Soil washing of As-contaminated stream sediments in the vicinity of an abandoned mine in Korea

Abstract

A soil washing process was applied to remediate arsenic (As)-contaminated stream sediments around an abandoned mine in Goro, Korea. Laboratory scale soil washing experiments for As-contaminated stream sediments were performed under various washing conditions in order to maximize As removal efficiency. Stream sediments were taken from two sites (S1 and S5) along the main stream connected to an abandoned mine. Stream sediments at the two sites were divided into two groups (>or=0.35 and <0.35 mm in diameter), giving four types of sediments, which were thereupon used for soil washing experiments. The results of soil washing experiments involving various pH conditions suggested that As removal efficiency is very high in both strongly acidic and basic solutions (pH 1 and 13), regardless of sediment type. Removal efficiencies for fine sediments from S1 and S5 were >95% after 1 h of washing with 0.2 M citric acid (C(6)H(8)O(7)). When using 0.2 M citric acid mixed with 0.1 M potassium phosphate (KH(2)PO(4)), the As removal efficiency increased to 100%. When recycled washing solution was applied, As removal efficiency was maintained at a level greater than 70%, even after eight recycling events. This suggests that the recycling of washing solution could be successfully applied as a means of decreasing the cost of the washing process. Results from the experiments suggest that soil washing is a potentially useful process for the remediation of As-contaminated stream sediments around abandoned mines.

Laboratory and pilot scale soil washing of PAH and arsenic from a wood preservation site: Changes in concentration and toxicity

“…Chelating agents [S,S]-EDDS (Enviomet TM C140, Innospec Ltd., Cheshire, UK) and MGDA (TrilonM powder, BASF, Germany) were also used for As-removal. Both chelating agents were evaluated at a concentration of 0.213 M, corresponding to a concentration of 5 times the concentration of heavy metals, As and Fe in the soil [20], and adjusted to neutral pH. In addition the effect of pH was evaluated using either NaOH (Merck, Darmstadt, Germany), adjusted daily to pH 12 or HNO 3 (Scharlau Chimie, Barcelona, Spain) adjusted daily to pH 3.…”

“…Efforts made to mobilize arsenic often include leaching of iron-arsenic complexes, utilizing for example oxalic acid [19], but also chelating agents, such as citric acid [20] have been used. Concerning cationic heavy metals, more complex biodegradable chelating agents are also interesting in soil washing applications due to their capacity to complex heavy metals.…”

“…For PAH, the threshold values also depend on the molecular weight. MKM values for PAH are: Light weight PAH (PAH-L; naphthalene, acenaphthene and acenaphthylene) 15 mg/kg, medium weight PAH (PAH-M; flourene, phenanthrene, anthracene, flouranthene and pyrene) 20 In general, risk assessment only includes measurement of total concentration of target compounds. Therefore, utilization of an ecotoxicological evaluation may provide the risk assessment and treatment selection with valuable data on the effect of degradation products and changes in bioavailability which may arise during the remedial action.…”

Removal of heavy metals and arsenic from a co-contaminated soil by sieving combined with washing process

“…The As content in the leaching of coarse particles (> 2 mm) slowly increased with time, whereas the concentration decreased in those of grains <0.1 mm. Lee et al (2007) conducted a similar study with sediments from an abandoned coal mining site in which the concentration of As tended to increase with decreasing particle size; the As concentration of the particles < 0.15 mm was 3.8-12.0 times higher than that of the particles of 4.76-2 mm. We concluded from the SEM-EDX results and correlation analysis that the concentrations of As demonstrate an outstanding positive linear correlation with Fe both before and after treatment, whereas during the process of soil washing, the As was independent of Fe.…”

Waste Treatment and Remediation Technologies for Arsenic

“…In soils, arsenic is often associated with humic materials, which are more soluble in highly alkaline solutions than acids (Sullivan, Bowman andLegiec, 2003, 2388). Chemical similarities also allow phosphate solutions to desorb As(V) from mineral surfaces and soils (Hering and Kneebone, 2002, 166;Stollenwerk, 2003, 85-86, 91;Lee et al, 2007;Jackson and Miller, 2000). Kahakachchi, Uden and Tyson (2004) investigated the ability of various liquids to extract As(III), As(V), DMA(V), and MMA(V) from spiked soils.…”