TXC Preparation And Its Effect On The Properties Of Residual Sludge Dewatering

Urban sewage treatment plants are developing rapidly in China,but the high moisture content of sludge hinders the disposal of sludge.The coagulant,especially inorganic flocculant aluminum salt and iron salt,are most widely used in sludge conditioning engineering over the world.Based on the extensive use of inorganic flocculants,aluminum salts and iron salts have gradually exposed their drawbacks.Compared with iron salt and aluminum salt flocculants,titanium flocculants have excellent performance.When treating sewage,they reduce sludge and avoid environmental pollution.A new type of titanium dry gel(TXC)was prepared by sol-gel method,which overcomes the disadvantages of titanium tetrachloride being acidic,resulting in too low water pH value,uncontrollable hydrolysis,fast hydrolysis rate of polytitanium chloride,liquid material not easy to retain for a long time,easy precipitation failure such as faults,but there are also use TXC sludge dosing quantity is too high.In order to improve the dehydration efficiency and reduce the processing cost,this paper studies the compounding of TXC with cationic polyacrylamide(CPAM)and chitosan(CTS)and the complexation of TXC with modified carboxymethyl chitosan(CMC)Respectively affect the sludge dewatering performance.Using Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD)and scanning electron microscope(SEM)as analysis tools,with sludge specific resistance(SRF),water content,capillary water absorption Time(CST),extracellular polymer(EPS)and Zeta potential are the main evaluation indexes of sludge dewatering performance to clarify the effect of titanium-based salts on remaining sludge.The main research conclusions are as follows:(1)Effect of TXC on sludge dewatering performance.Through characterization,preparation of TXC flocculating agent containing C=C,C=O,Ti-OH such as keys,interacts with the sludge particles,and gather more closely.The optimal dosage of TXC as a sludge conditioner was 75 mg/g,the moisture content was 73.8%,the sludge specific resistance was 2.9×1012 m/kg,and the capillary water absorption time was 12.1 s,respectively reduced by 2.5%,65.3%,and 34.2%.EPS decreased from 83.1 mg/L to 51.7 mg/L,a decrease of 37.8%.Through the infrared spectrum characterization,it is indicated that there are phenolic hydroxyl group or alcohol hydroxyl group-OH or C=O in the sludge,which belongs to the hydrophilic group.After TXC conditioning,the absorption peak of the sludge in these areas is significantly weakened.XRD showed that the treated sludge mainly contained CxHyClzNhOiTi compounds,while TXC hydrolyzed into a large network structure,which was conducive to sludge aggregation and precipitation.(2)Effect of TXC compound CPAM and CTS on sludge dehydration.The results show that TXC is combined with CPAM,and the optimal condition is:1.2mg/g CPAM was added to every gram of dried mud,followed by 45mg/g TXC,and the moisture content reached the lowest value of 68.8%.After the combination of CPAM,the amount of TXC was reduced,and the positive ions brought by CPAM increased the ionic strength.Due to the electric neutralization,the potential value was further reduced,the sludge particles collided and coalded,and the sludge moisture content was further reduced.For the combination of chitosan and TXC,the optimal condition is as follows:first add chitosan 21.3 mg/g,then add TXC 75 mg/g,the moisture content can be reduced to 68.1%.After the combination of CTS,free-NH2 on the molecular chain of CTS is combined with H+,and after protonation,cationic NH3+ is formed,forming a polyelectrolyte with positive charge,which increases the ionic strength,and the electric neutralization and adsorption further reduce the potential value.Through SEM observation,the surface energy of the conditioned sludge is relatively dense,uneven and has multiple pores.(3)Effect of TXC/CMC flocculant on sludge dewatering.Carboxymethyl chitosan(CMC)to increase the active group,enhance its water solubility,TXC and CMC crosslinked reaction,through infrared spectroscopy and XRD analysis,the new flocculant TXC/CMC composite flocculant was successfully obtained.Sludge to regulate the sludge after the initial pH value,reaction temperature,composite flocculant dosing amount of factors such as experiment,it is concluded that TXC with CMC by volume ratio of 5:1 preparation of flocculant effect is best,in the pH of 7,reaction temperature of 35℃,composite flocculant dosing amount to 30 mg/g,the optimal conditions,the TXC/CMC new composite flocculant CST achieve lowest after conditioning,decline of 54%,significantly higher than the two single flocculant TXC and CMC.