Experimental Study On Hydrothermal Regeneration Of Waste Activated Coke For Water Purification

Activated carbon is the most common adsorbent in the adsorption method,which is suitable for removing various pollutants in wastewater,especially for advanced treatment of wastewater.The high cost of activated carbon and the difficult treatment of waste activated carbon limit its wide application in the field of water treatment.It is urgent to find low-cost alternative adsorbents and effective waste activated carbon treatment and regeneration methods.Low-cost powdered activated coke has shown good adsorption performance in the field of water treatment and is a potential alternative adsorbent to activated carbon,but the research on its regeneration method is relatively lacking.The hydrothermal regeneration method,which degrades the desorbed pollutants while realizing the regeneration of activated carbon/coke,has received extensive attention in recent years.In this paper,the hydrothermal regeneration method is selected to regenerate the powdered activated coke that has adsorbed methylene blue in wastewater,to explore the hydrothermal regeneration performance of powdered activated coke,to study the degradation mechanism of pollutants in the hydrothermal regeneration process,and to explore how to improve the cycle regeneration of activated coke performance method.The results show that temperature is the main factor affecting hydrothermal regeneration of activated coke,the higher the temperature,the higher the regeneration efficiency.The addition of 8%KOH and 15%H2O2 in the hydrothermal process can significantly improve the regeneration effect of activated coke.The analysis of the physical and chemical properties of the surface of activated coke before and after regeneration showed that the adsorption of methylene blue by activated coke was comprehensively affected by multiple factors such as specific surface area,pore volume and pore size distribution,especially the mesopores with a size of 3～3.8 nm played an important role in the adsorption of methylene blue.Influence.The addition of H2O2 can significantly restore the microporous structure of active coke;the types of functional groups of active coke do not change significantly during the regeneration process,among which C=C,π-π and ArOH have been proved to participate in the chemical adsorption process,adding KOH has New C=O(lactone or anhydride group)is generated.The cycle regeneration experiment shows that under the optimal regeneration condition,the five-cycle regeneration rate of activated coke can still reach 48.3%,and increasing the cycle regeneration temperature can increase the five-cycle regeneration rate to 71.0%;low mass fraction(3%)H2O2 can also improve the recycling efficiency,but the improvement is very small,and the five-cycle regeneration rate is 58.2%.The high-quality fraction(15%)of H2O2 has a significant effect on improving the cycle regeneration rate,and the five-cycle regeneration rate is as high as 122.0%.The number of pores with medium and large pore diameters will decrease with the increase of regeneration times,and the content of Ar-OH,C=C and π-π functional groups of activated coke will recover after circulating hydrothermal regeneration,and the regeneration at 280℃ and 400℃ will The content of Ar-OH decreases with the increase of regeneration times,and the addition of H2O2 can prevent the decrease of Ar-OH.Finally,the experiment found that in the hydrothermal environment,activated coke acts as a catalyst,which can effectively catalyze the degradation of methylene blue.The TOC values in the regeneration condensate are all lower than 120 mg/L.Increase the regeneration temperature and add KOH and H2O2 Can further reduce the condensate TOC value.Using DFT quantum chemical calculation software to predict and analyze the reaction site combined with the experimental results,it is found that the C-N,C-S and-CH3 bonds in methylene blue are the most prone to reaction breakage.After the hydrothermal regeneration reaction,the nitrogen and sulfur in the condensate exist in two forms including organic matter and inorganic ions.The composition of pollutants in the condensate changes with the regeneration temperature,but does not change with the increase in the number of regeneration cycles;After regeneration,the content of nitrogen and sulfur in active coke decreases gradually with the increase of regeneration temperature,but the increase of cycle regeneration times will lead to a gradual increase of its content;high temperature and cycle regeneration under the condition of adding 15%H2O2 are beneficial to the removal of sulfur.