Phosphorus Recovery Process Of Wheat Straw Pretreated By Concentrated Phosphoric Acid And Hydrogen Peroxide

The unfettered utilization of fossil-derived fuels triggers the serious issues on energy security and environmental safety in current world.Bioethanol,as a renewable and environment friendly energy,has been attracting widespread attentions in many countries.The second-generation bioethanol derived from lignocellulosic feedstocks for the advantages of renewability,abundant and low price.Due to the complex and recalcitrant structure of lignocellulosic biomass,it needs pretreated by pretreatment method before efficient bioethanol conversion.Concentrated phosphoric acid plus hydrogen peroxide(PHP)pretreatment method is a newly developed method,which shows a strong performance on the deconstruction of lignocellulose resistant structures and high efficiency of enzymatic hydrolysis after PHP pretreated.Based on the previous research on PHP pretreatment,we realized recycle and reuse concentrated phosphoric acid(CPA)and control phosphorus emissions is the crucial step of the PHP pretreatment method used for lignocellulose bioethanol conversion.Therefore,this study designed a process to integrate lignocellulose bioethanol production,CPA recovery and reuse,lignin recovery and phosphorus wastewater treatment,and determine the optimal main parameters of this process.After determined the optimal process parameters,the stability of CPA recovery,the effects of PHP pretreatment with reuse CPA on wheat straw and the subsequent enzymatic hydrolysis efficiency,and the adsorption performance of crab shell biochar on P-contained wastewater were also investigated.The main research results are as follows:(1)This study designed an integrity process,and discussed the main parameters of this process.It is found that the addition ratio of ethanol/PHP solvent increased from 4: 1 to 11: 1,CPA recovery efficiency increased from 68.6% to 80.0%,and lignin recovery increased from 16.3% to 23.3%.However,when the ratio of ethanol solvent/PHP increased to 16: 1,the recovery efficiency of CPA and lignin were no longer increased dramatically.When the addition ratio of water/de-ethanol solution increased from 4:1 to 16:1,the lignin recovery hardly changed.Therefore,the optimal addition ratio of ethanol /PHP solvent and water/de-ethanol solution was determined to be 11:1 and 4:1.(2)Based on the optimal addition ratio of ethanol /PHP solvent and water/de-ethanol solution,11 batches of CPA were recovered and 10 batches of CPA were reused.The CPA recovery varied from 80.0% to 88.9% of 11 batches,and the average CPA recovery was 86.0%.With the recycle times increased,the CPA recovery was slightly increased,but the variation coefficient of the CPA recovery of 11 batches was 0.033,indicating that the CPA recovery was relatively stable.Furthermore,during the 11 batches,the lignin recovery increased from 21.1% to 38.5%.(3)The solid recovery of 11 batches after PHP pretreated with recovered CPA showed little change,which ranged from 42.1% to 49.0%.The hemicellulose removal was no significant change,which ranged from 92.9% to 95.2%.After the first pretreatment,the cellulose recovery was 87.1% and the lignin removal was 67.8%.After the third pretreatment,the cellulose recovery decreased to 71.0% and finally varied between 52.4% and 67.5% of 4-11 batches,and the lignin removal was decreased to 30.0% and finally changed from 35.5% to 42.9% of 4-11 batches.The average enzymatic hydrolysis efficiency of 11 batches was 96.3%,and there was no significant difference,proving that the subsequent ethanol conversion of this process was relatively stable.(4)Langmuir and Freundlich models were used to simulate the phosphorus adsorption capacity of CSB500 at different temperatures.The simulated results showed that the phosphorus adsorption capacity of CSB was 252.0 mg/g to 261.6 mg/g at 15 ? to 35 ?,and the results were more consistent with the Langmuir model.When 6.0g/L addition of CSB500 was added into the PHP pretreatment derived wastewater,78.1% phosphorus in wastewater could be removed at 25 ? for 24 h.(5)After the analysis of this process,1.1 kg CPA can pretreat 1.0 kg wheat straw to produce 155.0 g ethanol and 45.0 g high purity lignin.4.9 kg phosphorus-enriched biochar can obtain by adding 3.5 kg of crab shell biochar after P-contained wastewater treatment.