Nanoparticles And Their Synergistic Influence With Substrate Pretreatment On Biogas Augmentation From Enteromorpha

The process of ship ballast water treatment and algae disaster management has produced a large amount of algae waste,and its disposal has become a key problem in the field of marine environmental protection.The present study found that algae waste has great potential to become a raw material for biological hydrogen production,and can comprehend multiple benefits of waste treatment and resource utilization.In view of the key bottlenecks such as low substrate degradation rate and poor productivity of algae waste production process,this study innovatively used nanoparticles as an additive for algae waste production capacity,and examined metal(Ni and Co)and metal oxide(Fe3O4 and MgO)nanoparticles.The productivity characteristics of algae waste enhanced by nanoparticles and an in-depth discussion on the strengthening mechanism of nanoparticle on the production process of algae waste(Enteromorpha)achieved a significant increase in biogas and biohydrogen production.The response surface method was used to optimize the concentrations of nanoparticles.The optimal concentration of metal and metal oxide nanoparticles was 1 mg/L and 10 mg/L,respectively.The microbial dark fermentation hydrogen production experiment under the nanoparticles strengthening was carried out with green algae(Enteromorpha).The substrate and the fermentation temperature was maintained at 37?.The results showed that the increase of biogas production by Ni,Co,Fe3O4 and MgO nanoparticles is 26%,9%,28%and 8%,respectively.The maximum biogas production(624 ml)was achieved by Fe3O4 nanoparticles whereas the highest hydrogen content(51.42%)was achieved by Ni nanoparticles.The modified Gompertz and Logistic function model were used to simulate the biogas production process of nanoparticles.The results showed that the Logistic model can better simulate the bio gas production process of Enteromorpha.The experiment and simulation results showed that the hydrogen production process of green algae under the strengthening of nanoparticles has a long lag time(60 h).In order to shorten the lag time of the hydrogen production process of algae waste fermentation,the nanoparticles were combined with different substrate pretreatment methods to investigate the effect of the fermentation of Enteromorpha.The results showed that,out of the three pretreatment methods(microwave,ultrasonic and autoclave),the synergistic effect of microwave pretreatment and nanoparticles significantly increases the biohydrogen production.The optimal microwave power(600W),pretreatment time(6 min)and liquid to solid ratio(20:1)was obtained by RSM.Under optimal conditions,the COD and reducing sugars obtained in subsequent fermentation experiments increased by 10,420 mg/L and 0.77-0.79 g/L,respectively.The results of scanning electron microscopy showed that microwave pretreatment made the size of Enteromorpha particles smaller and irregular pits formed on the surface.Thermo gravimetric analysis showed that microwave pretreatment destroyed the cell wall structure of hemicellulose to a greater extent,and the structure of cellulose is slightly changed and open,this may be the main reason for the increase in hydrogen production in the hydrogen production process of Enteromorpha fermentation.In order to further investigate the synergistic effect of nanoparticles strengthening and microwave pretreatment,the dark fermentation hydrogen production experiment under different nanoparticle intensification experiments was carried out with Enteromorpha as raw material.The results show that in the late stage of fermentation hydrogen production,nanoparticles strengthening have a positive impact on the process of hydrogen production.The synergistic microwave pretreatment of Ni,Co,Fe3O4 and non-nanoparticles increased the hydrogen production by 32%,42%,54%and 24%,respectively.Co nanoparticles were combined with microwave pretreatment to achieve maximum biogas production of 53.60 ml/g TS,and Ni nanoparticles combined with microwave pretreatment to achieve the highest hydrogen yield of 59.52%.High-throughput sequenc ing technology was used to investigate the important microbial communities related to the process of hydrogen production by fermentation.The results showed that Firmicutes and Bacteroidetes were the main hydrogen-producing bacteria.At the level of the family,Ruminococcaceae,Enterobacteriaceae and Lachnospiraceae predominate.As an important hydrogen-producing genus,the relative abundances of rumen bacteria in the control group,Ni nanoparticles+microwave,Co nanoparticles+microwave and Fe3O4 nanoparticles+microwave group were 44.22%,46.28%,57.20%and 60.89%,respectively..Compared with the control,the content of the genus Lachnospiraceae increased by the synergistic effect of the nanoparticles and microwave treatment,indicating that the genus Lachnospiraceae has stronger cellulose degradation ability and higher hydrogen yield.