Globally, environmental pollution is an important issue. Various pollutants present in water resources, such as bacteria, heavy-metal ions, and organic pollutants, cause serious problems to the environment, animals, plants, and human health. Among the water resources, pollutants, dyestuff, which is discharged from dyeing, textile, and other industrial processes, is an important class of pollutants. Removing these dye pollutants from water resources and wastewater is vital and important due to their toxicity. In this work, a CrFeO₃-carbon nanotube (CNT) adsorbent was synthesized using environmentally friendly methods. The synthesized CrFeO3-CNT adsorbent was characterized stoichiometrically, spectroscopically, and morphologically. The synthesized CrFeO₃-CNT adsorbent was tested for the removal of two dyes: Methyl violet 2B (MV) and Azocarmine G2 (AC) from an aqueous solution. Crushing CrFeO₃ composite with multi-walled fullerene CNT to prepare CrFeO₃-CNT adsorbent improved the adsorption performance of free multi-walled fullerene CNT towards MV dye by 30% and towards AC dye by 33.3%.

The use of sewage sludge activated carbon (thickened samples ACS1 and non-thickened samples ACS2) in a variety of applications and simple environmentally friendly production techniques are attracting more and more attention. We offer here a novel environmentally friendly method based on the green synthesis of activated carbons (ACS1/ACS2) using sewage sludge (SS). These activated carbons are then used to effectively remove the water-based reactive dye phenol red (PR). The ACS1 and ACS2 produced are porous materials with an average diameter of 20.72–13.30 and 6.20–7.34 nm, respectively. These ACS1/ACS2 were analyzed using a range of characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis. Elimination of toxic PR dye was investigated using several operational factors, including ACS1/ACS2 dose, initial PR dye concentration, pH and temperature. Under the best experimental conditions, the ACS1 and ACS2 adsorbents absorbed nearly 89.58% and 97.69% of the PR dye, respectively. It was found that both ACS1 and ACS2 adsorption corresponded to pseudo-first-order kinetics (R = 0.996 and 0.980) and fulfilled Langmuir’s (ACS1) and Freundlich’s (ACS2) models well, with maximum adsorption capacities of 65.35 and 122.72 mg/g, respectively. It was found that the adsorption processes are basically exothermic. The results suggest that sewage sludge can be effective as a low-cost and environmentally beneficial synthesis of ACS1 and ACS2 in the purification of water sources contaminated with hazardous dyes.

The limited supply of drinking water has aroused people’s curiosity in recent decades. Adsorption is a popular method for removing hazardous substances from wastewater, especially heavy metals, as it is cheap, highly efficient, and easy to use. In this work, a new sludge-based activated carbon adsorbent (thickened samples SBAC1 and un-thickened samples SBAC2) was developed to remove hazardous metals such as cadmium (Cd⁺²) and lead (Pb⁺²) from an aqueous solution. The chemical structure and surface morphology of the produced SBAC1 and SBAC2 were investigated using a range of analytical tools such as CHNS, BET, FT-IR, XRD, XRF, SEM, TEM, N₂ adsorption/desorption isothermal, and zeta potential. BET surface areas were examined and SBAC2 was found to have a larger BET surface area (498.386 m²/g) than SBAC1 (336.339 m²/g). While the average pore size was 10–100 nm for SBAC1 and 45–50 nm for SBAC2. SBAC1 and SBAC2 eliminated approximately 99.99% of Cd⁺² and Pb⁺² out the water under all conditions tested. The results of the adsorption of Cd⁺² and Pb⁺² were in good agreement with the pseudo-second-order equation (R² = 1.00). Under the experimental conditions, the Cd⁺² and Pb⁺² adsorption equilibrium data were effectively linked to the Langmuir and Freundlich equations for SBAC1 and SBAC2, respectively. The regeneration showed a high recyclability for the fabricated SBAC1 and SBAC2 during five consecutive reuse cycles. As a result, the produced SBAC1 and SBAC2 are attractive adsorbents for the elimination of heavy metals from various environmental and industrial wastewater samples.

