Preparation Of Clay-modified Titanium-based Flocculant And The Application In Black And Odor Water

Water environmental pollution is one of the main challenges facing global environmental governance.Among them,coagulation is a key process in water treatment and restoration,and the choice of flocculant is very important to the coagulation effect.Titanium salt is an emerging environmentally friendly flocculant,has been applied in water environment treatment.In this paper,a new type of composite flocculant:sepiolite modified titanium-based flocculant（TXC-SE）,was prepared based on the sol-gel method,using titanium tetrachloride and natural clay sepiolite as raw materials;The coagulation effect and coagulation mechanism of the composite flocculant under different environmental conditions were studied;applied it to the treatment of black and odorous water bodies pollution,and further explored the treatment effect of the composite flocculant and the environmental effect.The main conclusions drawn in this paper are as follows:（1）In this paper,the sepiolite modified titanium-based flocculant was prepared by the sol-gel method.In order to determine the best adding ratio of sepiolite,the coagulation effect of TXC-SE under different addition amounts of sepiolite was compared,and its production method was optimized.On the whole,When the addition amount of sepiolite is 0.5 g,its application effect was the best.The morphology and element composition of TXC-SE were characterized by scanning electron microscopy and energy spectrum line scanning.The results showed that there were a lot of rod-like structures on the surface of the titanium-based flocculant.,the element content of Mg and Si increased significantly.In addition,the Zeta potential values under different dosages were tested,and the coagulation mechanism of TXC-SE was explored;the results showed that charge neutralization was the main coagulation mechanism of TXC-SE,and the phenomenon of catching and sweeping also existed in the coagulation process.（2）In the simulated water samples at different initial pH values,the optimal initial pH value of TXC-SE treatment was determined to be 6-7.At the initial pH of the water sample,the turbidity and organic matter removal effect in the water sample was better after the coagulation treatment,and the effluent pH was also more suitable.The coagulation effects of three flocculants polyaluminum ferric chloride（PAFS）,titanium-based flocculant（TXC）and TXC-SE were compared in landscape water bodies,and it was found that TXC-SE had the best turbidity removal effect.The removal rate can reach 73.31%,and the highest removal rate of UV₂₅₄ was 42.24%.With the increase of the dosage,the effluent pH value of TXC and TXC-SE changes more steadily.In this paper,the flocculant was added to the overlying water of the black and odorous water simulated column sample to observe the coagulation effect of water samples of different depths.It was found that the turbidity of water samples at different depths gradually decreased,and the turbidity removal rate gradually increased;UV₂₅₄ decreased with the increase of time;the chemical oxygen demand（COD）showed a change after dosing first increased and then decreased,but the removal effect of COD was poor;the concentration of dissolved reactive phosphorus（SRP）gradually decreased,and the maximum removal rate of upper water was as high as 95.06%.Due to the difference in water depth,the effect of coagulation treatment was small different in depth,and it had a higher removal effect on pollutants in the overlying water.（3）The physical and chemical indicators of the overlying water and the sediment-water interface were measured by using portable DO,pH,conductivity electrodes and planar photoelectrode technology（PO）.The results showed that the conductivity of the overlying water showed a decreasing trend;the overlying water pH obtained by PO fluctuates between6.70-7.08.Below the sediment-water interface,the pH continued to decrease with time;DO content in the overlying water increased,and there was no significant change below the sediment-water interface.DGT-laible and dissolved ammonia nitrogen（NH₄⁺-N）and nitrate nitrogen（NO₃--N）and phosphate（PO₄³-）content changes were obtained in sediments using the diffusive gradients in thin films technology（DGT）and high-resolution dialysis technology（HR-Peeper）at 30 days after coagulation treatment.The results showed that the removal rate of dissolved NO₃--N in the overlying water was 28.8%,and the DGT-availability NO₃--N did not change significantly;the removal rate of dissolved PO₄³-was 88.9%,and the DGT-availability PO₄³-removal rate was 84.4%;the removal effect of NH₄⁺-N was poor.After 30 days of monitoring,the overlying water pollutants have been at a relatively low level.The flocs produced by TXC-SE flocculation were stable,and there was no phenomenon of floc rupture and release.In addition,the diffusion reaction model PROFILE was used to calculate the yield,combined with the net diffusion flux and the solid replenishment ratio R,the analysis showed that NH₄⁺-N and PO₄³-in sediments after flocculation treatment had the risk of releasing overlying water.Therefore,in the treatment of black and odorous water bodies,coagulation treatment needs to be combined with corresponding sediment treatment measures to achieve the treatment effect more efficiently.