Search

In this study, a solar/chlorine/graphitic carbon nitride (g-C3N4) system for the highly efficient degradation of carbamazepine (CBZ) was constructed, and the degradation mechanism of CBZ in this sy...

As a new research focus in the field of biological resources, crayfish shells have great potential for development and utilization. In this review, the typical methods and research progress of separating the primary components such as chitosan, protein, and astaxanthin from crayfish shells and converting crayfish shells into functional carbon-based materials are introduced in detail. Then, the application of crayfish shell and typically modified crayfish-shell biochar in adsorption, antibacterial, electrochemical, etc. is reviewed. Finally, the future research outlook is proposed. This review can provide some perspectives on the development of the application of crayfish shells and crayfish-shell derivatives.

The production of renewable energy and chemicals from biomass can be performed sustainably using pyrolysis, but the production costs associated with biomass pyrolysis hinder its wider application. The use of renewable precursors and waste heat to fabricate high-quality functional carbon nanomaterials can considerably improve the sustainability and economic viability of this process. Here, we propose a method to maximize the economic benefits and the sustainability of biomass pyrolysis by utilizing waste pyrolysis gases and waste heat to prepare high-quality three-dimensional graphene foams (3DGFs). The resulting 3DGFs exhibit excellent performance in environmental and energy-storage applications. On the basis of a life-cycle assessment, the overall life-cycle impacts of the present synthetic route on human health, ecosystems and resources are less than those of the conventional chemical vapour deposition (CVD) process. Overall, incorporating the pyrolytic route for fabricating functional carbonaceous materials into the biomass pyrolysis process improves the sustainability and economic viability of the process and can support wider commercial application of biomass pyrolysis. Biomass pyrolysis for renewable energy and chemicals offers sustainability advantages but is expensive. This study shows a route to improve both the sustainability and economic viability of biomass pyrolysis by using pyrolytic gases and waste heat to fabricate high-quality carbon nanomaterials.

The catalytic hydrogenation of aromatic nitro compounds containing multiple functional groups into amino compounds with high conversion rates, selectivity, and stability under mild conditions is a great challenge. Herein, a well defined catalyst (Co@NC) is prepared through the pyrolysis of the Co-centered metal–organic framework (MOF) at the optimized temperature. The as-synthesized catalyst exhibits a high conversion rate and selectivity for the hydrogenation of 12 aromatic nitro compounds with different competing groups into desired amino compounds with hydrazine hydrate under mild conditions (80 °C, 30 min, and 1 atm). The catalyst also shows excellent stability and can be reused over 20 times without considerably losing its activity. It is found that the Co–Nx site is the main active site for catalytic hydrogenation, and the Mott–Schottky effect between the surface Co NPs and N-doped carbon can further promote the hydrogenation reaction. EXAFS, TEM, XPS, and Raman analyses confirm that cobalt nanoparticles (NPs) are properly encapsulated by the N-doped carbon matrix at the optimized temperature, and the Co species maintain a high spin state after the catalysis, which may be responsible for the high performance of Co@NC. This work demonstrates not only a highly efficient catalyst for hydrogenation under mild conditions, but also provides insight into the active sites in Co-based catalysts for hydrogenation.

The ever-increasing algae biomass due to eutrophication brings an enormous destruction and potential threat to the ecosystem. Hydrothermal carbonization (HTC) is a potential means converting algae to value added products such as sustainable bioenergy and biomaterials. However, the waste aqueous phase (AP) produced during the HTC of algae biomass needs to be treated carefully in case of the second pollution to environment. In this study, a model microbe (E. coli) was adopted for the microbial pretreatment of AP, by which the bioavailability of AP could be improved, and the nutrients could be reclaimed though struvite precipitation. Three-dimensional fluorescence spectra and GC-MS results illustrated that E. coli pretreatment could convert a large number of organic nitrogenous compounds to ammonia nitrogen by degrading aromatic protein substances and deaminating nitrogenous heterocyclic compounds. Afterwards, a serious of characterizations confirmed that 81.13% of ammonia nitrogen could be recovered as struvite though precipitation. Life cycle assessment indicates the cost of the two-step treatment process was much lower than that of conventional wastewater treatment processes, and is beneficial to environment. This work provides an environment-friendly strategy for the comprehensive utilization of algae, which may contribute to alleviating the algal disasters and bring certain economic benefits though algal treatment.

In this study, taking Ni enriched water hyacinth (WH, Eichhornia crassipes) as an example, we prepared porous Ni–N doped carbon material (WHPC@Ni) with high supercapacitive performance via fast pyr...

