Characterisation and use of innovative sorbents for metal/metalloid stabilisation in contaminated soils

Aikaterini Mitzia

Disertační práce

Abstract:

The main objective of the present thesis was to evaluate the efficiency of various soil amendments intended for metal(loid) immobilisation in contaminated soils. The two main studied materials, biochar (BC) and nano zero-valent iron (nZVI), were investigated individually or combined, modified, and originated from alternative sources. Although their metal(loid) retention efficiency has been well-established in laboratory solutions, knowledge gaps regarding their behaviour under various environmental conditions remained. Therefore, one of the aims of the current work was to answer questions about metal(loid) immobilisation efficiency and material functionality changes under relevant environmental conditions, i.e. different moisture content, flood, changing redox conditions, and increasing time. Keeping up with the current research trend concerning sustainability and circular economy, waste-derived amendments were also included in the presented experiments. Firstly, the efficiency of BC, nZVI, and a mixture of the two for the immobilisation of Zn, Pb, and Cd in contaminated soil was assessed under 60 and 100% of soil’s water holding capacity. Then, BC, nZVI and an nZVI-BC composite, were incubated from 1 up to 15 months in contaminated soil and their efficiency for Zn, Pb, Cd, and As retention over time was investigated. From these studies it occurred that nZVI was efficient for rapid but rather short-term immobilisation of Pb and As while BC seemed to be capable for long-term immobilisation of Zn and Cd along with soil pH retention. The promising behaviour of BC and the need for more sustainable remediation solutions lead to the use of sewage sludge as the source material for amendment production (sludgechar). Five sludgechars with variable compositions were pyrolysed and tested for their removal efficiency towards Cd, Co, Cu, Ni, Pb, Zn, As, Cr and Sb. Upon their efficiency for metal removal, the sludgechars were applied in five contrasting soils with different level and origin of contamination, variable soil use and properties. It was concluded that the efficiency of the studied sludgechars depends on all these factors. Redox fluctuations which typically occur in the field during flood events were simulated in the laboratory scale to investigate the amendment efficiency and metal(loid) mobility under such conditions. Our preliminary results highlight the effect of Eh and pH as the main factors controlling metal(loid) mobility followed by amendment efficiency. The presence of Fe and Mn oxides was considered as the most important immobilisation mechanism in all of the presented studies.

Keywords

soil remediation, biochar, nano zero-valent iron, metal(loid) contamination, immobilisation

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 29. 3. 2024

Obhajoba závěrečné práce

• Vedoucí: doc. Mgr. Martina Vítková, Ph.D.
• Oponent: Jan Filip, externi, Edgar Hiller, externi

Česká zemědělská univerzita v Praze

Fakulta životního prostředí

Doktorský studijní program / obor:
Environmental Sciences / Applied and Landscape Ecology