Study On Preparation Of Sludge Activated Carbon And Its Adsorption On Concentrate

With the rapid development of urban industrialization,the efficiency of sewage treatment in China is gradually increasing,but on the other hand,the amount of sludge discharged after the treatment of sewage is also increasing.At present,the sludge disposal scheme adopted in China is relatively backward.Stacking it arbitrarily or adopting simple landfill methods have seriously affected the surrounding environment and caused the situation of“sludge besieged the city”.This study used municipal sludge as raw materiall,and then added potassium carbonate as an activator,corn stalk as a carbon enhancer,and prepared a sludge-based activated carbon by chemical activation.It took the dry basis ratio of raw materials（sludge:straw:potassium carbonate）,carbonization temperature and carbonization time to perform orthogonal test,based on iodine adsorption value,specific surface area and activated carbon output data to determine the range and variance.In order to determine the best process conditions:the raw material dry basis ratio is 3:7:0.25,the carbonization temperature is 800°C,and the carbonization time is 2.0 h.Characterization analysis results showed that the average yield of sludge straw-based activated carbon was 51.10%,the average iodine adsorption value was641.91 mg/g,and the average specific surface area was 815.353 m²/g.The pore size analysis showed that the pore structure was well developed,the total pore volume was0.443 cm³/g,and the micropore volume was 0.2660 cm³/g,and the average pore diameter was 3.002 nm,which could be proved to be microporous activated carbon.Thermogravimetric/differential thermal analysis showed that the activator K₂CO₃could reduce the activation energy of the material and promoted the pyrolysis reaction to occur more easily.FT-IR analysis results showed that the surface was rich in functional groups,including O-H,C-H,–CH₂–and C=C.The presence of potassium carbonate had a certain effect on the surface properties of sludge activated carbon.Nitrogen adsorption and desorption isotherm analysis showed that the adsorption and desorption isotherm belonged to the combination of type I and type IV isotherms.The static adsorption of the concentrated liquid using the best activated carbon showed that it had a good adsorption capacity for the concentrated liquid.Taking 60m L of concentrated liquid,when the dosage of activated carbon was 1 g,the adsorption time reached 100 min,the p H of the solution is 9,and the adsorption temperature was narrow at 30°C,the effect of activated carbon on the removal rate of COD was optimal.In an ideal state,the COD concentration after adsorption was 276mg/L,the removal rate reached 78.43%,and the activated carbon adsorption amount was 60.24 mg/g.Fitting the adsorption isotherm equation,the results showed that the contribution rate of multi-layer adsorption was relatively higher during the adsorption process,the Freundlich model had a better fit and a larger correlation coefficient.