Study On Adsorption And Degradation Of Tannic Acid In Papermaking Wastewater By Sludge Carbon Supported Sulfurized Nano Zero Valent Iron

Tannic acid（TA）and other plant polyphenols in papermaking wastewater have biological toxicity,which significantly affects the efficiency of anaerobic and aerobic biological treatment of wastewater.At the same time,After aerobic treatment of papermaking wastewater,a large amount of excess sludge is generated,which faces a large number of disposal problems,but it has the potential to prepare sludge charcoal（SC）,which could be used to adsorb plant polyphenols and other pollutants.Therefore,in this study,the excess sludge was prepared into sulfide nano zero valent iron（S-n ZVI）modified biochar（SC-S-n ZVI）to realize the waste utilization of excess sludge,remove plant polyphenols and reduce its inhibition on anaerobic biological treatment.At the same time,S-n ZVI and SC could also improve microbial activity,increase the treatment efficiency of anaerobic section and improve the wastewater treatment capacity.In this paper,TA was used as the representative of plant polyphenols to explore the adsorption capacity of SC prepared under different conditions.Then loaded with S-n ZVI to improve the adsorption and degradation efficiency of TA.Finally,the effect of adsorption and degradation of TA by SC-S-n ZVI on anaerobic treatment was verified.The main conclusions were as follows:（1）The carbonization temperature significantly affects the structure and performance of SC.When the preparation temperature was 700-1200℃,the specific surface area and porosity of SC increase significantly with the increase of carbonization temperature,and the adsorption performance was better.When100 mg·L^-1 TA simulated wastewater was adsorbed by 1200℃SC,the adsorption content could reach 49.48 mg·g^-1 and the removal rate could reach 98.97%.（2）In order to improve the treatment effect of TA wastewater,S-n ZVI was loaded on SC to obtain stability and catalytic activity.The high catalytic activity of S-n ZVI was used to realize the rapid degradation of TA.The sulfur iron ratio of S-n ZVI was optimized,SC-S-n ZVI_0.05 has good structure and adsorption performance.When the dosage was 0.30 g·L^-1,the maximum adsorption content of TA was 332.75 mg·g^-1,and the removal rate was 99.84%.After exposure to high-purity oxygen and air for 7 days,the removal rate of TA was still as high as91.50%and 90.46%,with good stability.In the competitive experiment with similar substances such as sodium lignosulfonate,it was found that the removal rate of TA was still 89.86%,and it has a certain selective adsorption performance for TA.（3）In order to reduce the inhibition of TA on microorganisms,SC-S-n ZVI_0.05was added to the anaerobic treatment of papermaking wastewater containing TA.After adding TA alone,the performance of anaerobic granular sludge（An GS）was reduced,and the COD removal rate,extracellular polymer（EPS）secretion and specific methanogenic activity（SMA）of An GS were inhibited,including 12.37%SMA.The addition of 0.03 g·L^-1 SC-S-n ZVI_0.05 increased SMA by 28.68%,EPS secretion,C-type cytochrome secretion and interspecific electron transfer.Microbial community and dead and living cell analysis verified the toxicity of TA to microorganisms.SC-S-n ZVI_0.05 was added to remove TA,which weakened the toxicity of TA to microorganisms,and enriched a large number of functional microorganisms,such as Firmicutes and Euryarchaeota at the phylum level and Methanosaeta at the genus level,to improve microbial activity to increase the efficiency of anaerobic treatment.In this study,high-performance biochar was prepared from excess sludge and modified with S-n ZVI,which was applied to the treatment of plant polyphenol wastewater.It realizes the removal of TA,reduces its inhibition on anaerobic,significantly promotes anaerobic activity and improves wastewater treatment efficiency.It provides a new idea for the removal of plant polyphenols and the disposal of excess sludge.