Transformation of Pb, Cd, and Zn Minerals Using Phosphates

Abstract

Heavy metal contamination in soils has become one of the most critical environmental issues. The most efficient in-situ remediation technique is chemical immobilization that uses cost-effective soil amendments such as phosphate compounds to decrease Pb, Cd and Zn accessibility in the contaminated soils. The present study examined the effectiveness of KH2PO4 in immobilizing Pb, Cd and Zn in three samples of contaminated soils collected from ZGH “Bolesław” (Mining and Smelting Plant “Bolesław”). Effectiveness was evaluated using the following methods: a toxicity characteristic leaching procedure (TCLP)-based experiment, sequential extraction, X-ray diffraction analyses (XRD), and scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS). The most efficient percentage reduction of total leachable metal concentration assessed by TCLP was observed for lead (50%–80%), and the least reduction was observed for zinc (1%–17%). The most effective immobilization of stable compounds assessed by sequential extraction was noted for lead, while the weakest immobilization was noted for cadmium. New insoluble mineral phases were identified by SEM-EDS analysis. Cd, Zn, and Pb formed new stable mineral substances with phosphates. The predominant crystal forms were dripstones and groups of needles, which were easily formed by dissolved carbon rock surfaces containing zinc ions. The alkaline nature of the soil and a large number of carbonates mainly influenced the formation of new structures.

Restoration and risk reduction of lead mining waste by phosphate-enriched biosolid amendments

“…The insignificant formation of pyromorphites in the high organic matter (OM) amended soil could be caused by (1) pyromorphite formation might be decreased by Pb-OM complexation; (2) pyromorphite crystal could be coated by organic coats that inhibited further pyromorphite formation and detection; or (3) organic coatings might help pyromorphite crystals move out of soil by enhanced colloidal transport 37 . In addition, the formation of pyromorphite could be inhibited in the presence of iron oxides and carbonates 38 , 39 . The surface coating of FePO 4 or AlPO 4 formed on the Pb solids may also prevent the formation and detection of pyromorphites 40 .…”

Synthesis and characterization of novel dual-capped Zn–urea nanofertilizers and application in nutrient delivery in wheat

“…A concentration-dependent interaction of P and Zn in soil that results in the formation of insoluble Zn phosphate can limit the uptake of either or both elements by plants. [53][54][55] This knowledge led us to evaluate the effect of the urea-Zn nanofertilizers on P uptake by the sorghum plants. Our data indicate that coating of urea with these products does not inuence the Zn-P interaction, and hence, P uptake, any more than the conventional Zn sulfate.…”

The Microbiology of Metal Mine Waste: Bioremediation Applications and Implications for Planetary Health

“…The orthophosphate (PO 4 3− ) anion is well known to form complexes with transition metals (Van Wazer & Callis, 1958). Phosphate compounds can be applied directly to soils impacted by metals and mine waste to form insoluble metal phosphate minerals (Andrunik et al, 2020;Cotter-Howells & Caporn, 1996). In addition, phosphate applied to mine waste can form metal phosphate coatings on sulfide minerals, preventing them from being oxidized, and thus, the formation of acid and dissolution of metals, although this had little impact on metalloid mobility (Harris & Lottermoser, 2006).…”