Char as a carbon-rich material, can be produced under pyrolytic conditions, wildfires or prescribed burn offs for fire management. The objective of this study was to elucidate mechanistic interactions of copper (Cu2+) and nickel (Ni2+) with different chars produced by pyrolysis (green waste, GW; blue-Mallee, BM) and forest fires (fresh-burnt by prescribed fire, FC; aged char produced by wild fire, AC). The pyrolytic chars were more effective sorbents of Cu2+ (∼11 times) and Ni2+ (∼5 times) compared with the forest fire chars. Both cross-polarization (CPMAS-NMR) and Bloch decay (BDMAS-NMR) 13C NMR spectroscopies showed that forest fire chars have higher woody components (aromatic functional groups) and lower polar groups (e.g. O-alkyl C) compared with the pyrolytic chars. The polarity index was greater in the pyrolytic chars (0.99–1.34) than in the fire-generated chars (0.98–1.15), while aromaticity was lower in the former than in the latter. Fourier transform infrared (FTIR) and Raman spectroscopies indicated the binding of carbonate and phosphate with both Cu2+ and Ni2+ in all chars, but with a greater extent in pyrolytic than forest fire-generated chars. These findings have demonstrated the key role of char's oxygen-containing functional groups in determining their sorption capacity for the Cu2+ and Ni2+ in contaminated lands.

Magnetic biochars (MW) prepared by chemical co-precipitation of Fe2+/Fe3+ on water hyacinth biomass followed by pyrolysis exhibited important potential in aqueous As(V) elimination. In comparison, MW2501 outperformed other MWs and exhibited the highest As(V) sorption capacity which was estimated to be 7.4 mg g−1 based on Langmuir-Freundlic model. With solution pH ranging from 3 to 10, As(V) removal efficiency by MW2501 kept stable and consistently higher than 90%. Besides, ∼100% removal of 0.5 mM As(V) can be obtained in the presence of P ≤ 0.1 mM or Cr/Sb ≤ 0.5 mM, indicating a wide applicability of MW2501 for treatment of As-containing water. The predominance of Fe3O4 on MW2501 surface was evidenced by XRD. Ligand exchange between As(V) anion and the hydroxylated surface of Fe3O4 as well as H bond was largely responsible for As(V) sorption as suggested by FTIR. XPS analysis further revealed the dominance of As(V) in the sorbed As on MW2501 surface with co-occurrence of a minor proportion of As(III) (11.45%). In parallel, oxidative transformation of Fe3O4 to Fe2O3 was also suggested by XPS. By a lab-scale column test, the potential and suitability of MW2501 in As-containing water treatment was further confirmed, which could also provide an alternative way to manage and utilize this highly problematic invasive species.

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant worldwide. A detailed examination of the degradation products emitted during thermal decomposition of TBBPA is presented in the study. Runs were performed in a laboratory furnace at different temperatures (650 and 800 °C) and in different atmospheres (nitrogen and air). More than one hundred semivolatile compounds have been identified by GC/MS, with special interest in brominated ones. Presence of HBr and brominated light hydrocarbons increased with temperature and in the presence of oxygen. Maximum formation of PAHs is observed at pyrolytic condition at the higher temperature. High levels of 2,4-, 2,6- and 2,4,6- bromophenols were found. The levels of polybrominated dibenzo-p-dioxins and furans have been detected in the ppm range. The most abundant isomers are 2,4,6,8-TeBDF in pyrolysis and 1,2,3,7,8-PeBDF in combustion. These results should be considered in the assessment of thermal treatment of materials containing brominated flame retardants.

The main objective of this study was to understand the key factors and mechanisms controlling adsorption of sulfonamides to biochars. Batch adsorption experiments were performed for sulfamethoxazole and sulfapyridine to three pine-wood biochars prepared under different thermochemical conditions: pyrolysis at 400 °C (C400) and 500 °C (C500), and pyrolysis at 500 °C followed with hydrogenation (C500-H). For both sulfonamides, the adsorbent surface area-normalized adsorption was stronger to C500 than to C400. This is attributable to the enhanced π–π electron-donor–acceptor interaction with the carbon surface of C500 due to the higher degree of graphitization. Despite the relatively large difference in surface O-functionality content between C500 (12.2%) and C500-H (6.6%), the two biochars exhibited nearly identical adsorbent surface area-normalized adsorption, indicating negligible role of surface O-functionalities in the adsorption to these adsorbents. Effects of solution chemistry conditions (pH, Cu2+, and dissolved soil humic acid) on adsorption were examined.

