Photocatalytic degradation of trace-level of Microcystin-LR by nano-film of titanium dioxide

Abstract

Microcystins, a group of hepatotoxin produced by cyanobacteria in eutrophic freshwater, have proven unreliable to be removed by conventional treatments. In this study, the photocatalytic degradation experiments of Microcystin-LR were conducted using nano-TiO 2 thin film, prepared by solgel and dip-coating method, with low UVA intensity irradiation. Analysis results from SPE (solid-phase extraction) combined with HPLC method showed that Microcystin-LR whose initial concentration (μg/L) around that occurs naturally was easily to be removed by photocatalytic system. The degradation efficiency of toxin was influenced by the pH conditions, initial concentration and UV intensity. The maximum initial rate of photocatalytic degradation occurred at pH 4 and over 95% of 20 μg/L Microcystin-LR was decomposed within 120 min under 400 μW/cm 2 UV illumination. The kinetic equations and parameters revealed that degradation reaction of trace level MC-LR, which was depicted by LangmuirHinshelwood kinetics model, was in accordance with pseudo first order kinetics process in appearance well. Under the condition of pH=6.7, irradiation intensity=400 μW/cm 2 and initial concentration=20 μg/L, the corresponding pseudo-first-order rate constant k and half-life were determined to be 0.0157 min −1 and 44 min, respectively. During the range of 200-1000 μW/cm 2 , the degradation rate increases with incident intensity to the 0.82 power and the corresponding apparent quantum yield (Φ app ) was found to be 5.19× 10 -8 g/J approximately.

Photocatalytic degradation of eleven microcystin variants and nodularin by TiO2 coated glass microspheres

“…Consequently the removal of these toxins during water treatment is a key concern. The photocatalytic destruction of cyanotoxins using TiO2, particularly microcystin-LR, has been studied in detail and reported to be a very effective process for removal of these toxins from water [1][2][3][4][5][6][7][8][9].…”

Photocatalytic oxidation of gaseous benzene over nanosized TiO2 prepared by solvothermal method

“…Titanium (IV) oxide (TiO 2 ) has attracted much attention mainly in expection of being applied to environmental photocatalytic processes [1][2][3][4][5] . For the realization of its application, development of highly active TiO 2 photocatalyst is desired.…”

Photocatalytic degradation of cyanotoxins and water taste and odor compounds using TiO2 based nanocatalysts and polyoxometalates

“…A variety of traditional water treatment methods, including coagulation/sedimentation [143], activated carbon adsorption [144] and membrane separation [145], have been attempted for the removal of cyanotoxins and taste and odor compounds, but with limited success. Previous studies have demonstrated that TiO 2 photocatalysis [11][12][13][14][15][16][17][18] can effectively destroy cyanotoxins in aqueous solution and emphasis was given to the mechanistic understanding of the process by identification of the intermediates formed during photocatalysis [19].…”

“…Previous studies have demonstrated that TiO 2 photocatalysis can effectively degrade both cyanotoxins as well as taste and odor compounds in aqueous solutions [12,13,17,18,20,23,[234][235][236].…”

“…For these reasons, the removal of these compounds from water is very important for its use and consumption. [11][12][13][14][15][16][17][18]20] that can be effectively applied for the degradation of cyanotoxins and taste and odor compounds in aqueous solution [15,[20][21][22][23][24], while studies concerning the mineralization of cyanobacterial metabolites are limited. [25,26], chlorination [27], ultra-sonication [28], photolysis [29], TiO 2 /UV-A [18,19,30,31] and N-TiO 2 /UV-A [18].…”