Vol.:(0123456789)
Topics in Current Chemistry (2020) 378:7
https://doi.org/10.1007/s41061-019-0272-1
1 3
REVIEW
Limitations and Prospects for Wastewater Treatment by UV
and Visible‑Light‑Active Heterogeneous Photocatalysis:
A Critical Review
Giuseppina Iervolino
1
· Ian Zammit
2
· Vincenzo Vaiano
1
· Luigi Rizzo
2
Received: 12 July 2019 / Accepted: 26 November 2019 / Published online: 16 December 2019
© Springer Nature Switzerland AG 2019
Abstract
Heterogeneous photocatalysis (HPC) has been widely investigated in recent decades
for the removal of a number of contaminants from aqueous matrices, but its application in real wastewater treatment at full scale is still scarce. Indeed, process and technological limitations have made HPC uncompetitive with respect to consolidated
processes/technologies so far. In this manuscript, these issues are critically discussed
and reviewed with the aim of providing the reader with a realistic picture of the
prospective application of HPC in wastewater treatment. Accordingly, consolidated
and new photocatalysts (among which the visible active ones are attracting increasing interest among the scientific community), along with preparation methods, are
reviewed to understand whether, with increased process efficiency, these methods
can be realistically and competitively developed at industrial scale. Precipitation
is considered as an attractive method for photocatalyst preparation at the industrial
scale; sol–gel and ultrasound may be feasible only if no expensive metal precursor is
used, while hydrothermal and solution combustion synthesis are expected to be difficult (expensive) to scale up. The application of HPC in urban and industrial wastewater treatment and possible energy recovery by hydrogen production are discussed
in terms of current limitations and future prospects. Despite the fact that HPC has
been studied for the removal of pollutants in aqueous matrices for two decades, its
use in wastewater treatment is still at a “technological research” stage. In order to
accelerate the adoption of HPC at full scale, it is advisable to focus on investigations under real conditions and on developing/improving pilot-scale reactors to better investigate scale-up conditions and the potential to successfully address specific
challenges in wastewater treatment through HPC. In realistic terms, the prospective
use of HPC is more likely as a tertiary treatment of wastewater, particularly if more
stringent regulations come into force, than as pretreatment for industrial wastewater
to improve biodegradability.
Extended author information available on the last page of the article
225
Reprinted from the journal
Chapter 7 was originally published as Iervolino, G., Zammit, I., Vaiano, V. & Rizzo, L. Topics in Current
Chemistry (2020) 378: 7. https://doi.org/10.1007/s41061-019-0272-1.
Topics in Current Chemistry (2020) 378:7
https://doi.org/10.1007/s41061-019-0272-1
1 3
REVIEW
Limitations and Prospects for Wastewater Treatment by UV
and Visible‑Light‑Active Heterogeneous Photocatalysis:
A Critical Review
Giuseppina Iervolino
1
· Ian Zammit
2
· Vincenzo Vaiano
1
· Luigi Rizzo
2
Received: 12 July 2019 / Accepted: 26 November 2019 / Published online: 16 December 2019
© Springer Nature Switzerland AG 2019
Abstract
Heterogeneous photocatalysis (HPC) has been widely investigated in recent decades
for the removal of a number of contaminants from aqueous matrices, but its application in real wastewater treatment at full scale is still scarce. Indeed, process and technological limitations have made HPC uncompetitive with respect to consolidated
processes/technologies so far. In this manuscript, these issues are critically discussed
and reviewed with the aim of providing the reader with a realistic picture of the
prospective application of HPC in wastewater treatment. Accordingly, consolidated
and new photocatalysts (among which the visible active ones are attracting increasing interest among the scientific community), along with preparation methods, are
reviewed to understand whether, with increased process efficiency, these methods
can be realistically and competitively developed at industrial scale. Precipitation
is considered as an attractive method for photocatalyst preparation at the industrial
scale; sol–gel and ultrasound may be feasible only if no expensive metal precursor is
used, while hydrothermal and solution combustion synthesis are expected to be difficult (expensive) to scale up. The application of HPC in urban and industrial wastewater treatment and possible energy recovery by hydrogen production are discussed
in terms of current limitations and future prospects. Despite the fact that HPC has
been studied for the removal of pollutants in aqueous matrices for two decades, its
use in wastewater treatment is still at a “technological research” stage. In order to
accelerate the adoption of HPC at full scale, it is advisable to focus on investigations under real conditions and on developing/improving pilot-scale reactors to better investigate scale-up conditions and the potential to successfully address specific
challenges in wastewater treatment through HPC. In realistic terms, the prospective
use of HPC is more likely as a tertiary treatment of wastewater, particularly if more
stringent regulations come into force, than as pretreatment for industrial wastewater
to improve biodegradability.
Extended author information available on the last page of the article
225
Reprinted from the journal
Chapter 7 was originally published as Iervolino, G., Zammit, I., Vaiano, V. & Rizzo, L. Topics in Current
Chemistry (2020) 378: 7. https://doi.org/10.1007/s41061-019-0272-1.