Extensive use of biochar to mitigate N2O emission is limited by the lack of understanding on the exact mechanisms altering N2O emissions from biochar-amended soils. Biochars produced from giant reed were characterized and used to investigate their influence on N2O emission. Responses of N2O emission varied with pyrolysis temperature, and the reduction order of N2O emission by biochar (BC) was: BC200 ≈ BC600 > BC500 ≈ BC300 ≈ BC350 > BC400. The reduced emission was attributed to enhanced N immobilization and decreased denitrification in the biochar-amended soils. The remaining polycyclic aromatic hydrocarbons (PAHs) in low-temperature biochars (300–400 °C) played a major role in reducing N2O emission, but not for high-temperature biochars (500–600 °C). Removal of phenolic compounds from low-temperature (200–400 °C) biochars resulted in a surprising reduction of N2O emission, but the mechanism is still unknown. Overall, adding giant reed biochars could reduce N2O evolution from agricultural soil, thus possibly mitigating global warming.

The resource utilization of sewage sludge can solve its disposal issue essentially. Meanwhile the removal of diclofenac (DCF) in wastewater is an emerging environmental problem. In this study, a novel strategy of sludge utilizing via hydrothermal - peroxydisulfate (PDS) dewatering coupled pyrolysis process was proposed. The obtained sludge-derived biochar (HSC) could be as candidate to activate PDS to degrade DCF. Results indicated that exceed 90% of DCF was eliminated within 30 min in HSC-PDS/DCF ternary system under the optimized condition (0.6 mmol/L PDS and 0.5 mg/L HSC, without temperature and pH pre-adjusting). The inner mechanism of HSC-PDS/DCF system was revealed as follows: (1) Major: CO in quinones and ketone structure in HSC accelerated the degradation of DCF via non-radical pathway (electron transfer and ¹O₂). (2) Minor: Graphitic N structure accelerated the electron transfer and O₂•⁻ originated from defective sites involved into the redox. Several by-products were identified and two tentative degradation pathways of DCF (eg. dechlorination and C–N cleavage) were proposed.

Biochar modification by metal/metal oxide is promising for improving its adsorption capability for contaminants, especially the anions. However, conventional chemical modifications are complicated and costly. In this study, novel Fe/Fe oxide loaded biochars (RMBCs) were synthesized from a one-step co-pyrolysis of red mud (RM) and shaddock peel (SP), and their potential application for removing anionic azo dye (acid orange 7, AO7) from the aqueous environment was evaluated. Fe from red mud was successfully loaded onto biochars pyrolyzed at 300–800 °C, which presented from oxidation form (Fe₂O₃) to the reduction forms (FeO and Fe⁰) with increasing pyrolysis temperature. The RMBC produced at 800 °C with RM:SP mass ratio of 1:1 (RMBC800₁:₁) exhibited the best capability for AO7 removal (∼32 mg/g), attributed to both adsorption and degradation. The higher surface area of RMBC800₁:₁ and its greater affinity for AO7 led to the higher adsorption. In addition, RMBC800₁:₁-induced degradation of AO7 was another key mechanism for AO7 removal. The reduction forms of Fe (FeO or Fe⁰) in RMBC800₁:₁ may provide electrons for breaking down the azo bond in AO7 molecules and result in degradation, which is further enhanced in acid conditions due to the participation of readily release of Fe²⁺ and the available H⁺ in AO7 degradation. Furthermore, RMBC800₁:₁ can be easily separated from the treated water by using magnetic field, which significantly benefits its separation in wastewater treatment.

