Ho-McKay) model (R² ≥ 0.9998). Equilibrium data were best described by the Freundlich isotherm (R² ≥ 0.9886), confirming chemisorption via preferential inner-sphere complexation on a heterogeneous surface. Thermodynamic analysis verified that the process is spontaneous (ΔG ranging from −13.24 to −26.19 kJ/mol) and endothermic (ΔH from 11.21 to 14.83 kJ/mol). FTIR, SEM-EDX, and TG/DTG analyses confirmed successful Mn–O coordination involving phenolic hydroxyl and carboxylic groups. Furthermore, the lignin showed excellent recyclability, maintaining a retention efficiency over 70% (70.7–85.8%) after three desorption-resorption cycles using 1N HCl. Ecotoxicological validation via Sorghum bicolor L. germination tests confirmed the complete detoxification of the post-adsorption filtrates (up to 100% germination capacity), while the Mn(II)-loaded lignin completely suppressed seed germination (0%), proving secure metal immobilization. These findings establish raw Sarkanda grass lignin as an efficient, scalable, and ecologically sustainable biosorbent for heavy metal remediation. Full article

Studies on the relationships between structure and thermal stability, as well as on the pyrolysis behavior of cross-linked citronellyl methacrylate/hexyl acrylate and geranyl methacrylate/hexyl acrylate copolymers, are presented. These insoluble and highly chemically resistant polymeric materials exhibited glass transition temperatures (T_g) ranging from −55.2 °C to 7.6 °C, depending on their composition. The thermal stability of the prepared copolymers also depended on their composition and decreased with increasing geranyl methacrylate or citronellyl methacrylate content. The highest thermal stability was achieved for copolymers containing 20 wt% methacrylate and 80 wt% hexyl acrylate. The corresponding decomposition temperatures were 167 °C for citronellyl methacrylate-based copolymers and 190 °C for geranyl methacrylate-based copolymers. The thermal decomposition of the investigated copolymers proceeded in at least three stages, involving simultaneous pyrolysis processes and chemical reactions between the decomposition products. As a result, a mixture of low-molecular-weight saturated and unsaturated volatile compounds, as well as CO, CO₂, and H₂O, evolved. Based on the gaseous FTIR analysis, the pyrolysis pathways of the tested copolymers and the structures of the emitted saturated and unsaturated volatile products were proposed. Full article

Oily wastewater, especially stable oil-in-water (O/W) emulsions, threatens aquatic ecosystems and is difficult to treat using conventional separation technologies. Herein, a hydrophilic and underwater oleophobic chitosan/polyvinyl alcohol (PVA)/cellulose aerogel (CPCG) was fabricated through a facile one-pot dip-coating strategy. Cellulose aerogel (CG) was prepared by low-temperature dissolution, network reinforcement, washing, and freeze-drying, before being coated with a cross-linked CS/PVA layer using glutaraldehyde, followed by NaOH solidification. SEM revealed a honeycomb-like cellulose framework uniformly covered by the CS/PVA coating, which improved the structural integrity of the skeleton. FT-IR and TG analyses supported the successful construction of the coating and the enhanced thermal stability of CPCG. CPCG displayed a high underwater oil contact angle of 153.8°, which remained above 153° after 30 min, indicating robust underwater oil repellency. Wet CPCG retained 99% of its original height after 30 compression–recovery cycles. Owing to the stable hydration layer, interconnected channels, and improved wet-state resilience, CPCG efficiently separated light and heavy oil/water mixtures and various O/W emulsions. The separation efficiencies for different emulsions were above 99%, and CPCG retained about 93% efficiency after ten cyclohexane/water emulsion separation cycles. This work provides a green and scalable route for constructing biomass-based aerogels for oily wastewater treatment. Full article

