Titanium-salt flocculation and its sludge resource recovery to photocatalyst for advanced water treatment

University of Technology, Sydney. Faculty of Engineering and Information Technology.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

Characterisation of titanium tetrachloride and titanium sulfate flocculation in wastewater treatment

Flocculation with titanium tetrachloride (TiCl4) and titanium sulfate (Ti(SO4)2) was investigated in terms of different coagulant doses, pH, turbidity, dissolved organic carbon (DOC), UV-254, colour, zeta potential, particle size and molecular weight distribution. The two coagulants were compared with the commonly used coagulants such as ferric chloride (FeCl3) and aluminium sulfate (Al2(SO 4)3). Titanium tetrachloride showed the highest turbidity removal, while titanium sulfate showed the highest reduction of UV-254 and colour at all pH values. The four coagulants were found to have similar organic removal up to 60-67% and resulted in similar organic removal in terms of various MW ranges. The decantability of the settled flocs was very high for titanium tetrachloride, titanium sulfate and ferric chloride compared with aluminium sulfate. The dominating coagulation mechanisms for titanium tetrachloride and titanium sulfate are still to be studied, since different precipitation reactions might take place at different pH even without flocculant addition. Titanium tetrachloride and titanium sulfate were found as effective new coagulants in wastewater treatment not only in terms of organic matter removal, but also in sludge reduction through the production of titanium dioxide. © IWA Publishing 2009

Preparation and characterisation of titanium dioxide produced from Ti-salt flocculated sludge in water treatment

During the past few years, titanium salts were investigated as alternative coagulants for the removal of organic matter of different molecular sizes in contaminated water. The flocculation efficiency of Ti-salt was comparable to those of FeCl3 and Al2(SO4)3 salts, commonly used coagulants. Incinerated sludge-TiO2 showed higher surface area and photocatalytic activity than commercially available TiO2. Metal-doped forms were produced by adding coagulant aids such as iron (Fe-), aluminium (Al-) and (Ca-) calcium salts during Ti-salt flocculation to increase pH. Ca- and Al- doped TiO2 showed very high photocatalytic activity compared to Fe-doped TiO2. When tested in a pilot scale plant for treatment of dye wastewater to check practical feasibility of the novel process, the removal ratio of the chemical oxygen demand was comparable to those of commonly used coagulants but the settling of sludge was faster. The TiO2 generated after sludge incineration showed a high photocatalytic activity for degradation of volatile organic compounds and increased the rate of hydrogen production by water photosplitting. TiCl4 coagulant and TiO2 produced from different water sources with different concentrations had low acute toxicity compared to heavy metals and commercial TiO2 when examined based on D. Magna mortality. This paper presents the production, characterisation and the photoactivity of TiO2 produced from Ti-salt flocculated sludge. Different case studies are discussed to highlighted recent advances in this field

Hydrogen production affected by Pt concentration on TiO <inf>2</inf> produced from the incineration of dye wastewater flocculated sludge using titanium tetrachloride

TiO 2 from the incineration of dye wastewater flocculated sludge using TiCl 4 coagulant was produced. Optimal catalyst amount and Pt-loading on TiO 2 were studied for the production of H 2 by photocatalytic reforming of methanol (6% vol.). On the other hand, BTSE (biologically treated sewage effluent) was flocculated using TiCl4 and produced sludge was incinerated to generate TiO 2 . TiO 2 was loaded with optimum Pt and added to the supernatant in a photocatalytic reactor to test the efficiency of using remaining organics as a “sacrificial reagent” for photocatalytic hydrogen production. Dissolved organic carbon (DOC) and molecular weight distribution (MWD) were measured for nanofiltration (NF) and TiCl 4 flocculation followed by photocatalysis. TiO 2 (from the incineration of BTSE flocculated sludge using TiCl4) was produced and loaded with 0.5% Pt. Results showed that the optimum concentration of TiO 2 (from dye wastewater) for H 2 production was 0.3 g/L, while the optimum amount of Pt was 0.5%. DOC and MWD removal was similar for the flocculation of BTSE followed by photocatalytic reaction and the NF process. Remaining organic compounds after flocculation could not be used as sacrificial reagent to induce H 2 production. Further investigations on studying the UV intensity and/or identifying organic/inorganic scavengers to inhibit H 2 production are underway. © 2010, Taylor & Francis Group, LLC

Visible light responsive titanium dioxide (TiO<inf>2</inf>)

