The development of sustainable remediation technologies for heavy metal-contaminated soils remains a critical challenge in environmental engineering. This study presents a novel microwave (MA) irradiation-persulfate-formate system designed to simultaneously detoxify hexavalent chromium (CrVI) and enable alkali-activated composite geopolymerization of chromate-contaminated soil. The system leverages the synergistic effects of microwave energy, persulfate (PS), and formate (FS) to achieve both chemical reduction and structural immobilization. Three series of experiments were conducted: detoxification, MA irradiation, and coupling tests, systematically evaluating treatment performance under varying parameters.
In the detoxification phase, the molar ratio of formate to persulfate and the mass rate of fortifier to soil were optimized using variance analysis. Results showed that increasing the FS/PS ratio from 1 to 2 and the fortifier content from 4% to 8% significantly enhanced CrVI reduction efficiency, reaching up to 96.45%. The mechanism involves the thermal activation of persulfate at 80 °C, generating sulfate radicals (SO₄•⁻) with high redox potential (E⁰ = 2.01 V). Excess formate effectively quenches SO₄•⁻, promoting the formation of highly reductive CO₂•⁻ radicals (E⁰ = 1.PPM1D Antibody Epigenetics 9 V), which rapidly reduce CrVI to less toxic CrIII. This radical chain reaction is crucial for efficient detoxification under mild conditions.
The MA irradiation experiments demonstrated that microwave energy significantly accelerated geopolymerization. Increasing output power from 400 to 700 W and extending irradiation time from 7.5 to 15 min enhanced compressive strength from 37.6 MPa to 50.3 MPa and improved chromate immobilization efficiency from 85.6% to 99.2%. The MA-induced molecular vibrations, dipole rotation, and ionic conduction intensified the dissolution and polycondensation processes. Notably, elevating blast furnace slag (BFS) content from 50% to 80% further boosted mechanical strength and immobilization due to increased CaO availability, facilitating the formation of calcium-silicate-aluminate (Ca-Si-Al) phases.
In the coupling system, central composite design (CCD) was employed to optimize four factors: irradiation time (X₁), output power (X₂), FS/PS molar ratio (X₃), and fortifier-to-CCM mass rate (X₄).83150-76-9 Molecular Weight Response surface methodology revealed significant linear and quadratic effects on both responses. The optimal condition predicted by desirability function was X₁ = 15 min, X₂ = 660 W, X₃ = 1.36 (FS/PS), and X₄ = 5.38%, yielding maximum immobilization efficiency (99.16%) and compressive strength (50.32 MPa). The Avrami model confirmed accelerated geopolymerization kinetics, with reaction degree (α) rising rapidly before plateauing, indicating effective phase transformation.PMID:35132891
Characterization via FTIR, XRD, TGA, and SEM-EDS validated the mechanisms. FTIR showed new peaks at 1450 cm⁻¹ and 874 cm⁻¹, confirming C–O–C and Al–O/Si–O bond formation. XRD identified ettringite (Ca₁₂Al(OH)₂₄(SO₄)₆·50H₂O) in the coupling system, proving sulfate radicals contributed to both detoxification and cementitious bonding. TGA indicated enhanced thermal stability due to stable mineral formation. SEM revealed denser, layered structures in the coupled samples, confirming improved microstructure integrity.
Thermal durability tests showed only minor strength loss after 15 freeze-thaw cycles, demonstrating robustness. The system effectively stabilized chromate even at high soil loading (up to 70%). In conclusion, this MA-persulfate-formate system offers a highly efficient, green solution for treating CrVI-contaminated soils by combining radical-based detoxification with advanced geopolymerization, enabling safe long-term immobilization.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com