Due to the possibility of damage from earthquakes, vibrations, humidity, and the degradation of wooden joints, there is growing interest in new polyurethane adhesives for wooden structures. These adhesives often have two or more purposes in such structures. Such purposes include connection strength, resistance to environmental conditions at the point of application, and behaviour during fire or under vibration. Some fundamental data on the application of materials exhibiting these properties concern their adhesive thermal stability. This paper focuses on the thermal stability of a new blend of flexible and rigid polyurethanes and its correlation with the structural properties of the material. The new polyurethanes were investigated using hot-stage microscopy for thermal stability of shape, and the results were correlated with DSC, thermogravimetry, and evolved-gas analyses. The experiments showed that it is essential to use primary research methods, including FTIR, XRD, DSC-TG-QMS, and HSM, to identify and characterise new polyurethane adhesives. These research methods are crucial for understanding the properties and potential applications of these materials and providing deeper insight into the subject. The tested polyurethane adhesives, new materials for construction, meet strict ecological requirements and are suitable for patching both small and large wooden structures, as well as for other construction applications, such as insulation and soundproofing. Full article

The release of persistent azo dyes into aquatic systems remains a critical environmental and toxicological concern due to their high chemical stability, resistance to biodegradation, and potential to generate carcinogenic aromatic amines. This study evaluates the adsorption of Amberlite XAD-4 (X4), a hydrophobic polystyrene–divinylbenzene resin, for the removal of the toxic azo dye Direct Red 23 (DR 23) from aqueous solutions. Batch experiments were performed to assess the influence of contact time and initial dye concentration, supported by kinetic and equilibrium modeling. Adsorption proceeded through a multistage mechanism involving thin-layer diffusion, intraparticle diffusion, and final equilibrium, which was reached after 48 h. The pseudo-second-order kinetic model (PSO) with R² = 0.9648 best described the adsorption behavior. Equilibrium data was fitted by the Langmuir isotherm (R² = 0.9990), yielding a maximum adsorption capacity of 56.8 mg g⁻¹, consistent with the experimentally observed saturation plateau. FTIR spectra revealed characteristic shifts in aromatic, –N=N– (≈1500 cm⁻¹), and –SO₃²⁻ (1180–1040 cm⁻¹) bands, which, corroborating the data provided by SEM/EDX analysis, completes the adsorption of DR 23 on the X4 matrix. TG/DSC analysis showed modifications in thermal behavior after adsorption without compromising resin stability, supporting strong dye–resin interactions. Overall, the integrated kinetic, isotherm, spectroscopic, and thermal analyses demonstrate that X4 is stable and an adsorbent with desorption capability using chemical agents, highlighting its potential for mitigating the environmental and toxicological risks associated with azo dye contamination in wastewater. Full article

Infrastructure maintenance and emergency repairs require rapidly setting cementitious materials, yet conventional cement presents issues of high energy consumption and substantial CO₂ emissions. Addressing this challenge, this research has developed a ternary alkali-activated cementitious material (CGFM) composed of calcium carbide residue (CCR), granulated blast furnace slag and fly ash. This study separately investigates the effects of CCR content (0–10%), alkali content (6–12%) and activator modulus (1.0–1.5) on workability and early mechanical strength. The hydration mechanism was examined through X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Thermogravimetry-Derivative Thermogravimetry (TG-DTG) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis, whilst life cycle assessment was employed to quantify the ecological impacts. Results indicated that a 3% CCR dosage significantly improved the gel structure, achieving a 7-day compressive strength of 69.8 MPa and a 37% increase in flexural strength. At a CCR dosage of 3%, alkali content of 8%, and modulus of 1.4, CGFM achieved a peak compressive strength of 80.2 MPa by the seventh day. This performance is attributable to its substantial gel content and high degree of polymerisation, which results in a dense structure. Life cycle assessment confirmed that compared to sulphoaluminate cement mortar, CGFM mortar reduced CO₂ emissions by 64.6% and energy consumption by 48.6%. Full article

