Pyrolysis of Sedum plumbizincicola,a zinc and cadmium hyperaccumulator: pyrolysis kinetics,heavy metal behaviour and bio-oil production

Appropriate disposal of hyperaccumulator biomass is a problem inhibiting the widespread use of phytoremediation technology. In the present study, kinetic analysis of the pyrolysis process of Sedum plumbizincicola, the behaviour of heavy metals and bio-oil composition were studied. The kinetic analysis of the pyrolysis process shows that activation energy (E) changed from 150 to 186 kJ mol⁻¹ and the frequency factor (A) changed from 1.34 × 10¹¹ to 8.99 × 10¹⁵ s⁻¹. At temperatures of 450–750 °C more than 66.3 % of zinc (Zn) remained in the char. More than 87.6 % of the cadmium (Cd) was found in the bio-oil. Pyrolysis at 650 °C led to the highest yield of alkanes with low-oxygen compounds found in the bio-oil. Pyrolysis at 650 °C can likely offer a valuable processing method for S. plumbizincicola and recovery of Zn from the char and recovery of Cd from the bio-oil will be attempted in future research.

     

Solvent evaporation mediated preparation of hierarchically porous metal organic framework-derived carbon with controllable and accessible large-scale porosity

We report a template-free and easy solvent evaporation method during carbonizing a metal–organic framework (MOF) for the construction of large-scale meso- and macropore. While the direct thermal evaporation method of non-volatile solvent captured in micropore of a MOF is believed to reduce overall porosity of the resultant MOF, this method unprecedentedly directs the reorganization of MOFs toward the production of ultrahigh porous carbon materials. The obtained porous carbon materials possess a unique interconnected three-dimensional wormhole-like structure, high specific surface area (3000 m² g⁻¹), and exceptionally high pore volume (5.45 cm³ g⁻¹). The micropores, along with accessible meso- and macropores, provide ion storage site and ion transport channel, respectively, that contributes to a rapid elimination of large amounts of salt within a very short period of time.     

NiO decorated Mo:BiVO4 photoanode with enhanced visible-light photoelectrochemical activity

Photoelectrochemical water splitting has attracted increasing attention recently in the perspective of clean and sustainable energy economy. Herein, we reported the synthesis of NiO functionalized Mo doped BiVO₄ (denoted as NiO/Mo:BiVO₄) nanobelts and their enhanced photoelectrochemical activity for efficient water oxidation. The prepared NiO/Mo:BiVO₄ p–n junction structure showed much higher water splitting activity than the pristine BiVO₄ and Mo:BiVO₄. Such obvious enhancement are due to the increased donor density by doping with Mo and fast separation of the photoexcited electron–hole pairs by the novel p–n junction composite structure. Under light irradiation, photoexcited holes in the conduction band (CB) of Mo:BiVO₄ will conveniently transfer to the p-type NiO with the effect of the inner electric field. Meanwhile, the holes would oxidize the water into oxygen and the electrons transfer to the counter electrode (Pt electrode) to produce hydrogen. This novel p–n junction structure could open up new opportunities to develop high-performance photoanode for water splitting.     

Biomass-derived N-doped porous activated carbon as a high-performance and cost-effective pH-universal oxygen reduction catalyst in fuel cell

Nitrogen (N) doped porous activated carbons (TGC-T) derived from tofu gel are prepared through a facile, economic and eco-friendly method. The as-prepared TGC-900 possesses high specific surface area (651.78 m² g⁻¹) and homogeneous doping N (Content of N: 5.52 at.%). Reasonably, TGC-900 exhibits excellent oxygen reduction reaction (ORR) activity, stability and methanol resistance in neutral, alkaline and acidic medium. Moreover, TGC-900 also shows outstanding ORR performance in the application of microbial fuel cell (MFC) with the highest output voltage (544 ± 6 mV) and maximum power density (977 ± 32 mW m⁻²). Inspiringly, four single-chamber air cathode MFCs (AC-MFCs) in series can drive a light-emitting diode (LED) to work is firstly reported which further provides a more intuitively method to evaluate the performance of generating electricity for MFCs. Thus, the high performance and cost-effective ORR catalyst TGC-900 is expected to apply in the field of fuel cells.     

Noble metal-free bimetallic NiCo decorated Zn0.5Cd0.5S solid solution for enhanced photocatalytic H2 evolution under visible light

As we know, noble metal (Pt, Pd and Au) with appropriate adsorption free energy of H atoms and higher work function as cocatalyst has been considered to be an effective tactic to enhance photocatalytic activity. However, they are limited severely by scarcity and high-cost. Herein, Zn_0.5Cd_0.5S solid-solution photocatalyst decorated with noble metal-free NiCo cocatalyst has been successfully obtained through one-step photochemical route. It is found that the lifespan of charge carriers of Zn_0.5Cd_0.5S@NiCo can be prolonged dramatically after modification, and the photocatalytic H₂ rate reach to 34.7  mmol g⁻¹·h⁻¹ is nearly 9 times higher than the bare Zn_0.5Cd_0.5S (λ ≥ 420 nm). The superior photocatalytic activity for ZCS@NiCo could be mainly ascribed to higher separation and transfer efficiency of photogenerated carriers by introduced bimetallic NiCo cocatalysts possessing the superior electron transfer property and reducing the onset over-potential of water reduction, which was proved by experiment. This study can provide a potential strategy to design a more efficient noble metal-free cocatalyst over photocatalyst.     

