Combined application of <i>Azadirachta indica</i> leaf extract and zerovalent iron nanoparticles (nZVI) enhances phytoremediation potential of <i>Brassica napus</i> L. in surgical industry wastewater

This study investigated the potential of <i>Brassica napus</i> L. to remediate heavy metals from surgical industry wastewater through the application of neem (<i>Azadirachta indica</i> L.) leaf extract and nZVI. Plants exposed to untreated wastewater exhibited significant reductions in growth and photosynthetic pigments. However, the combined application of neem extract and nZVI improved plant height by 318%, number of leaves by 300%, leaf area by 329%, and root length by 63% at 100% wastewater concentration. The treatment also decreased oxidative stress indicators, including hydrogen peroxide (H₂O₂) by 16% in leaves and 8% in roots, malondialdehyde (MDA) by 21% and 39%, and electrolyte leakage (EL) by 27% and 50%, respectively. In contrast, antioxidant enzyme activities increased, with peroxidase (POD) enhanced by 47% in leaves and 81% in roots, superoxide dismutase (SOD) by 97% and 59%, ascorbate peroxidase (APX) by 55% and 29%, and catalase (CAT) by 38% and 52%. The accumulation of heavy metals also rose substantially under the combined treatment, with Ni, Cd, and Pb increasing by 33–126%, 23–106%, and 52–74% in roots; 29–87%, 36–140%, and 50–155% in stems; and 46–73%, 36–74%, and 71–186% in leaves, respectively, compared with control plants. The present study evaluated the successful combination of nZVI and neem leaf extract in removing heavy metals from surgical industry wastewater through <i>B.napus</i>. The nZVI and neem leaf extracts depicted plant growth promoting role and enhanced the HMs accumulation in root &gt; stem &gt; leaf. The research shows great potential for combining nZVI and neem leaf extract to remove HMs from heavily contaminated surgical wastewater.本研究探究了甘蓝型油菜（Brassica napus L.）在施加印楝（Azadirachta indica L.）叶提取物与纳米零价铁（nZVI）的条件下，修复外科行业废水中重金属的潜力。暴露于未处理废水的植株，其生长状况与光合色素含量均出现显著下降。然而，在100%废水浓度条件下，印楝提取物与nZVI的联合施用可使株高提升318%、叶片数增加300%、叶面积扩大329%、根长增长63%。该处理还可降低氧化应激指标：叶片中过氧化氢（H₂O₂）含量下降16%、根系中下降8%；丙二醛（MDA）分别下降21%与39%；电解质渗漏率（EL）分别下降27%与50%。与之相反，抗氧化酶活性显著提升：叶片中过氧化物酶（POD）活性提升47%、根系中提升81%；超氧化物歧化酶（SOD）分别提升97%与59%；抗坏血酸过氧化物酶（APX）分别提升55%与29%；过氧化氢酶（CAT）分别提升38%与52%。与对照植株相比，联合处理下重金属的积累量同样显著提升：根系中镍（Ni）、镉（Cd）与铅（Pb）的含量分别提升33%~126%、23%~106%与52%~74%；茎秆中分别提升29%~87%、36%~140%与50%~155%；叶片中分别提升46%~73%、36%~74%与71%~186%。本研究证实，通过甘蓝型油菜（B. napus）联合施用nZVI与印楝叶提取物，可有效去除外科行业废水中的重金属。nZVI与印楝叶提取物可发挥促生作用，并提升重金属在植株中的积累量，其积累规律为根＞茎＞叶。本研究表明，联合施用nZVI与印楝叶提取物修复高污染外科废水中的重金属，具有极高的应用潜力。