This study focuses on the design, optimization, and evaluation of a biodiesel production process involving the transesterification of waste cooking oil (WCO) using a heterogeneous calcium oxide (CaO) catalyst derived from waste eggshells. The work is divided into two main parts. The first focuses on the laboratory preparation, characterization, and performance of the CaO catalyst, while the second translates the experimentally optimized conditions into a process-scale model using Aspen HYSYS to assess industrial feasibility. Waste eggshells were cleaned, dried, ground, and calcined at high temperature to produce the CaO heterogenous catalyst. The catalyst was characterized by Simultaneous Thermogravimetric-Differential Scanning Calorimetry (TG-DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Transesterification experiments were conducted in a batch round-bottom flask reactor where CaO was added to sunflower oil and methanol, and multiple operating parameters were varied to determine the optimal conditions. The catalyst exhibited its best performance after calcination at 900 °C for 2 h. A maximum biodiesel yield of 95 wt.% was obtained at a methanol-to-oil molar ratio (MOMR) of 9:1, reaction time of 2 h, stirring speed of 700 rpm, temperature of 60 °C, and catalyst amount of 3 wt.%. In addition, the eggshell-derived CaO catalyst maintained a biodiesel yield close to 95% over three consecutive reuse cycles, demonstrating good reusability and catalytic stability. The produced biodiesel complied with ASTM standards. Based on these results, the process was then scaled up by simulating a continuous industrial biodiesel production plant using Aspen HYSYS. The model proved practical, achieving a biodiesel purity of 99.85%. Further process optimization, including methanol recovery and heat integration, reduced fresh methanol consumption by 60% and overall energy requirement by 25%. The combined experimental and simulation results demonstrate that energy efficiency and waste valorization enable a biodiesel production pathway that is both environmentally and economically sustainable and aligned with circular economy principles and sustainable development goals. Full article

To address the durability limitations of conventional crack sealants under coupled extreme temperatures and traffic loads in long-life pavements, a bio-oil composite-modified patching material was developed using 90# base asphalt as the matrix, synergistically modified with crumb rubber (CR) and epoxidized soybean oil (ESO). To resolve the contradictory requirements for high elasticity and thermal expansion/contraction coordination in sealants, ESO was introduced; its polar epoxy groups optimize phase compatibility and promote low-temperature stress relaxation without restricting thermal deformability. Rheological evaluations revealed that the optimal system (OPT) successfully extended the service temperature window from PG 76–−24 °C (baseline) to PG 82–−24 °C, significantly enhancing its adaptability to extreme climatic fluctuations. At −24 °C, OPT exhibited a reduced creep stiffness (S) of 164 MPa and an increased creep rate (m) of 0.312, with a cracking resistance ratio (k) as low as 525.6; the quantitative significance of these metrics lies in granting the sealant superior stress relaxation capacity, enabling it to accommodate dynamic crack widening without interfacial debonding or brittle fracture. Fatigue testing via time sweeps demonstrated that N_f50 reached 2890 cycles, highlighting robust long-term resistance against high-frequency shear strains induced by tire edges. Micro-mechanistic analyses (FTIR, TG/DTG, and DSC) confirmed that the modification is primarily driven by physical blending. The elevation of the thermal decomposition threshold (T5%) to 302.4 °C and the residue at 600 °C to 44.8% provide a critical safety margin for high-temperature construction heating, preventing thermal degradation. Furthermore, the glass transition temperature (T_g) decreased to approximately −35.2 °C. These findings establish a rigorous quantitative and mechanistic framework for designing sustainable, high-performance patching materials for resilient pavement maintenance. Full article

