RESUMO
BACKGROUND: The mixed-feedstock fermentation is a promising approach to enhancing the co-generation of cellulosic ethanol and methane from sugarcane bagasse (SCB) and molasses. However, the unmatched supply of the SCB and molasses remains a main obstacle built upon binary feedstock. Here, we propose a cellulose-starch-sugar ternary waste combinatory approach to overcome this bottleneck by integrating the starch-rich waste of Dioscorea composita Hemls. extracted residue (DER) in mixed fermentation. RESULTS: The substrates of the pretreated SCB, DER and molasses with varying ratios were conducted at a relatively low solids loading of 12%, and the optimal mixture ratio of 1:0.5:0.5 for the pretreated SCB/DER/molasses was determined by evaluating the ethanol concentration and yield. Nevertheless, it was found that the ethanol yield decreased from 79.19 ± 0.20 to 62.31 ± 0.61% when the solids loading increased from 12 to 44% in batch modes, regardless of the fact that the co-fermentation of three-component feedstock was performed under the optimal condition defined above. Hence, different fermentation processes such as fed-batch and fed-batch + Tween 80 were implemented to further improve the ethanol concentration and yield at higher solids loading ranging between 36 and 44%. The highest ethanol concentration of 91.82 ± 0.86 g/L (69.33 ± 0.46% of theoretical yield) was obtained with fed-batch + Tween 80 mode during the simultaneous saccharification and fermentation at a high solids loading of 44%. Moreover, after the ethanol recovery, the remaining stillage was digested for biomethane production and finally yielded 320.72 ± 6.98 mL/g of volatile solids. CONCLUSIONS: Integrated DER into the combination of SCB and molasses would be beneficial for ethanol production. The co-generation of bioethanol and biomethane by mixed cellulose-starch-sugar waste turns out to be a sustainable solution to improve the overall efficacy in biorefinery.
RESUMO
In the present work, nickel phosphide (Ni12P5) modified graphitic carbon nitride (g-C3N4) nanosheets were synthesized by a simple grinding method. The structural characterization clearly proved that Ni12P5 nanoparticles were well loaded on the surface of g-C3N4 nanosheets. The photocatalytic activity of the composites was tested by catalyzing the reduction of water to hydrogen under visible light irradiation. The results demonstrate that Ni12P5 is an efficient co-catalyst for photocatalytic H2 production of g-C3N4 nanosheets. The maximum photocatalytic H2-production rate of 126.61 µmol g-1 h-1 could be obtained by loading 2.0% Ni12P5 nanoparticles on the surface of g-C3N4, which is about 269.4 times higher than that of pure g-C3N4. It is believed that Ni12P5 nanoparticles on the surface of g-C3N4 could act as significant active sites to boost separation of photoexcited electrons and holes and accelerate the H2-evolution kinetics, thus achieving greatly enhanced hydrogen generation. It is expected that this work could contribute to further experimental investigation for exploiting the low cost, high-efficiency, and environmentally friendly g-C3N4-based nanocomposites for photocatalytic H2 production.
