Containment of phenol-impacted groundwater by vertical cutoff wall with backfill consisting of sand and bentonite modified with hydrophobic and hydrophilic polymers

Hao Ni; Ri-Dong Fan; Krishna R Reddy; Yan-Jun Du

doi:10.1016/j.jhazmat.2023.132627

Containment of phenol-impacted groundwater by vertical cutoff wall with backfill consisting of sand and bentonite modified with hydrophobic and hydrophilic polymers

J Hazard Mater. 2024 Jan 5:461:132627. doi: 10.1016/j.jhazmat.2023.132627. Epub 2023 Sep 29.

Authors

Hao Ni¹, Ri-Dong Fan², Krishna R Reddy³, Yan-Jun Du⁴

Affiliations

¹ Jiangsu Key Laboratory of Urban Underground Engineering & Environmental Safety, Institute of Geotechnical Engineering, Southeast University, Nanjing 210096, China. Electronic address: haoni@seu.edu.cn.
² College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China. Electronic address: fanrd@dhu.edu.cn.
³ Department of Civil, Materials, and Environmental Engineering, University of Illinois Chicago, IL 60607, USA. Electronic address: kreddy@uic.edu.
⁴ Jiangsu Key Laboratory of Urban Underground Engineering & Environmental Safety, Institute of Geotechnical Engineering, Southeast University, Nanjing 210096, China. Electronic address: duyanjun@seu.edu.cn.

PMID: 37793264
DOI: 10.1016/j.jhazmat.2023.132627

Abstract

A novel soil-bentonite backfill is proposed for use in vertical cutoff walls to contain phenol in groundwater at contaminated sites. The backfill consists of sand and bentonite modified with tetramethylammonium and carboxymethylcellulose, labeled as STCMB backfill. Flexible-wall permeability and double-reservoir diffusion tests were conducted to investigate the impact of phenol solution on hydraulic conductivity (k), effective diffusion coefficient (D*) and partition coefficient (K_p) of the backfill, respectively. The permeability results showed k of the STCMB backfill decreased by 0.91 times when the permeating liquid was changed from tap water to phenol solution. The diffusion testing results showed that D* values for the STCMB and conventional backfill (labeled as SCB backfill) were 4.0 × 10^-10 m²/s and 3.0 × 10^-10 m²/s, respectively, whereas K_p values for the STCMB and SCB backfills were 2.0 mL/g and 0.75 mL/g, respectively. The octanol-water partition coefficient model is suitable for estimating K_p for nonpolar organics. Furthermore, a series of solute transport simulations using Pollute V7 program was performed to evaluate the performance of vertical cutoff walls comprising STCMB and SCB backfills in containing phenol in lateral flowing groundwater. Overall, the STCMB backfill has demonstrated superior effectiveness in containing phenol in groundwater.

Keywords: Backfill; Diffusion test; Hydraulic conductivity; Modified bentonite; Vertical cutoff wall.