Study On The Preparation, Speciation Analysis And Coagulation Effects Of A New Type Of Flocculating Agent Of Poly Titanium Chloride Series

In this paper,based on the extensive application prospect of titanium chloride flocculants,the preparation,speciation analysis and coagulation effects of novel polytitanium tetrachloride were discussed systematically.The humic acid（HA）,As（III）and Cr（VI）were used as natural organic matter（NOM）or inorganic pollutants in water.The coagulation effects of three novel polytitanium tetrachloride flocculants prepared in the experiments were studied.The basicity,pH,dosage,temperature and co-existing irons for coagulation effects of three polytitanium tetrachloride flocculants are researched.The speciation of Ti（Ⅳ）was accurately distinguished by Ti-Ferron complexation timed spectrophotometric method and calculated for kinetic parameters.The main research as follows:（1）Novel polytitanium tetrachloride（PTC）as inorganic flocculants were prepared by a slow alkaline titration method.In further study iron and polysilicic acid were doped to obtain polytitanium ferric chloride（PTFC）and polytitanium silicon chloride（PTSC）,respectively.The stability of three flocculants decreased with the basicity increase,which the precipitation was occured within a week with the basicity value of 2.5.However,three flocculants can stably storage for more than three months with other basicity values.（2）As for the removal of HA,under the acid condition,the coagulation effects of three flocculants was the best with the the basicity value of 1.5,especially the compound PTSC that is close to 100%.When it is under the neutral and weak acid conditions,the coagulation effects of PTC,PTFC and PTSC were better than alkaline conditions with the removal of HA over 95%.With the dosage increase,removal of HA reached to maximum and then tended to be stable.When the dosage was low,compound PTFC and PTSC showed better coagulation effects than PTC.Moreover,temperature has little influence on coagulation effects.And coagulation effects is not been strongly affected by co-existing ions except for SiO₃^2-and H₂PO₄^-,which showed obvious inhibition effects with the removal of HA below 80%.To different molar ratio of Ti/Si of PTSC,the coagulation effects of PTSC for HA were better with the lower molar ratio of Ti/Si that meant higher content of Si.While the molar ratio of Ti/Si of 1:1,the stability of PTSC was worse.For actural water sample（east lake water）,the removal of HA were 86.58%,86.69%and 91.22%for PTC,PTFC and PTSC at the basicity value of 1.5,respectively,which performed good cogulation effects in actural water.（3）As for the removal of As（III）,the optimum cogulation effects of PTC for As（III）was obtaioned with the pH value of 6⁸,the basicity value of 1.5 and the dosage of 100mg L^-1.For PTSC,with the pH value of 5⁸,the basicity value of 1.5 and the dosage of 70mg L^-1,PTSC showed the optimum cogulation effects for As（III）.Besides,with the same conditions with PTSC except for the pH value of 5⁷,the PTFC had the most excellent property.There was no significant difference with different molar ratio of Ti/Si of PTSC,which the removal of As（III）was exceeding 95%.When three flocculants were applied to actural water sample,the removal of As（III）for PTC,PTSC and PTFC were 95.57%,96.69%and 96.08%,respectively.The results indicated good cogulation effects in actural water for As（III）.（3）As for the removal of Cr（VI）,the best coagulation effects of PTC,PTSC and PTFC were investigated.It showed that the removal of Cr（VI）was over 95%with the basicity value of 1.5 and the pH value of 3⁵.The coagulation effects were firstly rised and then tended to be stable with the dosage increase.In addition,three flocculants had a wider application range due to little influence on coagulation effects of PTC,PTSC and PTFC by temperature and co-existing ions.The coagulation effects of PTSC for Cr（VI）exhibited no significant difference with different molar ratio of Ti/Si（1:1,5:1,10:1,15:1）of PTSC,which the removal of Cr（VI）was over 95%.Three cogulations also had good coagulation effects for actural water sample,indicating a green and efficient method for dealing with Cr（VI）containing wastewater.（5）The speciations of Ti（Ⅳ）were accurately distinguished by Ti-Ferron complexation timed spectrophotometric method.The results showed that the basicity value had little effects on kinetic constant k₁ and k₂,but had much effects on speciations of Ti（Ⅳ）.The content of Ti_b was on the rise with the basicity value increase,and it was the main species in three kinds of hydrolysis speciation.Only when the basicity value was high（B=2.5）,the content of Tic was evidently added to be dominant speciation of 54.40%.Therefore,the speciations of Ti（Ⅳ）were analysed by Ti-Ferron complexation timed spectrophotometric method.