Geotechnical Engineering Journal of the SEAGS & AGSSEA ISSN 0046-5828
Vol. 54 No. 4 December 2023
Neutralization of Phosphogypsum for Use in Base Lining System of Phosphogypsum Dumping Yards
N. V. Satyanarayana Reddy, and K. Tulasi
ABSTRACT: Phosphogypsum is generated as a by-product during the manufacturing of phosphoric acid by wet process. Annually, the worldwide projected value of phosphogypsum generation is 100-280 metric tons. Due to its acidic nature, radioactivity, high fluorine content, presence of trace elements and huge volume, direct dumping of phosphogypsum on the ground results in subsoil and groundwater contamination. Hence, it is essential to dump phosphogypsum properly in engineered landfills. To overcome these issues in India, the Central Pollution Control Board (CPCB) has suggested a composite liner system for the safe disposal of phosphogypsum on the ground. The lower part of the suggested liner system comprises of placement of HDPE geomembrane over a layer of compacted clay or compacted amended soil layer or a mixture of native soil with bentonite and in the upper part of the composite liner system, a layer of mechanically compacted and neutralized phosphogypsum is placed above the drainage layer. Hence, the present work is intended to neutralize phosphogypsum with lime, fly ash, and pond ash and to assess the suitability of neutralized phosphogypsum for use in the upper part of the composite liner system of phosphogypsum ponds. The study indicated effective neutralization of phosphogypsum with 1.6% lime and 50% fly ash.
KEYWORDS: Phosphogypsum, Composite Liner System, Neutralization, Lime, Fly ash, and Pond ash.
