Investigation Of Poly-titanium Salt Coagulant

Based on the previous studied on titianium-based coagulants,preparation of composite/compound polytitanium coauglant and its water treatment performance,including coagulation performance and floc properties,were investigated in this study.In addition,along with the development and increasing researches on coagulation-ultrafiltration,polytitanium salt was applied in coagulation-ultrafiltration hybrid process,and its effects on membrane fouling were comparatively evaluated with common used polyalumium chloride.The main research and conclusions are as follows:?1?Polytitanium-slicate-chloride?PTSC??prepared in a composite or co-polymerization methods?and polytitanium-slicate-sulfate?PTS S??prepared by composite method?was applied in humic acid?HA?-kaolin synthestic water treatment in this study.PTSC and PTSS were characterized by Fourier Transform Infrared Spectroscopy and results showed Si-O-Ti bonds were formed in both PTSC and PTSS.Jar test results indicated that,especially at low dosage,the coagulation performance,including turbidity and organic matter removal,was improved by PTSC/PTSS compared with polytitanium chloride?PTC?/polytitanium sulfate?PTS?.The DOC removal efficiency increased 15%at most by the addtion of PSiA.The effects of Si/Ti molar ratio and synthetic method on the coagulation performance were considered in this study.Based on the organic matter removal performance,the optimal Si/Ti molar ratio was 0.07 in this study.In addition,PTSC prepared by co-polymerization was more effective in turbidity removal than that prepared by composite;as for organic matter removal,polytitanium-slicate-chloride prepared by composite method was more effective.Compared with flocs formed PTC/PTS,flocs formed by PTSC and PTSS grew more rapidly and achieved larger size,and floc size increased with the Si/Ti molar ratio of PTSC/PTSS.Floc strength was enhanced by PTSC/PTSS,while floc recovery ablity was not improved.Additionally,floes formed by PTSC/PTSS was more open and loose compared with those formed by PTC/PTS.Effect of solution pH on the coagulation performance and floc characteristics of PTSC were also studied.The addition of PSiA could enlarge the application pH range of PTC.Expecially at pH 4 and 5,PTSC was more effective in turbidiy and NOM removal compared with those of PTC.In general,under acidic condition,flocs formed by PTSC were small,weak and loose but had good recovery ability;while under alkaline condition,large,strong and compact flocs with inferior recovery ability were generated by PTSC.The addition of PSiA could weaken the charge neutralization effect of polytitanium salt,and meanwhile enhance the adsoption and 'brige effect.Above all,PTSC and PTSS are fine hybrid coagulants for water treatment.?2?Polytitanium salts including PTC and PTS combined with coagulant aid-polydimthyldiallyamonium choloride?PDMDAAC?was applied in humic acid/fulvic acid?HA/FA?-kaolin water treatment.Coagulation performance and floc charateristics of PTC/PTS were significantly affteted by PDMDAAC dosage and dosing sequence?PTC/PTS dosed first donated as PTC/PTS-PDMDAAC;PDMDAAC dosed first donated as PDMDAAC-PTC/PTS?.The PDMDAAC optimal dosage for PTC and PTS was 2 mg/L and 3 mg/L,respecitively.Results showed that compared with use of PTC/PTS alone,turbidity and FA removal were both enhanced by PTC/PTS+PDMDAAC.The charge neutralization effect of PDMDAAC was more effective when PDMDAAC was dosed after PTC.In addition,this study revealed that floc size and floc growth rate of PTC/PTS+PDMDAAC and PDMDAAC+ PTC/PTS were also significantly improved.Floc strength and recovery ability were also increased by PTC/PTS+PDMDAAC.AS for PDMDAAC+ PTC/PTS,floc size,growth rate,strength and recovery ability were similar to those of PTS.Floc fractal dimension of these three coagulants was in an order of PDMDAAC+ PTC/PTS>PTC/PTS>PTC/PTS+PDMDAAC.In the studied pH range,the coagulation performance and floc characteristics of PTC/PTS were improved by the addition of PDMDAAC.?3?The application of polyacrylamide?PAM?as a coagulant aid of polytitanium salts in humic