Titanium-salt flocculation and its sludge resource recovery to photocatalyst for advanced water treatment
- Publication Type:
- Thesis
- Issue Date:
- 2012
Open Access
Copyright Clearance Process
- Recently Added
- In Progress
- Open Access
This item is open access.
This research embraces several objectives targeting different aspects of environmental
concern in terms of wastewater flocculation, sludge disposal and removing of persistent
organic pollutants from water and wastewater. The production of a large amount of
sludge using coagulants of iron (Fe) and aluminium (Al) salts that needs disposal is
considered as the most costly and environmentally problematic challenge in wastewater
treatment. Titanium (Ti) salt used as an alternative coagulant reduces the cost of sludge
disposal and protects the environment by producing titania photocatalyst from the
incinerated sludge. However, titania photocatalyst is only a UV light responsive and its
pollutant-specific photocatalytic degradation for various organic pollutants has not
being examined. Thus, the main objectives of this study are:
1. Increase the efficiency of Ti-salt flocculation in terms of organic matter removal
and sludge reduction by using a natural polymer of chitosan as a coagulant-aid.
2. Trace the seasonal variation in the characteristics of Ti-salt flocculation and as
prepared-titania photocatalyst.
3. Produce pollutant-specific titania photocatalyst by synthesising titanate
nanotubes (TN) and thiourea (CSN2H4) doped-titanate nanotubes (TD-TN)
photocatalysts through the hydrothermal treatment of as prepared-titania.
4. Investigate the pollutant-specific photocatalytic activity of as prepared-titania
and the synthesised titania photocatalysts in photodegrading of organic pollutant
of gaseous acetaldehyde, humic acid (HA), dichloroacetic acid (DCA),
rhodamine B (RhB), metsulfuron methyl (M&M) and phenol under UV, visible
and solar light irradiation.
5. Then, select the best pollutant-specific titania for removing of 16
micropollutants of pharmaceutical and personal care products (PPCPs) and
endocrine disrupting chemicals (EDCs) in water.
Our findings indicated that Ti-salt flocculation exhibited more reduction in turbidity,
and colour of wastewater compared with Fe- and Al-salt flocculation. In addition, the
use of chitosan was very efficient for enhancing the performance of Ti-salt flocculation.
Ti-salt and chitosan flocculation improved significantly the turbidity and organic
removal of wastewater up to 85%, considerably reduced the optimum dose of Ti-salt
from 25 mg/L to less than 5 mg/L, solved the low pH of Ti-salt flocculation, and
achieved in 40% reduction of Ti-salt flocculation sludge. The change in wastewater
characteristics in different seasons has a negligible influence in the characteristics of Ti-salt
flocculation and as prepared-titania. During the whole seasons, the turbidity and
orthophosphate removal of Ti-salt flocculation were varied from 70 to 90% and 96 to
99%, respectively. As prepared-titania photocatalyst exhibited predominant anatase
structure, high BET surface area and insignificant change in its photocatalytic activity.
The photocatalytic degradation of HA and RhB was varied from 85 to 90% and 91 to
98%, respectively. The modified TD-TN photocatalyst exhibited superior photocatalytic
activity than as prepared-titania and TN photocatalysts for photocatalytic degradation of
the tested organic pollutants under visible and solar light. TD-TN photocatalyst was
selected to photodegrade a set of 16 micropollutants of PPCPS and EDCs in water,
exhibited a complete photocatalytic degradation of 7 micropollutants at TD-NT
concentration of 50 mg/L. The photocatalytic degradation significantly increased with
increasing in TD-NT concentration and complete photocatalytic degradation was
achieved at TD-NT concentration of 500 mg/L after 90 minutes. The high
photocatalysis activity of TD-NT in decomposing persistent organic pollutants and
micropollutants would increase the attention to use of Ti-salt coagulant and titania
photocatalyst as alternatives in water and wastewater treatment.
Please use this identifier to cite or link to this item: