Facilitate the preparation of naturally modified and self-healing superhydrophobic/superoleophilic biochar-based foams for efficient oil-water separation.

Oil spills are sudden, complex, and long-term hazardous, and the existing adsorption materials still have the disadvantages of small selective adsorption capacity, easy secondary contamination, and difficult to repair after breakage in practical applications. Herein, melamine foam (MF) coated by ball milled biochar (BMBC) and natural beeswax (Wax@BMBC@MF) was prepared by a bio-inspired functionalization method and further added with self-healing function (SH-Wax@BMBC@MF) to cope with complex environments, and applied to oil-water separation for oil adsorption. SEM and FTIR results showed that BMBC and natural beeswax nanoparticles successfully encapsulated the smooth surface of the melamine foam skeleton. The loading of natural beeswax increased the foam's ability to absorb oil and organic solvents from 0.6108-1.134 g to 0.850-1.391 g, and the oil-absorbing capacity of the foam remained at 0. 758-1.263 g after being cut by a knife and self-healing. The oil-absorbing capacity of SH-Wax@BMBC@MF remained in the range of 0.936-1.336 g under acid/alkali environment (pH =1-13). The surface functional groups of BMBC improved the surface roughness of the material and strengthen the MF skeleton to adsorb oils and organic solvents by capillary action. The generation of the di-coordinated structure by Fe3+ and catechol group contributed the restoration of SH-Wax@BMBC@MF structure and oil absorption capacity. SH-Wax@BMBC@MF has superiority of superhydrophobic, superoleophilic, self-healing after damage, and environmental friendliness, which provides a promising solution for the treatment of oil spills at sea.

Gas-Pressurized Torrefaction of Lignocellulosic Solid Wastes: Deoxygenation and Aromatization Mechanisms of Cellulose.

A novel gas-pressurized (GP) torrefaction method at 250 °C has recently been developed that realizes the deep decomposition of cellulose in lignocellulosic solid wastes (LSW) to as high as 90% through deoxygenation and aromatization reactions. However, the deoxygenation and aromatization mechanisms are currently unclear. In this work, these mechanisms were studied through a developed molecular structure calculation method and the GP torrefaction of pure cellulose. The results demonstrate that GP torrefaction at 250 °C causes 47 wt.% of mass loss and 72 wt.% of O removal for cellulose, while traditional torrefaction at atmospheric pressure has almost no impact on cellulose decomposition. The GP-torrefied cellulose is determined to be composed of an aromatic furans nucleus with branch aliphatic C through conventional characterization. A molecular structure calculation method and its principles were developed for further investigation of molecular-level mechanisms. It was found 2-ring furans aromatic compound intermediate is formed by intra- and inter-molecular dehydroxylation reactions of amorphous cellulose, and the removal of O-containing function groups is mainly through the production of H2O. The three-ring furans aromatic compound intermediate and GP-torrefied cellulose are further formed through the polymerization reaction, which enhances the removal of ketones and aldehydes function groups in intermediate torrefied cellulose and form gaseous CO and O-containing organic molecules. A deoxygenation and aromatization mechanism model was developed based on the above investigation. This work provides theoretical guidance for the optimization of the gas-pressurized torrefaction method and a study method for the determination of molecular-level structure and the mechanism investigation of the thermal conversion processes of LSW.

Gas-pressurized torrefaction of lignocellulosic solid wastes: Low-temperature deoxygenation and chemical structure evolution mechanisms.

A novel gas-pressurized (GP) torrefaction realizes deeper deoxygenation of lignocellulosic solid wastes (LSW) to as high as 79% compared to traditional torrefaction (AP) with the oxygen removal of 40% at the same temperature. However, the deoxygenation and chemical structure evolution mechanisms of LSW during GP torrefaction are currently unclear. In this work, the reaction process and mechanism of GP torrefaction were studied through follow-up analysis of the three-phase products. Results demonstrate gas pressure causes over 90.4% of cellulose decomposition and the conversion of volatile matter to fixed carbon through secondary polymerization reactions. Above phenomena are completely absent during AP torrefaction. A deoxygenation and structure evolution mechanism model is developed through analysis of fingerprint molecule and C structure. This model not only provides theoretical guidance for optimization of the GP torrefaction, but also contributes to the mechanism understanding of pressurized thermal conversion processes of solid fuel, such as coal and biomass.

Flue Gas-Enhanced Water Leaching: AAEM Removal from Agricultural Organic Solid Waste and Fouling and Slagging Suppression during Its Combustion.

