Green synthesis and characterization of silver and copper nanoparticles and their use as an effective adsorbent for chromium removal and recovery from wastewater.

Chromium (Cr) is one of the hazardous heavy metals that is naturally carcinogenic and causes various health problems. Metallic nanoparticles such as silver and copper nanoparticles (Ag NPs and Cu NPs) have gained great attention because of their unique chemical, physical, and biological attributes, serving diverse and significant role in various useful and sustainable applications. In the present study, both of these NPs were synthesized by green method in which Azadirachta indica plant extract was used. These nanoparticles were characterized by using advanced instrumental techniques such as Fourier transmission infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope attached with energy-dispersive spectroscopy (SEM-EDS), and elemental mapping. These environmentally friendly nanoparticles were utilized for the batch removal of Cr from the wastewater. For analysis of adsorption behaviour, a range of kinetic isotherm models (Freundlich, Temkin, Dubinin, and Langmuir) and kinetic models (pseudo-first-order and pseudo-second-order) were used for the Cu-NPs and Ag-NPs. Cu NPs exhibited the highest Cr removal efficiency (96%) within a contact time of 10-15 min, closely followed by Ag NPs which achieved a removal efficiency of 94% under the similar conditions. These optimal outcomes were observed at a sorbent dose of 0.5 g/L for Ag NPs and 0.7 g/L for Cu NPs. After effectively capturing Cr using these nanoparticles, the sorbates were examined through SEM-EDX analysis to observe how much Cr metal was attached to the nanoparticles, potentially for future use. The analysis found that Ag-NPs captured 18% of Cr, while Cu-NPs captured 12% from the aqueous solution. More precise experimental conditions are needed for higher Cr removal from wastewater and determination of the best conditions for industrial-level Cr reuse. Although nanomaterial exhibit high efficiency and selectivity for Cr removal and recovery from wastewater, more research is necessary to optimize their synthesis and performance for industrial-scale applications and develop efficient methods for Cr removal and recovery.

The effect of gibberellic acid on wheat growth and nutrient uptake under combined stress of cerium, zinc and titanium dioxide nanoparticles.

Nanoparticles (NPs) are released and dispersed in the environment because of increased manufacturing and use of nano products. NPs disturb the growth of plants depending upon types, exposure duration and plant species. The purpose of this research was to explore the role of gibberellic acid (GA) exposure through foliar route on wheat growth under alone or combined soil application of cerium oxide (CeO2), zinc oxide (ZnO), and titanium dioxide (TiO2) NPs. GA was foliar-applied (200 mg/L) on the wheat plants treated with individual and in all possible combination of the selected NPs. Explorations have revealed that the combination of NPs and GA worked well to enhance the plant growth and selected nutrient status than NPs alone. Furthermore, GA decreased the boosted antioxidant enzyme activities under the combination and individual NPs compared to the alone NPs treated plants, lowered the oxidative stress in wheat plants which provided the additional proof that GA decreased oxidative damage in plants. Combined NPs showed differential effects than individual NPs application irrespective of GA exposure which varied with NPs combination and studied parameters of plants. GA + NPs differentially affected the potassium, phosphorus, iron and manganese concentrations in wheat tissues than NPs alone treatments. Overall, GA can be applied when there is excess of NPs (either alone or in combination) in the growth medium to ensure the growth of crops. However, further studied are needed with other plant species and alone or combined use of different NPs under GA treatment before any final recommendation.

Green magnesium oxide nanoparticles-based modulation of cellular oxidative repair mechanisms to reduce arsenic uptake and translocation in rice (Oryza sativa L.) plants.

