Slow release of phosphate glass and its applications in the lead-contaminated soil remediation

ABSTRACT

This study examined the dissolution release performance of slow-release phosphate glass (SRPG), and the role this element plays in water and soil contaminated with heavy metals. It is known that the rate of dissolution ternary phosphate glass as XMgO–(50-X)Na₂O–50P₂O₅ (mol %) may be controlled by adjusting its content of MgO. The results showed that SRPG was uniformly dissolved in deionized water. Acidic or basic conditions induced the dissolution of SRPG; in contrast, lysate of SRPG in water decreased its rate of dissolution. Phosphate glass treatment of heavy metal lead (Pb)-contaminated soil effectively reduced the Pb content in H₂O and MgCl₂ extracts by 81.6% and 75.7%, respectively. Comparative tests showed that leaf and root portion of Pb uptake in cabbage grown in soil treated with SRPG was reduced by 65.1% and 51.6% compared to untreated soil. Analysis of SRPG with Pb immobilization in water and soil environment by X-ray diffraction demonstrated that low-solubility phosphate (PbHPO₄) and hydroxyphosphate [Pb₅(PO₄)₃OH] complex was formed. Data indicate that SRPG may be effective in removal of Pb from contaminated soils and diminish risk of toxicity from ingestion of this heavy metal by consumers.

KEYWORDS:

• Phosphate glass
• lead pollution
• soil remediation
• controlled release
• X-ray diffraction

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Hubei Province Natural Science Foundation of China [2009CDB017] and 2011 SME Technology Innovation Fund [11C26224212736].