Nanocomposites of natural bone that show some benefits in terms of both composition and microstructure were synthesized by an in situ precipitation method. Hydroxyapatite (Hap) was prepared from cost-effective precursors within chitosan (CS) dissolved in aqueous acetic acid solution. The nanocomposite was synthesized for the removal of brilliant green dye (BG) from a contaminated water solution. The compositional and morphological properties of the nanocomposite were studied by means of FTIR spectroscopy, X-ray diffraction (XRD), SEM, and TEM analysis. Batch experiments were carried out to investigate the effects of pH, contact time, and initial concentration, as well as the adsorbent dosage and zero point charge for the sorbent to determine a suitable medium for the adsorption process. The sorption models using Mories-Weber, Lagrange, and Bangham equations were used to identify the mechanism and reaction order. The isotherm model was carried out using Langmuir, Freundlich, and Dubinin-Radusekevisch-Kanager equations to calculate the adsorption capacity and type of adsorption. Thermodynamic parameters, enthalpy change (∆H^o), entropy change (∆S^o), and Gibbs free energy (∆G^o) were evaluated. All of the results suggest the feasibility of using nanocomposites as a sorbent for brilliant green dye removal.

Using a simple approach, silver nanoparticles (Ag NPs) were synthesized from green coffee bean extract. The optical color change from yellowish to reddish-brown of the green-produced Ag NPs was initially observed, which was confirmed by the UV-Visible spectrophotometer’s surface plasmonic resonance (SPR) bands at 329 and 425 nm. The functional groups of green coffee-capped Ag NPs (GC-capped Ag NPs) were studied using a Fourier transform infrared spectrometer, revealing that Ag NPs had been capped by phytochemicals, resulting in excellent stability, and preventing nanoparticle aggregation. The presence of elemental silver is confirmed by energy dispersive X-ray analysis. In addition to the measurement of the zeta potential of the prepared GC-capped Ag NPs, the size distribution is evaluated by the dynamic light scattering. Depending on the nano-morphological study, the particle diameter of Ag NPs is 8.6 ± 3.5 nm, while the particle size of GC-capped Ag NPs is 29.9 ± 4.3 nm, implying the presence of well-dispersed nanospheres with an average capsulation layer of thickness 10.7 nm. The phyto-capped Ag NPs were found to be crystalline, having a face-centered cubic (FCC) lattice structure and Ag crystallite size of ~7.2 nm, according to the XRD crystallographic analysis. The catalytic performance of phyto-capped Ag NPs in the removal of methylene blue dye by sodium borohydride (NaBH₄) was investigated for 12 min to reach a degradation efficiency of approximately 96%. The scavenging activities of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radicals are also examined in comparison to previously reported Ag-based nano-catalysts, demonstrating a remarkable IC₅₀ of 26.88 µg/mL, which is the first time it has been recorded.

Substantial improvement is needed in efficient and affordable decolorization and disinfection methods to solve the issues caused by dyes and harmful bacteria in water and wastewater. This work involves the photocatalytic degradation of methylene blue (MB) as well as gram-negative and gram-positive bacteria by cobalt-doped tin oxide (Co-SnO₂) nanoparticles (NPs) and Co-SnO₂/SGCN (sulfur-doped graphitic carbon nitride) nanocomposites (NCs) under sunlight. The coprecipitation approach was used to synthesize the photocatalysts. Maximum methylene blue (MB) photocatalytic degradation was seen with the 7% Co-SnO₂ NPs compared to other (1, 3, 5, and 9 wt.%) Co-SnO₂ NPs. The 7% Co-SnO₂ NPs were then homogenized with different amounts (10, 30, 50, and 70 weight %) of sulfur-doped graphitic carbon nitride (SGCN) to develop Co-SnO₂/SGCN heterostructures with the most significant degree of MB degradation. The synthesized samples were identified by modern characterization methods such as FT-IR, SEM, EDX, UV-visible, and XRD spectroscopies. The Co-SnO₂/50% SGCN composites showed a significant increase in MB degradation and degraded 96% of MB after 150 min of sunlight irradiation. Both gram-negative (E. coli) and gram-positive (B. subtiles) bacterial strains were subjected to antibacterial activity. All samples were shown to have vigorous antibacterial activity against gram-positive and gram-negative bacteria, but the Co-SnO₂/50% SGCN composites exhibited the maximum bactericidal action. Thus, the proposed NC is an efficient organic/inorganic photocatalyst that is recyclable and stable without lowering efficiency. Hence, Co-SnO₂/50% SGCNNC has the potential to be employed in water treatment as a dual-functional material that simultaneously removes organic pollutants and eradicates bacteria.

