This paper reports the successful synthesis of magnetic nanocomposite of calcium ferrite with nitrogen doped graphene oxide (CaFe₂O₄-NGO) for the effective removal of Pb(II) ions and photocatalytic degradation of congo red and p-nitrophenol. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) techniques confirmed the presence of NGO and CaFe₂O₄ in the nanocomposite. The Mössbauer studies depicted the presence of paramagnetic doublet and sextet due to presence of CaFe₂O₄ NPs in the nanocomposite. The higher BET surface area in case of CaFe₂O₄-NGO (52.86 m²/g) as compared to CaFe₂O₄ NPs (23.45 m²/g) was ascribed to the effective modulation of surface in the presence of NGO. Adsorption followed the Langmuir model with maximum adsorption capacity of 780.5 mg/g for Pb(II) ions. Photoluminescence spectrum of nanocomposite displayed four-fold decrease in the intensity, as compared to ferrite NPs, thus confirming its high light capturing potential and enhanced photocatalytic activity. The presence of NGO in nanocomposite offered an excellent visible light driven photocatalytic performance. The quenching experiments supported ^●OH and O₂^●− radicals as the main reactive species involved in carrying out the catalytic system. The presence of Pb(II) had synergistic effect on photocatalytic degradation of pollutants. This study highlights the synthesis of CaFe₂O₄-NGO nanocomposite as an efficient adsorbent and photocatalyst for remediating pollutants.

In the present study, nanocomposites having hierarchical nanoflowers (HNFs) -like morphology were synthesized by ultra-sonication approach. HNFs were ternary composite of MgFe₂O₄ and bentonite with boron-, phosphorous- co-doped graphene oxide (BPGO). The HNFs were fully characterized using different analytical tools viz. X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersion spectroscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry and Mössbauer analysis. Transmission electron micrographs showed that chiffon-like BPGO nanosheets were wrapped on the MgFe₂O₄-bentonite surface, resulting in a porous flower-like morphology. The red-shift in XPS binding energies of HNFs as compared to MgFe₂O₄-bentoniteand BPGO revealed the presence of strong interactions between the two materials. Box–Behnken statistical methodology was employed to optimize adsorptive and photocatalytic parameters using Pb(II) and malathion as model pollutants, respectively. HNFs exhibited excellent adsorption ability for Pb(II) ions, with the Langmuir adsorption capacity of 654 mg g⁻¹ at optimized pH 6.0 and 96% photocatalytic degradation of malathion at pH 9.0 as compared to MgFe₂O₄-bentonite and BPGO. Results obtained in this study clearly indicate that HNFs are promising nanocomposite for the removal of inorganic and organic contaminants from the aqueous solutions.

SUMMARY: Potassium concentrations in various plant parts of cotton (Gossypium hirsutum L.) at different growth stages were determined in field experiments in Punjab, India, in 1987, for plots fertilized at sowing and flowering, and these were compared with the final seed cotton yield. The optimum time of sampling for predicting relative yield depends on the time of K fertilizer application: if applied at sowing, plants should be sampled before the peak flowering stage (70 days after sowing, DAS); if applied at flowering (50 DAS), plants should be sampled 90–115 DAS. Critical K concentrations (% K. in dry matter) in the plant parts measured at different growth stages were 3·26 in the petioles of the third leaf from the top at flower initiation; 0·69 and 0·90 in blades and petioles of a lower leaf (first or second healthy leaf from the bottom of plant) respectively, and 2·60 in the petioles of the third leaf (young, fully mature leaf from the top of the plant) at peak flowering stage; 0·85 in blades of the third leaf, 0·53 and 0·50 in blades and petioles of a lower leaf, respectively, at the boll development stage; 0·70 and 2·85 in blades and petioles of the third leaf and 0·68 in petioles of a lower leaf at boll opening stage.