Preparation Of Printing And Dyeing Sludge Hydrothermal Carbon And Its Application In Printing And Dyeing Wastewater Treatment

With the rapid development of China's printing and dyeing industry in recent years,the total amount of printing and dyeing wastewater has increased year by year.So the reasonable and effective treatment of printing and dyeing wastewater and sludge has become very urgent at present.Hydrothermal carbonization,as a new sludge treatment technology,is widely concerned.It can not only reduce the amount of printing and dyeing sludge,but also apply sludge resource using to the process of wastewater treatment in which the application of the sludge resource utilization of the printing and dyeing industry into the front-end wastewater treatment realizes the concept of"sludge is taken from wastewater and used for wastewater".In this study,the printing and dyeing sludge was reduced and resourced.Firstly,the effect and mechanism of the reduction were studied.Then,the adsorption and Fenton properties of sludge hydrochar were studied taking the dye-water distribution as the target pollutant.Finally,the hydrochar was applied to the practical dyeing wastewater to check the feasibility of its treatment.The main conclusions of this study are as follows:?1?The hydrothermal treatment in disposing sludge can achieve a good reduction effect.By studying the influence of different reaction conditions on the hydrothermal reduction of excess sludge,the optimum conditions are obtained:time is 4 hours,temperature is 220?,the dosage of NaOH is 0.16g/gDS.Based on these conditions,the mechanism of hydrothermal reduction of printing and dyeing sludge was studied.The samples were characterized by dehydration performance analysis,elemental analysis,thermogravimetric analysis,metal analysis,scanning electron microscopy and Fourier infrared.The results show that the dewatering performance of the sludge is enhanced and the volume is reduced after hydrothermal treatment.A porous structure is formed and the surface is enriched with a small amount of iron which is effective for subsequent resource utilization.?2?Hydrochar can be used as an adsorbent to treat dye wastewater.Based on low concentration methylene blue as the target pollutant,the optimal adsorption conditions were as follows:the dosage of hydrochar was 2 g/L and the pH was neutral.The adsorption reaction can reach balance after 60min,and the removal rate of methylene blue dye with a concentration of 20 mg/L can reach 99%.The adsorption of methylene dye by sludge hydrochar is more compliant with pseudo-secondary adsorption kinetics and Langmuir model.In this adsorption,it is mainly about chemical adsorption and also is monolayer adsorption.?3?Hydrochar can be used as a Fenton catalyst to treat dye wastewater.Using high concentration methylene blue dye?50 mg/L?as the target pollutant,the best Fenton reaction conditions were studied:the dosage of hydrochar was 0.8 g/L,the dosage of hydrogen peroxide was0.8 ml/L,pH was 3,and the removal rate of the methylene blue dye is close to 100%.The samples were analyzed by XRD,XPS,SEM,BET,VSM and other characterization test methods.The results showed that Fe₃O₄ and Fe?OH?₂ contained in the sludge played a crucial role in the Fenton reaction.In addition,sludge hydrochar is magnetic and easy to recycle,increasing the value of sludge hydrochar resource utilization.?4?Above research results were used into the practical printing and dyeing wastewater.The wastewater was pretreated by acidification,and the results showed that the optimum pH of acidification was 3,COD removal rate was about 50%.The results of GC-MS showed that Acid precipitation can reduce the content of acids and esters in wastewater.In addition,the effect of sludge hydrochar as Fenton catalyst on actual wastewater treatment was studied.The optimal treatment conditions were:the dosage of hydrochar was 1 g/L,the dosage of hydrogen peroxide was1 ml/L,pH was 3.The results of GC-MS showed that most of the pollutants in the wastewater were removed after Fenton treatment,only remaining some benzenes.The results of FTIR and XPS showed that the type and quantity of functional groups increased after Fenton reaction,and the removal of pollutants was the result of the synergistic effect of adsorption and Fenton.Finally,the feasibility of hydrochar to enhance the biochemical treatment of actual wastewater was studied.The results showed that he removal effects of COD and total nitrogen were not significant,and the reaction conditions needed to be optimized further.