The present study reports the feasibility of synthesis of palladium nanoparticles (Pd NPs) by watermelon rind. The aqueous extract prepared from watermelon rind, an agro waste, was evaluated as capping and reducing agent for biosynthesis of palladium nanoparticles. The formation of Pd NPs was visually monitored with change in color from pale yellow to dark brown and later monitored with UV–Vis spectroscopy. The synthesized Pd NPs were further characterized by XRD, FTIR, DLS, AFM and TEM techniques. The synthesized Pd NPs were employed in Suzuki coupling reaction as catalyst. The results reveal that watermelon rind, an agro waste, is capable of synthesizing spherical-shaped Pd NPs with catalytic activity.

Watermelon rind (WR) an agro waste was evaluated as an adsorbent for the removal of Cr3+ ions from aqueous solution. Batch mode adsorption studies were performed by varying parameters such as pH, contact time, adsorbent dose and initial metal ion concentration. Maximum loading capacity of WR was found to be 172.6mgg−1 for Cr3+ ions at pH 3. Kinetic studies show that removal of Cr3+ ions is rapid and follows a pseudosecond order model. Equilibrium data fit better with the Langmuir isotherm than the Freundlich isotherm. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were derived for the current system. The negative values of ΔG° show that the nature of sorption process is spontaneous. FTIR studies reveal that hydroxyl and carboxyl groups were responsible for uptake of metal ions. Successive desorption of Cr3+ ions reveals that WR can be an economical sorbent for the removal of heavy metals from aqueous solution. The results conclude that watermelon rind an agro waste can effectively be used for the removal of chromium ions from aqueous solution

A green synthesis approach has been adopted to prepare nickel sulphide nanoparticles (NiS NPs) using banana peel extract (BPE) as a reducing and capping agent. Polyvinyl alcohol (PVA)/NiS nanocomposite films were fabricated using a cost-effective solution casting technique by dispersing different contents of NiS NPs (0–3 wt%) in the PVA matrix. Various characterization techniques were employed to analyze the structural, thermal and morphological properties of the PVA/NiS nanocomposite films. Further, the dielectric behaviour of these nanocomposite films was investigated at frequency range 50 Hz–20 MHz and in the temperature range 40 °C–140 °C. Also, there exists a significant interaction between the polymer matrix and the nanofiller as evident from the notable improvement in the dielectric properties of the nanocomposites. The dielectric constant (ε) value of PVA/NiS nanocomposite film with 3 wt % NiS NPs loading was found to be 154.55 at 50 Hz and at 140 °C which is 22 times greater than the dielectric constant value of neat PVA (6.90). These results suggest that NiS NPs were dispersed homogeneously in the PVA matrix.

This study reports the feasibility of waste watermelon rind as adsorbent for the removal of methylene blue in batch and continuous column studies. Batch mode adsorption studies were performed by varying the batch parameters such as pH, contact time, adsorbent dose, initial dye concentration, and temperature. The equilibrium data were analyzed with Langmuir, Freundlich, and Temkin isotherm models and found to better with Langmuir and Temkin models. The kinetic data reveal that the present system follows pseudo-second-order kinetic model. Thermodynamic studies reveal that the present process is spontaneous and exothermic in nature. Fixed bed column studies were performed by varying the column parameters such as flow rate, bed height, and initial inlet concentration. The breakthrough curves obtained were analyzed with Adams–Bohart, Thomas, and Yoon–Nelson models. The results show that watermelon rind an agro waste can be successfully employed for the elimination of methylene blue from aqueous solution.