Nowadays, for environmental remediation, photocatalytic process involving graphene-based semiconductors is considered a very promising oxidation process for water treatment. In the present study, nanocomposite (Cu/Ni/rGO) has been synthesized by Dypsis lutescens leaf extract. Characterization of the sample was carried out by UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Different parameters like contact time, nanocatalyst amount, dye concentration, effect of temperature. and pH factor were optimized to examine the maximum removal efficiency for dyes rhodamine B and alizarine R with and without visible light source. In both cases, i.e., with or without light, maximum removal was observed at 20 mg of nanocatalyst for 5 ppm concentration of both dyes at 45 °C temperature and pH 10 for rhodamine B and pH 4 for alizarine R, respectively with a 20 min contact time. Maximum removal of dyes 93% rhodamine B and 91% alizarine R were observed under a tungsten lamp as compared to without a tungsten lamp, i.e., 78% of RhB and 75% of AR from mixture solution of these dyes. To assess the rate of reaction, spontaneity, and nature of reaction thermodynamics, kinetics and adsorption isotherms were studied. Thermodynamic values indicated that both dyes depicted endothermic and spontaneous degradation processes. Isotherm data fitted best to a Freundlich isotherm, while results of kinetic studies of both dyes followed the pseudo 2nd order kinetic equation. In the end, scavenging radical studies concluded that hydroxyl radicals were the main active specie involved in the photocatalytic degradation process, and regeneration experiments resulted that Cu/Ni/rGO nanocomposites were re-utilized for about four times.

In this work, green synthesized cobalt monometallic and cobalt–zinc bimetallic NPs were prepared by bioreduction of metallic salts with Cymbopogan citratus plant extract. Biosynthesized cobalt nanoparticles (NPs) and cobalt–zinc bimetallic NPs were characterized using diverse techniques such as FTIR, UV-Visible spectroscopy, SEM, XRD, and EDX analyses. UV-visible spectra for green-synthesized cobalt monometallic and cobalt–zinc bimetallic NPs were in the range between 300 to 350 nm, which confirmed the formation of stable monometallic and bimetallic NPs. The average particle size of CoNPs calculated by XRD analysis was found to be 22.77 nm and that of Co-Zn BMNPs was 14.8 nm. Different functional groups in the Cymbopogan citratus plant extract, which served as a reducing and stabilizing agent for NPs, were identified by FTIR spectra. Cobalt NPs and cobalt–zinc bimetallic NPs were used in the evaluation of antioxidant, anti-inflammatory, and dye degradation activity. Green-synthesized cobalt monometallic NPs and cobalt–zinc bimetallic NPs exhibited excellent antioxidant activity with the scavenging of DPPH free radicals. Green synthesized cobalt NPs and cobalt–zinc bimetallic NPs were utilized for the removal of methylene blue (MB) dye. Different parameters such as the effect of temperature, pH, and dye concentration on adsorbent doses were analyzed and optimized. The best dye removal percentage was obtained with Co-Zn BMNPs compared with CoNPs. Cobalt NPs and cobalt–zinc bimetallic NPs did not display good anti-inflammatory activity because of the presence of secondary metabolites which inhibited them to react with proteins.

