Simultaneous decontamination of cross-polluted soils with heavy metals and PCBs using a nano-metallic Ca/CaO dispersion mixture

Abstract

In the present work, we investigated the use of nano-metallic calcium (Ca) and calcium oxide (CaO) dispersion mixture for the simultaneous remediation of contaminated soils with both heavy metals (As, Cd, Cr, and Pb) and polychlorinated biphenyls (PCBs). Regardless of soil moisture content, nano-metallic Ca/CaO dispersion mixture achieved about 95-99% of heavy metal immobilization by a simple grinding process. During the same treatment, reasonable PCB hydrodechlorination efficiencies were obtained (up to 97%), though higher hydrodechlorination efficiency by preliminary drying of soil was observed.

Novel separation and immobilization of heavy metals in municipal solid waste fly ash by grinding with nano‐Fe/Ca/CaO/[PO4] mixture

“…Indeed, on the FA surfaces, association of Ca/[PO 4 ]/H 2 O/[CO 3 ] compounds are present (e.g. apatite—Ca 10 (PO 4 ) 6 (OH) 2 ), calcium carbonate—CaCO 3 , or calcium hydroxide—Ca(OH) 2 ) (Figure b) .…”

“…Consequently, HMs (As, Cd, Cr, and Pb) are entrapped into the immobile [Ca]/[PO 4 ] salts. Based on our previous studies for soil treatment, in the XRD patterns of soil that was subjected to grinding with nanometallic Ca/ CaO, peaks related to Ca crystalline phases (CaCO 3 / Ca(OH) 2 ) appeared in addition to quartz, kaolinite, and bentonite, which probably indicate that the main fraction of enclosed/bound materials included Ca-associated complexes [18,19]. Furthermore, it was confirmed by electron probe microanalyzer (EPMA) analysis of a cross-section of a single soil particle that, enclosed on the soil surface, Ca associative complexes are present; their formation is a consequence to the treatment with nanometallic Ca/CaO [18,19].…”

“…However, during grinding with nano-Fe/Ca/CaO/PO 4 additives, FA particles are subjected to collisions that are expected to promote aggregation and breakage phenomena [23]. (Figure 3b) [16][17][18][19]. Furthermore, the transformations suffered by HMs in/on FA particles depend of the standard redox potential of the contaminant metal relatively to Fe.…”

Hybrid zero valent iron (ZVI)/H2O2oxidation process for landfill leachate treatment with novel nanosize metallic calcium/iron composite

“…On the other hand, we have previously reported that treatment of waste containing multipollutants (i.e., persistent organic pollutants [POPs], heavy metals, and radioactive cesium) with a nanometallic calcium/iron dispersion mixture is most effective (Mallampati et al, 2012;Mitoma et al, 2013;Mallampati et al, 2014a;Mallampati et al, 2014b;Mallampati et al, 2015). Nanometallic calcium/iron has been never used as a catalyst for the purpose of multicontaminant treatment in landfill leachate.…”

“…These floes are able to aggregate with suspended polluting matter. Therefore, nanocoagulantion initiates organic compounds encapsulation through the formation of immobile salts, for example, by reacting with water, yielding a Ca-associated (CaCO 3 /Ca(OH) 2 ) precipitate that encloses/binds organic particle surfaces (Mallampati et al, 2012;Mallampati et al, 2014b) (eq 1). On the other hand, with nFe/Ca/CaO, the iron particle addition in the aqueous phase dissolves ferrous ions and electrons transfer to react with the organic molecules on the iron's surface.…”