Biomass is a renewable resource that currently accounts for 10% of the total global energy load. Thermochemical technologies, particularly pyrolysis, are widely used in biomass conversion due to their high reaction and conversion rates compared with biochemical transformation. Understanding the pyrolysis process and the properties of pyrolytic products is essential to obtain further valorized pyrolytic products, such as bio-oil-based chemicals and biochar-based carbonaceous materials. Thus, fully characterizing pyrolysis and its products is imperative. This review focuses on recent advances in pyrolysis-characterization methods, particularly on the online characterization of biomass pyrolytic intermediates and spectroscopic and microscopic imaging methods for biochar and bio-oil. We further discuss how these characterizations help elucidate the pyrolysis mechanism and extend the utilization of pyrolytic products. The drawbacks and improvement prospects of current methods are also discussed.

The catalytic reduction of diverse pollutants by noble metal catalysts in the presence of reductants is a highly effective and widely used method. However, the considerable cost of noble metal catalysts impedes the practical application of this method, and the recovery of excessive reductants has not been reported previously. In this work, we prepared inexpensive biochar-supported magnetic noble metallic nanoparticles (NPs) and efficiently recovered the excessive reductants in the form of H2. The as-synthesized biochar-supported noble metallic NPs exhibited high H2 recovery during the 4-nitrophenol reduction reaction. Results showed that the catalysts with low noble metallic content have higher H2 recovery rate than commercial Pd/C, Ag/C, and Pt/C. The catalytic mechanism of magnetic biochar-supported noble metallic NPs was demonstrated to be a "synergetic effect", where biochar and Fe3O4 acted as accelerants that enable noble metallic NPs to produce active hydrogen for the reduction reaction, and the excess active hydrogen atoms combined to form H2.

Activation of peroxymonosulfate (PMS) to degrade recalcitrant organic pollutants has attracted much attention, however, this process usually needs expensive or toxic catalysts. Herein, we prepared a Fe functionalized biochar composite that contain Fe0, porous carbon with abundant functional groups and nanofibers (Fe-BC-700) to activate PMS and efficiently remove bisphenol A (BPA). The contribution of different participants in the complicated system involving Fe species, carbon composites, and radicals and nonradicals were quantitatively investigated. Under optimal conditions (0.2 g/L PMS and 0.15 g/L catalyst), 20 mg/L of BPA can be completely removed in 5 min by Fe-BC-700. The effects including the activation of PMS by Fe species to produce sulfate radicals (SO4 −), the electron transfer by the nanofiber-mesoporous carbon structure, and the inherent persistent free radicals (PFR) in biochar, were demonstrated to contribute to the high performance. A series of contrast experiments showed that PMS activated by Fe contributed to about 36% of BPA degradation, while the carbon composites, especially carbon nanofibers contributed to 17%, and the other 47% was ascribed to the adsorption of carbon composites (may further undergoing degradation). Meanwhile, the degradation by SO4 − accounted for about 23% (by quenching experiments), while the nonradical pathway contributed to 30%. This work suggests that the non-activation factors in PMS/porous catalyst/pollutant system cannot be neglected.

The efficient elimination of biotoxicity of halogenated antibiotics by electrochemical dehalogenation pretreatment is required by a subsequent biochemical treatment process. Molybdenum disulfide (MoS2) has been applied as an efficient catalyst for the hydrogen evolution and water splitting, without any investigation in electrochemical dehalogenation, particularly under complex environmental conditions. In this study, ultrathin MoS2 nanosheets are fabricated via a simple one-step hydrothermal process, and proved as a promising catalyst for enhancing electrochemical dehalogenation of halogenated antibiotics of a chlorinated antibiotic florfenicol (FLO) under relevant environmental conditions. Results showed that the reaction rate constant of the ultrathin MoS2 electrode (0.0135 min−1) was 4.1- and 28- fold higher than those of commercial MoS2 and bare carbon paper, respectively, and the biotoxicity of treated effluent could almost be neglected. Free radical scavenging experiments and electrochemical performance test suggested that the dechlorination of FLO on ultrathin MoS2 electrode was synergistically accomplished via the direct electron transfer and indirect reduction of active H*. Environmental conditions, namely, dissolved oxygen and humic acid had only a slight effect on the dechlorination efficiency. Electrochemical dechlorination of FLO was a gradual dechlorination process and FLO-2Cl (representing the removal of two chlorine atoms from FLO) was the final main product. Besides, the ultrathin MoS2 electrode retained a good stability and the energy consumption of the ultrathin MoS2 cathode at −1.2 V was 0.02643 kWh g−1, more than those of commercial MoS2 cathode and bare carbon paper. This study develops a new application of noble-metal-free electrode material for electrochemical dechlorination in wastewater.

