Simultaneous phenanthrene and cadmium removal from contaminated soil by a ligand/biosurfactant solution

Abstract

Surfactants and inorganic ligands are pointed as efficient to simultaneous removal of heavy metals and hydrophobic organic pollutants from soil. However, the biosurfactants are potentially less toxic to soil organisms than other chemical agents. Thus, in this study the efficiency of combinations of iodide (I(-)) ligand and surfactants produced by different bacterial species in the simultaneous removal of cadmium (Cd(2+)) and phenanthrene in a Haplustox soil sample was investigated. Four microbial surfactants and the synthetic surfactant Triton X-100 were tested with different concentrations of ligand. Soil samples contaminated with Cd(2+) and phenanthrene underwent consecutive washings with a surfactant/ligand solution. The removal of Cd(2+) increased with increased ligand concentration, particularly in solutions containing biosurfactants produced by the bacterial strains Bacillus subtilis LBBMA155 (lipopeptide) and Flavobacterium sp. LBBMA168 (mixture of flavolipids) and Triton X-100. Maximum Cd(2+) removal efficiency was 99.2% for biosurfactant produced by Arthrobacter oxydans LBBMA 201 (lipopeptide) and 99.2% for biosurfactant produced by Bacillus sp. LBBMA111A (mixed lipopeptide) in the presence of 0.336 mol iodide l(-1), while the maximum efficiency of Triton X-100 removal was 65.0%. The biosurfactant solutions removed from 80 to 88.0% of phenanthrene in soil, and the removal was not influenced by the presence of the ligand. Triton X-100 removed from 73 to 88% of the phenanthrene and, differently from the biosurfactants, iodide influenced the removal efficiency. The results indicate that the use of a single washing agent, called surfactant-ligand, affords simultaneous removal of organic contaminants and heavy metals.

Use of surfactants for the remediation of contaminated soils: A review

“…An electrokinetic washing of contaminated soils revealed that 73% of phenanthrene and 82% of Pb could be removed with the combined use of 1% Tween 80 and 0.1 M EDTA [143]. Cao [144] reported that the mixture of saponin and EDDS solution, the removal rates of Cd 2+ and phenanthrene can be improved by 36.3% and 15.2% [146]. In addition to above mentioned additives, biological additives [100,126], water-soluble polymers [147] and inorganic salts [148] were reported as the admixtures of surfactant solution for soil remediation.…”

Impact of bioaccessible pyrene on the abundance of antibiotic resistance genes during Sphingobium sp.- and sophorolipid-enhanced bioremediation in soil

“…Among these efforts, bioremediation with degrading bacteria and surfactant application proved to be one of the most efficient ways for the simultaneous removal of mixed pollutants from soil [5,6]. However, there is emerging evidence indicating that the co-existence of persistent organic pollutants with antibiotics or antibiotic resistance genes (ARGs) is a concern, which is not yet fully understood [7,8].…”

Remediation of Heavy Metal-Contaminated Agricultural Soils Using Microbes

“…These biosurfactants produced by microbes form complexes with heavy metals at the soil interface, desorb metals from soil matrix and, therefore, enhance metal solubility and bioavailability in the soil solution. Interestingly, there is substantial evidence which suggests that the microbes producing surfactants increase the heavy metal mobilization in contaminated soils (Juwarkar et Lima et al 2011 ). The Cd and Pb metal compounds' mobilization potential of P. aeruginosa BS2 under in vitro column experiments (artifi cial metal-contaminated soil) have been reported through the production of a dirhamnolipid biosurfactant (Juwarkar et al 2007 ).…”