The Oxidative Precipitation of Thallium at Alkaline pH for Treatment of Mining Influenced Water

Abstract

Thallium (Tl) may exceed regulatory limits in mining-influenced water (MIW) associated with processing cadmium, copper, gold, lead, and zinc ores. It is a toxic metal that is soluble over a wide pH range, resulting in both persistence in the environment and poor removal by conventional lime precipitation. This study evaluated the effect of potassium permanganate (KMnO 4 ) at alkaline pH on Tl removal from MIW in batch experiments. The oxidation of Tl ? to Tl 3? by KMnO 4 and subsequent Tl removal was explored at Tl concentrations of B1 mg/L in synthetic and actual MIW. In addition to Tl, the synthetic MIW contained &5 mg/L of Mn, while the actual MIW contained [10 mg/L of Al, Cu, Fe, Mn, and Zn and had a pH & 2.5. Dissolved Tl \2 lg/L in synthetic MIW was achieved at a pH & 9 (CaO addition) and C5 mg/L of KMnO 4 . In the actual MIW, dissolved Tl \2 lg/L was achieved at pH & 9 and C12 mg/L of KMnO 4 . The Tl removal mechanism is complicated due to the presence of reduced Mn in the synthetic MIW and multiple metals in the actual MIW. However, effective Tl removal was achieved by adding KMnO 4 to synthetic and actual MIW at alkaline pH.

Abundance and fate of thallium and its stable isotopes in the environment

“…This is what ultimately results in the extreme isotopic fractionation of Tl by Mn (? Fe) Davies et al 2016;Xu et al 2019) oxides, which leads to very positive isotope compositions. The Eh-pH diagram showing the strong predominance of Tl ?…”

Removal of Trace Thallium from Industrial Wastewater by Fe0-Electrocoagulation

“…Currently available methods for Tl removal mainly include adsorption [15][16][17][18], oxidation-reduction precipitation [19,20], solvent extraction [21], and ion exchange processes [22]. Most of these studies were conducted at a higher Tl concentration using model water [7], which is not consistent with the actual circumstances, i.e., real wastewater, where Tl concentration therein generally ranges from only a few µg/L to a few mg/L [23], while rarely exceeding 10 mg/L [24].…”

“…In this case, further research on the treatment of wastewater with lower Tl concentration (<1 mg/L) is essential. In their recent review of Tl removal processes, Xu et al [7] highlighted that, until now, only a few studies, where strong oxidants [20,25] or advanced oxidation [19,26] methods were used, reported that the effluent Tl concentration can meet the Tl emission standards of industrial wastewater in China (5 µg/L) and of some provincial standards (2 µg/L). Therefore, it is crucial to introduce a cost-effective technology for deep purification of low Tl concentration industrial wastewater to meet the strict emission requirements and reduce the risk of Tl pollution.…”

Bioremoval of Tl (I) by PVA-Immobilized Sulfate-Reducing Bacteria

“…Considering its high environmental toxicity and undoubted risks to human health, Tl-bearing wastewater with Tl concentrations above 2 μg.L -1 have required being treated if discharged into surface water identified as a drinking water source [5][6][7]. Generally, Tl-bearing wastewater was treated with adsorption, oxidative precipitation, ion exchange, filtration, electrodialysis, and reverse osmosis for decontamination [7][8][9].…”

“…Generally, Tl-bearing wastewater was treated with adsorption, oxidative precipitation, ion exchange, filtration, electrodialysis, and reverse osmosis for decontamination [7][8][9]. However, these processes were expensive and complex facilities or they led to secondary pollution [6]. For example, ion exchange was easily affected by environmental factors.…”