Alkali and alkaline earth metals (AAEMs) in agricultural organic solid waste (AOSW) contribute to the fouling and slagging during its combustion. In this study, a novel flue gas-enhanced water leaching (FG-WL) method using flue gas as the heat and CO2 source was proposed for effective AAEM removal from AOSW before combustion. The removal rate of AAEMs by FG-WL was significantly superior to that by conventional water leaching (WL) under the same pretreatment conditions. Furthermore, FG-WL also obviously reduced the release of AAEMs, S, and Cl during AOSW combustion. The ash fusion temperatures of the FG-WL-treated AOSW was higher than that of WL. The fouling and slagging tendency of AOSW greatly decreased through FG-WL treatment. Thus, FG-WL is a simple and feasible method for AAEM removal from AOSW and suppressing fouling and slagging during its combustion. Besides, it also provides a new pathway for the resource utilization of power plant flue gas.

Gas-pressurized torrefaction of biomass wastes: Co-gasification of gas-pressurized torrefied biomass with coal.

Co-gasification of coal and biomass offers a relatively cleaner utilization way of fossil fuel. The fuel property improvement of biomass can not only improve the property of syngas but also enhance the synergistic effect during the co-gasification. In our previous work, a novel gas-pressurized (abbreviated as GP) torrefaction was proposed to effectively upgrade the biomass under mild condition. In this work, the co-gasification of GP torrefied biomass and coal were conducted to explore the synergistic effect and kinetics. Significant synergistic effect during the co-gasification was proved. The CO yield of co-gasification increased to as high as 70.70 mol/kg, resulting from the promotion of carbon in coal converting into CO by GPRS. Furthermore, the kinetic model of RPM was most fitting for the co-gasification, and the activation energy of co-gasification was reduced. Thus, the coal gasification was promoted significantly by GP torrefied biomass through obvious synergistic effect during the co-gasification.

Gas-pressurized torrefaction of biomass wastes: The optimization of pressurization condition and the pyrolysis of torrefied biomass.

A novel gas-pressurized (GP) torrefaction with high oxygen removal efficiency at mild temperature was proposed in our previous work. However, the optimal condition of the GP torrefaction and subsequent pyrolysis of the torrefied biomass were not clear. In this work, the effect of pressure on the GP torrefaction and pyrolysis product properties of the torrefied biomass were studied in detail. The results show that the pressure increasing from 1.7 MPa to 5.0 MPa just slightly contributed to further oxygen removal, and 1.7 MPa was thus selected as the optimum pressure. The GP torrefaction significantly improved the product property of biomass pyrolysis compared to the conventional torrefaction (AP torrefaction). The acids content in bio-oil was reduced from 15-20% to less than 5%, and the calorific value of biogas increased to as high as 16.57-19.31 MJ/Nm3. Furthermore, an overall conversion mechanism of combined GP torrefaction and subsequent pyrolysis of biomass was proposed.

Gas-pressurized torrefaction of biomass wastes: Roles of pressure and secondary reactions.

A gas-pressurized (GP) torrefaction method, proposed in our resent work, can significantly promote the upgrading and oxygen removal of biomass wastes, compared to the traditional torrefaction (AP). However, the mechanism of the GP torrefaction process is not clear. In present work, semi-closed (SC) torrefaction, GP torrefaction, and AP torrefaction were conducted to reveal the roles of pressure and secondary reactions during GP torrefaction quantitatively. The results showed that the pressure significantly promoted the upgrading of biomass during GP torrefaction at 200 °C. The contribution of pressure on the oxygen removal of GP torrefaction at 200 °C was 63.87%. At relatively high temperature of around 250 °C, the promotions were caused by the synergistic effect of pressure and secondary reactions. The contribution of secondary reactions on the oxygen removal was 53.99%. Thus, the process of the GP torrefaction of biomass wastes was preliminarily understood.

MIL-100(Fe) supported Mn-based catalyst and its behavior in Hg0 removal from flue gas.

A novel magnetic composite catalyst of MnOx loaded on MIL-100(Fe) was prepared for the removal of Hg0 from flue gas, via incipient wetness impregnation followed with calcination at 300 °C. The MIL-100(Fe) supported catalyst showed greater capacity of Hg0 adsorption and oxidation than Fe2O3 supported catalyst at all test temperatures, showing Hg0 removal efficiency of 77.4% at 250 °C with high GHSV of 18,000 h-1. Besides the merit of high BET surface area and developed porous, the ultra-highly dispersed and homogeneous Fe sites on MIL(Fe) significantly promoted Hg0 adsorption and oxidation via the synergy effect with MnOx. Furthermore, the catalyst exhibited magnetic property, which allowed easy separation of the catalyst from fly ash with a recovery of 104%. SO2, H2O and NH3 in flue gas were proved inhibited Hg0 removal via different mechanisms. SO2 and H2O competed and desorbed Hg2+ on the surface of catalyst, while NH3 was more likely to compete adsorption sites with Hg0.