Iron deficiency has been becoming a worldwide problem in crop cultivation. New approaches are desired to alleviate the iron-deficit chlorosis. Iron-containing nanomaterials could be effective to supply the iron to plants and promote plant growth. In this study, soil cultured watermelon plants were treated with 100, 200, and 400 ppm α- and γ-Fe₂O₃ nanoparticles (NPs), respectively. Growth and physiology parameters were investigated in a period of time. The study also evaluated the nutritional quality of watermelon fruit. Results showed that no elevation of plant growth or chlorophyll content was observed. All α- and γ-Fe₂O₃ NPs treatments had no positive influence on nutritional components including central and edge sugar content, and total amino acid content. An interesting result was that the vitamin C (VC) content of all NP treatments was significantly improved compared with the control group (without iron). In addition, we found that iron distribution of α- and γ-Fe₂O₃ NPs treatments was closely related to the concentrations of NPs. Both α- and γ-Fe₂O₃ NPs could accumulate in root, stem, and leaf of watermelon plants, but only 400 ppm γ-Fe₂O₃ NPs treatment was found to exist in watermelon fruit. Although no promotion of α- and γ-Fe₂O₃ NPs on the growth of watermelon plants was occurred, our results showed that both α- and γ-Fe₂O₃ NPs could enter plant roots and translocate upwards to other tissues. Our finds will provide data for the future applications of iron-containing nanomaterials in agricultural production. Graphical Abstract

By using the activated carbon obtained from Citrullus lanatus rind by zinc chloride activation, methylene blue (MB) removal from aqueous solutions was studied, and the adsorption mechanism was solved through Weber-Morris intraparticle diffusion model, Bangham model, Boyd model, Fourier transform infrared spectra, and scanning electron microscopy. The effects of adsorption parameters (adsorbent concentration, temperature, initial dye concentration, and pH) were investigated. The equilibrium data of MB adsorption were described by applying the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The obtained results from adsorption isotherms indicated that Langmuir model is the best-fitted model with the maximum adsorption capacities of 231.48, 243.90, 244.50, and 259.74 mg/g at 25, 35, 45, and 55 °C, respectively. The analysis of the kinetic data by pseudo-first-order, pseudo-second-order, and Elovich models displayed that MB adsorption followed pseudo-second-order model. Also, the date obtained from intraparticle diffusion model, Bangham model, and Boyd model presented that intraparticle diffusion, pore diffusion, and film diffusion played significant role in MB adsorption. The thermodynamic studies demonstrated that MB adsorption onto the activated carbon obtained from C. lanatus rind was physical, spontaneous, feasible, and endothermic. Thus, the activated carbon prepared from C. lanatus rind has been an efficient adsorbent for MB removal from an aqueous solution. Graphical Abstract ᅟ