Solar assisted photo degradation of wastewater by compound parabolic collectors: Review of design and operational parameters

Tanveer, Muhammad; Guyer, Gokce Tezcanli

doi:10.1016/j.rser.2013.03.053

Cited by 85 publications

(33 citation statements)

References 81 publications

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“…When dealing with solar photochemistry, the most important aspects of the process are constituted by reactor design and photon-harvesting techniques, critical for process performance. Although solar photochemical reactions can be performed in batch using standard laboratory glassware [57], flatbed reactors or tubular reactors featuring concentrating (or nonconcentrating) parabolic collectors (Figure 3A) are commonly used, especially for the treatment of wastewater, which is currently still the main application of solar photochemistry [58,59]. These devices are typically used under flow conditions and the reaction mixture is recirculated to ensure high conversions.…”

Section: Solar Photochemistrymentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

297

223

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Continuous-flow chemistry has recently attracted significant interest from chemists in both academia and industry working in different disciplines and from different backgrounds. Flow methods are now being used in reaction discovery/methodology, in scale-up and production, and for rapid screening and optimization. Photochemical processes are currently an important research field in the scientific community and the recent exploitation of flow methods for these methodologies has made clear the advantages of flow chemistry and its importance in modern chemistry and technology worldwide. This review highlights the most important features of continuous-flow technology applied to photochemical processes and provides a general perspective on this rapidly evolving research field. Microflow Technology and Photochemistry: A Perfect MatchThe use of light to promote chemical reactions has been exploited since the 18th century, but only recently a resurgence has been observed in synthetic organic chemistry, in particular due to the development of visible-light photoredox catalysis [1-5]. All transformations involving light (e.g., Figure 1A-D) must consider, besides classical chemical parameters (i.e., reaction conditions), the photophysical aspects of the sensitizer (see Glossary)/photocatalyst (when used), and the reactor design. The latter, although often neglected by chemists, is a critical aspect for the outcome of the studied chemical transformation. This includes, for example, the size, shape, and material of the reaction vessel, the characteristics and positioning of the light source(s), and heat-transfer properties, particularly when high-intensity lamps are used [6,7]. The engineering and technological aspects of photochemical processes are often at the basis of the irreproducibility and non-scalability of such transformations.According to the Beer-Lambert law, light transmittance decreases exponentially with the distance from the light source ( Figure 1F). For a standard batch reactor (diameter at least in the centimeter range), light intensity decreases considerably from the flask walls to the middle of the reaction mixture, resulting in slow reactions and nonhomogeneous irradiation of the reaction mixture. Performing photochemical reactions in microchannels (ID < 1 mm) allows a higher and more homogeneous photon flux, resulting in shorter reaction times and consequently less side-product formation due to over-irradiation, often observed in batch [8,9]. Another advantage of microflow chemistry, correlated with the large surface:volume ratio, is improved heat and mass transfer, with the possibility to perform mass-transfer-limited multiphasic reactions efficiently [10]. Reactive chemicals and intermediates can be handled more safely in flow than in batch, as no accumulation of dangerous components occurs within the confined reactor volume due to the continuous nature of the process. Together, these result in often faster, safer, and higher-yielding reactions, with the possibility to perform reactions under condition...

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Section: Solar Photochemistrymentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

297

223

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“…An improvement on the removal efficiency of the hybrid process with an increase in the TiO 2 −SiO 2 dosage is not remarkable for concentrations of >0.4 g L −1 . High turbidity of the solution caused by high catalyst loading leads to a reduction in UV light penetration into the solution . A further increase in the TiO 2 −SiO 2 dosage from 0.4 to 0.6 g L −1 decreased the removal rate of AF and MG dyes from 59 and 89% to 55 and 82%, respectively.…”

Section: Resultsmentioning

confidence: 99%

Hybrid Homogeneous and Heterogeneous Photocatalytic Processes for Removal of Triphenylmethane Dyes: Artificial Neural Network Modeling

Eskandarloo

Badiei

Behnajady

et al. 2016

CLEAN Soil Air Water

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Removal of two triphenylmethane dyes, Acid Fuchsin (AF) and Malachite green (MG), was studied by hybrid advanced oxidation processes of homogeneous (UV/Fe 2þ /H 2 O 2 ) and heterogeneous (UV/TiO 2 ÀSiO 2 ) photocatalysis. A comparison of various processes for removal of model pollutants was performed. The results showed that the utilizing hybrid photocatalytic processes in the presence of silica leads to rapid removal of pollutants, which may be ascribable to the synergistic influence of produced various radical species. The effects of operational variables were studied on the efficiency of the UV/Fe 2þ /H 2 O 2 /TiO 2 ÀSiO 2 hybrid process. An artificial neural network (ANN) model was intended to predict the removal efficiency of the UV/Fe 2þ /H 2 O 2 /TiO 2 ÀSiO 2 hybrid process under different operational conditions. The results indicated that there is a good concurrence between the ANN predicted values and experimental results with a correlation coefficient of 0.9873 and 0.9774 for removal of AF and MG dyes, respectively. The designed neural network model gives a dependable technique for modeling the removal efficiency of the UV/Fe 2þ /H 2 O 2 /TiO 2 ÀSiO 2 hybrid process. Moreover, the relative significance of each variable was computed based on the input-hidden and hidden-output connection weights of the neural network model. The initial concentration of dyes was the most significant variable in the removal efficiency.

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“…1) with the following key points: (1) the artificial illuminator is planar and produces steady-state UV radiation of intensity similar to that of solar illumination (20–30 W/m 2 ) [4–5 21]; (2) the reactor is a rectangular cell, so that the influence of the UV intensity is only two-dimensional; (3) the thickness of the reactor is small to diminish the shielding effect in the non-illuminated region [22]; and (4) most importantly, the reactor operates based on a PFR as the absorbent tube in the solar collecting reactors [4,23–26]. …”

Section: Methodsmentioning

confidence: 99%

Impact of ultrasonic dispersion on the photocatalytic activity of titania aggregates

Le¹,

Babick²,

Kühn³

et al. 2015

Beilstein J. Nanotechnol.

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SummaryThe effectiveness of photocatalytic materials increases with the specific surface area, thus nanoscale photocatalyst particles are preferred. However, such nanomaterials are frequently found in an aggregated state, which may reduce the photocatalytic activity due to internal obscuration and the extended diffusion path of the molecules to be treated. This paper investigates the effect of aggregate size on the photocatalytic activity of pyrogenic titania (Aeroxide® P25, Evonik), which is widely used in fundamental photocatalysis research. Well-defined and reproducible aggregate sizes were achieved by ultrasonic dispersion. The photocatalytic activity was examined by the color removal of methylene blue (MB) with a laboratory-scale setup based on a plug flow reactor (PFR) and planar UV illumination. The process parameters such as flow regime, optical path length and UV intensity are well-defined and can be varied. Our results firstly show that a complete dispersion of the P25 aggregates is not practical. Secondly, the photocatalytic activity is not further increased beyond a certain degree of dispersion, which probably corresponds to a critical size for which UV irradiation can penetrate the aggregate without significant obscuration.

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Solar assisted photo degradation of wastewater by compound parabolic collectors: Review of design and operational parameters

Cited by 85 publications

References 81 publications

Flow Photochemistry: Shine Some Light on Those Tubes!

Flow Photochemistry: Shine Some Light on Those Tubes!

Hybrid Homogeneous and Heterogeneous Photocatalytic Processes for Removal of Triphenylmethane Dyes: Artificial Neural Network Modeling

Impact of ultrasonic dispersion on the photocatalytic activity of titania aggregates

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