Role of nanohybrid NiO–Fe3O4 in enhancing the adsorptive performance of activated carbon synthesized from Yemeni-Khat leave in removal of Pb (II) and Hg (II) from aquatic systems

Sustainable synthesis of magnetic Sargassum siliquastrum activated carbon loaded with NiS nanorods for adsorption of 2,4-D herbicide

The upgrade of sustainable resource waste into a valuable and beneficial material is an urgent task. The current paper outlines the development of an economical, sustainable, and prolonged adsorbent derived from Sargassum siliquastrum biomass and its use for potent 2,4-dichlorophenoxyacetic acid (2,4-D) removal. A simple carbonization approach was applied to obtain the highly functionalized carbon structure, which was subsequently transformed into a novel magnetic nanoadsorbent. The magnetic nanoadsorbent was characterized using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET)-specific surface area, and vibrating sample magnetometer (VSM). The characterization results confirm the successful formation of a high specific surface area and a uniform distribution of Fe3O4/NiS NPs grafted activated carbon. The adsorption kinetics was more accurately described via the pseudo-second order model; nevertheless, the isothermal data showed that the Langmuir model was most suitable. The monolayer adsorption capacity for 2,4-D was 208.26 ± 15.75 mg/g at 328 K. The favourability and spontaneity of the adsorption process were demonstrated by thermodynamic studies. The adsorbent displayed exceptional selectivity for 2,4-D and high stability in multi-cycle use. Electrostatic attraction, π-π stacking, and hydrogen bonding were all believed to have an impact on the sorbent's robust 2,4-D adsorption. Analyses of real tap and Nile River water samples showed little effect of the sample matrix on 2,4-D adsorption. This study presents an innovative approach for developing highly efficient adsorbent from natural biomass and offers an affordable way to recycle algal waste into beneficial materials.

Capability of TiO2 and Fe3O4 nanoparticles loaded onto Algae (Scendesmus sp.) as a novel bio-magnetic photocatalyst to degration of Red195 dye in the sonophotocatalytic treatment process under ultrasonic/UVA irradiation

In this study, the magnetic photocatalyst Scendesmus/Fe3O4/TiO2 was synthesized, and its sonophotocatalytic properties in relation to the degradation of the Red195 dye were evaluated. Particles were characterized using a scanning electron microscope (SEM), Fourier's transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and a vibrating-sample magnetometer (VSM). At a pH of 5, a photocatalyst dosage of 100 mg, an initial R195 concentration of 100 mg/l, an ultrasound power of 38W, and an exposure time of 20 min, the maximum Red195 removal efficiency (100%) was achieved. After five cycles of recycling, the composite's sonophotocatalytic degradation stability for R195 remains above 95%. Experiments on scavenging indicate that electrons (h+) and hydroxyls (OH-) are indispensable decomposition agents. The removal of R195 by Scendesmus/Fe3O4/TiO2 is consistent with the pseudo-first-order kinetic, Freundlich, and Henderson's isotherm models, as determined by kinetic and isotherm investigations. The negative activation enthalpy of the standard (ΔH°) illuminates the exothermic adsorption mechanism. The increase in standard Gibbs activation free energy (ΔG°) with increasing temperature reveals the process is not spontaneous. As indicated by the negative value of the standard entropy of activation (ΔS°), activation of the reactants resulted in a loss of freedom.