Effects Of Lignosulfonate And Its Derived Carbon On Hydrogen And Methane Production

Anaerobic biological treatment is a common wastewater treatment method.Different additives can effectively improve?inhibit?the stability of the anaerobic process and the production of biogas.The recalcitrance of lignin substances in the papermaking wastewater results in the limited efficiency of anaerobic digestion of papermaking wastewater,which endangers the environment and increases the cost of papermaking wastewater treatment.It is an effective way to solve the pollution of papermaking wastewater by seeking other utilization methods of lignin components in papermaking waste liquid that are difficult to anaerobic treatment.The high-value utilization of lignin sulfonate can be realized by the thermal chemical modification of lignin sulfonate to prepare carbon material.In this study,lignin sulfonate,main components of papermaking red liquor,was used to prepare derivatized carbon and both of them were applied to anaerobic digestion processes to investigate their effects on the promotion or inhibition of hydrogen and methane production processes as an external additive.In the first part,BC250 was prepared from calcium lignosulfonate?CL?by low temperature pyrolysis,and and the two samples are used as external additives in the thermophilic fermentation.The effects of CL and BC250 on hydrogen fermentation were explored through the characterization of samples and the investigation of biogas production,p H of fermentation broth,and concentration of metabolic end products.The results showed that the specific surface area,the ash and p H value of the samples increased after pyrolysis.With the increase of CL concentration,the biogas production of the experimental group with CL decreased,and 537 m L hydrogen was harvested with adding 20 g/L of CL,which was 32.1%less than that of the control group,while the same concentration of BC250 increased the hydrogen production by 59.8%compared with the control group.According to the analysis of the end products of hydrogen production,the groups with CL and BC250 showed butyric fermentation.After adding CL,the VFAs concentration was 34.2%lower than that of the control group,while after adding BC250,the VFAs concentration was 23.79%higher than that of the control group,which indicated that CL could inhibit the activity of butyric fermentation microorganisms.On the contrary,BC250 could effectively improve its activity and eventually improve the biogas production performance of anaerobic fermentation systemIn the second part,BC500 was prepared by pyrolysis of sodium lignosulfonate?SL?.The two samples were applied to the process of anaerobic digestion and the effects of SL and BC500 on anaerobic digestion were studied from the aspects of sample characterization,biogas production and end metabolite concentration.The results showed that after pyrolysis the specific surface area of 51.342 m²/g of the BC500 is 66times larger than SL,and the p H value increased from 4.7 to 8.82.After 14 d of anaerobic digestion,the cumulative methane production of the experimental group with SL decreased by 31.99%,41.3%,62.93%,and 69.36%compared with the control group,respectively,which shows that lignin sulfonate can not only inhibit the anaerobic digestion process,but also has a stronger inhibitory effect on methanogens than hydrogen-producing microorganisms.The proper concentration of BC500 can promote the anaerobic digestion process.However,when the concentration is higher than 10 g/L,the promotion effect of BC500 on anaerobic digestion process was reduced.Compared with the control group,methane production was increased by 24.7%with 10 g/L of BC500.Through the daily analysis and measurement of the liquid phase index of the system,it is found that VFAs of the system decreases rapidly in the methanogenic stage after the addition of BC500,which indicates that the utilization rate of VFAs by methanogens is higher,and that the addition of BC500 can improve the activity of methanogens.In the third part,three kinds of calcium doped magnetic biochar?Ca-MBC?were prepared by loading different concentrations of Fe²⁺and Fe³⁺with CL as raw material.The effects of Ca-MBC on the continuous hydrogen and methane production process were investigated by characterization of samples,biogas production,liquid phase index,characteristic enzyme activity and microbial community analysis.The results showed that all three Ca-MBCs could increase cumulative biogas production.The best among them is Ca-MBC2 with 1050 m L.Ca-MBC2 was added to hydrogen and methane production process with different concentrations and the maximum hydrogen production was 948 m L,the maximum methane production was 1599 m L,64.9%and40.8%higher than that of the control group,respectively.In addition,the addition of Ca-MBC2 promoted the activity of Butyric acid fermentation microorganism in the hydrogen production stage and greatly increased the relative abundance of Clostridium;in the methanogenic stage,the addition of Ca-MBC2 increased the content of coenzyme F420.High-throughput sequencing show that Ca-MBC2 can change methanogenic dominant bacteria,strengthen the dominant position of Methanolena,and improve the relative abundance of hydrogen and acetic acid nutritious strains such as Methanosaeta and Methanosarcina.Combined with the effects of CL,SL and different derived carbons on hydrogen and methane production process and microbial community,the mechanisms of additives on anaerobic process are as follows:?1?CL and SL have dispersibility and surface activities,which make them wrap and disperse anaerobic sludge,reduce the concentration of microorganisms,weaken the interaction between microorganisms and substrates,and reduce the conversion rate of substrates to biogas.?2?The higher sulfur content in CL and SL is strongly toxic to anaerobic microorganism,in particular methanogens.?3?The large specific surface area of biochars can enrich microorganisms,reduce the impact of external environment on microorganisms,improve the stability of anaerobic digestion process,and their own basicity can alleviate acid inhibition during anaerobic process and maintain microbial activity.?4?Ca-MBC can slowly release Ca²⁺and Fe²⁺,both of which are the metal elements needed for microbial growth.Fe²⁺can promote the synthesis of enzymes,improve the activity of key enzymes such as coenzyme F420,and improve the efficiency of electronic transmission.Ca²⁺is an important part of cell membrane,which can affect the transmission of microbial cells,the signal transmission between cells,and the formation of anaerobic granular sludge,and improve the biogas production performance and cumulative biogas production.