TiO2 photocatalysis of naproxen : effect of the water matrix, anions and diclofenac on degradation rates

The TiO2 photocatalytic degradation of the active pharmaceutical ingredient (API) naproxen (NPX) has been studied using a laboratory-scale photoreactor equipped with a medium pressure mercury lamp. UV/TiO2 photocatalysis proved highly efficient in the elimination of NPX from a variety of water matrices, including distilled water, unfiltered river water and drinking water, although the rate of reaction was not always proportional to TiO2 concentration. However, the NPX degradation rate, which follows first-order kinetics, was appreciably reduced in river water spiked with phosphate and chloride ions, a dual anion system. Addition of chloride into drinking water enhanced the TiO2-photocatalysed degradation rate. Competitive degradation studies also revealed that the NPX degradation was greatly reduced in the presence of increased concentrations of another API, diclofenac (DCF). This was established by (i) the extent of mineralization, as determined by dissolved organic carbon (DOC) content, and (ii) the formation of intermediate NPX by-products, identified using liquid chromatography and electrospray ionization (positive and negative mode) mass spectrometry techniques. This study demonstrates that competition for active sites (anions or DCF) and formation of multiple photoproducts resulting from synergistic interactions (between both APIs) are key to the TiO2-photocatalysed NPX degradation

Fe Doped Titania Photocatalyst for Degradation of Methyl Orange

Surface modification of titanium dioxide (TiO2) by doping method is one of the ways to lower TiO2 band gap and thus increasing its absorption to the visible region. This study was conducted to demonstrate a feasible modification of TiO2 by using iron (Fe) metal as the doping agent. Fe-doped TiO2 photocatalyst with the ratio of 1:1 was prepared by using the wet-impregnation method. The prepared photocatalyst was applied for the degradation of methyl orange (MO) under ultraviolet (UV) and visible light irradiation. A 0.20 g/L of Fe-doped TiO2 efficiently degraded 82.8% and 74.4% of 5 ppm MO under UV light and visible light irradiation, respectively. MO removal up to 85%was attained using bare TiO2 in the presence of UV compared to only 11% under visible light. The UV-Vis Diffuse Reflectance spectroscopy confirmed the reduction of TiO2 band gap upon Fe doping

Growth performance of roselle (Hibiscus sabdariffa) under application of food waste compost and Fe3O4 nanoparticle treatment

Purpose Utilization of food waste as composting materials offers a sustainable solution to manage waste and reduce reliance on fertilizers. Method This study is focused on the efficiency of food waste compost and the effect of the addition of magnetite (Fe3O4) nanoparticles on the growth and heavy metals uptake by roselle (Hibiscus sabdariffa) for the cultivation period of 127 days. Five different treatments were applied, namely soil (S), food waste compost (F), a mixture of soil and Fe3O4 (SM), a mixture of soil and food waste compost (SF), and a mixture of soil, food waste compost, and Fe3O4 (SFM). Results After 127 days of cultivation, the plant height averaged at 803 mm with 26 leaves produced across all treatments. Total leaf area, fruit production, and biomass yield were different (P 0.05) from its control (without Fe3O4) in relation to growth performance. Conclusion The findings of this study showed that food waste can be applied in composting to promote plant growth. Therefore, it can be considered as a substitute for chemical fertilizers. Meanwhile, the application of Fe3O4 appeared to be experimental-condition dependent

Growth performance of roselle (Hibiscus sabdariffa) under application of food waste compost and Fe3O4 nanoparticle treatment