Titanium dioxide (TiO2) is one of the most researched semiconductor oxides that has revolutionised technologies in the field of environmental purification and energy generation. It has found extensive applications in heterogenous photocatalysis for removing organic pollutants from air and water and also in hydrogen production from photocatalytic water-splitting. Its use is popular because of its low cost, low toxicity, high chemical and thermal stability, But one of the critical limitations of TiO 2 as photocatalyst is its poor response to visible light. Several attempts have been made to modify the surface and electronic structures of TiO2 to enhance its activity in the visible light region such as noble metal deposition, metal ion loading, cationic and anionic doping and sensitisation, Most of the results improved photocatalytic performance under visible light irradiation. This paper attempts to review and update some of the information on the TiO2 photocatalytic technology and its accomplishment towards visible light region

SPARC 2018 Internationalisation and collaboration : Salford postgraduate annual research conference book of abstracts

Welcome to the Book of Abstracts for the 2018 SPARC conference. This year we not only celebrate the work of our PGRs but also the launch of our Doctoral School, which makes this year’s conference extra special. Once again we have received a tremendous contribution from our postgraduate research community; with over 100 presenters, the conference truly showcases a vibrant PGR community at Salford. These abstracts provide a taster of the research strengths of their works, and provide delegates with a reference point for networking and initiating critical debate. With such wide-ranging topics being showcased, we encourage you to take up this great opportunity to engage with researchers working in different subject areas from your own. To meet global challenges, high impact research inevitably requires interdisciplinary collaboration. This is recognised by all major research funders. Therefore engaging with the work of others and forging collaborations across subject areas is an essential skill for the next generation of researchers

Ti-salt flocculation for dissolved organic matter removal in seawater

In this study, the removal of different fractions of organic matter in seawater was investigated using titanium tetrachloride (TiCl4) flocculation and compared with ferric chloride (FeCl3) flocculation. The organic matter fractions were characterised using liquid chromatography-organic carbon detector (LC-OCD). Results showed the hydrophobic compounds removal was dominant by both flocculants. However, the removal of hydrophilic organic compounds, such as humics and low-molecular weight neutral compounds of seawater, was superior by TiCl4 flocculation compared to FeCl3 flocculation and this removal increased considerably with the increase of TiCl4 doses. The flocculated sludge after TiCl4 flocculation was incinerated to produce titanium dioxide (TiO2) nanoparticle. TiO2 from seawater sludge characterised by X-ray diffraction (XRD) and scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDS) showed predominant anatase phase with Si as a main dopant. © 2013 Copyright Balaban Desalination Publications

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity. © 2010 Elsevier Ltd

Effect of phosphorous on the properties of titania produced from Ti-salt flocculated sludge in water treatment

In this study, the removal of phosphorous (P) using Ti-salt flocculation of biologically treated sewage effluent (BTSE) was investigated for a year. The pH, alkalinity and concentration of P, before and after Ti-salt flocculation, were measured and compared. The sludge of Ti-salt flocculation was incinerated at 600 °C to produce titania nanoparticles which found to be doped with P. Titania nanoparti-cles were characterised and their photocatalytic activity under UV light irradiation were also tested. Results indicated that the removal of P, which exceeded 97% in average, was not affected by the pH and the alkalinity of BTSE. The concentration of P in titania had no effect on the characteristics of titania nanoparticles in different seasons. Titania nanoparticles exhibited superior properties in terms of BET surface area and photocatalytic activity. © 2011 American Scientific Publishers

Titania produced from Ti-salt flocculated sludge: Photocatalytic activity under solar light

In this study, titania photocatalyst was produced from the wastewater sludge of Ti-salt flocculation. The high photocatalytic activity of titania reported was evaluated based on a single organic substrate. However, the photocatalytic activity is a substrate-specific; one photocatalyst showed different photocatalytic degradation rates for different substrates. Thus, to investigate the substrate-specific photocatalytic activity of titania, various substrates of humic acid (HA), dichloroacetic acid (DCA), rhodamine B (RhB), metsulfuron methyl (M&M) and phenol were used under simulated solar light irradiation. Results showed titania had a high activity rate for RhB, moderate activity for HA and DCA and low activity for M&M and phenol indicating substrate-specific activities. When compared with Degussa-P25, titania showed higher activity for M&M, while the opposite was observed for HA and phenol. The specific-substrate behaviour of titania could depend on specific physicochemical and electronic interactions between titania, substrates, and their intermediates compounds formed. Copyright © 2014 American Scientific Publishers