Study On The Preparation Of The Activated Carbon-supported TiO₂ Catalyst And Its Removal Of Microcystin-LR In Environmental Water

The occurrence of toxic water bloom of cyanobacteria algae has been a serious pollution problem in recent years.Microcystins(MCs)is a group of extremely hepatotoxic toxin produced by the species of cyanobacteria.Due to cyclic structure and interval double-bond,the MCs pollution is characteristic of trace-level,recalcitrant and complex in eutrophic freshwater.It has been proven difficult to be removed by conventional water treatments and constitute potential hazard to public health.some necessary measures of removing MCs which are high efficiency ,safe ,stable has been urgently needed.The doped titanium dioxode supported on activated carbon was prepared by sol-gel method.The effects of adsorption and oxidation on the removal of microcystin-LR were investigated with this catalyst.The TiO₂ Sol was prepared by butyl titanate as precursor, ethanol as solvent, acetic acid as suppression hydrolysis.Effect of different raw materials ratio on the formation of the Sol-gel turbidity and arrive at the time was investigated.The results showed that optimal system in proportion as V (butyl titanate): V (ethanol): V (acetic acid): V(water) = 5: 20: 10: 1.The adoption of the mulching impregnated TiO₂ photocatalytic load-activated carbon substrate.The experimental techniques of XRD ,SEM and TEM were used to characterize the prepared specimens. The effects of loading times on removal of microcystin-LR were investigated.The results showed that both adsorption and oxidation were the most effective under the photocatalyst that coated one time.When 3g/L doped photocatalyst was applied in 100μg/L microcystin-LR solution,the removal efficiency of microcystin-LR at 15min and 20min were 94% and almost 100% respectively. Moreover,this combined roles of the activated carbon and TiO₂ showed a synergetic effects ,which enhanced the absorption and shifted target contaminant to the surface of TiO₂ particles continuously.The effects of adsorption and oxidation on the removal of microcystin-LR were investigated with this catalyst.Models on the quasi second-order of Lagergren and the internal particles diffusion were used to fit the adsorptive data,while Langmuir-Hinshelwood and Freundlich-Hinshelwood models were used to fit the oxidation data.The results showed that adsorption and oxidation process were explained by quasi second-order of Lagergren and Langmuir-Hinshelwood models respectively,among which degradation rate constant would gradually dwindle with the increase of the initial concentration of MCLR ,while the adsorption equilibrium constant kept invariant.The effects of adsorption and oxidation on the removal of microcystin-LR were investigated with this catalyst,then supported and suspenged TiO₂ photocatalysts for MCLR removals were compared.The results showed that TiO₂/GAC has not only favorable absorption and photocatalysis activity,but also posses synergistic effect.Finally natural lake water during cyanobacteria outbreak stage was adsorbed and then photo-catalytic degraded by TiO₂/GAC adsorption column,of which MCLR was 19.6μg/L.And the dynamic adsorption and the degeneration activity of reuse of the catalyst were inspected simultaneously.The results showed that effluent during the 37h was lower than the definition standard,and then were nearly degraded completely in 15 min,especially the catalyst also has the high adsorption and photochemical activeness after reused two times.