Purpose Utilization of food waste as composting materials offers a sustainable solution to manage waste and reduce reliance on fertilizers. Method This study is focused on the efficiency of food waste compost and the effect of the addition of magnetite (Fe3O4) nanoparticles on the growth and heavy metals uptake by roselle (Hibiscus sabdariffa) for the cultivation period of 127 days. Five different treatments were applied, namely soil (S), food waste compost (F), a mixture of soil and Fe3O4 (SM), a mixture of soil and food waste compost (SF), and a mixture of soil, food waste compost, and Fe3O4 (SFM). Results After 127 days of cultivation, the plant height averaged at 803 mm with 26 leaves produced across all treatments. Total leaf area, fruit production, and biomass yield were different (P 0.05) from its control (without Fe3O4) in relation to growth performance. Conclusion The findings of this study showed that food waste can be applied in composting to promote plant growth. Therefore, it can be considered as a substitute for chemical fertilizers. Meanwhile, the application of Fe3O4 appeared to be experimental-condition dependent

Heavy Metals Leachability In Fly Ash Remediated Soil

This study focused on recycling fly ash, a by-product of power plants, to stabilize heavy metals in contaminated soil. Fly ash collected from the Sejingkat power plant in Kuching, Sarawak, was applied to soil from the roadside. The potential risk associated with the application of fly ash on the soil was assessed in terms of heavy metal concentration in leaching experiments. Deionized water and acidified water (deionized water acidified to pH 4.0 with nitric acid) were used as leaching agents and and passed through columns filled with untreated soil and soil-fly ash mixture (9:1). The Cd, Zn, Ni, Mn, Cu and Fe content in leachates were asessed at Day 0, 5, 10 and 15 after stabilization. Leacheate from the soil-fly ash mixture with acidified water had low pH range (4.5-6.2) compared to soil-fly ash mixture with deionized water (5.8-6.2), and this affected the solubility of heavy metals. The concentration of the metals in soil-fly ash mixture with acidified water leacheate was higher than soil-fly ash mixture with deionized water. In contrast, untreated soil did not show any clear pattern of heavy metal reduction except for Ni. Except for Cr, the concentrations of all the tested heavy metals in treated soil decreased with increasing pH as well as electrical conductivity from Day 0 to 15 of contact time. The results suggested that the solubility of heavy metals in soil leacheate was influenced by pH and the type of leaching agent. Therefore, the application of fly ash as a soil remediation agent may be a sustainable option to manage this by-product

Photolysis and TiO₂-catalysed degradation of diclofenac in surface and drinking water using circulating batch photoreactors

The occurrence of diclofenac (DCF) as an emerging pollutant in surface waters and drinking water has been attributed to elevated global consumption and the inability of sewage treatment plants to remove DCF. In this study, DCF spiked drinking water and river water was subjected to photolysis and TiO₂ photocatalytic treatments in a circulating laboratory-scale (immersion-well) and a demonstration-scale loop reactor (Laboclean). The operational parameters for the immersion-well reactor were optimised as follows: TiO₂ P25 loading, 0.1 g L⁻¹; natural pH, 6.2; initial concentration, 30 mg L⁻¹; water type, distilled water. Complete DCF removal was realised within 15 min under the optimised conditions using the immersion-well reactor. Sunlight-mediated photochemical degradation required a prolonged exposure period of up to 360 min for complete DCF removal. DCF in distilled and drinking water was efficiently degraded in the larger Laboclean reactor. Differences were, however, observed based on their pseudo-first-order rate constants, which implies that the water matrix has an effect on the degradation rate. Six major photoproducts, 2-(8-chloro-9H-carbazol-1-yl)acetic acid, 2-(8-hydroxy-9H-carbazol-1-yl)acetic acid, 2,6-dichloro-N-o-tolylbenzenamine, 2-(phenylamino)benzaldehyde, 1-chloromethyl-9H-carbazole and 1-methyl-9H-carbazole, generated from TiO₂ photocatalysis of DCF were identified by liquid chromatography–mass spectrometry (LCMS) and Fourier transform–ion cyclotron resonance–mass spectrometry (FT-ICR-MS). This work has shown that photocatalytic degradation kinetics of DCF are dependent on both the geometry of the photoreactor and the nature of the water matrices