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Enhanced phosphorus removal from wastewater using virgin and modified slags: performance, speciation and mechanisms
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Argon oxygen decarburization slag (AOD) was tested in batch and column experiments to investigate its phosphorus (P) removal performance. The effects of factors such as AOD dose, initial P concentration of the feeding solution, and aging on the P removal ability of the slags were analyzed. In a column experiment, electric arc furnace slag (EAF), blast furnace slag (BFS) and AOD were combined in five different ways to determine optimal conditions for P removal. In another column experiment, the three types of slag were modified with polyethylene glycol (PEG) and NaOH to adjust their dissolution properties and the effect on P removal performance was examined. In the batch experiments, AOD exhibited very promising P removal ability. It removed 94.8% of P from 6.5 mg P L-1 synthetic solution in 4 hours with a dose of 5 g L-1. Maximum P removal capacity of 27.5 mg P g-1 was achieved. In the dual-filter column experiment, the column packed with only EAF had the best P removal performance (consistently above 93%). Amorphous calcium phosphate (ACP) was identified as the main P species in the five slag samples collected from the outlet chambers. The contributions from crystalline calcium phosphate (Ca-P) and P adsorbed on iron/aluminum (hydr)oxides were greater in samples from the inlet chambers. The P speciation results revealed that P was predominantly removed by the slags through formation of ACP. The second column experiment showed that modification with PEG and NaOH solution only enhanced short-term P removal by the slags. However, exhaustion of the modified slags occurred much earlier, indicating that the modification process had shortened the lifespan of the slags. Untreated AOD showed better P removal than untreated EAF until pore volume 244, probably due to faster dissolution rate of gamma dicalcium silicate (dominating in AOD according to the XRD results) than of beta dicalcium silicate (dominating in EAF).

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. , p. 54
Series
TRITA-SEED-PHD ; 2017:01
Keywords [en]
AOD, EAF, BFS, Calcium phosphate, XANES, slag mineralogy
National Category
Water Engineering
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-213415ISBN: 978-91-7729-516-7 (print)OAI: oai:DiVA.org:kth-213415DiVA, id: diva2:1137206
Public defence
2017-09-29, Sal V1, Teknikringen 76, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170830

Available from: 2017-08-31 Created: 2017-08-30 Last updated: 2017-08-31Bibliographically approved
List of papers
1. Phosphorus removal performance and speciation in virgin and modified argon oxygen decarburisation slag designed for wastewater treatment
Open this publication in new window or tab >>Phosphorus removal performance and speciation in virgin and modified argon oxygen decarburisation slag designed for wastewater treatment
2015 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 87, p. 271-281Article in journal (Refereed) Published
Abstract [en]

Argon oxygen decarburisation (ADD) slag may be used for phosphorus (P) removal, as its high pH and weatherable calcium (Ca) minerals provide sufficient Ca2+ and OH- for calcium phosphate (Ca-PO4) precipitation. This study examined the P removal performance of AOD slag for use as wastewater treatment material. Batch experiments were carried out using both synthetic P solution and real wastewater, followed by chemical modelling and X-ray absorption near edge structure (XANES) spectroscopy. The influences of initial P concentration, slag dose and modification by polyethylene glycol (PEG), an effective agent for generation of porous materials, were investigated to determine the optimal conditions for P removal by AOD slag. It was found that virgin AOD slag removed 94.8% of P from a synthetic P solution in 4 h and 97.8% in 10 h. This high P removal was accompanied by a rapid increase in pH from 7.0 to 10.74. The maximum P removal capacity (PRC) from synthetic P solution ranged from 1.3 to 27.5 mg P g(-1). The optimal AOD dose for P removal from wastewater, determined in 8-h batch experiments, was 25 g L-1. PEG modification increased the reaction rate and resulted in higher final pH, increasing PRC by 47.9%. Combined Visual MINTEQ and XANES analysis for detailed examination of P removal mechanisms revealed that the main P removal mechanism was precipitation of calcium phosphate. According to the XANES analysis, the main Ca-PO4 precipitate formed on virgin AOD slag under low initial P concentration and high pH was apatite, while brushite was the dominant product at high initial P concentration and low pH.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Phosphorus, Slag, Apatite, Brushite, Visual MINTEQ, XANES
National Category
Environmental Sciences
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-180991 (URN)10.1016/j.watres.2015.09.035 (DOI)000367413000028 ()26433005 (PubMedID)2-s2.0-84943241467 (Scopus ID)
Note

QC 20160127

Available from: 2016-01-27 Created: 2016-01-26 Last updated: 2020-03-09Bibliographically approved
2. Dual slag filters for enhanced phosphorus removal from domestic wastewater: performance and mechanisms
Open this publication in new window or tab >>Dual slag filters for enhanced phosphorus removal from domestic wastewater: performance and mechanisms
(English)In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
Springer
Keywords
metallurgical slags, calcium phosphate, phosphates speciation, precipitation, adsorption, metal release
National Category
Water Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-213407 (URN)
Note

QC 20170830

Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2017-08-30Bibliographically approved
3. Phosphorus removal performance and lifespan prediction through mineralogical composition: A comparative study of AOD and EAF slags
Open this publication in new window or tab >>Phosphorus removal performance and lifespan prediction through mineralogical composition: A comparative study of AOD and EAF slags
(English)Manuscript (preprint) (Other academic)
Keywords
amorphous calcium phosphate, carbonate apatite, fluoroapatite, larbite, gamma dicalcium silicate
National Category
Engineering and Technology
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-213411 (URN)
Note

QC 20170830

Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2017-08-30Bibliographically approved
4. Effect of aging on phosphorus removal of metallurgical slag and heat reactivation of aged slag
Open this publication in new window or tab >>Effect of aging on phosphorus removal of metallurgical slag and heat reactivation of aged slag
2016 (English)Conference paper, Oral presentation only (Other academic)
Keywords
ageing, heating, AOD, EAF, BFS
National Category
Civil Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-213412 (URN)
Conference
2016 IWA water congress & exhibition
Note

QC 20170830

Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2017-08-30Bibliographically approved

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Zuo, Minyu

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