Fundamental understanding of the biomass pyrolysis process on a molecular level provides important guidelines for designing advanced porous carbon materials. In this study, the effects of KOH and K₂CO₃ activators on the thermal decomposition of agarose were elucidated using TG-FTIR-GCMS coupling techniques. The results demonstrate that the presence of KOH/K₂CO₃ shifts the pyrolysis gaseous products from organic fragments to CO₂ and H₂O, thereby preserving more C-C bonds in the solid phase and facilitating the subsequent aromatization process. Furthermore, compared to using KOH as the sole activator, the K₂CO₃/KOH co-activation strategy suppresses the violent evolution of CO₂ within the 300–400 °C range, thereby alleviating the structural shock to the material skeleton and ensuring its integrity. Therefore, the HPC-KCO prepared via a synergistic KOH/K₂CO₃ co-activation and one-step carbonization process exhibits a high specific surface area of 1670 m² g⁻¹ and successfully retains its interconnected hierarchical porous framework. Benefiting from its well-developed porous structure, HPC-KCO exhibits an impressive specific capacitance of 370 F g⁻¹ when employed in zinc-ion capacitors. Furthermore, the assembled symmetric supercapacitor demonstrates robust stability over a wide temperature range from −60 to 100 °C, delivering a remarkable capacitance of 121 F g⁻¹ even at −60 °C. This work offers a new insight for synthesizing porous structures of biomass-derived carbon. Full article

This study aimed to produce biocarbons from pistachio shells and estimate the effect of physical activation with CO₂ and overheated steam on their physicochemical, thermal, and adsorption properties in relation to methyl orange. Biocarbons were obtained by pyrolysis at 800 °C and subsequently activated under different conditions. From the results, the type of activating agent substantially determined the development of pore structure and surface chemistry. CO₂ activation favored the formation of primarily microporous materials with a very large specific surface area, whereas steam activation led to a more open, hierarchical pore system with a greater pore volume and a larger contribution to external surface area. The most favorable textural properties were found for the samples PM-8-CO₂-3 and PM-8-H₂O-2. The FTIR, Raman, Boehm titration, CHN, SEM-EDS, and TG/DTG/DTA analyses confirmed that activation caused reconstruction of the carbon matrix, modification of the surface functional groups, and a decrease in thermal stability with increasing activation intensity. The adsorption studies proved that the sample PM-8-H₂O-2 exhibited the largest efficiency in methyl orange removal. The adsorption kinetics were best described by the pseudo-second-order model, whereas the equilibrium data were best fitted by the Freundlich model. The adsorption process was spontaneous and exothermic. Full article

In this study, the amination-based modification of kraft lignin (KL) was implemented through phenolization treatment combined with the Mannich reaction to synthesize the aminated lignin (APKL) with high nitrogen content. Afterward, the chemical structural changes and reaction mechanism of KL during the modification process were surveyed in depth using diverse analytical techniques. The results revealed that the phenolization treatment markedly raised the active site number in KL from 5.79 to 25.5 mmol/g, which led to a significant increase in the chemical reactivity of KL. Meanwhile, the amine group was successfully grafted onto the best phenolized kraft lignin (PKL) after the Mannich reaction. Furthermore, the effects of amination reagent, reactant mass ratio, temperature and time on the nitrogen content of APKL were systematically examined to optimize the reaction conditions for amination. Using FTIR, molecular weight and elemental analyses, the optimal amination conditions were determined as a reaction temperature of 75 °C, reaction time of 3 h and PKL₆/arginine/formaldehyde mass ratio of 3:21:28. Under these parameters, APKL₁₀ with a higher nitrogen content of 19.2% and lower C/N ratio of 2.46 was acquired. In addition, TG and SEM results revealed that the obtained APKL₁₀ possessed a flake-like structure and outstanding thermal stability, which was beneficial for its subsequent application as a slow-release soil fertilizer. More importantly, the soil column leaching test confirmed that the as-prepared APKL₁₀ had excellent nitrogen slow-release properties in the soil. As a result, this kraft lignin derivative generated by phenol treatment followed by amination-based modification could serve as an efficient nitrogen fertilizer, providing a long-term nitrogen source for plant growth in soil. Full article