Removal of Arsenic, Boron, and Selenium from Excavated Rocks by Consecutive Washing

Abstract

This paper describes the leaching behavior and release mechanisms of arsenic (As), boron (B) and selenium (Se) from excavated rocks using sequential extraction for solid-phase fractionation, batch experiments with pH variation, and consecutive batch experiments with changes in the solid-liquid mixing ratios. Arsenic in the excavated rock was mostly found with the sulfides/organic matter fraction while majority of the leachable B and Se were associated with the exchangeable phases. The leaching of As was strongly pH dependent, Se was pH dependent only around the acidic region, and B was pH independent. Consecutive washing technique with deionized water effectively lowered the B and Se concentrations in the leachate below the drinking water standards of Japan, but was inefficient in the removal of As. Arsenic exhibited non-conservative leaching behavior and its movement was affected by processes like dissolution, precipitation and pyrite oxidation. In contrast, B and Se behaved more conservatively, resulting in their easy removal from the excavated rock by simple washing and dilution.

Fe‐modified Clinoptilolite is Effective to Recover Plant Biosurfactants Used for Removing Arsenic From Soil

“…Similarly, Krysiak and Karczewska have found that during the extraction of soils from Złoty Stok with Ca(NO 3 ) 2 at a pH < 2, intensive dissolution of Fe oxides occurred, and subsequently As was removed in a more soluble form. Arsenic mobility in soil is strongly limited by its high adsorption affinity for Fe/Al‐oxyhydroxides/oxides and clay minerals like kaolinite . By lowering the pH, protons can promote dissolution of arsenopyrite and/or metal oxide .…”

“…By lowering the pH, protons can promote dissolution of arsenopyrite and/or metal oxide . Moreover, an acidic pH prevents the precipitation of dissolved Fe as Fe‐oxyhydroxides/oxides . This can explain the reason of enhancing the removal of Fe at low pH values.…”

Suppression of the release of arsenic from arsenopyrite by carrier-microencapsulation using Ti-catechol complex

“…Mining, mineral processing and tunnel/underground construction for roads and railways often generate large amounts of wastes that contain sulfide minerals such as pyrite (FeS 2 ) and arsenopyrite (FeAsS), which produce acid mine drainage (AMD) when exposed to the environment [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. AMD is very acidic and could further extract heavy metals (e.g., Fe, Cu, Zn, and Pb) from other minerals found in the wastes.…”

“…In the first CME study of Satur et al [21], titanium (Ti)-catechol complex was synthesized by mixing TiO 2 minerals (rutile and anatase) and pyrocatechol (1,2-dihydroxybenzene). These authors showed that although catechol could extract 6 Ti-ions from TiO 2 directly, extraction efficiency was very low. CME was also successfully applied to suppress pyrite oxidation in this previous study but the mechanism(s) involved remained unclear because the authors mixed TiO 2 and catechol together with pyrite.…”

Solid-phase partitioning of mercury in artisanal gold mine tailings from selected key areas in Mindanao, Philippines, and its implications for mercury detoxification

“…Like other heavy metals and metalloids, mercury toxicity is closely related to its chemical form (i.e. methylmercury is more toxic than metallic/ionic mercury), while its mobility is strongly dependent on its solid-phase partitioning with different mineral phases in sediments and soils (Bakir et al, 1973; Millán et al, 2006; Tabelin et al, 2012a, 2012b). One of the most commonly used methods to determine the solid-phase partitioning of mercury is sequential extraction, a technique that involves treatment of the sample with a series of solvents that specifically attack certain minerals in the sample matrix (e.g.…”