Nickel adsorption on chalk and calcite.

Area of Science:

• Geochemistry
• Environmental Science
• Materials Science

Background:

• Calcite and chalk are common minerals in aquatic and terrestrial environments.
• Understanding metal sorption onto these minerals is crucial for environmental remediation.
• Nickel (Ni) is a common pollutant with potential toxic effects.

Purpose of the Study:

• To investigate nickel (Ni) sorption onto synthetic calcite and two types of biogenic chalk.
• To elucidate the differences in Ni sorption behavior between synthetic and biogenic calcite.
• To determine the factors influencing Ni uptake, including pH, surface area, and sorbent type.

Main Methods:

• Batch sorption experiments were conducted under controlled conditions.
• Solutions were equilibrated with calcite and chalk at a pH range of 7.7 to 8.8.
• Nickel uptake was quantified, and a surface complexation model was applied.

Main Results:

• Nickel adsorption increased with higher surface area and pH.
• The surface complexation model effectively described the observed sorption data.
• Stability constants (log KNi) for Ni surface complexation were determined: -1.12 for calcite, -0.43 and -0.50 for the chalk samples.
• Biogenic chalk exhibited stronger Ni binding compared to synthetic calcite.

Conclusions:

• Both synthetic calcite and chalk effectively sorb nickel from solution.
• Biogenic calcite demonstrates superior nickel sorption capacity compared to synthetic calcite.
• Trace amounts of polysaccharides and clay nanoparticles on the biogenic chalk surface enhance nickel binding affinity.