Applying physicochemical approaches to control phosphogypsum heavy metal releases in aquatic environment

摘要

One of the most important sources of solid waste in the Mediterranean Basin ecosystem originated from the phos phate fertilizer industries, which discharge phosphogypsum (PG) directly into aquatic environments or are stacked on stockpiles. The present study investigates metal release from PG under the influence of variable pH, increasing PG mass content, and complexing organic matter ligands. Major ions from PG leachates, grain size and charge, main functional groups along with metal teachability (Pb, Cd, Cr, Cu, and Zn) were determined using ion chromatography, laser diffrac tion, zetameter, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy, respectively. The complete dissolution of PG recorded is at 2 g/L. Saturation and super-saturation with respect to PG may occur at concentrations of 3 and 4 g/L, respectively, revealing a clustering phenomenon leading to heavy metal encapsulation within the aggregates. Organic ligands such as citrate may trigger the cationic ex change within the PG suspension leading to ion release. Asthese factors are considered as specific process involving the release of contaminants from PG during storage under natural conditions, this study could set the foundations for PG reme diation in aquatic environment. Organic ligands under con trolled pH conditions could be utilized in treating fertilizer industrial wastes by taking into consideration the particularity of the receiving area, thus decreasing metal hazardous impact on natural media.