Arsenic (As) accumulation catastrophically disturbs the stability of agricultural systems and human health. Rice easily accumulates a high amount of As from agriculture fields as compare with other cereal crops. Hence, innovative soil remediation methods are needed to deal with the detrimental effects of As on human health causing food security challenges. Here, we report the green synthesis and characterization of magnesium oxide nanoparticles (MgO-NPs) from a native Enterobacter sp. strain RTN2, which was genetically identified through 16S rRNA gene sequence analysis. The biosynthesis of MgO-NPs in reaction mixture was confirmed by UV-vis spectral analysis. X-ray diffraction (XRD) and fourier transform-infrared spectroscopy (FTIR) analysis showed the crystalline nature and surface properties of MgO-NPs, respectively. Moreover, electron microscopy (SEM-EDS, and TEM) imaging confirmed the synthesis of spherical shape of MgO-NPs with variable NPs sizes ranging from 38 to 57 nm. The results revealed that application of MgO-NPs (200 mg kg-1) in As contaminated soil significantly increased the plant biomass, antioxidant enzymatic contents, and decreased reactive oxygen species and acropetal As translocation as compared with control treatment. The study concluded that biogenic MgO-NPs could be used to formulate a potent nanofertilizer for sustainable rice production in metal contaminated soils.

Effect of gibberellic acid and titanium dioxide nanoparticles on growth, antioxidant defense system and mineral nutrient uptake in wheat.

Nanoparticles (NPs), as a novel source of industrial materials, have been extensively used in recent years which ultimately ends up in soils and may cause toxic effects on plants. Gibberellic acid (GA), phytohormone, has ability to minimize abiotic stresses in plants. The role of GA in minimizing titanium dioxide (TiO2) NPs stress in plants is still unknown. In current study, soil was spiked with TiO2 NPs (0, 100, 200, 400, 600 mg/kg) while GA was foliar-sprayed at different concentrations during wheat growth. The findings revealed that TiO2 NPs increased the growth, chlorophyll contents, and nutrient (P, K, Fe, Mn) concentrations in tissues till 400 mg/kg and then decrease was observed at 600 mg/kg level of NPs whereas the values of these parameters were higher compared to control irrespective of NPs levels. The NPs enhanced the antioxidant activities (SOD, POD, CAT, APX) and reduced the oxidative stress (EL, H2O2, MDA) in leaves over the control. Foliar GA further improved the growth, yield, nutrients and antioxidant activities while minimized the oxidative stress compared to respective sole NPs- treatments. The interactive effects of NPs and GA were dose dependent. The results proved that studied doses of TiO2 NPs were not toxic to wheat plants except the highest level (600 mg/kg) used and GA positively affected the yield of wheat under TiO2 NPs application. The GA can be used to improve crop growth in the presence of NPs which, however, needs further investigation at higher doses of TiO2 NPs in various crops.

Hydrogeochemical and health risk evaluation of arsenic in shallow and deep aquifers along the different floodplains of Punjab, Pakistan.

The current study delineated the distribution, (hydro)geochemical behavior and health risk of arsenic (As) in shallow (depth < 35 m; handpumps and electric pumps) and deep (depth > 35 m; tube wells) aquifers in five areas along the Indus River (Bhakar, Kallur Kot), Jhelum River (Jhelum) and Chenab River (Hafizabad, Gujranwala) floodplains of Punjab, Pakistan. Relatively, greater As concentration was observed in deep wells (mean: 24.3 µg L-1) compared to shallow wells (19.4 µg L-1), with groundwater As spanning 0.1-121.7 µg L-1 (n = 133) in three floodplains. Groundwater from Hafizabad (Chenab River floodplain) possessed the highest As (121.7 µg L-1), Na+ (180 mg L-1), Ca2+ (95 mg L-1), Cl- (101 mg L-1) and SO42- (1353 mg L-1) concentrations. Arsenic health risk modeling indicated the potential carcinogenic (value > 10-4) and non-carcinogenic (hazard quotient > 1.0) risks for groundwater of all areas, with the utmost risk estimated for Chenab floodplain and deep aquifers. Positive saturation index values for Fe oxide mineral phases may suggest their potential role in As mobilization/release in these aquifer environments. This study provides critically-important and baseline knowledge for a widespread groundwater As examination along these three floodplains, which is vital for launching suitable As mitigation and remediation programs to reduce the potential health risk.