In reported work, zinc oxide nanoparticles (ZnONPs) had been synthesised by a green method using aqueous extract of Cannabis sativa leaves. A facile, eco-friendly, time saving and beneficial procedure for the preparation of metal nanoparticles had been developed. UV-visible spectroscopy, Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterise the ZnONPs composition, their shape, size and crystallinity. Ultraviolet-visible spectra showed the absorbance band between 300 and 400 nm, which indicated the synthesis of stable ZnO nanoparticles. Average size of ZnONPs was calculated from XRD as 46 nm. SEM and EDX spectra confirmed the synthesis of spherical shaped ZnONPs. FTIR spectra showed that different functional groups were present in aqueous extract of plant’s leaves, which acted as reducing agents in the formation of stable ZnONPs. The value of DPPH radical inhibition percentage shown by ZnONPs was 88 ± 0.08% at 1500 µg/ml concentration revealing its good antioxidant activity. The total antioxidant activity calculated for ZnONPs was 0.521 ± 0.34 against BHT as standard. Total phenolic contents for ZnONPs was calculated to be 292.60 ± 1.12 mg/g GAE. Then the synthesised ZnONPs were utilised as catalyst for the removal of harmful organic dyes methylene blue (MB) and Congo red (CR). Various factors like adsorbent dosage, dye concentration, pH and temperature were studied and optimised for maximum removal of dyes. Pseudo-first-order model was followed for adsorption kinetics of both dyes. Adsorption isotherms were also assessed using Freundlich and Langmuir isotherm models. Hence, green approach was easy and cost effective for the removal of organic dyes and found as efficient antioxidant in current study.

Antibiotics are resistant compounds that become emerging contaminants that cause hazards to human health and the ecological environment due to their wide production and consumption. The present research reveals the remediation of amoxicillin (AMX) antibiotic by catalytic degradation using fabricated zinc oxide (ZnO) and zinc oxide-reduced graphene oxide (ZnO-rGO) catalysts. The characterization of the catalyst was carried out via UV–Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and scanning electron microscopy to evaluate the morphology and composition of synthesised catalyst. The catalytic ability of ZnO-rGO and ZnO was investigated by analysing the degradation of AMX. The ZnO-rGO nanocomposites (NCs) showed improved catalytic performance towards AMX degradation (96%) than pure ZnO nanoparticles (85%), which may be attributed to the incorporation of rGO, which enhanced the adsorption rate and changed the electron–hole recombination rate. The antioxidant potential of synthesised nanomaterials was also analysed by three different methods. The adsorption behaviour was explained through the Langmuir and Freundlich models, and the results revealed that AMX adsorption followed the Freundlich model more closely for both catalysts. The adsorption of AMX was also studied thermodynamically at different temperatures. The negative Gibbs energy change, positive enthalpy change, and entropy change showed the reaction’s spontaneity and endothermic nature. Finally, it can be assumed that the ZnO-rGO NCs could be an effective semiconductor for the degradation of AMX from wastewater.

Many compounds containing sulfur and phosphorous are present in wastewater of various industries like food processing, paper making, etc. The higher level of phosphate and sulfate ions causes many problems in everyday life. Based on this, nickel monometallic and nickel-cobalt bimetallic nanoparticles were synthesized using leaves extract of Coix lacryma-jobi L. and applied for sulfate and phosphate ions removal. UV-Vis. spectroscopy, fourier transformed infrared spectroscopy; scanning electron microscopy; X-ray diffraction, and energy-dispersive X-ray spectroscopy were used as characterizing techniques for synthesized nanoparticles. UV spectra for Ni nanoparticles showed the absorption band in the 380–400 nm range, while for Ni-Co bimetallic nanoparticles was noticed at 396 nm and 513 nm. Different functional groups were observed in FTIR spectra of leaves extract which acted as reducing and capping agents to form stable NPs. Different factors like adsorbent dosage, pH, temperature, adsorbate concentration, and time were optimized for maximum removal of sulfate and phosphate anions. The antioxidant potential of prepared nanoparticles was assessed by three different methods. The kinetics, thermodynamics, and adsorption isotherms were also studied for these ions removal. In the current study, the green approach was easy, time-saving and proved to be beneficial to remove sulfate and phosphate anions from wastewater. The leaves extract of Coix lacryma-jobi L. were employed for the synthesis of nickel monometallic and nickel-cobalt bimetallic nanoparticles and employed for the removal of sulfate and phosphate ions from aqueous solution. Antioxidant potential of biosynthesized nanoparticles was also assessed. Hence, the biosynthesized nanomaterial found to be novel adsorbent for removal of sulfate and phosphate from waste water. This research work has not been previously reported in literature. Graphical Abstract