Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman Research article Polymer extraction and ex situ biodegradation of xenobiotic contaminated soil: Modelling of the process concept Domenica Mosca Angelucci a , M. Cristina Annesini b , Andrew J. Daugulis c , M. Concetta Tomei a,∗ a Water Research Institute, C.N.R., Via Salaria Km 29.300, CP 10, 00015, Monterotondo Stazione, Rome, Italy b Department of Chemical Engineering Materials & Environment, Sapienza University of Rome, Via Eudossiana 18, 00184, Rome, Italy c Department of Chemical Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada ARTICLE INFO Keywords: Ex situ soil bioremediation Absorptive polymers 4-Nitrophenol Two-phase partitioning bioreactors Process modelling ABSTRACT An integrated model of a two-step process for the ex situ bioremediation of xenobiotic contaminated soil has been formulated. The process is characterized by an initial extraction step of the organic contaminants from the polluted soil by contact with inexpensive and commercially-available polymer beads, followed by release and biodegradation of the xenobiotics, with parallel polymer bioregeneration, in a Two-Phase Partitioning Bioreactor (TPPB). The regenerated polymer is cyclically reused in the extraction step, so refecting the robust and otherwise-inert properties of such polymers. The model was calibrated and validated for a soil contaminated with 4-nitrophenol (4NP) and treated with the DuPont polymer Hytrel 8206. In the model calibration, the partition coefcient polymer-soil, P ps , and the mass transfer coefcient, K, were evaluated, as 105.3 and 0.24 h −1 respectively. A difusion coefcient within the polymer of 6.3 10 −8 cm 2 s −1 was determined from the ftting of sorption/desorption data. The model was then tested for two alternative process confgurations consisting of either one or two soil extraction units, followed by the biodegradation/bioregeneration step. The latter con- fguration resulted in more efective polymer utilization and is suitable if each extraction step requires a shorter time than the regeneration step. The model predicted that an extraction time of 12 h was sufcient to reach removal efciencies ≥90% while the biodegradation/bioregeneration step required 24 h to reach efciencies ≥93%, with a good agreement with experimental data (R 2 > 0.98 for both cases). The simulation of the process operated with two extraction units showed a better performance with a fnal concentration ∼0.2 g 4NP kg ds −1 vs. 1.69 g 4NP kg ds −1 obtained with single extraction unit, for a soil contaminated with 10 g 4NP kg ds −1 . Corresponding extraction efciencies were 96 and 83%, respectively. 1. Introduction An innovative bio-treatment system has recently been shown to be efective for the ex situ remediation of soils contaminated with re- fractory organic compounds: solid phase extraction performed with amorphous polymer beads followed by their biological regenera- tion, and contaminant biodegradation, in Two-Phase Partitioning Bioreactors (TPPB) as depicted in Fig. 1. This decontamination strategy involves two sequential process steps: contacting contaminated soil with polymers, during which the pollutants are sorbed from the soil into the polymeric absorbent phase (polymer-extraction step), followed by pollutant release and biodegradation under controlled conditions (bioregeneration step) in a pre-inoculated TPPB. The strategy behind the use of inert and commercially available polymers to extract con- taminants from soil is based on the high afnity of the target organic contaminants for the polymeric phase and on the ease of regenerating the “contaminated polymer”, thus generating “fresh” polymer for its subsequent reuse. A variety of chemically distinct polymers, under a number of op- erating conditions (i.e. use of various mobilizing agents, polymer-to-soil ratio and contaminant soil concentration), have been tested to char- acterize the polymer-extraction step. Prpich et al. (2006) used Hytrel 8206 to remove phenol from a contaminated soil achieving removal of 95% in 24 h. Similar results were obtained with the same polymer in treating soil contaminated with 4-nitrophenol: 4 h were sufcient to reach 77% extraction efciency by using only tap water (100% w/w) as a mobilizing agent (Tomei et al., 2013). Rehmann and Daugulis (2008) treated a soil contaminated by the polychlorinated biphenyl (PCB) Aroclor 1242 with Hytrel: after two days of contact time and using 15% w/w of isopropyl alcohol as mobilizing agent, the PCB concentration in https://doi.org/10.1016/j.jenvman.2018.09.045 Received 3 October 2017; Received in revised form 12 September 2018; Accepted 12 September 2018 ∗ Corresponding author. E-mail address: tomei@irsa.cnr.it (M.C. Tomei). Journal of Environmental Management 230 (2019) 63–74 0301-4797/ © 2018 Elsevier Ltd. All rights reserved. T