Heavy metal removal from aqueous solution using carbonaceous K2S-impregnated adsorbent

Area of Science:

• Materials Science
• Environmental Chemistry
• Chemical Engineering

Background:

• Heavy metal contamination poses significant environmental and health risks.
• Development of efficient and cost-effective adsorbents is crucial for remediation.
• Coal, an abundant resource, can be modified for advanced applications.

Purpose of the Study:

• To develop a novel carbonaceous adsorbent from raw coal for heavy metal removal.
• To investigate the effectiveness of sulfur impregnation using potassium sulfide (K2S) on coal.
• To evaluate the adsorption capacity and metal retention of the prepared adsorbent.

Main Methods:

• One-step sulfur impregnation of raw coal with K2S powder.
• Pyrolysis of K2S-impregnated coal at 800°C under nitrogen atmosphere.
• Characterization of sulfur content and forms in the resulting K2S char.
• Batch adsorption experiments for Zn2+, Cd2+, and Pb2+ removal.
• Elution studies to assess metal retention.

Main Results:

• Sulfur impregnation successfully introduced elemental, thiophenic, and sulfatic sulfur into the coal.
• K2S char exhibited higher sulfur content compared to raw coal and pyrolysis char.
• 100% removal of Zn2+ from a 2.4 mmol/L solution was achieved.
• K2S char adsorbed 97% of Pb2+ and 35% of Cd2+ from 24 mmol/L solutions.
• Adsorbed Pb2+ and Cd2+ showed zero elution in distilled water, indicating strong retention.

Conclusions:

• A novel, effective heavy metal adsorbent was successfully prepared from coal via K2S sulfur impregnation.
• The K2S char demonstrates excellent adsorption capabilities for target heavy metal ions.
• The strong retention of adsorbed metals suggests the potential for stable sequestration and removal from contaminated water.