Characteristics and metal leachability of incinerated sewage sludge ash and air pollution control residues from Hong Kong evaluated by different methods

Li, Jiangshan; Xue, Qi‐Kun; Fang, Le; Poon, Chi Sun

doi:10.1016/j.wasman.2017.03.033

Cited by 73 publications

(33 citation statements)

References 48 publications

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“…NaOH was the only extraction liquid dissolving almost no heavy metals (see Fig. 5e-j), mainly due to the high pH at the end of the ex traction procedure (12.5-13.0) (Ali and Kim, 2016;Li et al, 2017;Zhang et al, 2016). However, NaOH was not effective for P extraction from WWT sludge ash since only 40% of total P was extracted, which is in line with the findings of Xu et al (2012) and Biswas et al (2009).…”

Section: Multi-criteria Optimizationsupporting

confidence: 81%

Closing the phosphorus cycle: Multi-criteria techno-economic optimization of phosphorus extraction from wastewater treatment sludge ash

Luyckx

Geerts

Caneghem

2020

Science of The Total Environment

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The presence of heavy metals in concentrations above legal limit values is one of the main obstacles preventing closure of the phosphorus (P) cycle through directly applying wastewater treatment sludge ash as a fertilizer. Therefore, an alternative procedure is proposed to recover the valuable P from the sludge ash via wet chemical extraction. This comprehensive study uses several inorganic and organic acids, chelating agents and an alkaline solution to establish optimal and cost-effective conditions for wet P extraction from sludge ash. The optimization takes into account co-extraction of the following heavy metals: Cd, Cr, Cu, Ni, Pb and Zn. Design of experiments results show extraction liquid concentration, liquid/solid ratio and contact time all affect P and heavy metal extraction efficiency, both individually and through interaction. In addition, type of extraction liquid and pH at the end of the extraction procedure also affect P and heavy metal extraction efficiency. Combining results of XRD and SEM-EDX analysis with extraction data shows that at a pH < 2, both Ca-and Al-phosphates in the ash dissolve easily. However, at slightly higher pH only Ca-phosphates dissolve well and at alkaline pH only Al-phosphates. The best trade-off between high P extraction, low heavy metal co-extraction and low operational costs is obtained with H 2 SO 4 (0.5 N, 10 ml/g, 120 min) and oxalic acid (0.5 N, 12.8 ml/g, 120 min). H 2 SO 4 outperforms the other extraction liquids in terms of extraction liquid costs per kg P extracted, whereas extraction with oxalic acid results in the lowest heavy metal co-extraction, thus reducing the downstream processing costs. None of the extraction liquids considered is appropriate for heavy metal removal prior to P extraction due to loss of P and insufficient heavy metal removal.

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Section: Multi-criteria Optimizationsupporting

confidence: 81%

Closing the phosphorus cycle: Multi-criteria techno-economic optimization of phosphorus extraction from wastewater treatment sludge ash

Luyckx

Geerts

Caneghem

2020

Science of The Total Environment

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“…The ISSA used in this study was from the Sludge Treatment Facility (T-park) in Hong Kong and it has been characterised in previous studies [14,15]. The H 2 SO 4 (AR, 98%) and EDTA (ACS, 99.5%) were supplied by RCI Labscan limited and Anaqur Chemicals, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…These metal(loid)s can be easily dissolved by acids or chelates [15,41], while the effect of chelates was mainly related to the dissolution of metallic carbonates or sulfides by the chelating effect [42]. When using EDTA to remove undesirable impurities, it is necessary to consider (i) the molar ratios of impurities:EDTA present in ISSA, (ii) the potential solubilities of these impurities in the pH range studied and (iii) different affinities (chelating coefficients) of different impurities for chelation by EDTA.…”

Section: Co-dissolution Of Major Metal(loid)smentioning

confidence: 99%

“…Incinerated sewage sludge ash (ISSA) consists of small glassy particles partially sintered together into irregularly shaped porous agglomerates containing Fe, Al, Si and P [13,14]. The P is preferentially deposited on the surface of particles, thus facilitating ease of recovery [5,10,15]. The main crystalline phases containing P in ISSA are whitlockite, beta-tricalcium phosphate mineral and AlPO 4 [5,16,17].…”

Section: Introductionmentioning

confidence: 99%

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Recovery of phosphorus from incinerated sewage sludge ash by combined two-step extraction and selective precipitation

Fang

Donatello

et al. 2018

Chemical Engineering Journal

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115

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“…Zinc concentration in eluates indicated a significant partial correlation with pH (ρc = 0.592) and cumulative L/S ratio (ρc = 0.444). Its high immobilization level ( Table 8 ) could have resulted from a significant share of the residual fraction [ 43 ] in the total metal content in the slurry [ 44 ].…”

Section: Results and Analysismentioning

confidence: 99%

Hardening Slurries with Fluidized-Bed Combustion By-Products and Their Potential Significance in Terms of Circular Economy

et al. 2021

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Hardening slurries (water-bentonite-binder mixtures) constitute a well-established material used broadly, i.a., for cut-off walls in civil and water engineering. Although they usually contain Portland cement, similar to common concrete, their properties differ greatly, mostly due to a much higher water content. This characteristic of hardening slurries creates unique opportunities for the utilization of significant quantities of industrial by-products that are deemed problematic in the concrete industry. This article investigates the effect of the addition of by-products of fluidized-bed combustion of hard, brown coal and municipal sewage sludge, as well as ground granulated blast furnace slag, on the properties of slurries. Unconfined compressive strength tests, as well as mercury porosimetry, scanning electron microscopy, and X-ray diffraction analyses were performed. The results suggest that it is possible to design hardening slurry mixes of desired properties, both in liquid and solid state, containing at least 100–300 kg/m3 of industrial waste. This includes cement-free slurries based entirely on industrial by-products as binders. In addition, the analyzed slurries exhibited good chemical resistance to landfill eluates, at the same time effectively immobilizing heavy metals. It was concluded that hardening slurry technology can ensure the safe deposition of significant amounts of waste that would be otherwise difficult to manage, thus contributing to the circular economy concept.

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Characteristics and metal leachability of incinerated sewage sludge ash and air pollution control residues from Hong Kong evaluated by different methods

Cited by 73 publications

References 48 publications

Closing the phosphorus cycle: Multi-criteria techno-economic optimization of phosphorus extraction from wastewater treatment sludge ash

Closing the phosphorus cycle: Multi-criteria techno-economic optimization of phosphorus extraction from wastewater treatment sludge ash

Recovery of phosphorus from incinerated sewage sludge ash by combined two-step extraction and selective precipitation

Hardening Slurries with Fluidized-Bed Combustion By-Products and Their Potential Significance in Terms of Circular Economy

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