Band 236, Heft 5

In this study, chemical modification of chitosan has been carried out using epichlorohydrin as crosslinking agent and ethyl acetoacetate as a modifier to graft acetoacetyl moiety. The said organo-functionalization on chitosan and sodium alginate not only offered a novel support for TiO 2 immobilization but also enhanced sorption performance for Ni(II) recovery from aqueous medium. So, a composite consisting of acetoacetyl moiety grafted chitosan, sodium alginate and titanium oxide (EAA-MCS/TiO 2 ) was prepared and characterized by fourier transform-infra red (FT-IR) spectroscopy and scanning electron microscopy (SEM). The hybrid composite (3EAA-MCS/TiO 2 ) which had TiO 2 to EAA-MCS mass ratio of 20.0% by weight showed maximum sorption efficiency. The formulated sorbent was conditioned in the form of hydrogel beads for operation. Isothermal sorption and kinetics studies were performed at pH = 6.0 to configure the nature of sorption. Pseudo-2nd order rate expression better explained the sorption kinetics and chemisorption is the predominant mode of uptake. Langmuir adsorption model better explained the sorption process ( R 2  ∼ 0.99) and maximum monolayer sorption capacity ( q m ) at sorption/desorption dynamic equilibrium was computed as 403 mg/g at optimized pH.

Extract of Hibiscus rosa-sinensis plant s was used for the green synthesis of PbO nanoparticles. The prepared nanoparticles were conformed with the help of SEM, X-ray diffraction, FTIR and UV-visible spectroscopy. The prepared PbO nanoparticles were dispersed in deionized water and mixed with graphite to get graphite-PbO (G-PbO) filler. Seven different nanocomposite membranes with variable compositions (5, 10, 15, 20, 25, 30 and 35%) of PVC/G-PbO were prepared in tetrahydrofuran (THF) solvent using solution casting method. Different physiochemical parameters of the nanocomposite membranes studied included morphology, porosity, density, water uptake, swelling degree, electrical conductivity and proton adsorption capacity. All these physiochemical parameters were compared with pure PVC membranes available in literature. It was found that the addition of G-PbO filler in PVC polymer improved all the physiochemical properties except density. PVC/G-PbO membranes showed 42.65 times more electrical conductivity and 5.90 times more ion adsorption capacities compare to pure PVC membranes.

The heavy metal cadmium (Cd) is known to be a widespread environmental contaminant and a potential toxin that may adversely affect human health across the globe. Green nanotechnology has recently received a lot of attention for developing eco-friendly, low-cost renewable and sustainable materials for the efficient removal of persistent contaminants from wastewater, including heavy metals (HMs). The current study compared the ability of titanium dioxide nanoparticles (TiO 2 NPs) synthesized from Trianthema portulacastrum (A) and Chenopodium quinoa (B) extracts to remove Cd from wastewater. The washed biomass of both the plants was dried under shade for a few days and was ground into the fine particles in a blender. The powdered biomass of T. portulacastrum and C. quinoa was soaked separately in distilled water (@ 10 g/100 ml) for 36 h. The stock solution of titanium (0.3 M) was prepared from concentrated titanium tetraisopropoxide (TTIP) and was mixed with the plant extracts at 1:2 ratio of extract to TTIP solution with continuous stirring at room temperature. A light brown scum like TiO 2 -NPs were obtained at the bottom of china dish and calcined at 450 °C for 4 h. Finally, after natural cooling, the TiO 2 -NPs were collected and used for the sorption of Cd through wastewater. Sorption attributes of both TiO 2 NPs (A, B) were investigated over contact time, dosage of adsorbent, pH, and initial concentration of Cd. Maximum sorption was obtained (46 mgg −1 ) by TiO 2 NPs (A), followed by 44 mg Cd g −1 with TiO 2 NPs (B) at pH 4.2, an optimum adsorbent dosage 0.7 g L −1 , Cd initial level 30 mg L −1 , with contact time of 2 h. Pseudo-second-order kinetic model was suited for adsorption experimental data using both nanoparticles. These results validated the potential use of TiO 2 NPs to remove liquified cadmium at high concentrations from the industrial wastewater.

Zinc oxide nanoparticles (ZnO NPs) were fabricated using Syzygium cumini leave extract as a reducing and capping agent. The ZnO NPs were characterized using various techniques including scanning electron microscopy, UV-Visible and energy dispersive X-ray (EDX) techniques. The ZnO nanoparticles size was in 0.2–1 µm range and spherical in shape. Photocatalytic efficiency of ZnO NPs for the removal of MB (methylene blue) and MO (methyl orange) was investigated under solar and UV light expire. Photocatalytic efficiency of ZnO NPs was promising, which was found to be high under UV irradiation versus solar light. The ZnO NPs was confirmed as appropriate photocatalytic agent with significant potential for the removal of dye from wastewater.

The release of unsafe color dyes into various industrial effluents can harm the environment and human health and therefore needs remediation. The current research assesses the environmental friendly photo-less catalytic performance of zinc oxide/reduced graphene oxide (ZnO/RGO) nanocomposites, prepared via green synthetic route, for the degradation, and decontamination of methylene blue (MB) dye from industrial aqueous effluents and compared with that of zinc oxide (ZnO), hydrogen peroxide (H 2 O 2 ), and reduced graphene oxide (RGO). The materials were characterized for surface morphology, functional groups, and crystallinity by using Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analysis, respectively, showing that ZnO nanoparticles (NPs) were well-formed on the RGO surface and were having uniform pore sizes and large surface area. The degradation pattern of MB from its 40, 60, 80, and 100 ppm solutions by employing the degradation materials were examined using UV–Visible spectral analysis. The pH before and after the degradation of the MB in all the sample solutions was noted and found to change slightly after the degradation of MB. The results demonstrate that the ZnO/RGO nanocomposites display a better catalytic degradation efficiency (99.57%) as compared to the other degradation materials with the order of efficiency as ZnO/RGO > RGO > H 2 O 2  > ZnO which shows that the degradation efficiency of ZnO (∼14%) can be significantly improved while fabricating its nanocomposite with RGO (99.57%). These findings can be utilized on a large-scale decontamination of dyes from industrial wastes without the involvement of light i.e., photo-less degradation.