In this study, the catalytic activity and stability of Pd nanoparticles during the reduction of 4-nitrophenol (4-NP) were significantly enhanced by the interaction of Fe3O4/biochar support prepared by pyrolysis of fir sawdust. Compared with the commercial Pd/C with 5% of Pd content, the as-synthesized Pd@Fe3O4/biochar with only 1.58% of Pd content exhibited twice higher catalytic performance toward the 4-NP reduction. The significant enhancement of catalytic activity was ascribed to the interaction between Fe and Pd NPs which lowers the binding energy of Pd on surface of Pd@Fe3O4/biochar, resulting the fast desorption of the intermediate species during the reaction. Furthermore, the carbon skeleton expedites the electron transfer and facilitates the formation of active hydrogen and deprotonation of 4-NP which are key steps of reduction of 4-NP. The abundant oxygen containing groups in biochar may act as pinchers to tightly fix the Pd NPs and improve the stability of Pd@Fe3O4/biochar.

Pyrolysis, as a convenient and fast technology, has been proved to be promising in the remediation of oil-contaminated soil. However, little is known about the dissolved organic matter (DOM) associated with pyrolyzed oil-contaminated soil and its environmental impact. Herein, optical spectroscopic techniques (i.e., absorbance and fluorescence) were adopted to reveal the relationship between the pyrolysis temperature and the characteristics of the DOM and the associated phytotoxicity. Results show that one of the main factors determining the properties and phytotoxicity of DOM leached from the pyrolyzed soil is the critical temperature (approximately 325 °C) during pyrolysis. When the temperature was lower than 325 °C, more types and quantities of DOM, mainly fulvic acid-like substances, were desorbed from the soil with the temperature, which have little effect on wheat growth. However, when the temperature was in the range of 325–550 °C, the type and quantity of DOM increased first and then decreased as the temperature increased, during which the organic matter in the soil decomposed. The wheat growth was first inhibited and then promoted. Finally, the correlation between the spectral indices of DOM with the phytotoxicity suggested that fluorescent components identified by parallel factor analysis were positively correlated with phytotoxicity. This study indicates the pyrolytic remediation of oil-contaminated soil should avoid some critical temperature ranges.

Preventing release of refractory pollutants from contaminated sediments is of growing concern. In situ remediation of sediments becomes more popular because of its low cost and noninterference of benthic ecosystems compared with conventional sediment dredging. In this study, a low-cost rice husk biochar (RHB) was used as a capping material to prevent the release of representative inorganic (Cu2+) and organic (4-chlorophenol, 4-CP) pollutants from synthetic contaminated sediments. In addition, the release dynamics of pollutants was investigated under different environmentally relevant conditions. The experimental results indicated that RHB can efficiently suppress the release of Cu2+ and 4-chlorophenol from the sediments and a select thickness of RHB can maintain the concentrations of these model pollutants below the national criterion at pH = 5 and 7, even when the concentrations of these pollutants are very high (1600 mg kg–1 of Cu2+ or 100 mg kg–1 of 4-CP). Fitting the release data of pollutants to the ...

A new type of energy is produced via a fast pyrolysis coupled with atmospheric distillation from lignocellulosic biomass wastes., Development of renewable energy is essential to mitigating the fossil fuel shortage and climate change issues. Here, we propose to produce a new type of energy, bio-coal, via a fast pyrolysis coupled with atmospheric distillation process. The high heating values of the as-prepared bio-coals from the representative biomass are within 25.4 to 28.2 MJ kg−1, which are comparable to that of the commercial coals. Life cycle assessment further shows that the bio-coal production process could achieve net positive energy, financial, and environmental benefits. By using available biomass wastes as feedstock, China is expected to have a total bio-coal production of 402 million tons of standard coal equivalent, which is equal to 13% of national coal consumption. It would grant China an opportunity to additionally cut 738 million tons of CO2 emission by substituting an equal amount of coal with bio-coal in 2030.

Carbon-based functional materials have extensive applications in the fields of catalysis, energy storage, and conversion, as well as environmental science. However, it remains challenging to synthesize these materials in an economically sustainable way. This work demonstrates an in situ carbothermal reduction route to prepare biochar stabilized Ru–Cu nanoalloys (Ru–Cu/biochar) with low Ru loading (0.16 wt%) by pyrolysis of lignocellulosic biomass waste. The as-synthesized Ru–Cu/biochar shows excellent catalytic performance toward Cr(VI) reduction by hydrazine (N2H4·H2O), with 94% of the Cr(VI) reduced in aqueous solution within 150 s without any additional precipitation process. The catalyst also demonstrates high stability without significant loss of activity after nine cycles. This work offers a sustainable approach to utilize biomass waste to synthesize functional materials as highly efficient and durable catalysts.