This work aimed to assess the potential for valorisation of waste materials in order to minimise the environmental impact of hazardous air pollution control residues by
solidification/stabilisation. The potential for immobilisation in a primarily pozzolanic
matrix was examined. Pulverised fuel ash resulting from the co-combustion of coal and biomass, which did not meet end of waste criteria for construction purposes, and a waste caustic solution resulting from the cleaning of aluminium extrusion dyes were utilised as reagents.
A range of variables were examined with regards to mix design and curing conditions. The mineralogy, reaction kinetics and pore structure of the samples were
examined and performance assessed based on physical tests and leaching performance with regard given to current legislation within the UK. A detailed understanding of the treatments potential was thereby developed along with an
understanding of the factors determining the observed performance.
The treatment option proved unsuccessful primarily due to the lack of potential for immobilisation of the high levels of soluble chloride salts present in the air pollution
control residues and the gas production typically observed when blending air pollution control residues with a caustic solution. Compared to more traditional cement based solidification/stabilisation systems other disadvantages were observed relating to slower reaction kinetics and therefore the need for increased curing temperatures, matrix durability, and increased sulphate leaching.
Nevertheless the reagents showed some potential and may be suitable for use treating alternative waste streams, providing an economic option which is beneficial
for the environment as a whole.
In addition the impact of the known variability in air pollution control residue composition, on the potential treatment by solidification/stabilisation with cement
was assessed. Significantly different performance was observed which implied the necessity to modify any such treatment.
Altmetric
Altmetric