Simultaneous Immobilization of Heavy Metals in MKPC-Based Mortar-Experimental Assessment

Area of Science:

• Environmental Science
• Materials Science
• Civil Engineering

Background:

• Heavy metal contamination from industrial activities poses significant environmental and health risks.
• Ecotoxic heavy metals (HMs) hinder sustainable development and degrade environmental quality.
• Stabilization and immobilization of heavy metals are critical environmental remediation challenges.

Purpose of the Study:

• To investigate the simultaneous immobilization of barium (Ba2+), lead (Pb2+), and zinc (Zn2+) using magnesium potassium phosphate cement (MKPC) mortar.
• To evaluate the structural, mechanical, and hygric properties of HM-contaminated MKPC mortars.
• To determine the effectiveness of MKPC as a matrix for heavy metal stabilization.

Main Methods:

• Artificially contaminated MKPC mortars with Ba2+, Pb2+, and Zn2+ salt solutions.
• Analysis of structural and hydration products.
• Measurement of heavy metal content in leachates to determine immobilization ratios.
• Assessment of mechanical properties (compressive and flexural strength).
• Evaluation of water transport properties (water absorption coefficient and sorptivity).

Main Results:

• Immobilization rates for all investigated HMs exceeded 98.7%.
• Leachate HM content remained below limits for non-hazardous waste.
• Heavy metals reduced mortar strength by 46.5% (compressive) and 57.3% (flexural), yet maintained sufficient mechanical resistance.
• Low water transport parameters (Aw = 4.26 × 10-3 kg·m-2·s-1/2, S = 4.0 × 10-6 m·s-1/2) indicated limited HM leaching.

Conclusions:

• MKPC-based mortar is highly effective for the simultaneous stabilization of Ba2+, Pb2+, and Zn2+.
• The MKPC matrix provides a safe and environmentally sound method for treating heavy metal-contaminated waste.
• Despite reduced strength, HM-contaminated MKPC mortars retain adequate mechanical properties for various construction applications, demonstrating low heavy metal leaching potential.