Bentonite addition to a PCB-contaminated sandy soil improved the growth and phytoremediation efficiency of <i>Zea mays</i> L. and <i>Alternanthera sessilis</i> L. SalimizadehMaryam ShirvaniMehran ShariatmadariHossein MortazaviMohammad Seddiq 2019 <p>In this study, the removal of 17 selected PCB<sub>i</sub> congeners was assessed in a transformer oil-contaminated soil amended with bentonite clay powder applied at the three levels of 0, 2, and 4% and cultivated by <i>Zea mays</i> L. or <i>Alternanthera sessilis</i> L. in a pot experiment. Results showed that <i>Z. mays</i> and <i>A</i>. <i>sessilis</i> were able to reduce the residual concentrations of the PCB<sub>i</sub> congeners in the contaminated soil significantly (<i>p</i> < 0.05). The average reductions in the ƩPCB<sub>i</sub> due to <i>Z. mays</i> or <i>A</i>. <i>sessilis</i> cultivations were 34.3 and 21.4%, respectively, depending on initial soil ƩPCB<sub>i</sub> loading and plant growth period. Moreover, addition of bentonite led to significant (<i>p</i> < 0.05) enhancements in plant growth and dissipation of residual soil PCB<sub>i</sub> congeners under <i>Z. mays</i> and <i>A</i>. <i>sessilis</i> cultivations. Addition of 4% bentonite to the soil was found to have the greatest positive impact on PCB<sub>i</sub> removal so that average PCB<sub>i</sub> dissipations in the soil were 56.1 and 51.8% after growing <i>Z. mays</i> and <i>A</i>. <i>sessilis</i>, respectively. It might be concluded that the combined phytoremediation and bentonite addition is an effective technique for removing PCB<sub>i</sub> and remediating transformer oil-contaminated coarse-textured soils.</p>