Study On The Properties Of Polyaluminum-Titanium Chloride And Its Composite Flocculant In Treatment Of Low Temperature And Low Turbidity Water

Low temperature and low turbidity water refers to raw water with low temperature and turbidity,which leads to adverse effects on coagulation and precipitation.The rate of coagulation reaction in such water is slow,and the flocs that subsequently form are small,light,loose,and difficult to efficiently precipitate.Several reasons may explain these phenomena.One of the reasons is the slow Brownian motion due to the increase in the inertia of impurity particles at low temperature.The other reason is the increase in viscosity and subsequent increase in resistance between liquid layers;the enhanced resistance limits the collision between particles.In low turbidity water,the number of impurity particles is small,and the distribution is relatively uniform.Colloidal particles have small negative potential and strong interparticle rejection.Accordingly,colloids are difficult to remove,and the aggregation effect is poor.Therefore,improving the purification efficiency of low-temperature and low-turbidity water is a great challenge.In this study,aluminum chloride,sodium silicate,titanium tetrachloride and PDMDAAC were used as raw materials to prepare the inorganic flocculant PATC and the composite flocculant PATC-PDMDAAC to study of the processing of low temperature and low turbidity water,the optimal synthesis and reaction conditions were determined by single control variable method,orthogonal test and other methods,and turbidity and removal rates of HA and DOC were used as evaluation indexes.The reaction mechanism of low temperature and low turbidity water treated by flocculant was studied by FTIR,XRD,Al morphology analysis,zeta potential analysis and kinetic analysis.The synthetic PATC showed the best coagulating effect in treated water under the following experimental conditions: Reaction temperature of50 ℃,and n(Ti)/n(Al),n(-OH)/n(Ti+Al),and n(Si)/n(Ti+Al)were 0.3,0.2,and 1.0,respectively.the optimal reaction conditions were an initial turbidity of 10 nephelometric turbidity unit(NTU),PATC dosage of 9 mg/L,p H of 8 for the simulated water sample,stirring speed of 50 r/min,and settling time of 50 min.The characterization results of FTIR,XRD and SEM-EDS showed that the aluminum chloride,sodium silicate and titanium tetrachloride were not simply mechanically mixed but had complex chemical changes,resulting in new functional groups and chemical bonds.The prepared PATC presented a network structure under the scanning electron microscope,which improved the flocculation effect;the results of Al morphological analysis showed that Al mainly existed in the form of Ala in PATC.Combined with zeta potential analysis and treatment effect analysis of orthogonal test,it showed that the treatment effect of PATC on low turbidity water wasmainly electric neutralization,adsorption bridging and net trapping.The results showed that the treatment effect of PATC on low turbidity water was better than that of polyaluminum chloride,the initial turbidity of 10.3 NTU can be reduced to 0.43 NTU.Coagulation performance results showed that the PATC-PDMDAAC had an organic and inorganic ratio of 0.15 and exhibited excellent removal efficiency at p H 9.0,dosage of1.80mg/L,sedimentation time of 30 min,and a stirring speed of 110 r/min.The structure and physicochemical properties of PATC-PDMDAAC were analyzed by Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis/differential scanning calorimetry(TG/DSC),X-ray diffraction spectroscopy(XRD),and scanning electron microscopy–energy dispersion spectrum(SEM-EDS).The compound flocculant produced new functional groups exhibiting great thermal stability,and the complex chemical reaction between the two monomers generated new substances with reticular structures.The zeta potential and three-dimensional fluorescence spectrum were used to analyze the changes of different p H values of simulated water samples with different dosages,and the characterization analysis suggested that the reaction mechanism between PATC-PDMDAAC and low temperature and low turbidity water may be due to the electric neutralization and adsorption bridging.Based on the investigation of turbidity removal rate of low temperature and low turbidity water with different dosage and flocculation time,it is found that under the condition of the appropriate dosage of flocculant,the particles collide effectively,and the dosage too high or too low is not conducive to the treatment of low temperature and low turbidity water.In order to better implement the preparation of this study is PATC and PATC-PDMDAAC flocculant in the practical application of low temperature and low water treatment,this study adopts the Xiangjiang river real low temperature and low water as treatment object,analyzing the conventional flocculants PAC and PATC PATC-PDMDAAC’s handling of the actual samples,the results show that laboratory preparation of flocculant on the Xiangjiang river actual low temperature and low water has good treatment effect,and compared with traditional flocculants,composite flocculant can not only guarantee good processing effect,but also can reduce the dosing amount of coagulant.When the dosage of patc-pdmdaac is 3.6 mg/L,the turbidity of the actual low temperature and low turbid water in xiangjiang river can be reduced to 0.45 NTU,and the same dosage of PATC can reduce the turbidity to 0.58 NTU.