Prospective chemisorption of fluoride utilizing coastal molluscan (Crassostrea Sp.) shell from phosphatic fertilizer pond wastewater, Paradeep, Odisha

Ray, Arati ; Kumar, Manish ; Dhal, Nabin Kumar; Hariprasad, Durgasi

Abstract

The present study explores the utilization of very acidic (pH 1.46) and high fluoride (F-) containing (9290 ppm) phosphatic fertilizer industry (Paradeep, Odisha, India) pond wastewater (PW) generated from phosphogypsum (PG) stacks by using Crassostrea Sp. molluscan shell (MS) as an adsorbent. F- chemisorption batch experiments on molluscan shells (MS) powder (212 - 500 micron) varying 6 different MS (Solid-S) to PW (Liquid-L) i.e. S/L ratios (1: 8 to 1: 30), time (0.08 to 48 hours) and fluoride concentration (4645 – 8361 ppm) as diluted PW. Chemisorption of F- peaked with 1: 20 S/L ratio at 24 hrs and its concentration in the supernatant reduced by 99.9 %. XRF, FTIR and XRD analysis of MS and its chemisorbed residues confirmes the role of relatively high calcium containing MS (72 % CaO) towards formation of Fluorapatite (FA) [Ca5(PO4)3F]. Desorption experiments of FA residue for 24 hrs, highlights the stability of F- chemisorption process on MS, which is confirmed by presence of FA in desorbed residue through XRD analysis. The research findings establish prospects of F- recovery from PW through chemisorption process utilizing selected MS.

Keyword(s)

Chemisorption; Fertilizer industry; Fluorapatite; Fluoride; Molluscan shell; Pond wastewater


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