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UV-C assisted disinfection processes are among the well-known tertiary processes for water reuse, wastewater reclamation and domestic water disinfection. However, treated wastewaters normally contain several organic compounds and pollutants that can be partially degraded under UV-C irradiation to different by-products, often more toxic than their parent compounds, and/or, for longer treatment times, completely mineralized. For this reason, kinetic modeling of pollutants degradation in UV-C assisted processes is of crucial importance in plants design. This work aims to the characterization of a reactor configuration consisting of 6 lamps placed following a symmetric hexagonal geometry. Specifically, a mathematical model is proposed to estimate the mean optical length and degradation kinetics for UV-C and UV-C/H2O2 processes. The model has been tested with different reference organic compounds and represents a significant characterization of a modular geometric unit used in a great variety of applications. Finally, the characterized reactor was used to estimate the quantum yield of direct photolysis at 254 nm ( Φ 254 CPC = ( 8.04 ± 0.36 ) · 10 - 3 mol · ein - 1 ) and kinetic constant of reaction with hydroxyl radical of cetylpyridinium chloride (CPC) ( ( 1.11 ± 0.0778 ) · 10 9 L · mol - 1 · s - 1 ) , an emerging pollutant of wide interest.

This paper aims to evaluate how condensational growth may be used to improve the performances of a Venturi scrubber in removing soot particles, which are among the most relevant air pollutants emitted in industrial and power plants exhaust gases. Former studies on this system, called Condensational Growth assisted Venturi scrubbers (CGVS), suggested that the most relevant step to address their efficiency is the assessment of the amount of water that condense on the soot particles, which determines the actual aerosol size distribution entering the Venturi. Unfortunately, a definite physical mathematical model to predict the actual condensational growth of an ensemble of non-spherical particles is not yet available and experimental investigation is better suited to assess this point. This study reports experimental data on the size distribution achieved by exposing model soot particles to a water supersaturated gas for different residence times. The obtained size distributions are used to estimate the efficiency of a Venturi scrubber in removing the water-soot aerosols, allowing a comparison with the removal of parent soot particles. The experiments were carried out at lab scale by using a laminar-flow growth tube, a simple device to perform a controlled condensational growth. The experiments indicated that, even for a hydrophobic material as soot, condensational growth is effective even at supersaturation levels as low as 1.02. Liquid-solid aerosols from nearly 2 to >3 times larger than the parent particles are produced with a supersaturation level lower than 1.15. Finally, the analysis of experimental data indicated that the fraction of particles subjected to condensational growth is relevant. Indeed, calling as ψ the fraction of particles that become larger than the 98% percentile of the original particle size distribution, we found that ψ can be as high as 78%. The analysis of data indicated that an appreciable linear correlation exits among ψ and the 95th percentile of the supersaturation level, S95, while not being dependent on the exposure time. The experimental evidences suggest that the adsorption of water molecules over the soot surface overcome the effects of hydrophobicity and of line tension effects, favouring condensation of water over the soot surface and leading to a higher nucleation rate even at low supersaturation. Application of the Venturi scrubber model to the water-soot aerosol leaving the growth tube indicate that the CGVS may remove particles with an efficiency far higher than that achieved by the stand alone Venturi. For a given Venturi's throat length and velocity and a given liquid-to-gas ratio, the CGVS efficiency depends almost linearly on ψ and, in turns on S95. Experimental and model results suggested that the CGVS can be a valuable and effective device to capture soot particles and that condensational growth can be used as a retrofit method for existing units. © 2018 Elsevier B.V.

Photocatalytic degradation of atenolol in aqueous suspensions using specifically synthetized mesoporous based TiO2 materials as photocatalysts under UVC (254 nm) irradiation was investigated. A batch reactor and a UV lamp 16 W power were used to test the ATL removal with several initial concentrations of ATL (4.5 - 30 mg/L) and four synthetized TiO2 photocatalysts, characterized by different BET surface areas and average pore sizes. Moreover, the effect of solution pH (4.8 - 9.0) and of the oxygen presence were investigated. The performances of the synthetized photocatalysts were compared with commercial Degussa P25. The atenolol degradation was studied using different concentration of catalyst (50 and 1000 mg/L) showing a maximum removal efficiency of 65%. Although the new catalysts showed a lower efficiency when compared to commercial P25, they can be easily recovered from water being in the form of micro-aggregate, and then reused without remarkable changes. The experimental data were fitted using a pseudo first order kinetic model. © 2017 Elsevier Ltd. All rights reserved.

The presence of bromide ions in waters treated with ozone can lead to bromate ions and brominated compounds formation, potentially carcinogenic. This poses a need to remove the bromates through other treatment, as UV. In this work the effects of the water composition, and the corresponding variation due to oxidation, on the UV efficiency for the reduction of bromate to bromide ions in groundwater (GW) were investigated. For this purpose an experimental apparatus was specifically designed and experimental tests with ozone and with a UV lamp 6 W were performed. The experimental results show that the reduction of the bromates to bromides by UV is max 41% in GW, depending on ozone dose and initial bromate concentration. The experimental data were fitted with a first order model and the kinetic constant determined. The effects of the ozone and UV treatment on others groundwater components, as TOC and inorganic nitrogen, were taken into account and the corresponding influence on the bromate removal efficiency was evaluated. To this aim, comparative tests with UV in purified water (PW) (reagent grade) and GW spiked with controlled amount of bromates were performed. It was verified that the removal efficiency of bromate by UV increases with increasing of ammonia concentration, but decreases with increasing of TOC and when intermediate bromide species, produced by ozonation, are presents. © 2016 Elsevier Ltd. All rights reserved.

Recently the potential environmental hazard of photovoltaic modules together with their management as waste has attracted the attention of scientists. Particular concern is aroused by the several metals contained in photovoltaic panels whose potential release in the environment were scarcely investigated. Here, for the first time, the potential environmental hazard of panels produced in the last 30 years was investigated through the assessment of up to 18 releasable metals. Besides, the corresponding ecotoxicological effects were also evaluated. Experimental data were compared with the current European and Italian law limits for drinking water, discharge on soil and landfill inert disposal in order to understand the actual pollution load. Results showed that less than 3% of the samples respected all law limits and around 21% was not ecotoxic. By considering the technological evolutions in manufacturing, we have shown that during the years crystalline silicon panels have lower tendency to release hazardous metals with respect to thin film panels. In addition, a prediction of the amounts of lead, chromium, cadmium and nickel releasable from next photovoltaic waste was performed. The prevision up to 2050 showed high amounts of lead (30 t) and cadmium (2.9 t) releasable from crystalline and thin film panels respectively. © 2015 Elsevier B.V.