acid-kaolin water treatment was studied.Results showed that PTC/PTS-PAM?PTC/PTS dosed firstly?attained better natural organic matter removal and PAM-PTC/PTS?PAM dosed firstly?attained better turbidity removal.The addition of PAM also widened the application range of polytitanium salts.In consideration of coagulation performance and cost,the optimal dosage of PAM was 1 mg/L for both PTC and PTS in this study.Floc size was significantly enlarged by the PTC/PTS-PAM,while floc size of PAM-PTC/PTS attained similar size as that of PTC/PTS alone.Floc strength and recovery ability were also significantly improved by PTC/PTS-PAM.Moreover,flocs formed by PTC/PTS-PAM had a looser structure than those formed by PTC/PTS,while PAM-PTC/PTS floc and PTC/PTS floc had similar and more compact structure.In general,under acidic condition,flocs formed by PTC/PTS-PAM and PAM-PTC/PTS were small,weak and loose but had good recovery ability;while under alkaline condition,large,strong and compact flocs with inferior recovery ability were generated by PTC/PTS-PAM and PAM-PTC/PTS?4?Effects of epichlorohydrin-dimethylamine?DAM-ECH?used as coagulant aid on coagulation performance and floc properties of PTC and PTS in humic acid-kaolin water treatment was investigated in this study.The factors including DAM-ECH dosage,dosing sequence?PTC/PTS dosed first donated as PTC/PTS-DAM-ECH;DAM-ECH dosed first donated as DAM-ECH-PTC/PTS?and initial solution pH were considered.Results showed that the addition of DAM-ECH could enhance turbidity removal and dissolved organic matter?DOM?removal efficiency of PTC.The chosen dosage of DAM-ECH was 1.0 mg/L for the consideration of cost and coagulation performance.In addition,dosing sequence and solution pH of PTC and DAM-ECH also significantly affected coagulation behaviour and floc properties.Results indicated that residual turbidity was significantly reduced by the addition of DAM-ECH.Moreover,PTC/PTS-DAM-ECH achieved better DOM removal when pH<6,while DAM-ECH-PTC/PTS achieved better DOM removal efficiency when pH>6.DAM-ECH-PTC/PTS flocs grew faster and attained larger size compared with PTC/PTS-DAM-ECH flocs.Flocs formed by PTC/PTS-DAM-ECH and DAM-ECH-PTC both were stronger than those formed by PTC when pH<6.When pH was above 6,floc strength was only enhanced by PTC/PTS-DAM-ECH.Meanwhile,floc recovery ability was only improved by PTC/PTS-DAM-ECH.In addition,flocs formed by PTC/PTS-DAM-ECH were more compact than those formed by PTC,while flocs formed by DAM-ECH-PTC/PTS were looser.?5?This study compared the application of polytitanium chloride?PTC?and polyaluminum chloride?PAC?in coagulation-ultrafiltration?C-UF?process in real water treatment.Coagulation experiments were also conducted to determine the dosage of PTC and PAC.The chosen dosage for PTC and PAC was 18 mg/L as Ti and 8 mg/L as Al,respectively.Floc properties also comparatively studied to further analyze the membrane fouling.PTC formed larger and stronger flocs with higher Df value compared with those formed by PAC.Moreover,PTC coagulation effluent achieved less serious decline of permeates flux during the filtration process.The external membrane resistance of PTC C-UF process was lower than that of PAC C-UF process,while the cake layer formed by PTC coagulation effluent seemed to be more strongly attached on the membrane.For the total internal membrane resistance,PAC C-UF process achieved lower degree compared with PTC C-UF process.However,the irreversible membrane resistance of PAC C-UF process was more serious than that of PTC C-UF process.Thus,PTC was an effective coagulant for C-UF process.?6?The coagulation sluge was reused to prepared widely used photocatalyst TiO₂-The sludege prepared TiO₂ was anatase according to the X-Ray Diffraction spectrum when the calcination temperature was 600 ? or 700 ??Additionally,sluge prepared TiO₂ was applied to photocatalytic degradation of dye wastewater.The color removal performance of sluge prepared TiO₂ was slightly enhanced by the addition of PSiA and organic polymer?including PDMDAAC,PAM and DAM-ECH?due to that their effects on titanium hydrolysis process.