P. Ferrantelli

Recovery of EDTA and metal precipitation from soil flushing solutions

This work studies the effectiveness of a process proposed for the recovery of ethylenediaminetetraacetic acid (EDTA) and metal precipitation from soil flushing solutions. Two series of experimental tests were carried out on two samples of a soil artificially contaminated with copper or lead. The metals were extracted from the soil by flushing with a 0.05 M aqueous solution of EDTA sodium salt (E-Na(2)). Cu or Pb extraction efficiencies of about 95 and 98% were observed, respectively. The two extracted solutions were then treated to obtain EDTA recovery and metal precipitation from the aqueous solution. EDTA recovery was achieved in two steps. An initial evaporation treatment lead to reduce the solution volume by about 75%. This was followed by the acidification of the residue solution, which precipitated more than 93% of the used EDTA. The precipitated EDTA was removed by filtration, and was suitable for reuse after adding an alkaline agent. Metal precipitation from the filtered solution was performed using two different methods: an almost total (99.5%) Pb precipitation in alkaline conditions was achieved after complex destabilization through the sequential addition of ferric ions and sodium phosphate, while 93.6% copper precipitation was achieved with ferrous sulfate as a destabilization agent.

Treatment of industrial landfill leachate by means of evaporation and reverse osmosis.

In this paper a process for the treatment of landfill leachate involving evaporation and reverse osmosis was proposed. Experimental tests were performed on an industrial landfill leachate. The leachate was subjected to evaporation so as to obtain a distillate containing a small amount of organic material and a substantial amount of inorganic substances (consisting primarily of metals and ammonium salts). The distillate of the evaporation treatment was then subjected to reverse osmosis. The reverie osmosis tests were performed using two different membranes: the AD membrane (thin two-ply film of polyamide) and the SC membrane (thin three-ply film of polyamide). Tests carried out at different values of pH showed a reduction of organic content of about 88% when AD membranes were used and about 80% with SC membranes independently of pH. As regards ammonium, comparable reductions of over 97% were registered for both types of membrane in the optimal conditions of pH = 6.4 (97.1% for AD membranes and 97.7% for SC).

Influence of Soil Organic Matter on Copper Extraction from Contaminated Soil

Column experiments of copper extraction from four contaminated soils characterized by a content of Soil Organic Matter (SOM) ranging from 1% to 25% are presented and discussed. The extraction was performed by flushing the soil with an aqueous solution of a sodium salt of ethylene diamminotetraacetic acid (EDTA). Preliminary tests were performed on a soil containing 25% of organic matter, to investigate the influence of pH, concentration and volumes of EDTA on its chelant action and on the dissolution of SOM. Having selected the optimal conditions for the extraction process, a further series of tests was conducted on the four soils to evaluate the influence of organic content on copper extraction yields. EDTA solutions at 0.01 M, 0.05 M, 0.1 and 0.2 M were injected at 0.33 ml/s; copper and organic matter extraction yield were determined. At a pH of 5, 15 pore volume (PV) of a solution containing 0.05M EDTA, extracted about 99% of copper contained by the soil with the higher organic matter content. Under the same conditions, and for soil with > 6% SOM, extraction yields over 80% were achieved, while at lower organic content, copper extraction was dramatically reduced. This was attributed to the formation of highly stable copper-humate complexes and to their increasingly dissolution that occurred in the soils with higher organic matter level. Experimental tests performed at different contamination levels (1200 mg/kg, 2400 mg/kg) showed that EDTA extraction effectiveness also depended upon initial soil Cu concentration.

Experimental study of the remediation of atrazine contaminated soils through soil extraction and subsequent peroxidation

This paper presents a feasibility study in the field of the remediation of soils contaminated with atrazine. Experimental tests were performed on an artificially contaminated synthetic soil. Atrazine was removed from the soil by flushing with an aqueous solution at 5 vol.% of ethanol. Experimental tests of evaporation and Fentons oxidation on the extracted solution were then performed in order to transform atrazine into its oxidation products. Tests were performed in the presence of a peroxide excess the ratio between Fe(2+) and H(2)O(2) was 1:10. Peroxide was first added in order to reduce the consumption of hydroxyl radicals by their reaction with the excess of Fe(2+). The degradation mechanism of atrazine during oxidation with Fentons reagent in the presence of ethanol was investigated. Results showed that due to the non selective nature of Fentons reagent a high consumption of reagent was needed to achieve a significant atrazine oxidation from solutions at 4.5 vol.% of ethanol. While at a Fe(2+) concentration of 3mM atrazine practically disappeared from pure aqueous solutions within 2h, a degradation yield of only 28.1% was observed in the presence of ethanol even when Fe(2+) concentration was 15 mM.

EDTA Leaching of Copper from Contaminated Soils: Experimental Study and Transport Model Application for Parameters Estimation

EDTA columns extraction were performed on four artificially contaminated soils, followed by the percolation of pure water to ensure the removal of EDTA entrapped in soil. The investigated soils were characterized by a content of organic matter ranging from 1% to 25%. A mathematical model was developed for copper leaching from the soils. The correlation of experimental data shows that while the EDTA transport was not affected by the soil organic fraction, the simulated transport of Cu-EDTA complexes in solution exhibited a delay effect due to the chemical adsorption of such complexes onto the soil organic matter. The distribution coefficient (Kd ), between the solid and liquid phases showed a logarithmic increase when the organic content of soil increased. The columns hydrodynamic characteristics (αL ) and the kinetic coefficients (k) of chelant extraction were estimated independently for each soil. A correlation of kinetic coefficients data versus soils organic content was also proposed: experimental data showed, in the investigated range, a logarithmic dependence of k on the organic content of soil.

Ethylene glycol recovery from dilute aqueous solution

This paper deals with an experimental study performed to evaluate the feasibility of a process for the recovery of ethylene glycol from a dilute aqueous solution, such as Poly-Ethylene-Terephtalate wastewater. According to the proposed process aqueous solutions, at 1.3% by weight of ethylene, glycol was submitted to a preliminary evaporation stage, followed by the treatment of the collected distillate in a reverse osmosis unit. The main aim of this study was to find the operative conditions of each treatment unit that ensured the concentration of the solution up to the grade required in the pure ethylene glycol production process, to allow the recovery of ethylene glycol and to minimize its consumption.

Experimental assessment of the operative conditions of copper extraction from three contaminated soils

Column experiments of EDTA extraction of copper from a sandy, a calcareous, and a highly organic soil, were performed. The influence of EDTA concentration, pH, and the flow rate of a flushing solution on copper extraction yield was investigated. Extraction yields of 84.8%, 93.0% and 96.9% were achieved respectively for sandy soil, calcareous soil and highly organic soil, after the injection of a volume of flushing solution equal to 15 pore volumes. TOC measurements performed on the extracted solution showed that, after the extraction phase, the percolation of an equal volume of water was necessary to ensure complete EDTA removal from the treated soils. In addition, results showed that the simultaneous dissolution of calcite consumed approximately 93.6% of the chelant agent when EDTA concentration in the flushing solution was 0.05 M.