Polybrominated diphenyl ether (PBDE) pollution in E-waste recycling areas has garnered great concern by scientists, the government and the public. In the current study, two typical kinds of E-wastes (printed wiring boards and plastic casings of household or office appliances) were selected to investigate the emission behaviors of individual PBDEs during the pyrolysis process. Emission factors (EFs), compositional profile, particle size distribution and gas-particle partitioning of PBDEs were explored. The mean EF values of the total PBDEs were determined at 8.1 ± 4.6 μg/g and 10.4 ± 11.3 μg/g for printed wiring boards and plastic casings, respectively. Significantly positive correlations were observed between EFs and original addition contents of PBDEs. BDE209 was the most abundant in the E-waste materials, while lowly brominated and highly brominated components (excluding BDE209) were predominant in the exhaust fumes. The distribution of total PBDEs on different particle sizes was characterized by a concentration of finer particles with an aerodynamic diameter between 0.4 μm and 2.1 μm and followed by less than 0.4 μm. Similarly, the distribution of individual species was dominated by finer particles. Most of the freshly emitted PBDEs (via pyrolysis) were liable to exist in the particulate phase with respect to the gaseous phase, particularly for finer particles. In addition, a linear relationship between the partitioning coefficient (KP) and the subcooled liquid vapor pressure (PL⁰) of the different components indicated non-equilibrium gas-particle partitioning during the pyrolysis process and suggested that absorption by particulate organic carbon, rather than surface adsorption, governed gas-particle partitioning.

Biomass derived biochar is a stable carbon-rich product with potential for soil amendment. Introduced into the natural environment, biochar will naturally experience ‘ageing’ processes that are liable to change its physicochemical properties and the mobility of sorbed pollutants over the longer term. To elucidate the reciprocal effects of biochar ageing and heavy metal adsorption on the affinity of biochar for organic pollutants, we systematically assessed the adsorption of diethyl phthalate (DEP), representative of phthalic acid esters (PAEs), to fresh and aged biochars with and without coexistence of Cd²⁺. Long-term oxidative ageing was simulated using 5% H₂O₂ and applied to biochar samples made from corn cob, maize straw and wheat straw made by pyrolysis at both 450 °C and 650 °C. Our results showed that biochar made at lower temperature (450 °C) and from straw exhibited the higher adsorption capacity, owing to their greater polarity and abundance of O-containing functional groups. The adsorption of DEP onto fresh biochars was found to be driven by van der Waals force and H-bonding. Biochar made at the higher temperature (650 °C) displayed higher carbon stability than that produced at lower pyrolysis temperature. Oxidized biochar showed lower adsorption capacity than fresh biochar owing to the formation of three-dimensional water clusters on biochar surface, which blocked accessible sites and decreased the H-bonding effect between DEP and biochars. The coexistence of Cd²⁺ suppressed the sorption of DEP, via competition for the same electron-rich sites. This indicates that cation/π-π EDA interactions are the primary mechanism for PAE and Cd²⁺ stabilization on biochar. Our study sheds light on the mechanism of organic pollutant sorption by biochar, as well as the potential susceptibilities of this sorption to ageing effects in the natural environment.

Creosol and 4-ethylguaiacol are two important methoxyphenols, lignin pyrolysis products, which are discharge into the atmosphere in large quantities. In this work, theoretical calculations of the reaction mechanism towards the two compounds with NO₃ radicals was performed using DFT method. The rate constants and toxicity assessment were also investigated. The atmospheric lifetime for creosol and 4-ethylguaiacol were 0.82 and 0.19 h, respectively. A new reaction pathway was proposed for the transformation of methoxyl into hydroxyl, which has not yet been clarified in previous studies. The toxicity of methoxyphenols and their degradation products is closely related to their hydrophobicity. Although most degradation products are less toxic, they also should be pay more attention, especially for nitro-substituents.A new reaction pathway was proposed for the transformation of methoxyl into hydroxyl. The toxicity is closely related to their hydrophobicity.

