Geopolymers as active capping materials for in situ remediation of metal(loid)-contaminated lake sediments

Abstract

Metal(loid) contamination in sediments is a widespread environmental issue. Sediments act normally as metal(loid) sinks, but if chemical conditions (such as pH or redox potential) change, they can become sources of secondary pollution. Consequently, various strategies for both in and ex situ remediation of contaminated sediments have been developed. One promising method is active capping, which involves the injection of adsorbents as a layer on the sediment surface or the mixing of adsorbents within the sediment. Adsorbents decrease the bioavailability of metal(loid)s.In the present work, the suitability of alkali-activated blast-furnace-slag, metakaolin geopolymer, and exfoliated vermiculite were evaluated for in situ stabilization of two metal(loid)-contaminated lake sediments through laboratory-scale experiments. The results indicated that adsorbent 2 amendments had metal(loid)-specific performance: alkali-activated blast-furnace slag was suitable for Al, Cu, Fe, and Ni; metakaolin geopolymer for Cu, Cr (total), and Fe; and vermiculite for Al and Zn. None of the materials could stabilize Ba, Sr, or Ti. Furthermore, the amendments performed differently in two different lake sediments, implying that the effectiveness of the amendments needs to be confirmed on a case-by-case basis.

Geopolymer foams: An overview of recent advancements

“…The main bottleneck hindering the wider use of geopolymer adsorbents is the gap between research studies, often using unrealistic scenarios (e.g. synthetic wastewaters), and real effluents which are much more complex than synthetic wastewaters [139,203]. Studies focusing on industrial effluents are anticipated to be a hot topic in the near future.…”

In situ remediation of metal(loid)-contaminated lake sediments with alkali-activated blast furnace slag granule amendment: A field experiment

“…The stability of Al, Fe, Ti, Zn, Ni, Cr, and Cu was studied in amended and unamended sediments. Cd, Co, and U were excluded as their concentrations were low, as also reported in our previous study (Kutuniva et al 2019). Pore water was collected from the sediments in the field using a disposable vacuum filter with 0.2 µm pore size and conserved with nitric acid.…”

“…Alkali-activated materials (AAMs) could represent another active capping or augmentation material option since they have been successfully used for the removal of a number of aqueous metal(loid)s (e.g., As, Cd, Cr, Co, Cs, Cu, Mn, Ni, Pb, Sb, Sr, and Zn) as summarized by Luukkonen et al 2019. Furthermore, the use of alkali-activated metakaolin and blast furnace slag (BFS) decreased the potential bioaccessibility of Ni, Zn, Al, Cu, Cr, and Fe in laboratory-scale in situ sediment remediation experiments (Kutuniva et al 2019). AAMs are hydrous alkali or alkaline-earth metal aluminosilicates with mesoporous and amorphous structures.…”

Contaminated aquatic sediments

“…The materials reportedly worked well by inhibiting release of the metals and stabilizing them in the sediment. In the laboratory, Kutuniva et al (2019) studied whether certain amendments (exfoliated vermiculite, metakaolin geopolymer, and blast furnace slag) were suitable as capping materials for metals in sediment. They observed a range of success with each amendment being suitable to specific groups of metals and not to others.…”