Electro-Absorbers: A Comparison on Their Performance with Jet-Absorbers and Absorption Columns

Abstract

This work focuses on the removal of perchloroethylene (PCE) from gaseous streams using absorbers connected with electrolyzers. Two types of absorption devices (jet absorber and absorption column) were compared. In addition, it has been evaluated the different by-products generated when a simultaneous electrolysis with diamond anodes is carried out. PCE was not mineralized, but it was transformed into phosgene that mainly derivates into carbon tetrachloride. Trichloroacetic acid was also formed, but in much lower amounts. Results showed a more efficient absorption of PCE in the packed column, which it is associated to the higher gas–liquid contact surface. Jet absorber seems to favor the production of carbon tetrachloride in gaseous phase, whereas the packed column promotes a higher concentration of trichloroacetic acid in liquid. It was also evaluated the scale up of the electrolytic stage of these electro-absorption devices by using a stack with five perforated electrode packages instead of a single cell. Clarification of the effect of the applied current density on the speciation attained after the electrolysis of the absorbent has been attempted. Experiments reveal similar results in terms of PCE removal and a reduced generation of gaseous intermediates at lower current densities.

Influence of current density and inlet gas flow in the treatment of gaseous streams polluted with benzene by electro-absorption

“…Thus, as it can be observed, there is a fluctuation of nearly 15% in the inlet measurements (188 ± 28 mg C L -1 ), that can be explained in terms of the high turbulence produced by the bubbling of air in the benzene tank. This dispersion is also observed in the mass flow fed and the average values was observed in the degradation of toluene [26]. Physical adsorption of benzene in water is not affected by the concentration of the electrolyte used (0.05 M H2SO4) [36].…”

“…Important parameters in electro-oxidation are electrodes material, electrolyte, current density and cell voltage [22][23][24][25]. This process is now developed at technology readiness levels (TRL) of 3-4, and the interest has been mainly focused on the removal of VOCs and odour substances [26][27][28][29][30] but applicability may be extended also to atmospheric pollutants. Hence, there is a great need for further research up to meet an industrial TRL of 7-9, and in the incoming years many scientific and technically sound works are expected on this topic.…”

Relevance of gaseous flows in electrochemically assisted soil thermal remediation

“…The size of the bubbles generated by the jet-absorber had a paramount influence on the mass-transport and on the removal pathway. Castañeda-Juárez et al [33] proposed the development of electro-absorption and photoelectro-absorption technologies to treat gases produced by a synthetic waste containing the highly volatile perchloroethylene (PCE). To do this, a packed absorption column coupled with a UV lamp and an undivided electrooxidation cell was used.…”

“…Furthermore, phenoxide anion, which is an important material in the pharmaceutical industry was also detected. Hence, electrochemical technology, coupled with other processes, contributes to the removal of contaminants present in gaseous flow, as well as it may generate important compounds during the regeneration of the absorbent [33]. It is important to highlight that estimated energy requirements and costs of the adsorptionabsorption-electrolysis, it is not easy to obtain for all information to do a complete techno-economic because depend manly on electrode materials, materials absorption or adsorption, reactor configuration, operational parameters, as well as the electricity cost varies for different gaseous effluents.…”

Production of value-added substances from the electrochemical oxidation of volatile organic compounds in methanol medium

“…Recently, the interest in the application of the anodic oxidation has also been shifted to the treatment of gases by combining the exhaustively evaluated anodic oxidation with gas/liquid absorption processes into a technology, the electrochemically assisted absorption, which is becoming a very promising alternative [21][22][23][24][25].…”