Co-application of TiO2 nanoparticles and hyperaccumulator Brassica juncea L. for effective Cd removal from soil: Assessing the feasibility of using nano-phytoremediation

Design and construction of magnetic nanomaterials and their remediation mechanisms for heavy metal contaminated soil

Soil heavy metal pollution poses huge threat to ecosystem and human health. In-situ chemical remediation aims to immobilize free heavy metals in soil through adding passivators, thereby greatly reducing the mobility and bioavailability of heavy metals. Magnetic nanomaterials (MaN) have strong adsorption and immobilization capabilities for heavy metals due to their significant surface effects, small size effects and interfacial effects. Compared with traditional remediation materials, MaN can be recovered and reused using external magnetic fields. These advantages give MaN broad application prospects in the field of soil remediation. This work provides a comprehensive review of the application of MaN in heavy metal contaminated soil, including the design and application effect of various types of MaN, the influence of MaN on soil properties, environmental toxicity, and microbial composition, the in-situ remediation mechanism of MaN on heavy metal contaminated soil. On the other hand, there are potential risks associated with the remediation of heavy metal contaminated soil using MaN, including their impact on the soil ecosystem and biosafety concerns, requiring further research. Finally, this review proposes the future prospects for the application of MaN in the remediation of heavy metal polluted soil.

Nutrient strengthening and lead alleviation in Brassica Napus L. by foliar ZnO and TiO2-NPs modulating antioxidant system, improving photosynthetic efficiency and reducing lead uptake

With the anticipated foliar application of nanoparticles (NPs) as a potential strategy to improve crop production and ameliorate heavy metal toxicity, it is crucial to evaluate the role of NPs in improving the nutrient content of plants under Lead (Pb) stress for achieving higher agriculture productivity to ensure food security. Herein, Brassica napus L. grown under Pb contaminated soil (300 mg/kg) was sprayed with different rates (0, 25, 50, and 100 mg/L) of TiO2 and ZnO-NPs. The plants were evaluated for growth attributes, photosynthetic pigments, leaf exchange attributes, oxidant and antioxidant enzyme activities. The results revealed that 100 mg/L NPs foliar application significantly augmented plant growth, photosynthetic pigments, and leaf gas exchange attributes. Furthermore, 100 mg/L TiO2 and ZnO-NPs application showed a maximum increase in SPAD values (79.1%, 68.9%). NPs foliar application (100 mg/L TiO2 and ZnO-NPs) also substantially reduced malondialdehyde (44.3%, 38.3%), hydrogen peroxide (59.9%, 53.1%), electrolyte leakage (74.8%, 68.3%), and increased peroxidase (93.8%, 89.1%), catalase (91.3%, 84.1%), superoxide dismutase (81.8%, 73.5%) and ascorbate peroxidase (78.5%, 73.7%) thereby reducing Pb accumulation. NPs foliar application (100 mg/L) significantly reduced root Pb (45.7%, 42.3%) and shoot Pb (84.1%, 76.7%) concentration in TiO2 and ZnO-NPs respectively, as compared to control. Importantly, macro and micronutrient analysis showed that foliar application 100 mg/L TiO2 and ZnO-NPs increased shoot zinc (58.4%, 78.7%) iron (79.3%, 89.9%), manganese (62.8%, 68.6%), magnesium (72.1%, 93.7%), calcium (58.2%, 69.9%) and potassium (81.5%, 68.6%) when compared to control without NPs. The same trend was observed for root nutrient concentration. In conclusion, we found that the TiO2 and ZnO-NPs have the greatest efficiency at 100 mg/L concentration to alleviate Pb induced toxicity on growth, photosynthesis, and nutrient content of Brassica napus L. NPs foliar application is a promising strategy to ensure sustainable agriculture and food safety under metal contamination.

A unified framework of response surface methodology and coalescing of Firefly with random forest algorithm for enhancing nano-phytoremediation efficiency of chromium via in vitro regenerated aquatic macrophyte coontail (Ceratophyllum demersum L.)

Nano-phytoremediation is a novel green technique to remove toxic pollutants from the environment. In vitro regenerated Ceratophyllum demersum (L.) plants were exposed to different concentrations of chromium (Cr) and exposure times in the presence of titania nanoparticles (TiO2NPs). Response surface methodology was used for multiple statistical analyses like regression analysis and optimizing plots. The supplementation of NPs significantly impacted Cr in water and Cr removal (%), whereas NP × exposure time (T) statistically regulated all output parameters. The Firefly metaheuristic algorithm and the random forest (Firefly-RF) machine learning algorithms were coalesced to optimize hyperparameters, aiming to achieve the highest level of accuracy in predicted models. The R2 scores were recorded as 0.956 for Cr in water, 0.987 for Cr in the plant, 0.992 for bioconcentration factor (BCF), and 0.957 for Cr removal through the Firefly-RF model. The findings illustrated superior prediction performance from the random forest models when compared to the response surface methodology. The conclusion is drawn that metal-based nanoparticles (NPs) can effectively be utilized for nano-phytoremediation of heavy metals. This study has uncovered a promising outlook for the utilization of nanoparticles in nano-phytoremediation. This study is expected to pave the way for future research on the topic, facilitating further exploration of various nanoparticles and a thorough evaluation of their potential in aquatic ecosystems.

