To address the dual challenges of solid waste management and the performance limitations of conventional vegetated concrete, this study develops a novel cleaner material strategy for the large-scale valorization of phosphogypsum (PG). A synergistic innovation is proposed by utilizing narrowly graded, high-sphericity phosphogypsum aggregates (PGA) as the sole coarse aggregate, coupled with a novel mix design methodology for phosphogypsum aggregate vegetated concrete (PGAVC). Systematic experiments were conducted to investigate the individual effects of water-to-binder ratio (W/B), aggregate-to-binder ratio (A/B), and silica fume (SF) content on pore structure, permeability, and compressive strength, thereby enabling precise regulation of key performance parameters. Under optimized mix proportions, PGAVC achieves a balanced performance portfolio: Connected porosity of 9.7%–27.8%, permeability coefficient of 0.94–22.56 mm/s, compressive strength of 4.2–15.1 MPa, 28 day vegetation coverage of 98%, and effective pH self-regulation to near-neutrality (≈7.5). Leaching tests validate that the release of soluble phosphorus (P), fluorine (F), and heavy metals is effectively immobilized, fully complying with environmental safety criteria. This work not only establishes a sustainable and cleaner production pathway for large-scale PG recycling but also provides critical theoretical and technical support for advancing eco-friendly slope protection and green infrastructure development
Graphene oxide (GO) has been used for heavy metal-polluted water remediation due to its high adsorption performance. Nevertheless, the regulatory effects and intrinsic mechanisms of GO on phytoremediation crops under cadmium (Cd) stress remain poorly clarified, representing a critical research gap in nano-assisted phytoremediation. In this study, GO exhibited concentration-dependent promotional effects on ramie growth. Specifically, 50 mg/L GO substantially alleviated Cd phytotoxicity, improved shoot and root growth, and increased root Cd accumulation by 134.00% relative to Cd alone. Physiologically, GO enhanced ramie antioxidant capacity by maintaining cell membrane integrity and activating defense enzyme activities. Molecularly, GO upregulated metal transporter gene expression and improved essential nutrient accumulation in ramie. Metabolomic analysis further revealed that GO reprogrammed metabolic profiles of Cd-stressed ramie and specifically activated β-alanine metabolism and pantothenate and CoA biosynthesis pathways, which are closely associated with plant growth regulation and Cd toxicity mitigation. Moreover, 16S rRNA sequencing showed that GO enriched plant-growth-promoting endophytic Proteobacteria and Actinobacteriota, which facilitate nutrient uptake, Cd resistance and phytoremediation. Synergistic crosstalk between endophytic bacteria and metabolites improved ramie Cd tolerance and enrichment capacity. Collectively, this study explored the potential association mechanisms underlying GO-mediated Cd responses in ramie at physiological, genetic, metabolic and microbial levels under hydroponic conditions, and the application of GO was further verified by soil-pot experiments, while further field validation is still required for practical engineering promotion.
Globally, approximately 40% of industrial solid waste (SW) generated annually remains improperly managed, posing severe environmental risks due to its stockpiling. This study proposes a novel hydrogel-assisted strategy for converting SW stockpiles into engineering materials. The addition of hydrogel established a homogeneous network within SW particles, thereby increasing the compressive and flexural strength of the SW stockpiles by 82 and 219 times (reaching 15.1 and 17.6 MPa), respectively. Compared with the brittle network formed by conventional cement binders, the tough hydrogel network preserved structural integrity under loading, thereby maintaining effective confinement of SW particles. Thus, the compressive and flexural strength of hydrogel-SW composites were higher than that of cement-SW composites by 237% and 794%, respectively. Besides, the applicability of hydrogel-assisted strategy was verified using various solid wastes, including slag, fly ash, phosphogypsum, silica fume, calcined clay, and red mud. Accordingly, this strategy offers a promising approach to cleaner material development through resource utilization of SW and reduced reliance on conventional cement binders.
Graphene oxide (GO) has been used for heavy metal-polluted water remediation due to its high adsorption performance. Nevertheless, the regulatory effects and intrinsic mechanisms of GO on phytoremediation crops under cadmium (Cd) stress remain poorly clarified, representing a critical research gap in nano-assisted phytoremediation. In this study, GO exhibited concentration-dependent promotional effects on ramie growth. Specifically, 50 mg/L GO substantially alleviated Cd phytotoxicity, improved shoot and root growth, and increased root Cd accumulation by 134.00% relative to Cd alone. Physiologically, GO enhanced ramie antioxidant capacity by maintaining cell membrane integrity and activating defense enzyme activities. Molecularly, GO upregulated metal transporter gene expression and improved essential nutrient accumulation in ramie. Metabolomic analysis further revealed that GO reprogrammed metabolic profiles of Cd-stressed ramie and specifically activated β-alanine metabolism and pantothenate and CoA biosynthesis pathways, which are closely associated with plant growth regulation and Cd toxicity mitigation. Moreover, 16S rRNA sequencing showed that GO enriched plant-growth-promoting endophytic Proteobacteria and Actinobacteriota, which facilitate nutrient uptake, Cd resistance and phytoremediation. Synergistic crosstalk between endophytic bacteria and metabolites improved ramie Cd tolerance and enrichment capacity. Collectively, this study explored the potential association mechanisms underlying GO-mediated Cd responses in ramie at physiological, genetic, metabolic and microbial levels under hydroponic conditions, and the application of GO was further verified by soil-pot experiments, while further field validation is still required for practical engineering promotion.
Decarbonising road materials requires scalable strategies that enhance durability while valorising waste streams. This study investigates the effect of antioxidant biochar derived from European hazelnut shells (BH) on the operational and rheological performance of a PG 64–22 asphalt binder. BH was produced via slow pyrolysis at 300 °C and incorporated at contents of 2.5, 5.0 and 7.5 wt% using two particle size fractions (S < 20 μm and L < 75 μm). Owing to its carbon-rich composition and the presence of antioxidant compounds reported in previous studies, BH was evaluated as a sustainable modifier with the potential to improve the ageing resistance of asphalt binders. Commercial graphite was included as a control modifier for comparison. Operational properties were assessed through rotational viscosity and storage stability, while rheological performance was evaluated using the rutting parameter G*/sin(δ), Bending Beam Rheometer (BBR), Multiple Stress Creep and Recovery (MSCR), |G*| and δ master curves, rheological ageing index (RAI), and time sweep fatigue tests. BH increased rotational viscosity and mixing and compaction temperatures without compromising storage stability. At high temperatures, BH enhanced rutting resistance by increasing G*/sin(δ) and reducing the non-recoverable creep compliance (Jnr), particularly for the finer particle size fraction. At low temperatures, BH increased creep stiffness without significantly affecting the stress relaxation capacity compared with control binders. Master curve and RAI analysis indicated lower susceptibility to long-term ageing-induced stiffening at higher BH contents. BH also improved the fatigue response by increasing accumulated dissipated energy and tended to delay the 50% reduction of the initial |G*| compared with the unmodified binder. Based on the combined rheological response, 5.0 wt% BH with a particle size below 20 μm was selected as the final formulation for this type of modifier.
