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The massive production and accumulation of industrial solid waste-iron tailings not only occupy valuable land resources but also easily cause environmental pollution and personnel injury. Based on this, the thermoplastic polyurethane (TPU)/modified iron tailings (MIT) composites were prepared by surface modification of iron tailings (MIT) and adding it as flame retardant to TPU. The combustion performance and smoke toxicity of TPU/MIT composites were analyzed by thermogravimetric analysis (TG), thermogravimetric-spectroscopy (TG-IR) and cone calorimetry (CCT). The morphology and structure of the carbon slag of the composites were analyzed by scanning electron microscopy(SEM) and Raman spectroscopy. The results showed that the initial thermal decomposition temperature (T-5%) of TPU/MIT30 composite increased at about 7oC, and the residual carbon content at 700oC increased from 3.13 wt% to 32.17 wt%. The peak heat release rate(PHRR), total heat release(THR) and total smoke release(TSR) of TPU/MIT30 composite decreased from 800.6 kW/m2, 83.1 MJ/m2 and 827.6 m2/m2 of pure TPU to 488.0 kW/m2, 63.6 MJ/m2 and 517.4 m2/m2, respectively. The SEM and Raman1 spectroscopy of char residue showed that the compactness and graphitization degree of char residue for TPU/MIT30 composite was the highest, indicating that the MIT could effectively improve the fire safety of TPU composites. This study provided some ideas for the high-value utilization of iron tailings. [ABSTRACT FROM AUTHOR]

• Steel slag was used as co-flame retardants for rigid polyurethane foams (RPUFs). • The PHRR value of RPUF-2 reduced by 47% compared to that of original RPUF. • The presence of steel slag improved the thermal resistance of intermediates in TGA. • The addition of steel slag enhanced the graphitization degree of the residues. To explore the potential application of industrial waste, steel slag powder in combination with melamine pyrophosphate (MPP) was adopted to improve the flame retardancy of rigid polyurethane foam (RPUF). The incorporation of steel slag slightly reduced the thermal conductivity of the resulting flame-retardant RPUF samples. The addition of MPP and/or steel slag did not significantly alter the thermal stability in terms of T -10% and T max but did obviously increase the T -50% value, suggesting the improved thermal resistance of the residues. The coaddition of MPP and steel slag into RPUF resulted in higher LOI values and lower peak heat release rates than the samples incorporating either MPP or steel slag alone. The superior flame retardancy could be attributed to MPP promoting char formation, which then acted as a barrier at the beginning of RPUF thermal decomposition; simultaneously, the thermally stable inorganics in the steel slag powder strengthened the thermal resistance of this char layer. [ABSTRACT FROM AUTHOR]

Although constructed wetlands (CWs) are used as one relatively low-cost technology for livestock wastewater treatment, the improvement of phosphorus removal in CWs is urgently needed. In this study, a three-stage pilot-scale CW system consisting of three surface flow CWs (SFCWs; CW1, CW2, and CW3) in series from inlet to outlet was constructed to treat swine wastewater (SW) from a lagoon. The CWs were planted with Myriophyllum aquaticum . Considering different inlet loading rates, three strengths of swine wastewater (low: 33% SW, medium: 66% SW, and high: 100% SW) were fed to the CW system to determine total phosphorus (TP) removal efficiency and clarify the important role of plant harvest. Results from the period 2014–2016 indicate that the three-stage CW system had mean TP cumulative removal efficiencies and removal rates of 78.2–89.8% and 0.412–0.779 g m − 2 d − 1 respectively, under different inlet loading rates. The TP removal efficiency and removal rate constant had temporal variations, which depended on temperature condition and the annual growth pattern of M . aquaticum . The harvested phosphorus mass was 15.1–40.9 g m − 2 yr − 1 in the CWs except for CW1 with high strength SW, and contributed 22.5–59.6% of TP mass removal rate by the SFCWs. The TP removal was mainly by adsorption and precipitation in the substrate in CW1 but by uptake and multiple harvests of M . aquaticum in CW2 and CW3. The results suggest the three-stage CW system planted with M . aquaticum is suited for removing high TP concentrations from swine wastewater with a high removal efficiency. However, TP removal in high strength SW amounted to 70.1 ± 23.3%, and the outflow concentration of 17.0 ± 14.9 mg L − 1 was still high. Optimal loading rates for high strength SW still need to be investigated for the CW system presented here. [ABSTRACT FROM AUTHOR]