# Remediation Opportunities for Arsenic-Contaminated Gold Mine Waste
## 3 Mitigating Arsenic-Contaminated Mine Waste
### Arsenic Remediation Techniques  
#### 3.3.1 Physical and Chemical  
Traditional methods for remediating potentially toxic elements (PTEs) from contaminated soil involve physical and chemical techniques. Physical techniques include excavation, soil washing, diluting with clean soil, deep ploughing to mix surface soil with subsurface soil, and extracting soil for relocation to landfill (Table 2) [16; 73; 74]. Currently, physical mine waste disposal, i.e., tailings dams, is common practice. For example, in Turkey, 71.2% of total mine waste was sent to spoil locations, tailings dams, and designated long term storage [75]. Chemical treatments of contaminated soil involve ion exchange, chemical precipitation, adsorption, and encapsulation [76]. Some common chemicals used for the oxidation of arsenite to arsenite are hydrogen peroxide, potassium permanganate, and sulphur dioxide [31]. One chemical treatment that has gained attention is containment of mine waste with repositories to limit oxidation and achieve cement encapsulation [31; 77]. Encapsulation aims to stabilise toxic elements and pollutants by immobilising and/or insolibilising elements to prevent leaching and bioavailability. Some examples are solidifying mine waste onite in a monolithic structure and utilising mine tailings to produce cement for building infrastructure [31; 77; 78]. Recently, a study by [PERSON] et al. [78] proposed cement encapsulation by replacing sand with mine tailings in the cement matrix for the construction industry. This cement would be used to build infrastructure such as housing materials, roads, and sidewalks [78]. Results stated that ecological toxicity (ecotoxicity) and human health toxicity decreased, and encapsulation was achieved; however, PTEs like As were not quantified or discussed. Additionally, no toxicity tests were conducted on cement dust such as the Microx bioassay. The primary carcinogenic elements in cement dust are As, silica (Si), and chromium (Cr) [79]. A study by [PERSON] et al. [79] addressed the toxic effects of exposure to As-, Si-, and Cr-rich cement dust for cement workers and administrative staff in the cement industry. Administrative staff had higher risk of exposure and health impacts such as lung damage because of the absence of control measures (e.g., N95 masks) [79]. [PERSON] et al. [80] researched dust sediments from the Mount Etna region in Sicily to study the toxic effects using the Microtax method. Dust sediments included basalt, volcanic ash, basalt + cement, and cement; the Microx results were 19.31%, 31.22%, 99.05%, and 98.95% toxicity, respectively, which confirmed that cement dust sediments had a significantly higher toxicity percentage and risk to the ecological environment and human health [79; 80]. It is dangerous to substitute sand with As-rich mine tailings to produce cement/bricks as there is currently a toxicity problem with cement dust without the addition of mine tailings. [PERSON] et al. [78] performed a compressive strength \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Site** & **Soil Type** & **As (mg/kg)** &
\begin{tabular}{c} **Legislated** \\ **Values (mg/kg)** \\ \end{tabular} & **References** \\ \hline Zloty Stok Gold Mine, Poland & Soil & 860–5751 & & [59] \\ Griffies Mine, Jachymov, Czech & Soil & 74–3697 & & [60] \\ Republic & & & & \\ Hilligrove Mine, New South & & & & \\ Wales, Australia & Soil & 826–1606 & 100 & [5; 70] \\ Victoria, Australia & Soil & 9–9900 & 100 & [5; 49] \\ Victoria, Australia & Mine waste & 1210–22,000 & 100 & [5; 63] \\ Macares Mine, South Island, & Mine waste & 65–98,300 & & [71] \\ Dawdong, Liaoning Province, & Soil & 1944 & & [72] \\ China & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: \(Cont.\)analysis on varying sand to tailings ratios over twenty-eight days. Tailings that replaced 5% of sand had slightly weaker strength compared to the control; however, a tailings ratio beyond 10% decreased strength.