Addressing dye phytotoxicity and soil contamination: The dual action of chemically synthesized zinc nanoparticles in simultaneous adsorption and soil health improvement.

Dyes are synthetic organic compounds that induce the development of color in the substances. A large volume of dye effluent is released every year and hence, contaminates water and agricultural land. Nanoparticles are efficient adsorbents of pollutants, however, their potential for remediation of dyes in water and soil is not well studied. Therefore, this study evaluates the efficacy of seed dressing with chemically synthesized zinc nanoparticles for simultaneously reaching dye adsorption and alleviation of dye-induced phytotoxicity in mung bean plants, cultivated in dye-contaminated soil. Zinc nanoparticles (Zn NPs) were chemically synthesized, and characterized in the laboratory. The Zn NPs were evaluated for different optimization factors affecting the adsorption of reactive black (RB) dye. The experimental data showed a satisfactory fitting to pseudo second-order kinetics, and to the Langmuir adsorption isotherm, with R values reaching 0.996 (for dye concentrations in the range 50-200 mg L). Under disperse orange dye (at 25 mg L) stress level, Zn NPs (at 100 mg L) considerably improved (30-36.5%) mung bean germination and other morpho-physiological attributes. The application of Zn NPs caused an increase in biochemical compounds (20-22%). Additionally, Zn NPs triggered the production of soil enzymes (11-45%) and the value of the membrane stability index (4%). The results indicate that Zn NPs plays a substantial role in the mitigation of dye toxicity affecting soils, specifically due to the immobilization of dye molecules, and supported the growth of mung bean plants under textile dyes phytotoxicity. The present study demonstrates the efficacy of Zn NPs in mitigating the toxicity of azo dyes in water and soil, showing its potential as a dye adsorbent, as well as a soil amendment to promote the growth of plants affected by dye toxicity.

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