Scoping candidate minerals for stabilization of arsenic-bearing solid residuals

Abstract

Arsenic Crystallization Technology (ACT) is a potentially eco-friendly, effective technology for stabilization of arsenic-bearing solid residuals (ABSRs). The strategy is to convert ABSRs generated by water treatment facilities into minerals with a high arsenic capacity and long-term stability in mature, municipal solid waste landfills. Candidate minerals considered in this study include scorodite, arsenate hydroxyapatites, ferrous arsenates (symplesite-type minerals), tooeleite, and arsenated-schwertmannite. These minerals were evaluated as to ease of synthesis, applicability to use of iron-based ABSRs as a starting material, and arsenic leachability. The Toxicity Characteristic Leaching Procedure (TCLP) was used for preliminary assessment of candidate mineral leaching. Minerals that passed the TCLP and whose synthesis route was promising were subjected to a more aggressive leaching test using a simulated landfill leachate (SLL) solution. Scorodite and arsenate hydroxyapatites were not considered further because their synthesis conditions were not found to be favorable for general application. Tooeleite and silica-amended tooeleite showed high TCLP arsenic leaching and were also not investigated further. The synthesis process and leaching of ferrous arsenate and arsenated-schwertmannite were promising and of these, arsenated-schwertmannite was most stable during SLL testing. The latter two candidate minerals warrant synthesis optimization and more extensive testing.

Opposite effects of dissolved oxygen on the removal of As(III) and As(V) by carbonate structural Fe(II)

“… 39 used goethite, lepidocrocite and green rust to remediate arsenic and found that green rust was also transformed to parasymplesite in a reducing environment, resulting in significant attenuation of arsenic. Parasymplesite was previously demonstrated to be a good candidate for treating arsenic-bearing solid residuals, and it also passed the toxicity characteristic leaching procedure (arsenic leaching < 5 mg/L) 40 . The removal of As(V) under anoxic conditions by CSF was thus established as a promising approach for achieving highly efficient arsenic removal and forming stable products at the same time.…”

Stability of As(V)-sorbed schwertmannite under porphyry copper mine conditions

“…This indicates that the As(V) incorporated into schwertmannite may retard or significantly inhibit the Fe 2+ -catalyzed transformation of schwertmannite to goethite. It has also been reported that the presence of As(V) stabilizes schwertmannite and inhibits or significantly retards Fe(II)-catalyzed transformation to goethite (Burton et al, 2010;Raghav et al, 2013).…”

“…7b), indicating that Sch-As products here may be stable and that no solid transformation occurs. As(V) incorporated into schwertmannite may retard or significantly inhibit the transformation into more stable iron oxides (Fukushi et al, 2003;Burton et al, 2010Burton et al, , 2009Raghav et al, 2013;Regenspurg and Peiffer, 2005).…”

Leaching of Oxide Copper Ores by Addition of Weak Acid from Copper Smelters

“…The crystallization technology promotes the earth-mimetic mineral precipitation phenomena, compounds with a high capacity of crystallizing the toxic elements with long-term stability. Scorodite (FeAsO 4 •2H 2 O), tooeleite (Fe 6 (AsO 3 ) 4 SO 4 (OH) 4 •4H 2 O), and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) are examples of minerals that contain high quantities of toxic elements [25]. Scorodite is a very attractive compound for stabilizing arsenic due to its low solubility, high removal efficiency, low iron demand, and low volumes of waste material produced [26][27][28].…”

“…Tooeleite is an attractive mineral for wastewater treatment because of its high arsenic load (20-25% wt/wt) and natural stabilization during long periods [17,29]. The hydroxyapatites are a series of minerals that have been studied for the immobilization of lead, cadmium, nickel, copper, mercury, and arsenic [25].…”