The increased release and accumulation of Bisphenol A (BPA) in contaminated wastewater has resulted in the world wide concerns because of its potential negative effects on human health and aquatic ecosystems. Starting with metal-organic frameworks, we present a simple method to synthesize magnetic porous microcubes (N-doped Fe⁰/Fe₃C@C) with graphitized shell and highly dispersed active kernel via the pyrolysis process under N₂ atmosphere. Batch adsorption experimental results showed that N-doped Fe⁰/Fe₃C@C had high adsorption capacity for BPA (∼138 mg g⁻¹ at pH = 7 and 298 K). Degradation of BPA adsorbed on N-doped Fe⁰/Fe₃C@C was further investigated as a function of BPA concentration, persulfate amount, temperature and solution pH. It was found that potassium peroxodisulfate could be activated by N-doped Fe⁰/Fe₃C@C, and a large number of free radicals were generated which was crucial for the degradation of BPA. The concentration of BPA was barely changed in the individual persulfate system. BPA (10 mg L⁻¹) was almost completely degraded within 60 min in the presence of N-doped Fe⁰/Fe₃C@C (∼0.2 g L⁻¹). When the BPA content increased to 25 mg L⁻¹, the removal efficiency of BPA achieved to 98.4% after 150 min. From the XRD, Raman, and XPS analysis, the main adsorption mechanism of BPA was π-π interactions between the π orbital on the carbon basal planes and the electronic density in the BPA aromatic rings. While the superior degradation was attributed to the radical generation and evolution in phenol oxidation. This work not only proved the potential application of N-doped Fe⁰/Fe₃C@C in the adsorption and degradation of BPA, but also opened the new possibilities to eliminate organic pollutants using this kind of magnetic materials in organic pollutants’ cleanup.

Gasification and pyrolysis technologies have been widely employed to produce fuels and chemicals from solid wastes. Rare studies have been conducted to compare the particulate emissions from gasification and pyrolysis, and relevant inhalation exposure assessment is still lacking. In this work, we characterized the particles emitted from the gasification and pyrolysis experiments under different temperatures (500, 600, and 700 °C). The collection efficiencies of existing cyclones were compared based on particle respiratory deposition. Sensitivity analysis was conducted to identify the most effective design parameters. The particles emitted from both gasification and pyrolysis process are mainly in the size range 0.25–1.0 μm and 1.0–2.5 μm. Particle respiratory deposition modelling showed that most particles penetrate deeply into the last stage of the respiratory system. At the nasal breathing mode, particles with sizes ranging from 0.25 to 1.0 μm account for around 91%, 74%, 76%, 90%, 84%, and 79% of the total number of particles that deposit onto the last stage in the cases of 500 °C gasification, 600 °C gasification, 700 °C gasification, 500 °C pyrolysis, 600 °C pyrolysis, and 700 °C pyrolysis, respectively. At the oral breathing mode, particles with sizes ranging from 0.25 to 1.0 μm account for around 92%, 77%, 79%, 91%, 86%, and 81% of the total number of particles that deposit onto the last stage in the six cases, respectively. Sensitivity analysis showed that the particle removal efficiency was found to be most sensitive to the cyclone vortex finder diameter (D₀). This work could potentially serve as the basis for proposing health protective measures against the particulate pollution from gasification and pyrolysis technologies.

Magnetic biochar (MBC) has been used to remove hexavalent chromium (Cr(VI)) from water, but the roles of Fe₃O₄ and persistent free radicals (PFRs) in MBC in Cr(VI) removal are still less investigated. In this work, the MBC synthesized by microwave co-pyrolysis of solid-state FeSO₄ and rice husk was employed to remove Cr(VI) from water. In comparison to the rice husk biochar (BC), the MBC exhibits the 3.2- and 11.7-fold higher adsorption and reduction efficiency of Cr(VI), resulting in the higher Cr(VI) removal efficiency (84.3%) and equilibrium adsorption capacity of MBC (8.35 mg g⁻¹) than that (26.5% and 2.63 mg g⁻¹) of BC. Multiple characterization results revealed that the high Cr(VI) removal performance of MBC was mainly attributed to the presence of active Fe₃O₄ and carbon-centered PFRs in the porous and graphitic MBC. The Fe₃O₄ not only provided active chemisorption/reduction sites for Cr(VI) via its Fe(II)ₒcₜ and Fe(III)ₒcₜ coordination, but also facilitated the generation of more active electron donating carbon-centered PFRs than carbon-centered PFRs with an oxygen atom in the graphitic structure to reduce Cr(VI). The presence of Fe₃O₄ also elevated 36.7 m² g⁻¹ of BET-surface area and 0.043 cm² g⁻¹ of pore volume of MBC, promoting the Cr(VI) removal. The Fe₃O₄ and carbon-centered PFRs contributed to ∼81.8% and ∼18.2% of total Cr(III) generation, respectively. In addition, the initial solution pH was responsible for determining the relative significance of Cr(VI) adsorption and reduction. This study provides new insights into the mechanisms of Cr(VI) removal from water by the MBC.

