A tube-in-tube membrane microreactor for tertiary treatment of urban wastewaters by photo-Fenton at neutral pH: A proof of concept

This work presents a disruptive approach to promote highly-efficient photo-Fenton process at neutral pH under continuous mode operation. The system consists of a tube-in-tube membrane reactor designed for continuous-flow titration of low iron doses to the annular reaction zone (ARZ). A concentrated acidic ferrous ion (Fe²⁺) solution is fed by the lumen-side of the membrane, permeating through the membrane pores (inside-out mode), being dosed and uniformly delivered to the membrane shell-side. Polluted water, containing amoxicillin (AMX) and oxidant (H₂O₂), flows continuously in the reactor annulus (space between the membrane shell-side and an outer quartz tube). The catalyst radial dispersion is enhanced by the helicoidal movement of water around the membrane shell-side, efficiently promoting its contact with H₂O₂ and UV light. The efficiency of photochemical and photocatalytic oxidation was evaluated as a function of catalyst dose, catalyst injection mode (radial permeation vs injection upstream from the reactor inlet), light source (UVA vs UVC) and aqueous solution matrix (synthetic vs real wastewater). At steady-state, photo-Fenton reaction with Fe²⁺ radial addition, driven by UVC light, showed the highest AMX removal for synthetic (∼65%, removal rate of 44 μM_AMX/min, using [Fe²⁺]_ARZ = 2 mg/L and [H₂O₂]_inlet = 10 mg/L) and real municipal wastewaters (∼45%, removal rate of 31 μM_AMX/min, with [Fe²⁺]_ARZ = 5 mg/L and [H₂O₂]_inlet = 40 mg/L), with a residence time of only 4.6 s.

Experimental data on the relationship between dyes sensitizers and wavelength during the photocatalytic degradation of diclofenac

Sensitizers are being used to improve the photocatalytic activity of semiconductors in the visible light region of the solar spectrum. Different types of dyes are reported as sensitizer agents, such as ruthenium complex molecules, porphyrins and Pt complexes, which are critically assessed because they are hazardous substance. Therefore, it is necessary to replace these compounds with safer sensitizer like organic dyes. This work evaluated the photocatalytic degradation of diclofenac using two different types of organic dyes (Perinaphtenone and Eosin-Y) as sensitizer agents. The catalyst concentration [0.15; 0.35 g/l], source of light (UVA - Vis) and type of dye were evaluated. The data obtained can be useful to classify organic dyes that could be employees as sensitizers and which is the wavelength more adequate to use as an energy source. The Kapp for the reaction has values between 1*10^-3 to 5*10^-3 min^-1 for UVA, 3*10^-4 to 3*10^-3 min^-1 for Vis and 2*10^-3 to 6*10^-3 min^-1 for UV-Vis.

Intensification of the O3/TiO2/UV advanced oxidation process using a modified flotation cell

A novel approach for the ozone and TiO₂ intensification process for wastewater treatment is presented using a modified flotation cell.

Visible-light activation of TiO2 by dye-sensitization for degradation of pharmaceutical compounds

A kinetic model for the dye sensitization process of TiO₂ that considered photon absorption was developed.