The Effect of Chromium on the Chemical and Physical Properties of Industrial Sludge Based Geopolymer

This paper investigates the immobilization of chromium in the industrial sludge-based geopolymer. Mechanical, physical and microstructure properties were used to characterize different samples. The results show that lower heavy metals addition has less effect on the compressive strength. However, excessive addition of Cr(VI) (1.5 and 3%) causes a deterioration of geopolymer matrix with a significant drop of the compressive strength. The compressive strength shows that the use of sodium hydroxide as an alkaline activator is not suitable for chromium immobilization. The use of 1.5 and 3% amount of chromium increases the conductivity of leachates, which explains a change in the microstructure of materials. This is in agreement with the results of compressive strength. XRD patterns of all samples show an amorphous structure with less effect of chromium on the crystalline phases. SEM of the reference sample demonstrates a dense structure of binder. However, the porosity of the matrix increases with the addition of 3% Cr(VI).