Sugarcane Bagasse Pretreatment And Differential Degradation Of Cellulose And Lignin By BiFeO₃ Fenton-like System

The world's energy situation is becoming more and more serious.And the excessive consumption of fossil energy makes it urgent for people to find a substitute with great potential and sustainable utilization.The biomass resources represented by lignocellulose have been recognized as a renewable energy material.Fenton technology has attracted a lot of attention in lignocellulose pretreatment due to its mild reaction conditions and environmental friendliness.However,due to its requirements in strict p H range and the large amount of reagent dosage,the practical application of its pretreatment has been hindered.With the development of Fenton technology,iron-containing Fenton-like technology has become a very effective method for the treatment of unbiodegradable organic pollutants.Its catalyst can be separated and reused from the reaction system,and the applicable p H range is wider.Bi Fe O₃Fenton-like catalyst has a good catalytic oxidation performance due to its special structure.At present,Bi Fe O₃Fenton-like system has been studied in the degradation of lignin model,but it has not been applied to the pretreatment of lignocellulose.In this study,Bi Fe O₃Fenton-like system was used to pretreat sugarcane bagasse,and Fenton pretreatment was used as a control to compare the effects of two pretreatments in enhancing the enzymatic saccharification of sugarcane bagasse and related pretreatment mechanisms were revealed.On this basis,pure cellulose and pure lignin were used to replace the sugarcane bagasse,and their degradation differences and mechanisms in these two systems were compared.Combined with the removal of cellulose and lignin in sugarcane bagasse in different pretreatment systems,it was concluded that Bi Fe O₃Fenton-like system can improve the efficiency of lignocellulose pretreatment and the utilization of biomass,providing an efficient and economical new technology for lignocellulose pretreatment.The results were as follows:?1?The optimal conditions of Bi Fe O₃Fenton-like pretreatment screened from the single factor experiments was:1 g of 40-100 mesh sugarcane bagasse was pretreated with15 mg Bi Fe O₃and 20 m L of 40 g/L H₂O₂at 60oC for 72 h.Under these conditions,the reducing sugar yield of pretreated sugarcane bagasse was 25.8%,which were 1.3 times of that of 40 g/L H₂O₂pretreatment and 9.5 times of that of the sugarcane bagasse without pretreatment,respectively.?2?Compared with Fenton system,Bi Fe O₃Fenton-like system was more effective.Under the optimal conditions,the removal rates of hemicellulose and lignin of Bi Fe O₃Fenton-like system were 63.13%and 55.56%,which were 1.43 and 1.99 times of those of Fenton system,respectively.And the reducing sugar yield was 25.8%,which was 2.2times of that of Fenton system.?3?Fenton and Bi Fe O₃Fenton-like systems could produce·OH faster and with higher concentrations than control H₂O₂systems?25 g/L H₂O₂and 40 g/L H₂O₂?.The·OH concentration generated by the Fenton system reached its highest value at 0.5 h?0.83 mmol/L?,and then decreased to 0 at 2 h.The·OH concentration generated by the Bi Fe O₃Fenton-like system reached its highest value at 12 h?0.98 mmol/L?,and it could be detected at 0-24 h,indicating that Bi Fe O₃Fenton-like system could produce more·OH in a longer time,which was the key reason why the Bi Fe O₃Fenton-like system had better pretreatment effect of sugarcane bagasse than Fenton system.?4?In the pretreatment process of Bi Fe O₃Fenton-like system?sugarcane bagasse was 1 g?,the dissolving amount of Fe³⁺ions has exceeded 50%of the total iron amount in the catalyst.The high dissolution loss resulted in a decrease in the enzymatic reducing sugar yield of sugarcane bagasse after two cycles of Bi Fe O₃Fenton-like pretreatment,which was even no difference with 40 g/L H₂O₂pretreatment.?5?Fenton and Bi Fe O₃Fenton-like systems could degrade more cellulose and lignin than control H₂O₂systems?25 g/L H₂O₂and 40 g/L H₂O₂?.Under the optimal conditions,Bi Fe O₃Fenton-like system had the highest degradation rates of cellulose and lignin with removal rate of 74.6%and 60.7%,respectively,which were 10.7 and 7.9 times of those of Fenton system,respectively,the degradation effect of the cellulose was the most prominent.?6?The first-order reaction kinetics were used to fit degradation of cellulose and lignin under Fenton and Bi Fe O₃Fenton-like systems.The values of rate constant K of cellulose and lignin in Fenton and Bi Fe O₃Fenton-like systems were higher than those in control H₂O₂systems.In Bi Fe O₃Fenton-like system,it was 1.8?6.9 times and 20?137times of those in other systems,indicating that Bi Fe O₃Fenton-like system could degrade cellulose and lignin faster.?7?The changes of p H,Eh and H₂O₂concentration were important reflections in the degradation of cellulose and lignin.Bi Fe O₃Fenton-like system had the strongest acidity,and its Eh value was generally the highest along with the largest change.Moreover,the consumption of H₂O₂in Bi Fe O₃Fenton-like system for the longest time resulted in the strongest oxidizability to degrade cellulose and lignin,and the presence of Fe³⁺further promoted the degradation of cellulose.