Soil Washing Technology for Removing Heavy Metals from a Contaminated Soil: A Case Study

Abstract

Although EDTA solution is considered an efficient soil washing liquid for extraction of heavy metals from soils, its low biodegradability may alter soil properties and suppress plant growth. Alternatively, chlorides are safer and cheaper washing liquids than EDTA. To investigate the efficiency of chlorides versus EDTA in extracting heavy metals from contaminated soils, soil samples (pH 6.14±0.11) were collected from a local agriculture soil in Australia, artificially contaminated with either Pb, Cd or Cr at three different levels of 200, 400 and 600 mg kg -1 , and then packed in capped plastic flasks. Batch washing techniques were followed with either EDTA or FeCl 3 solutions (prepared at 4 different concentrations of 0.05, 0.1, 0.25 and 0.5 M), and soil suspensions were agitated for different time periods (from 5.0 min. to 60.0 min); afterward, the extraction efficiencies of the investigated metals were considered. The removal efficiency of Pb from the contaminated soil (200 mg Pb kg -1 ) after 5 minutes of EDTA application seemed to be relatively high (≈75%). Afterward this efficiency decreased gradually with time. The efficiencies of the extracted Cd and Cr by soil washing with EDTA increased significantly with increases in the agitating period. Generally, the extraction efficiencies by EDTA decreased noticeably with increasing levels of soil contamination. On the other hand, the efficiencies of Pb, Cd and Cr extractions were high -especially when increasing both the concentrations of applied FeCl 3 solution and the time of agitation. The results also highlighted that soil washing with FeCl 3 seemed to be more favourable over EDTA for rapid extraction of heavy metals from contaminated soils. The efficiencies of extracting heavy metals by soil washing with 0.5M FeCl 3 for only one hour were 93.79±2.35%, 97.4±2.45% and 81.75±7.86% for Pb, Cd and Cr, respectively.

Circular bioprocess for phosphorus nutrient recovery to grow lettuce in lunar space

“…This omission of molecular change following P leaching permits for selection and design of equipment aligned with principles of (process) simplicity, that likely will be needed to support operation in lunar space. 51 Leaching of P from the root ash included three (3) steps, namely; 52 (1) mixing of ash with an acidic leachate to form a fine suspension via intense stirring, or a microfluidic settingtraditional leaching agents use hydrochloric acid, nitric acid and sulphuric acid, 53 together with organic acids including citric and oxalic acid; 54 (2) solid-liquid separation ( preferably) by filtration; and (3) potential removal of toxic compounds including heavy metals that might otherwise accumulate from the biomass and biofertiliser during recycling. However, this step might be ultimately obviated because a well-operated space farm will ensure an absence of inflow of heavy metals.…”

Feasibility of a Chemical Washing Method for Treating Soil Enriched with Fluorine Derived from Mica

“…Chemical washing has been widely used as a treatment method for soil contaminated with metals and metalloids [17][18][19][20][21][22][23][24]. The chemical washing process can be implemented within a short period of time compared to solidification and stabilization technologies, and this means that it may be possible to reuse the site quickly.…”

Chemical Leaching of Contaminated Soil – Case Study

“…The EDTA leaching can be used to treat a broad range of soil types [3,4,5,6]. However, EDTA is of low biodegradability in soil and persists under natural conditions [6]. The management of spent washing solutions makes up a significant cost of the whole remediation process.…”