Research On Paper Sludge Conditioning/Mechanical Dewatering And Its Resource Utilization

Paper sludge is a kind of solid waste generated in the process of papermaking wastewater treatment.It can be divided into primary sludge,deinking sludge,biochemical sludge and chemical sludge according to the source,it posses the characteristics of high organic content,high water content and difficult dewatering.At present,paper sludge is mainly disposed of by landfill,and the utilization rate of resources is low,which not only wastes resources,but also have risks of secondary pollution to the environment.Aiming at the common technical problem of“sludge dewatering difficulty”in the utilization of paper sludge,this paper studies a new method of paper sludge conditioning and mechanical dewatering,which can significantly reduce the moisture content of paper sludge,and created the resource utilization conditions to paper sludge.In addition,the paper studies the method of preparing heavy metal adsorption materials from paper sludge,and realize the high value-added resource utilization of paper sludge.The main conclusions are as follows:The main influencing factors of conditioning and mechanical dewatering of paper sludge based on biochar were discussed by vacuum suction filtration,the mechanism of conditioning and mechanical dewatering of paper sludge by biochar was revealed by particle size analysis,infrared spectroscopy and SEM.The results showed that the biochar?HC550?prepared at a pyrolysis temperature of 550°C,when the particle size was 75-200?m,and the addition amount was 5 g/100 mL sludge,the effect of the conditioning and mechanical dewatering of HC550 on paper sludge is better.The mechanical dewatering time,filter cake moisture content and sludge specific resistance of paper sludge after HC550conditioning are reduced from 15 min,80.67%and 2.531×10¹³ m·kg^-1 before conditioning to 1.6 min,63.67%and 9.67×10¹¹ m·kg^-1 after conditioning,the calorific value increased from 3.58 MJ·kg^-1 of the original sludge to 9.43 MJ·kg^-1,indicating that biochar can not only significantly improve the dewatering performance of paper sludge,but also increase the calorific value of sludge,and create conditions for the resource utilization of sludge.At a certain temperature,the paper sludge was pyrolyzed to prepare biochar,and the material?SAM or NAM?with the ability to adsorb heavy metal ions was obtained by modification method,the adsorption performance and influencing factors of SAM on Cu²⁺(NAM to Pb²⁺)were discussed.The mechanism of SAM adsorption of Cu²⁺(NAM adsorption of Pb²⁺)was revealed by means of BET,SEM and infrared spectroscopy.The results showed that the paper sludge was pyrolyzed at 300°C for 2 h and then modified with 5 mol/L NaOH to prepare a SAM with good adsorption performance for Cu²⁺,when the pH of 100 mg/L Cu²⁺simulated wastewater was 6⁷,the dosage of SAM is 0.01 g/mL simulated wastewater,the Cu²⁺removal rate is 99.15%,and when the SAM dosage is0.0025 g/mL simulated wastewater,the adsorption capacity of SAM is 28.788 mg/g;the paper sludge is pyrolyzed at 400°C for 2 h,and modified with a mass fraction of 33%nitric acid to prepare NAM with good adsorption performance for Pb²⁺,when the pH of the 200mg/L Pb²⁺simulated wastewater was 6,the dosage of NAM was 0.0025g/mL simulated wastewater,the removal rate of Pb²⁺was 55.7%,and the adsorption capacity was 43.83mg/g.When the dosage of NAM was 0.0075g/mL simulated wastewater,the removal rate of Pb²⁺could reach to 89.96%.SAM adsorption of Cu²⁺(NAM adsorption of Pb²⁺)is consistent with the Langmuir equation and belongs to monolayer adsorption.The polymeric ferric sulfate?PFS?prepared by chemical sludge treated by Fenton method,the optimum process conditions for the preparation of PFS were investigated,the total iron content,reducing Fe²⁺content and salt basicity of PFS were measured.The results showed that the optimum conditions for the preparation of PFS were as follows:take100mL of chemical sludge,add 3 mL of concentrated sulfuric acid,stir at a constant temperature of 50°C for 30 min,solid-liquid separation to obtain iron ion filtrate,take 33mL of filtrate and add 35 gFeSO₄,constant temperature 35?,add 2 mL concentrated sulfuric acid,then stirred at a constant speed for 10min,and then oxidizing agent?2ml hydrogen peroxide,2g potassium chlorate?was added to fully react for 24h to obtain red-brown viscous liquid PFS,the total iron content,reducing Fe²⁺content and salt base of PFS were 10.45%,0.007237%and 12.925%respectively,which conforms to the national standard first-class quality index,and the concentrated sulfuric acid can dissolve and decrease the iron hydroxide precipitate in the chemical sludge,when the concentrated sulfuric acid is 4 mL,the solid content of the original sludge decreased from 3%to 0.58%,the reduction was 2.42%,the sludge solids content decreased to about 20%,and the chemical sludge heat value before and after acid leaching changed significantly,and the no-heat value before acid leaching rose up to 6.01 MJ/kg after acid leaching.