Study On The Effect Of Activated Peroxymonosulfate By Iron-manganese Tea Biochar On The Dewatering Performance Of Municipal Sludge

In recent years,the output of urban sludge in China has increased greatly.Sludge dewatering can reduce the moisture content of sludge for subsequent treatment and disposal.Extracellular polymeric substances of sludge is the important factor limiting the complete separation of sludge and water.At present,it is an effective way to improve the dewatering performance of sludge by using advanced oxidation process to destroy the sludge cell structure and reconstruct sludge flocs.Among them,the activated persulfate can effectively realize the sludge deep dehydration.However,it is rare to report that activated persulfate with biochar composite can improve sludge dewatering performance,and the effect of this method on sludge dewatering has not been clarified.Therefore,it is necessary to further study.In this paper,the effect of iron-manganese tea biochar activated peroxymonosulfate（PMS）combined with tannic acid（TA）on sludge dewatering performance was studied.It was verified that the biochar composite material activates PMS to degrade organic matter feasibility by using iron-based biochar activation PMS to degradation humic acid（HA）and fulvic acid（FA）,which were used to simulate the EPS components of sludge.Then,the sludge was treated by iron-manganese tea biochar activation PMS combined with TA,and the engineering application prospect of the technology was verified by the combination of the high pressure filtration equipment.At the same time,the physical and chemical characteristics of sludge and the changes of EPS components were discussed,and the mechanism of combined conditioning technology was analyzed,which provided data reference and theoretical support for the realization of deep sludge dewatering.Firstly,the modified tea biochar was prepared and characterized.The results showed that H₃PO₄ and Zn Cl₂ could effectively improve the pore structure of the biochar,which could increase the specific surface area of the biochar and the type and number of functional groups.Under the optimal preparation conditions,the iodine adsorption value and specific surface area of Zn Cl₂ modified biochar were 1066.32 mg/g and 890.89 cm²/g,respectively.Secondly,the iron-based biochar was prepared on the basis of modified tea biochar,which was used to activate PMS and degrade HA and FA.The results showed that iron based biochar was supported on the surface of biochar with Fe₃O₄.Single factor experiments were carried to optimize the degradation conditions of HA and FA,including initial concentration of HA and FA,PMS concentration,dosage of iron based biochar and initial p H.The removal rate of HA and FA reached 95.3%and 77.4%respectively under the optimal conditions.The results of quenching test and electron paramagnetic resonance（EPR）showed that singlet oxygen（¹O₂）played a leading role in the degradation process,which confirmed that activated PMS of biochar composites could effectively degrade organic matter.Finally,the iron-manganese biochar was prepared and used to activate PMS combined with tannic acid to condition the municipal sludge.The results showed that iron and manganese were loaded on the surface of biochar with Mn Fe₂O₄.Single factor experiments were used to optimize the operating parameters,including PMS concentration,iron-manganese biochar dosage,TA concentration and initial p H.The specific resistance to filtration（SRF）of sludge was 83.68%compared with the raw sludge under the optimum conditions.The moisture content of sludge cake was as low as 40.8%after 6 Mpa pressure filtration.Moreover,the results of quenching test and electron paramagnetic resonance showed that SO₄^-·and OH·were the key free radicals to enhance sludge dewatering performance.Tannic acid could accelerate the transformation of valence state of metal ions,improve the activation efficiency of PMS and enhance the oxidation of the system,which was beneficial to destroy the cellular structure of sludge.At the same time,tannic acid made proteins flocculate and precipitated again through bridging and complexing,forming insoluble compounds for improving the compressibility of sludge,thus improving the sludge dewatering performance.