To better promote environment friendly development of the coal chemical industry, this study investigated effects of methanol, sodium citrate, and chlorella powder (a type of microalgae) as co-metabolic substances on enhanced anaerobic treatment of coal pyrolysis wastewater with anaerobic sludge. The anaerobic sludge was loaded into four 2 L anaerobic reactors for co-metabolism enhanced anaerobic experiments. Anaerobic reactor 1 (R1) as control group did not add a co-metabolic substance; anaerobic reactor 2 (R2) added methanol; anaerobic reactor 3 (R3) added sodium citrate; and anaerobic reactor 4 (R4) added chlorella powder. In the blank control group, the removal ratios of total phenol (TPh), quinoline, and indole were only 12.07%, 42.15%, and 50.47%, respectively, indicating that 50 mg/L quinoline, 50 mg/L indole, and 600 mg/L TPh produced strong toxicity inhibition function on the anaerobic microorganism in reactor. When the concentration of methanol, sodium citrate, and chlorella was 400 μg/L, the reactors with co-metabolic substances had better treatment effect on TPh. Among them, the strengthening effects of sodium citrate (TPh removal ratio: 44.87%) and chlorella (47.85%) were better than that of methanol (38.72%) and the control group (10.62%). Additionally, the reactors with co-metabolic substances had higher degradation ratios on quinoline, indole, and chemical oxygen demand (COD). The data of extracellular polymeric substances showed that with the co-metabolic substances, anaerobic microorganisms produced more humic acids by degrading phenols and nitrogen-containing heterocyclic compounds (NHCs). Compared with the control group, the reactors added with sodium citrate and chlorella had larger average particle size of sludge. Thus, sodium citrate and chlorella could improve sludge sedimentation performance by increasing the sludge particle size. The bacterial community structures of reactors were explored and the results showed that Aminicenantes genera incertae sedis, Levinea, Geobacter, Smithella, Brachymonas, and Longilinea were the main functional bacteria in reactor added with chlorella.

Heavy metals pollution in mining soils seriously threatens the ecological environment and human health worldwide. Phytoremediation is considered to be an ideal method to reduce the toxicity, mobility, and bioavailability of heavy metals in the soils. However, the disposal of plant-enriched heavy metals has become a thorny problem. To estimate the effect of pyrolysis on the stabilization of heavy metals in post-phytoremediation plant residues, different biochars were prepared from Conyza canadensis (CC), Gahnia tristis (GT), and Betula luminifera (BL) at different pyrolysis temperatures (300, 450, and 600 °C). Results indicated that pyrolysis was effective in the stabilization of heavy metals (Cr, Ni, As, Sb, Hg, and Pb) in plants and significantly (P < 0.05) decreased the bioavailability of most heavy metals. Among them, GT₆₀₀ prepared by pyrolysis of GT at 600 °C has the best stabilization effect on Sb, which increases the residual fraction by 7.32 times, up to 82.05%. The results of environmental risk assessment show that pyrolysis of biomass at high temperature (600 °C) can effectively mitigate the environmental impact of As, Sb, and Hg. Additionally, the reutilization potential of biochar produced by post-phytoremediation plant residues as adsorbents was investigated. The results of adsorption experiments revealed that all biochars have an excellent performance to adsorb Pb(II), and the maximum adsorption capacity is 139.16 mg g⁻¹ for CC₄₅₀. The adsorption mechanism could be attributed to complexation, electrostatic attraction, and cation exchange. This study demonstrates that pyrolysis is an effective and environment-friendly alternative method to stabilize heavy metals in plants, and their pyrolysis products can be reused for heavy metal adsorption.

Survivorship of early life stages is key for the well-being of sea turtle populations, yet studies on animals that distribute around oceanic areas are very challenging. So far, the information on green turtles (Chelonia mydas) that use the open NE Atlantic as feeding grounds is scarce. Strandings occurring in oceanic archipelagos can provide relevant information about the biology, ecology and current anthropogenic pressures for megafauna inhabiting the open ocean. In this study, we analysed stranding events of green turtles found in the Azores archipelago to investigate interactions with marine litter. In addition, we quantified and characterized litter items stranded on beaches to provide a direct comparison between the ingested items with the debris found in the environment. A total of 21 juvenile green turtles were found stranded in the region between 2000 and 2020 (size range: 12–49 cm, CCL). Overall, 14% of the animals were entangled in marine litter and 86% of the turtles necropsied had ingested plastic. The mean abundance of items ingested was 27.86 ± 23.40 and 98% were white/transparent. Hard plastic fragments between 1 and 25 mm were the most common shape recovered in the turtles, similarly to what was found on the coastline. All of the litter items analysed with pyrolysis GC-MS revealed to be polyethylene (PE). This study provides the first baseline assessment of interactions of plastic litter with juvenile green turtles found at the east edge of the North Atlantic Subtropical Gyre. The combination of these results supports the hypothesis that migratory megafauna that use remote oceanic islands as a feeding ground are exposed to anthropogenic litter contamination dominated by plastics, even when these regions are located far away from big industrial centers or populated cities.