Abstract
PurposePolymeric substances, as soil conditioners, limit the erosion process as well as improve the soil structure. The same macromolecular compounds may influence the heavy metal accumulation in soil environment. The main aim of this study was investigation of anionic polyacrylamide (AN PAM) effect on the lead(II) ion sorption on the montmorillonite surface. The effects of Pb(II) ion concentration, sequence of heavy metal and anionic polymer addition into the system as well as anionic group content in the PAM macromolecules were also studied.Materials and methodsThe study was performed on montmorillonite (clay mineral). Two types of polymers were used: AN PAM 5% and AN PAM 30% containing 5% and 30% of carboxylic groups, respectively. The adsorbed amounts of Pb(II) ions or AN PAM on the solid were determined spectrophotometrically. Electrokinetic properties of the examined systems were established using potentiometric titration and microelectrophoresis method. The montmorillonite aggregation without and with selected substances was described based on the sedimentation study.ResultsAt pH 5 the Pb(II) adsorbed amount on montmorillonite equaled 0.05 mg/m2 (for the initial concentration 10 ppm). Anionic polyacrylamide increased this value significantly (it was 0.11 mg/m2 with AN PAM 5% and 0.11 mg/m2 with AN PAM 30%). The lead(II) ions presence causes a slight increase of the anionic PAM adsorption on the montmorillonite surface. For example, for the initial polymer concentration 100 ppm, the AN PAM 5% adsorbed amount without Pb(II) equaled 0.49 mg/m2, whereas with Pb(II) – 0.57 mg/m2. What is more, anionic polyacrylamide and lead(II) ions affected electrokinetic properties and stability of the montmorillonite suspension.ConclusionsAnionic polyacrylamide makes the Pb(II) accumulation on the montmorillonite surface larger and, as a consequence, reduces the Pb(II) availability to organisms. Therefore, this macromolecular compound can certainly be used to remediate soils contaminated with heavy metals.
Highlights
Contamination of water, air and soil with heavy metals is one of the most distressing environmental issue.Due to development of civilization, the number of contaminated places becomes larger and larger
The adsorbed amounts of anionic polyacrylamide (AN PAM) and Pb(II) ions on the montmorillonite surface were determined based on decrease in their concentration in the solution after the adsorption process
At pH 5 the montmorillonite surface was neutral and, due to this fact, anionic polyacrylamides were adsorbed on the clay mineral surface mainly through hydrogen bonds
Summary
Contamination of water, air and soil with heavy metals is one of the most distressing environmental issue.Due to development of civilization, the number of contaminated places becomes larger and larger. Contamination of water, air and soil with heavy metals is one of the most distressing environmental issue. The accumulation of toxic elements in the environment depends on many factors, e.g. physicochemical properties of the element, its tendency to form soluble complexes, water solubility as well as reduction/oxidation potentials. The environmental factors, such as pH value and ionic strength, are important. Heavy metals are immobilized on the soil minerals (due to chemisorption or physical sorption processes) or taken up by the plants. The toxicity of selected compound to organisms is dependent on, inter alia, its solubility in
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