Machine learning-aided hydrothermal carbonization of biomass for coal-like hydrochar production: Parameters optimization and experimental verification.

Biomass to coal-like hydrochar via hydrothermal carbonization (HTC) is a promising route for sustainability development. Yet conventional experimental method is time-consuming and costly to optimize HTC conditions and characterize hydrochar. Herein, machine learning was employed to predict the fuel properties of hydrochar. Random forest (RF), support vector machine (SVM), and extreme gradient boosting (XGB) models were developed, presenting acceptable prediction performance with R2 at 0.825---0.985 and root mean square error (RMSE) at 1.119---5.426, and XGB outperformed RF and SVM. The model interpretation indicated feedstock ash content, reaction temperature, and solid to liquid ratio were the three decisive factors. The optimized XGB multi-task model via feature re-examination illustrated improved generalization ability with R2 at 0.927 and RMSE at 3.279. Besides, the parameters optimization and experimental verification with wheat straw as feedstock further demonstrated the huge application potential of machine learning in hydrochar engineering.

CO2-mediated catalytic upcycling of plastic waste for H2-rich syngas and carbon nanomaterials.

To establish a reliable disposal platform of plastic waste, this work developed a novel dual-stage CO2-medaited decomposition-catalysis route by applying multi-functional zeolite-supported bimetallic catalysts. Catalytic upcycling of plastic was first performed in Ar as a reference environment. Bimetallic Fe-Co/ZSM5 catalyst achieved the highest gas yield (53.98 mmol/g), with a H2 proportion of 62.17 vol%. It was evidenced that the Fe-Co alloy had an apparent positive synergistic effect on catalytic cracking and reforming of intermediate volatiles into H2-rich fuel gas and pure carbon nanotubes (CNTs). Regarding CO2-mediated decomposition-catalysis of plastic, there was an apparent synergistic effect between metallic Ni and Fe on gas production so that bimetallic Ni-Fe catalyst gained the maximum cumulative gas yield of 82.33 mmol/g, with a syngas purity of ∼74%. Ni-Fe/ZSM5 also achieved the maximum hydrogen efficiency (87.38%) and CO2-to-CO conversion efficiency (98.62%), implying hydrogen content in plastic and oxygen content in CO2 were essentially converted into gases. Additionally, bimetallic Ni-Fe catalyst revealed the highest carbon production (33.74 wt%), witnessing a synergistic enhancement of 43.45%; specially, approximately 257 mg/g CNTs were anchored on Ni-Fe/ZSM5, with a CNTs purity of over 76%. Overall, this study offers a superb solution in plastic waste valorization and greenhouse gas emission management.

Improving hydrogen-rich gas production from biomass catalytic steam gasification over metal-doping porous biochar.

Biomass to green H2 is a new route to produce sustainable energy. This study aimed to boost H2-enriched gas production via gasification-catalytic steam reforming (GCSR) process of wheat straw (WS) over Ni, Fe, or Zn-doped carbon materials (MDCMs). Initially, steam injection rate (1 g/min) and residence time (15 min) was optimized based on the tradeoff between energy consumption and H2-rich gas generation. The largest gas yield (90.77 mmol/g) and the lowest H2 production efficiency (ƞ: 7.89 g CO2/g H2) were observed for WS-derived biochar. Clearly, it was found MDCMs were favorable for reducing CO2 production due to the strengthened CO2 reforming reactions catalyzed by metal active sites. A higher ƞ (6.72 g CO2/g H2) was achieved for Ni-doping biochar (Ni/C). Importantly, Ni/C showed the ultrahigh carbon conversion efficiency (99.47%) and great tar elimination performance. Overall, GCSR process over MDCMs is a newly promising way to valorize biomass into H2-rich gas.

Torrefaction/carbonization-enhanced gasification-steam reforming of biomass for promoting hydrogen-enriched syngas production and tar elimination over gasification biochars.

