Metal Removal from Contaminated Soil and Sediments by the Biosurfactant Surfactin

Abstract

Batch soil washing experiments were performed to evaluate the feasibility of using surfactin from Bacillus subtilis, a lipopeptide biosurfactant, for the removal of heavy metals from a contaminated soil and sediments. The soil contained high levels of metals and hydrocarbons (890 mg/kg of zinc, 420 mg/kg of copper, and 12.6% oil and grease), and the sediments contained 110 mg/kg of copper and 3300 mg/kg of zinc. The contaminated soil was spiked to increase the levels of copper, zinc, and cadmium to 550, 1200, and 2000 mg/kg, respectively. Water alone removed minimal amounts of copper and zinc (less than 1%). Results showed that 0.25% surfactin/1% NaOH could remove 25% of the copper and 6% of the zinc from the soil and 15% of the copper and 6% of the zinc from the sediments. A series of five washings of the soil with 0.25% surfactin (1% NaOH) was able to remove 70% of the copper and 22% of the zinc. The technique of ultrafiltration and the measurement of octanol−water partitioning and ζ-potential were used to determine the mechanism of metal removal by surfactin. It was indicated that surfactin was able to remove the metals by sorption at the soil interphase and metal complexation, followed by desorption of the metal through interfacial tension lowering and fluid forces and finally complexation of the metal with the micelles.

Effect of copper on the adsorption of p-nitrophenol onto soils

“…Heavy metals and organic contaminants coexist in soil. Several studies have been undertaken to investigate the adsorption and desorption on soil of either heavy metals (Liu and Richard, 2000;Du¨ring et al, 2003;Mulligan et al, 1999) or organic contaminants (Gimsing et al, 2004b;Pusino et al, 2003) separately. However, little attention has been given to determine the effect of heavy metals on the adsorption of organic contaminants on soils.…”

“…Soil suspension pH was measured at a soil to water ratio of 1:1 (w/v). Organic carbon content in soils was determined by the Walkley-Black's method (Nelson and Sommers, 1982). Amorphous Fe-, Al-and Mn-oxides were determined by ammonium oxalate extraction methods (McKeague and Day, 1966).…”

Surfactina: propriedades químicas, tecnológicas e funcionais para aplicações em alimentos

“…Surfactantes produzidos por diferentes linhagens de Bacillus subtilis, além de serem obtidos por processos menos agressivos sob o ponto de vista ambiental, apresentaram efeitos significativos na biodegradação de hidrocarbonetos alifáticos e aromáticos [18][19][20] , remoção de óleo de areia contaminada 19,21 , formação de emulsões estáveis em óleo 21 , bem como na degradação do pesticida endosulfan 22 e biorremediação de solos altamente contaminados por zinco e cádmio 23 .…”

Research Progress in Lipopeptide Biosurfactants

“…Meanwhile, Lipopeptide biosurfactants can be used to remove many kinds of metal ions existing in the soil, such as copper, zinc and lead, of which copper ions are the easiest to remove [21].…”