Assessment of bimetallic Zn/Fe0 nanoparticles stabilized Tween-80 and rhamnolipid foams for the remediation of diesel contaminated clay soil

Abstract

Diesel contamination of soil due to oil spills, disposal of refinery waste, oil exploration constitutes a major environmental problem. This paper reports the remediation of diesel contaminated clay soil using Zn/Fe⁰ bimetallic nanoparticle stabilized Rhamnolipid (RMLP) and Tween-80 (TW-80) surfactant foams. Fe⁰, and Zn (x wt%)/Fe⁰ (x = 0.2, 2.0, and 10.0) bimetallic nanoparticles are synthesized by using sodium borohydride reduction method. The average particle size (from FESEM) is calculated to be 62, 57, 42 and 35 nm for the Fe⁰, Zn (0.2)/Fe⁰, Zn (2)/Fe⁰ and Zn (10)/Fe⁰ nanopowders, respectively. The highest foamability and foam stability of 109.6 and 108.5 mL, respectively are observed for the RMLP (12 mg/l) surfactant foam stabilized with 6 mg/l Zn (10)/Fe⁰ nanoparticles. The surface tension values reduce to the lowest value of 28.1 and 31.4 mN/m with the addition of 6 mg/l of Zn (10)/Fe⁰ powder in RMLP and TW-80 solutions of 12 mg/l, respectively. The maximum diesel removal efficiency of 83.8 and 59%, is achieved by RMLP (12 mg/l) foam stabilized by Zn (10)/Fe⁰ nanoparticles (6 mg/l) for the clay soil contaminated with 100 and 500 μl/g of diesel, respectively. The physicochemical properties of the nanoparticles are studied to explain the foam properties and the remediation behavior. These findings regarding the nanoparticle stabilized foams can offer a cost-effective environment friendly commercial solution for soil remediation in the future.

Keywords: Diesel contaminated clay soil; Rhamnolipid surfactant foam; Soil remediation; Tween-80 surfactant foam; Zinc/ zero valent iron nanoparticles.