Abstract
Leaching behaviour of heavy metals (HMs) from simulated soil (SS), prepared according to standard guidelines, as well as its constituents (quartz sand (QS), bentonite clay (BC), and peat moss (PM)) were investigated. The study focused on a batch process with the aim of comparing the leaching potentials and metals solubilisation of ethylene diamine tetraacetic acid (EDTA), ethylene diamine disuccinic acid (EDDS), acetylacetone (Hacac), citric acid (CA), and tartaric acid (TA) for sustainable metal extraction purposes after a maximum leaching time of 60 min. The HMs concentrations with which the constituents were spiked with was such that reflected a contaminated site. The recovery potentials of both the SS and its constituents were found to vary for single metal (SM) and multi-metal (MM) systems. EDTA was the most efficient (on average 31% and 33% for SM and MM) and TA the least efficient (on average of 2% and 3% for SM and MM) extractant. For Hacac, preferential recovery for Cu and Ni were significant when compared to the other metals, while, metal recovery by EDDS in SS was lower than could be expected. The leaching trend for the targeted metals was studied using conventional leaching models.
Highlights
Soil pollution is a global issue [1] [2] [3] and is usually the result of human activities, such as mining and metallurgical activities [4], oil refining [5], traffic [6], chemical plant processes [7] and agricultural production [8]
The goodness of fit of each model was evaluated according to its correlation coefficient (R2) and standard error of estimate (SE) calculated from Equation (6), where q and q’ are measured and predicted amounts of metals leached at time t, respectively, and n is the number of measurements
tartaric acid (TA) was again the poorest performer of all the extractants with a maximum extraction of 29% for Ni followed by Cu, Zn, Pb, and Cd. These results suggest that sequential extraction of the different metals could be achieved by exploiting the differences in efficiencies of the different washing/leaching agents on the different metals
Summary
Soil pollution is a global issue [1] [2] [3] and is usually the result of human activities, such as mining and metallurgical activities [4], oil refining [5], traffic [6], chemical plant processes [7] and agricultural production [8]. Mineralogical and geo-metallurgical factors are of prime importance in metals recovery from any mined ore It can, be expected that leaching and extraction of heavy metals from contaminated soils and wastes will be influenced by the soil composition and constituents. The profiles of the process of metal removal will be gauged to provide guidelines for choosing an appropriate unit process or combination of processes, which could be selected for such an operation This could provide the necessary basis for design purposes of treatment equipment, which can be applied to other applications in this field, e.g. mining and metallurgical wastes or oil-polluted areas such as the Niger Delta. This paper will describe and discuss the results obtained in the investigation
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