Rice husk was converted into activated carbon (AC) as a byproduct of agricultural waste in an electric furnace at 700 °C and chemically activated using three distinct processes: NaOH AC(C), acetic acid AC(C-1), phosphoric acid AC(C-2), and carbonization AC(C-3) without any chemical activation. To characterize the activated carbon and the removal efficiencies of Fe(III) and Mn(II) from aqueous solutions, various analytical tools were used. The results revealed that the capacities of the four adsorbents to adsorb Fe(III) or Mn(II) from an aqueous solution differ significantly. AC(C-3) was chosen for additional research. The impact of different operational factors, including pH, contact time, adsorbent dosage, starting metal ion concentration, interfering ions, and temperature, were investigated. The optimum pH values for Fe(III) and Mn(II) adsorption were found to be pH 3 and pH 6, respectively. The results obtained were utilized to assess the kinetics and thermodynamics of the adsorption process. The sorption of Fe(III) and Mn(II) ions was found to be a pseudo-second-order kinetic process, and the equilibrium data were fitted with the Langmuir isotherm. Additionally, the evidence suggests that an endothermic mechanism governs the adsorption process. The maximum adsorption capacities of Fe(III) and Mn(II) were 28.9 and 73.47 mg/g, respectively.

Globally, efforts are being made to upgrade and improvise the current wastewater treatment technologies. Industrial wastewater is being generated exponentially, owing to the expansion in chemical industries and civilizations necessitating remediation to prevent further environmental damage and lower associated human risks. In this work, iron oxide nanoparticles (IONPs) have been developed and employed as an efficient nanocatalyst for heavy metal adsorption via the chemical route. The shape, absorbance optical, crystal phase, and magnetization of as-prepared magnetic nanostructures were characterized using XRD (X-ray diffraction), UV-Vis (ultraviolet-visible), HRTEM (High-resolution transmission electron microscopy), FTIR (Fourier transfer infrared spectroscopy), and VSM. Further, the adsorption ability of iron oxide to remove the bulk metallic elements considering cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), copper (Cu), and nickel (Ni), present in industrial effluents, were studied. The Maghemite Fe₂O₃ crystal phase having an R-3c group is observed in the XRD results. An identical shape of spherical nanostructures is determined using TEM including ≈21 nm for pure Fe₂O₃. A removal % was studied by using ICP-OES, and showed a Cr (61.2%), Cd (98%), Cu (66%), Ni (64%), Zn (97%), and Pb (98%) removal ability. The application of such monitored nanomaterials to effluent cleaning and sewage discharge emitted via labs and petrochemical industries could be expanded.

A novel chitosan/grafted halloysitenanotubes@Znγmagnetite quaternary nanocomposite (Ch/g-HNTs@ZnγM) was fabricated using the chemical co-precipitation method to remove the ions of Cr (III), Fe (III), and Mn (II) from wastewater. The characteristics of the synthesized Ch/g-HNTs@ZnγM quaternary nanocomposite were investigated using FTIR, SEM, XRD, GPC, TGA, TEM, and surface zeta potential. The characterization analysis proved that the mentioned nanocomposite structure contains multiple functional groups with variable efficiencies. Additionally, they proved the existence of magnetic iron in the nanocomposite internal structure with the clarity of presentation of gaps and holes of high electron density on its surface. The results showed that the pH and time to reach an equilibrium system for all the studied metal ions were obtained at 9.0 and 60 min, respectively. The synthesized Ch/g-HNTs@ZnγM nanocomposite exhibited maximum adsorption removal of 95.2%, 99.06%, and 87.1% for Cr (III), Fe (III), and Mn (II) ions, respectively. The pseudo-second-order kinetic model and, for isotherm, the Langmuir model were best fitted with the experimental data. The thermodynamic parameters indicated the exothermic and spontaneous nature of the adsorption reaction as proven by the ΔH° and ΔG° values. Additionally, chemical adsorption by the coordination bond is supposed as the main mechanism of adsorption of the mentioned metal ions on the nanocomposite. Finally, Ch/g-HNTs@ZnγM displays prospected advantages, such as a low-expense adsorbent, high efficiency and availability, and an eco-friendly source, that will reduce the environmental load via an environmentally friendly method.