Biochars are being increasingly applied in soil for carbon sequestration, fertility improvement, as well as contamination remediation. Phosphoric acid (H3PO4) pretreatment is a method for biochar modification, but the mechanism is not yet fully understood. In this work, biochars and the raw biomass were treated by H3PO4 prior to pyrolysis. Due to an acid catalysis and crosslink, the micropores of the pretreated particles were much more than those without H3PO4 pretreatment, resulting in the dramatical enhancement of specific surface areas of the pretreated particles. Crystalline cellulose (CL) exhibited a greater advantage in the formation of micropores than of amorphous lignin (LG) with H3PO4 modification. The formation mechanisms of micropores were: (a) H+ from H3PO4 contributes to micropores generation via H+ catalysis process; (b) the organic phosphate bridge protected the carbon skeleton from micropore collapse via the crosslinking of phosphate radical. The sorption capacities to carbamazepine (CBZ) and bisphenol A (BPA) increased after H3PO4 modification, which is ascribed to the large hydrophobic surface areas and more abundant micropores. Overall, H3PO4 pretreatment produced biochars with large surface area and high abundance of porous structures. Furthermore, the H3PO4 modified biochars can be applied as high adsorbing material as well as P-rich fertilizer.

Although the abiotic and biotic transformation/degradation (T/D) processes of tetrabromobisphenol A (TBBPA) have been widely investigated in model experiments, few reviews have focused on these processes along with their metabolites or degradation products. In this paper, we summarize the current knowledge on the T/D of TBBPA and its derivatives, including abiotic and biotic T/D strategies/conditions, mechanisms, metabolites and environmental occurrences. Various treatments, such as pyrolysis, photolysis, chemical reactions and biotransformation, have been employed to study the metabolic mechanism of TBBPA and its derivatives and to remediate associated contaminated environments. To date, more than 100 degradation products and metabolites have been identified, dominated by less brominated compounds such as bisphenol A, 2,6-dibromo-4-isopropylphenol, 2,6-dibromo-4-hydroxyl-phenol, 2,6-dibromophenol, isopropylene-2,6-dibromophenol, 4-(2-hydroxyisopropyl)-2,6-dibromophenol, etc. It can be concluded that the T/D of TBBPA mainly takes place through debromination and β-scission. In some environmental media and human and animal tissues, brominated metabolites, glucoside and sulfate derivatives are also important T/D products. Here, the T/D products of TBBPA and its derivatives have been most comprehensively presented from the literature in recent 20 years. This review will enhance the understanding of the environmental behaviors of TBBPA-associated brominated flame retardants along with their ecological and health risks.

This paper deals with marine plastic debris and its collection and recycling methods as one possible answer to the rising amount of plastic in marine environments. A novel approach is to use energy recovery, for example pyrolysis of marine plastic debris into high-energy products. Compared to other thermal processes, pyrolysis requires less technical effort and the end products can be stored or directly reused. In order to design such an onboard pyrolysis reactor, it is necessary to know more facts about the feedstock, especially the thermochemical behaviour and kinetic parameters. Therefore, a thermogravimetric analysis was carried out for three selected plastic sizes with a temperature range of 34–1000 °C. The results obtained from TGA showed the same curve shape for all samples: single stage degradation in the temperature region of 700–780 K with most of the total weight loss (95%). Small microplastics had an average activation energy of 320–325 kJ/mol.

A mixture of polyethylene (PE), polyethylene-terephtalate (PET), polypropylene (PP) and Nylon was submerged in marine water during 12 moths. The chlorine content of these plastics was measured through the passing time. Thermobalance was used to look for differences in the thermal decomposition of the plastics during in that time interval. Degradation of PET, PP and Nylon produced changes in the weight loss curve, but behaviour of PE is confusing. Pyrolysis and combustion at 850 °C was finally performed to get knowledge of the possible differences in the emission of main gases, volatiles and semivolatiles including polycyclic aromatic hydrocarbons (PAHs), polychlorinated benzenes (ClBzs), polychlorinated phenols (ClPhs), polybrominated phenols (BrPhs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Results show that the emission of chlorinated species is somewhat not affected by the chlorine content of the plastics mix. The production of PCBs and PCDD/Fs was very low, under 4 pg WHO-TEQ/g.