The Effect of Titanium Dioxide Alumina Beads on the Photocatalytic Degradation of Picloram in Water

Abstract

Photocatalytic degradation of pesticides with titanium dioxide (TiO(2)) and other catalysts has shown promise as a potential water remediation method. Titanium-based powders have been used in photocatalytic degradation studies but have limitations. The objective of this study was to determine picloram degradation in water using various UV light sources and low-pressure metal organic chemical vapor deposition titanium dioxide alumina beads (TDABs) as a catalyst. A triple-annular, flow-through photoreactor was used as a degradation chamber. A picloram test solution of 50 microg/mL was introduced to the photoreactor inlet and recycled for 10 h at a flow rate of 50 mL/min. Three ultraviolet light sources were compared for their photocatalytic capacity (UV-A, UV-B, and UV-C) both with and without TDABs. TDABs were added to the photoreactor at 1.8 g/cm(3). Dark treatments with and without TDABs were included to quantify hydrolysis or adsorption. A 500-microL aliquot was taken from the test solution 14 times during the 10-h recycling period. Sampling times ranged from 0 to 600 min (10 h). These aliquots were placed in a vial and analyzed by high performance liquid chromatography equipped with a photodiode array detector. Picloram was not significantly hydrolyzed or adsorbed to TDABs during the experiment. The picloram degradation rate with UV-A and TDABs (t(1/2) = 119.5 min) was greater than the degradation rate of UV-A alone (t(1/2)=2288 min). Picloram degradation was not enhanced by the presence of TDABs with either UV-B or UV-C. This may be attributed to inadequate TDAB densities and/or poor light penetration in the photoreactor. Rapid picloram degradation occurred with both UV-B and UV-C, regardless of the presence of TDABs with mean half-lives ranging from 7 to 18 min. These rates were 8 to 16 times faster than picloram degradation using UV-A with TDABs. TDABs' greatest photocatalytic effect was with the lowest energy light source (UV-A). However, picloram degradation was not enhanced when TDABs were combined with more powerful, shorter wavelength light.

Nanomaterials and plant abiotic stress in agroecosystems

“…Titanium has significant biological effects on plants, being beneficial at low levels but toxic at higher concentrations. Photo-catalytic degradation of pesticides with TiO 2 and other catalyst has shown promise as potential water remediation method (Lee et al 2003). Nano-TiO 2 can improve photosynthetic apparatus and enhance a plant's ability to capture sunlight, that affects the manufacture of pigments and the transformation of light energy to active electron and chemical activity and thus increase photosynthetic efficiency as in maize, especially under drought stress (Akbari et al 2014).…”

Electrochemical degradation of the herbicide picloram using a filter-press flow reactor with a boron-doped diamond or β-PbO 2 anode

“…SC-1 in the supplementary content file) is extensively used in many countries, being one of the many herbicides that are applied in the cultivation of sugarcane [1,2]. As noted by Padoley et al [3], nitrogen-containing heteroaromatic compounds and their derivatives may be potentially toxic and carcinogenic, thus posing risks to ecosystems and human health.…”

“…The degradation or removal of PCL from aqueous media has been investigated using different methods ever since the end of the 1960s, with varying degrees of success: photolysis [7][8][9][10][11], photocatalysis [1,[12][13][14], Fenton reaction [15,16], photoFenton reaction [10,17], electro-Fenton reaction [4], chemical oxidation and hydrolysis [11], biosorption [18,19], and biodegradation [20]. As far as we could ascertain, although electrochemical methods have been extensively used for the electrodegradation of organics [21], the degradation of PCL has only been investigated by the electro-Fenton process [4], when 30 mg L -1 PCL solutions were degraded.…”

Nano-sized titanium dioxide-induced splenic toxicity: A biological pathway explored using microarray technology

“…For example, silver nanoparticles can be used for fruit and vegetable preservation [1]; nano-copper particles are used as an additive in lubricants and plastics [2]. Particularly, titanium dioxide nanoparticles (TiO 2 NPs), owning excellent photocatalytic properties, anticorrosion and high stability [3,4], are used in paints, sunscreen cosmetics, food additive, drugs, antiseptics, etc. that might lead to tumor formation in the processes of innate and adaptive immunity [35].…”