Polymer assisted ultrafiltration for copper?citric acid chelate removal from wash solutions of contaminated soil

Abstract

The removal of heavy metals from aqueous systems such as wash-solutions of contaminated soil by using PolymerAssisted Ultrafiltration (PAUF) has been studied. For the extraction of metal ions from contaminated soil citric acid is used as a chelating agent. Cu 2+ as metal ion and the polymer polyethylenimine (PEI) as ligand were used in the various experiments. Optimal chemical conditions for copper complexation by citric acid were determined by means of complexation tests. The results showed that citric acid is able to chelate copper ions at pH 5.5, while decomplexation occurs at pH £ 2. Maximum bonding capacity (saturation condition) was 0.625 mg Cu 2+ per mg citric acid, meaning 2 mol Cu 2+ per mol citric acid. Complexation tests in the system polyethylenimine-citric acid-copper showed that the polymer is able to complex the copper-citric acid chelate at pH = 6 while release occurs at pH < 3. The saturation condition was 0.333 mg Cu 2+ per mg PEI. The ultrafiltration tests, carried out at three trans-membrane pressures (2, 3 and 4 bar), showed the possibility of using the PAUF technique for copper ion removal from aqueous solutions.

Polymer in Agriculture: a Review

“…For remediating sites contaminated with inorganic pollutants, several techniques have been developed. All these technique are based on two principles referred to as immobilization or mobilization principle [57] . In the first case, the retention of heavy metals on soil is increased, but in this way a not permanent solution is raised, because metals still remain in the soil with possible long-term side effect on bio-systems.…”

Chemical and operational aspects in running the polymer assisted ultrafiltration for separation of copper(II)–citrate complexes from aqueous media

“…For evaluating membrane permeability the membranes were characterized with ultrapure water (Elix 5, Millipore) before their use by progressively decreasing the trans-membrane pressure as reported in our previous works [24][25][26][27]. The obtained ultrapure water flux J 0 was compared with the permeate flux J P obtained during ultrafiltration runs for estimating membrane fouling.…”

“…Citric acid is able to chelate copper ion at pH between 5 and 6, while the decomplexation happens at pH ≤ 2 [24]. Indeed, a pH 5.5 is usually employed in soil washing operation using aqueous solutions of citric acid as chelating agent [7].…”

“…Indeed, a pH 5.5 is usually employed in soil washing operation using aqueous solutions of citric acid as chelating agent [7]. The optimal citrate/copper weight ratio is 1.6/1, corresponding to a stoichiometric ratio of 1/2 [24].…”

“…In a preliminary work [24] we examined the retention of copper(II)-citrate chelates from dilute aqueous solutions by polyethylenimine assisted UF process. The separation of the model ion Cu 2+ from a solution containing citric acid (thus hypothesising its use as extracting chelating agent in soil washing) and the water soluble polymer polyethylenimine (PEI), as macromolecular complexing agent, was carried out.…”