Eight polymer-metal complexes were synthesized from complexation of divalent Mn(II), Ni(II), Co(II), and Cu(II) metal ions with modified polystyrene-alt-(maleic anhydride) (PSMAP and PSMAM) ligands. The structures of these new complexes were characterized using a variety of techniques, including magnetic moment susceptibility, conductance measurements, FT-IR spectroscopy, ultraviolet-visible (UV-VIS), thermogravimetric analysis (TGA), as well as scanning electron microscopy (SEM). All metal-polymer complexes have a non-electrolytic nature based on conductance measurements. The polymer molecule behaves as neutral bidentate NO ligand through O atoms of carbonyl (C=O) and N atoms of amide (O=C-NH). Divalent Mn²⁺, Ni²⁺, Co²⁺ and Cu²⁺ complexes have an octahedral geometry based on their electronic spectra and magnetic values. Based on thermal analysis data, those new complexes are more thermally stable than the ligands. SEM and TEM are manipulated to give the surface structure and the particle size measurements where they give different shapes and sizes of the synthesized complexes.

Silver nanoparticles (Ag-NPs) are attracting great attention for their use in various applications, along with methods for their green and facile production. In this study, we present a new eco-friendly approach based on the use of Euphorbia balsamifera extract (EBE) in the green synthesis of silver nanoparticles (Ag-NPs), which are then applied as a reducing and stabilizing agent for the efficient removal of water-based reactive dyes such as bromocresol green (BCG) and bromophenol blue (BPB). The as-prepared Ag-NPs are quasi-spherical in shape, with an average diameter of 20–34 nm. Diverse characterization methods, including X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) analysis, were used to analyze these Ag-NPs. The results reveal that water-soluble biomolecules in the Euphorbia balsamifera extract play an important role in the formation of the Ag-NPs. The removal of toxic dyes was studied under varied operational parameters such as Ag-NP dosage, initial dye concentration, pH, stirring time, and temperature. Under the optimum investigated conditions, nearly 99.12% and 97.25% of the bromocresol green and bromophenol blue dyes, respectively, were removed. Both BCG and BPB adsorption were found to adhere to pseudo-second-order kinetics (r₂² = 1 and 0.995) and fit the Langmuir isotherm models well (R₁² = 0.998 and 0.994), with maximal monolayer adsorption capacities of 20.40 and 41.03 mg/g, respectively. Their adsorption processes were observed to be intrinsically endothermic. The results confirm the potential of the Euphorbia balsamifera extract as a low-cost, nontoxic, and eco-friendly natural resource for the synthesis of Ag-NPs that may be useful in the remediation of hazardous dye-contaminated water sources.

The limited supply of drinking water has aroused people's curiosity in recent decades. Adsorption is a popular method for removing hazardous substances from wastewater, especially heavy metals, as it is cheap, highly efficient and easy to use. In this work, a new sludge-based activated carbon adsorbent (SBAC1 / SBAC2) was developed to remove hazardous metals such as cadmium (Cd+2) and lead (Pb+2) from an aqueous solution. The chemical structure and surface morphology of the produced SBAC1 and SBAC2 were investigated using a range of analytical tools such as CHNS, BET, FT-IR, XRD, XRF, SEM, TEM, N2 adsorption/desorption isothermal and zeta potential. BET surface areas were examined and SBAC2 was found to have a larger BET surface area (498.386 m2/g) than SBAC1 (336.339 m2/g). SBAC2 had a lower VBJH (1.5026 cm3 g-1) than SBAC1 (1.59873 cm3 g-1), but a higher VT (0.3748 cm3 g-1) than SBAC1 (0.2688 cm3 g-1), while the average pore size was 10-100 nm for SBAC1 and 45-50 nm for SBAC2. The ideal conditions investigated for the removal of Pb+2 and Cd+2 were 10 mg SBAC1 / SBAC2, Pb+2 / Cd+2 at an starting concentration of 30 mg/L, a temperature of 40 and 50 °C, pH = 6, 8 and contact times of 10 and 15 minutes for Pb+2 and Cd+2, respectively. SBAC1 and SBAC2 eliminated approximately 99.99% of Cd+2 and Pb+2 out the water under all conditions tested. The results of the adsorption of Cd+2 and Pb+2 were in good agreement with the pseudo-second-order equation (R2 = 1.00). Under the experimental conditions, the Cd+2 and Pb+2 adsorption equilibrium data were effectively linked to the Langmuir and Freundlich equations for SBAC1 and SBAC2, respectively. Langmuir model calculated the adsorption capacities of SBAC1 and SBAC2 for Cd+2 (309.24 and 329.62 mg/g) and for Pb+2 (318.46 and 339.61 mg/g), respectively. The regeneration showed high recyclability for the fabricated SBAC1 and SBAC2 during five consecutive reuse cycles. As a result, the produced SBAC1 and SBAC2 are attractive adsorbent for the elimination of heavy metals from various environmental and industrial wastewater samples.