Photoreactors for Wastewater Treatment: A Review

Abstract

Photochemical oxidation of organic and inorganic pollutants is rapidly becoming an attractive technique for water purification and wastewater treatment. Since artificial sources of light require much energy delivery, this method is recommended for toxic contaminants in a specific concentration range below the recommended levels for recovery and above the levels for conventional biological treatment. Selection of a light source and an oxidation system and determination of key-parameters play an important role in the treatment efficiency. Sufficient UV penetration into the radiated liquid is of crucial importance; especially for an opaque environment the UV radiation is only available very close to the UV lamp surface. High mass transfer rates for efficient interaction between the pollutant and the photocatalyst and for high oxygen uptake at the gas-liquid interface is another requirement for practical applications. In this regard, reactor design for efficient wastewater treatment has been a challenging problem. Many types of photoreactors have already been studied, reported and patented. This paper presents a revision of some conventional and novel photoreactors equipped with UV/vis lamps or working under solar radiation for wastewater treatment in laboratory and industrial scales.

Plasmonic Titania Photocatalysts Active under UV and Visible-Light Irradiation: Influence of Gold Amount, Size, and Shape

“…The absence of oxygen in the tubes was checked chromatographically before starting irradiation. The suspensions were simultaneously photoirradiated with a 400 W high-pressure mercury lamp under magnetic stirring (500 rpm) in the irradiation system shown previously [36]. The temperature of the suspensions during photoirradiation was maintained at 298 ± 5 K using a thermostatically controlled water bath.…”

“…• min −1 ) and three scan ranges • , [35][36][37][38][39][40] • , and 42-47 • ), the slower one for narrower ranges being used for particle size Journal of Nanotechnology 3 determination. To determine primary particle sizes of gold deposits, XRD data were calculated using Scherrer's equation with appropriate corrections [37].…”

“…For testing visible activity, elimination of influence of NPs support (often active photocatalyst under UV irradiation, such as titania (shown above)) must be performed. It can be achieved by use of [36]:…”

Silver- and copper-modified decahedral anatase titania particles as visible light-responsive plasmonic photocatalyst

“…% in respect to titania) were photodeposited on titania in a sealed and deaerated (15 min Ar prebubbling) suspension of DAPs (500 mg) containing methanol (25 mL, 50 vol. %) and an aqueous solution of noble metal (AgNO 3 , CuSO 4 · 5H 2 O) under UV/vis irradiation [high-pressure mercury lamp of 22-mW light intensity, under magnetic stirring (500 rpm) in a thermostated water bath (298 AE 5 K), set-up shown and described elsewhere 56 ]. During the irradiation, the amount of generated hydrogen in the gas phase was measured every 15 min by gas chromatography (GC-TCD).…”

“…%) under UV/ vis irradiation (set-up used for metal photodeposition) and (2) oxidation of 2-propanol (5 vol. %) under vis irradiation [for two irradiation ranges: λ > 420 nm and λ > 450 nm: Xe lamp, water IR filter, quartz mirror, and cut-off filter Y45 and Y48, respectively (vis light intensity: 250 to 350 μW, lamp spectrum, and set-up shown previously) 42,56 ]. Amounts of liberated (1) carbon dioxide in the gas phase and (2) acetone in the liquid phase (after powder separation) were determined by gas chromatography (GC-TCD and GC-FID, respectively), details shown elsewhere.…”