Removal of Some Heavy Metals by Geopolymer Cement

Abstract

nvironmental pollution caused by various wastes has been a concern in the world and these pollutants are becoming hazardous to a human, animal, and environmental health as they accumulate for a long time. Get rid of these wastes by landfilling or dumping is harmful to the environment and has a high transport cost. Many efforts are therefore made using the solidification/stabilization (S/S) method inside a solid matrix to minimize the escape of heavy metals through leaching. Blast furnace slag, fly ash, and cement klin dust are the most popular solidification agents for inorganic wastes. Therefore, this study aims to investigate the immobilization of some heavy metal salts by three geopolymer pastes, alkali-activated ground granulated blast furnace slag (GGBFS), a mixture of GGBFS/FA, and a mixture of GGBFS/CKD pastes. The heavy metals salts used in this study were lead nitrate and the chloride salt of copper and cadmium. The ratios used of these salt were 0.5 and 1%w.t of solid and the activator type is (NaOH/Na2SiO3) liquid by fixed ratio of (1:1)(5M NaOH). In this study the effect of using heavy metal salts on the performance, physicomechanical, and hydration properties of different geopolymer pastes (alkali-activated slag, alkali activated GGBFS/FA, and alkali-activated GGBFS/CKD), as well as the degree of leachability, was examined via the following tests: 1. Determination of the compressive strength 2. Determination of chemically combined water contents 3. Determination of total porosity. 4. Determination of bulk density. 5. Leaching measurements. 6. X-ray diffraction analysis (XRD). 7. Infrared analysis. 8. Atomic absorption. The main observation for obtained results can be summarized as the following: 1. The result of the chemically combined water contents increases for all -pastes with curing time up to 90 days for all alkali-activated mixtures due to the progress of formation of hydration products. 2. The value of compressive strength increase with curing time up to 90 days for alkali-activated pastes due to the formation of hydration products. The value of compressive strength of pastes with heavy metal salts is lower than those of pastes without heavy metal salts. As the ratio of heavy metals salts increases, the compressive strength decrease at all hydration ages.