Biomass to H2-enriched syngas is a very promising route to produce clean energy. This work proposed a new concept of promoting H2-enriched syngas production and tar elimination through torrefaction/carbonization-enhanced gasification-steam reforming (T/CEGSR) of wheat straw (WS) over its gasification biochar materials (GCMs). WS torrefied at 280 °C (WS-280) subjected to gasification-steam reforming (GSR) over C-control presented the maximum gas yields and H2/CO molar ratio (1.72). By introducing C[10 %O2] for GSR of WS-280, the maximum cumulative gas yield (112.10 mmol/greactants), H2 yield (59.91 mmol/greactants), and syngas yield (94.10 mmol/greactants) were achieved. Furthermore, C[10 %O2] were superior to C-control, C[Ar] and C[CO2] in light of carbon conversion efficiency, cold gas efficiency, and tar yield, reaching 97.45C%, 118.40 %, and 3.36 g/Nm3, respectively. Simply put, this study provides a newly sustainable and promising route by combining biomass torrefaction/carbonization with GSR using gasification biochar for enhancing H2-enriched syngas production while reducing tar formation.

Steam Gasification of Torrefied/Carbonized Wheat Straw for H2-Enriched Syngas Production and Tar Reduction.

Torrefaction/carbonization integrated with steam gasification of agricultural biomass for gas production and tar reduction was not investigated. The aim of this study was to evaluate the influence of the torrefaction/carbonization severity on H2-enriched syngas production and tar reduction during steam gasification of wheat straw (WS). The torrefaction/carbonization experiments were initially performed at 220-500 °C to examine the effect of pretreated temperature on the fuel properties of torrefied/carbonized WS. Then, the gasification temperature (700-900 °C) was optimized at 900 °C in terms of gas formation behaviors. Afterward, steam gasification of raw and torrefied/carbonized WS feedstocks was conducted. WS carbonized at 500 °C (WS-500) possessed the highest H2 concentration (54.21 vol%) and syngas purity (85.59%), while the maximum H2/CO molar ratio (1.83), high carbon conversion efficiency (90.33 C%) and cold gas efficiency (109.24%) were observed for WS torrefied at 280 °C. Notably, the cumulative gas yield, H2 yield, and syngas yield respectively reached 102.68 mmol/g, 55.66 mmol/g, and 87.89 mmol/g from steam gasification of WS-500. In addition, the carbonized WS feedstocks, especially WS-500, revealed a lower tar content. Simply put, integrating torrefaction/carbonization with steam gasification provided a novel and effective route to manufacture H2-enriched syngas with extremely low tar content from agricultural biomass.

Aptamer-functionalized nanoscale metal-organic frameworks for targeted photodynamic therapy.

Photodynamic therapy (PDT) has been applied in clinical cancer treatment. Here we report an aptamer-functionalized nanoscale metal-organic framework for targeted PDT. Our nanosystem can be easily prepared and successfully used for targeted PDT with a significantly enhanced therapeutic efficacy in vitro and in vivo. Methods: By combining the strong binding ability between phosphate-terminated aptamers and Zr-based nanoscale metal-organic frameworks (Zr-NMOFs) and the intercalation of photosensitizer TMPyP4 within the G-quadruplex DNA structure, TMPyP4-G4-aptamer-NMOFs were prepared. The characteristics and photodynamic performance of TMPyP4-G4-aptamer-NMOFs were examined after preparation. Then, we studied their stability, specific recognition ability, and phototoxicity in vitro. For in vivo experiments, the nanosystem was intratumorally injected into a HeLa subcutaneous xenograft tumor mouse model. After irradiation on day 0, mice were further injected with the nanosystem on day 5 and were again subjected to laser irradiation for 30 min. Tumor volumes and body weights of all mice were measured by caliper every 2 days after the treatment. Results: The nanosystem induced 90% cell death of targeted cells. In contrast, the control cells maintained about 40% cell viability at the same concentration of nanosystem. For the in vivo experiments, the nanosystem-treated group maintained more than 76% inhibition within the entire experimental period. Conclusion: We have demonstrated that our smart TMPyP4-G4-sgc8-NMOFs nanosystem can be used for targeted cancer therapy with high efficiency.