The synergistic potential of biochar and nanoparticles in phytoremediation and enhancing cadmium tolerance in plants

Cadmium (Cd) is classified as a heavy metal (HM) and is found into the environment through both natural processes and intensified anthropogenic activities such as industrial operations, mining, disposal of metal-laden waste like batteries, as well as sludge disposal, excessive fertilizer application, and Cd-related product usage. This rising Cd disposal into the environment carries substantial risks to the food chain and human well-being. Inadequate regulatory measures have led to Cd bio-accumulation in plants, which is increasing in an alarming rate and further jeopardizing higher trophic organisms, including humans. In response, an effective Cd decontamination strategy such as phytoremediation emerges as a potent solution, with innovations in nanotechnology like biochar (BC) and nanoparticles (NPs) further augmenting its effectiveness for Cd phytoremediation. BC, derived from biomass pyrolysis, and a variety of NPs, both natural and less toxic, actively engage in Cd removal during phytoremediation, mitigating plant toxicity and associated hazards. This review scrutinizes the application of BC and NPs in Cd phytoremediation, assessing their synergistic mechanism in influencing plant growth, genetic regulations, structural transformations, and phytohormone dynamics. Additionally, the review also underscores the adoption of this sustainable and environmentally friendly strategies for future research in employing BC-NP microaggregates to ameliorate Cd phytoremediation from soil, thereby curbing ecological damage due to Cd toxicity.

Insight into the mechanism of nano-TiO2-doped biochar in mitigating cadmium mobility in soil-pak choi system

Soil cadmium (Cd) pollution poses severe threats to food security and human health. Previous studies have reported that both nanoparticles (NPs) and biochar have potential for soil Cd remediation. In this study, a composite material (BN) was synthesized using low-dose TiO2 NPs and silkworm excrement-based biochar, and the mechanism of its effect on the Cd-contaminated soil-pak choi system was investigated. The application of 0.5 % BN to the soil effectively reduced 24.8 % of diethylenetriaminepentaacetic acid (DTPA) Cd in the soil and promoted the conversion of Cd from leaching and HOAc-extractive to reducible forms. BN could improve the adsorption capacity of soil for Cd by promoting the formation of humic acid (HA) and increasing the cation exchange capacity (CEC), as well as activating the oxygen-containing functional groups such as CO and CO. BN also increased soil urease and catalase activities and improved the synergistic network among soil bacterial communities to promote soil microbial carbon (C) and nitrogen (N) cycling, thus enhancing Cd passivation. Moreover, BN increased soil biological activity-associated metabolites like T-2 Triol and altered lipid metabolism-related fatty acids, especially hexadecanoic acid and dodecanoic acid, crucial for bacterial Cd tolerance. In addition, BN inhibited Cd uptake and root-to-shoot translocation in pak choi, which ultimately decreased Cd accumulation in shoots by 51.0 %. BN significantly increased the phosphorus (P) uptake in shoots by 59.4 % by improving the soil microbial P cycling. This may serve as a beneficial strategy for pak choi to counteract Cd toxicity. These findings provide new insights into nanomaterial-doped biochar for remediation of heavy metal contamination in soil-plant systems.

Bacterial nano-factories as a tool for the biosynthesis of TiO2 nanoparticles: characterization and potential application in wastewater treatment

The development of reliable and eco-conscious processes for nanoparticle synthesis constitutes a significant element in nanotechnology. TiO2 nanoparticles (NPs) are becoming essential due to their potential uses in dentistry, surgery, agriculture, and pharmacy. This leads to the development of various procedures for producing TiO2 NPs using various physicochemical methods. Still, the drawbacks of these conventional methods are associated with the emission of toxic chemicals into the atmosphere and high energy demands in production, hence endangering the health and the environment. Problems issued are solved by green nanotechnology, which offers tools as nano-factories by utilizing biological sources to subside the improper effects of conventional methods and produces nanoparticles through synthesis methods that are clean, safe, energy-efficient, and cost-effective. Among the biogenic sources, microbial cells such as bacteria possess intrinsic pathways of converting metallic salt to nanoparticles due to their ability to produce reductase enzymes. Also, they can offer features to products such as high dispersity and produce sustainable nanoparticles at a large scale. Biosynthesized TiO2 NPs have high oxidizing potential and a wide range of applications, specifically as photosensitizers and antimicrobial agents. This review will address bacterial nano-factories that can be utilized for the biosynthesis of TiO2 NPs, the characterization of biosynthesized nanoparticles, and their potential application in wastewater treatment.