| Activated silicic acid is made of sodium silicate,which is toxic to humans and inexpensive.However,polymerization degree and stability of PS are not as organic coagulant,which to some extent limit its application.In order to enhance the polymerization degree and stability of activated silicic acid,in this study,a certain amount of TiCl4 was added to the acidified sodium silicate solution during the activation process,and for the first time,examined the effects of activation temperature in the preparation of polysilicate-titanium?PTS?on its characteristics.The results indicate that with the increase of activation temperature?from 15 to 40??the dispersed particle size of PTS in solution increased gradually?from 11.09 to 13.5?m?,while zeta potential was slightly decreased?from-15 to-17.5mV?.At a higher activation temperature of 40?,the dispersed particle size,zeta potentials as well as the infrared spectrum of the prepared flocculant aid showed that,addition of titanium promoted polymerization of silicate and the degree of PTS polymerization was higher than polysilicate?PS?.Using the prepared PTS as a coagulant aid and Al2?SO4?3 as coagulant,the coagulation efficiency on turbidity removal for low temperature and low turbidity water has been studied.The results show that addition of a small amount of Al2?SO4?3?2mg Al/L?with an appropriate amount of PTS?i.e.7.5mg SiO2/L?coagulation exibited a good turbidity removal for the treatment of low temperature and low turbidity water.From the experimental results for systhetic water samples made with pure water and background alkalinity,when solution pH value ? 6.0,flocculation effect with PS is slightly better than PTS and,if solution pH value ? 7.0 flocculation effect with PTS as coagulation aid is noticeabley better than PS.Perticularly,when solution pH=8.0,coagulation effect with the aid of PTS was significantly greater than with PS as a coagulation aid.Finaly,for water samples made with tap water,when solution pH range from 6 to 8 turbidity removal by coagulation with the aid of PTS was much better than PS.In addition,at pH=7 PTS showed a much better coagulation aid effect for turbidity removal as compared with PS.In conclusion,this study demostrated that coagulation aid can improve turbidity removal efficiency and PTS could be a much better coagulation aid than PS for the neutral or alkaline low temperture and turbidity water.At the same time,when addition of PTS in coagulation is used to remove the humic acid in water,UV254 and DOC of the water after treatment were measured.The results show that the addition of PTS has improved the overall coagulant effect than that of PS,which can significantly increase the effect of DOC removal.When the dosage of Al2?SO4?3 is 4mg Al/L,Si/Al=1,and when solution pH=6,the rate of UV254 removal is higher than 90%,DOC in the water after treatment can reach as low as 2.031mg/L.or a DOC removal of 79.69%.In addition,the difference of ability between the two coagulants to remove the disinfection byproducts was investigated under the conditions of the optimum dosage of coagulant remove humic acid.The results show that,in the range of p H=58,the combination of coagulant?PTS or PS?and Al2?SO4?3 could reduce the production of disinfection by-products?TCAA and DCAA?,and the effect of PTS better than PS. |
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