Bioaccumulation and metabolism of polybrominated diphenyl ethers in carp (Cyprinus carpio) in a water/sediment microcosm: important role of particulate matter exposure

Microcosms were built up to simulate a pond system with polybrominated diphenyl ether (PBDE) contaminated sediment and bioorganisms. The microcosms were divided into groups A and B. In group A, both benthic invertebrates (tubificid worms) and carp (Cyprinu carpio) were added, while in group B, only fish were added. After exposure for 20 d, the fish were sampled (exposure I). A net was fixed in the microcosms, and new fish were added (exposure II). These fish were prohibited from contacting the sediment by the net, and the accumulation and depuration of PBDEs in the fish were investigated. Among 11 monitored PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-206, BDE-207, BDE-208, and BDE-209), only 5 congeners (BDE-28, BDE-47, BDE-100, BDE-153, and BDE-154) were detected in the carp fillets and liver. BDE-99 and BDE-183 were not detected in the fish because of the efficient metabolic debromination in carp tissues. The uptake of PBDEs in exposure I was significantly higher/faster than that in exposure II, since the fish in exposure I had an opportunity to take in more of the highly contaminated particles. The uptake kinetics (k(s)) and elimination (k(e)) rate coefficients showed a general trend of decreasing with increasing log K(ow). No significant difference was observed in uptake/depuration kinetics between groups A and B, indicating that the tubificids' reworking does not affect the bioaccumulation of sediment-associated PBDEs in fish significantly. All the PBDE congeners, including nona- and deca-BDEs, were bioaccumulated in the tubificid worms. The PBDE concentrations in the worms were significantly higher than those in the fish, and the congener profile of the sevem major congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183) was distinctly different from that of fish tissues. The biota-sediment accumulation factors in the worms ranged from 0.01 to 5.89 and declined with increasing bromination and log K(ow.).     

Adsorption of polar and nonpolar organic chemicals to carbon nanotubes

Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical-chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitrofunctional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the pi-pi electron-donor-acceptor (EDA) interaction between nitroaromatic molecules (electron acceptors) and the highly polarizable graphene sheets (electron donors) of carbon nanotubes. Additionally, we attribute the stronger adsorption of nonpolar aromatics compared to that of nonpolar aliphatics to the pi-electron coupling between the flat surfaces of both aromatic molecules and carbon nanotubes. For tetrachlorobenzene, the bulkiest adsorbate, adsorption affinity (on a unit surface area basis) to the SWNT was much stronger than to the two MWNTs, indicating a probable molecular sieving effect.     

Combination of a non-thermal plasma and a catalyst for toluene removal from air: Manganese based oxide catalysts

A series of manganese based catalysts have been tested in a combined plasma-catalyst reactor in the reaction of toluene removal from air. In the standard conditions (toluene = 240 ppm, energy density = 172 J/L, 1 g of catalyst, 315 mL/min), the best catalyst (manganese oxide supported on active carbon) is able to transform 55% of the toluene into carbon oxides. According to the study of the reaction mechanism, it appears that the toluene is oxidized both in-plasma by short-lived species generated by plasma and in post-plasma on the catalyst surface by the ozone formed in the plasma, the reaction on the catalyst being more selective in carbon dioxide formation than the reaction in plasma. We have shown that the toluene conversion increases when the toluene concentration in air decreases. A model able to describe the behavior of the plasma reactor and the plasma-catalyst reactor is proposed.     

Hydrothermal and Pyrolytic Conversion of Biomasses into Catalysts for Advanced Oxidation Treatments

Biomasses are very important natural products. Transferring biomass into catalysts for the advanced oxidation process (AOP) via heat treatment has attracted extensive attention. This review systematically introduces and summarizes two kinds of innovative biomass-based catalysts according to the treating temperature. At low temperature ( < 300  ° C), biomasses are converted into hydrothermal carbonation carbon (HTCC) with semiconductive properties for photocatalysis application. At high temperature ( > 300  ° C), by contrast, the products lose their semiconductive nature and become a conductive carbon-based conductor (biochar). They usually work as AOP catalysts by activating oxidant of O₂, H₂O₂, and peroxysulfate for environmental treatment. This review summarizes and compares HTCC and biochar according to their formation process, structure, catalytic mechanism, and key points for the activity enhancement. The active units in HTCC are the sp²-hybridized polyfuran unit while those in biochar are the persistent free radicals, nitrogen-containing unit, or defects. HTCC converts water into OH radicals by using the photoexcited electron/hole pairs induced by solar illumination, while biochar activates oxidants via the active unit on its surface. More importantly, this review summarizes and demonstrates the key points to obtain high-efficiency HTCC and biochar catalysts. Finally, conclusions are drawn and the future aspects for biomass-based catalysis are given.