Equilibrium, kinetics and thermodynamic parameters for adsorptive removal of dye Basic Blue 9 by ground nut shells and Eichhornia

Membrane process and adsorption on pine nut shell for removal of dye from synthetic wastewater

Purification methods such as membrane technology and adsorption have been studied for the purification of textile effluents. This article aimed to evaluate the membrane separation process and adsorption on pine nut shell, separately and sequentially, for reactive dye blue 5G removal from a synthetic effluent. The membrane separation process was carried out in a front filtration module using polymeric membranes. The maximum dye retention was 35.9% using a regenerated cellulose membrane, with agitation and a pressure of 0.5 bar. The permeate flux was fully restored after cleaning the membrane. In the adsorption using pine nut shell, the best results were at pH 2, 50°C, and 50 ppm, with 85% dye removal. The Freundlich isotherm showed the best fit to the data, as did the pseudo-second-order kinetic model. The thermodynamic parameters indicated that the adsorption is of the physical type, with the process being endothermic and spontaneous. In the combined process, the permeate from the membrane separation process was subjected to adsorption on pine nut shell, achieving a removal rate of 98.7 for the initial concentration of 50 ppm. Therefore, this work shows the potential of pine nut shell as an adsorbent, not only to purify textile effluents but also to add value to a waste product, indicating that the combination of membrane technology and adsorption on pine nut shell could be an alternative for the treatment of textile effluents containing the reactive dye 5G blue.

Parameters optimization of Fe3O4 NPs synthesis by Tamarindus indica leaf extract possessing both peroxidase as well as excellent dye removal activity

This study reports optimized conditions for the green synthesis of iron (II,III) oxide nanoparticles (Fe₃O₄ NPs) from Tamarindus indica (T. indica) leaf extract. The synthetic parameters like concentration of leaf extract, solvent system, buffer, electrolyte, pH, and time were optimized for Fe₃O₄ NPs synthesis. Fe₃O₄ NPs were obtained from the synthesis protocol by measuring size (80 ± 3 nm approx.), characteristics color changes, and an absorption peak between 270 nm and 280 nm using a UV-visible spectrophotometer, scanning electron microscope (SEM), and an energy dispersive X-ray spectrometer (EDS) study. Peroxidase activity was tested with 3,3,5,5-Tetramethylbenzidine (TMB) oxidation in the presence of hydrogen peroxide and dye removal activity was tested with malachite green (MG). The results indicated that the successful synthesis of Fe₃O₄ nanoparticles using aqueous leaf extract of T. indica is a practical alternative for biomedical applications due to its potent peroxidase activity and high dye removal capacity (about 93% with UV light and 55% with room light).

Mesoporous calcium hydroxide nanoparticle synthesis from waste bivalve clamshells and evaluation of its adsorptive potential for the removal of Acid Blue 113 dye

Calcium hydroxide nanoadsorbent was prepared from waste bivalve clamshells and used for the adsorptive removal of Acid Blue 113 (AB113) dye. The morphology, elemental nature, functional groups, and thermal stability of the nanoadsorbent were characterized by various methods. The nanoadsorbent had a high monolayer adsorption capacity (153.53 mg/g) for AB113 dye. Langmuir and Temkin isotherms better fitted (R² > 0.95) the experimental data. The adsorption rate followed pseudo-second-order kinetics (R² > 0.99). The thermodynamic study ascertained spontaneous and exothermic adsorption. This study confirmed the possibility of using calcium hydroxide as an adsorbent to effectively remove AB113 dye from aqueous solutions.

Hydrophobic Modification of ZrO2-SiO2 Xerogel and Its Adsorption Properties to Rhodamine B

Zirconium nitrate pentahydrate (Zr(NO₃)₄·5H₂O) and tetraethyl orthosilicate (TEOS) are used as the zirconium source and silicon source, respectively, and methyltriethoxysilane (MTES) as the hydrophobic modifier; the hydrophilic and hydrophobic ZrO₂-SiO₂ xerogels were prepared successfully. The xerogels were characterized using Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and N₂ adsorption-desorption measurement. The adsorption mechanism of hydrophobic ZrO₂-SiO₂ xerogels to RhB was described by the kinetic and adsorption isotherms. The results showed that the introduction of Si-CH₃ groups can make the average pore size, BET surface area, and total pore volume of ZrO₂-SiO₂ xerogel increase. The hydrophobic ZrO₂-SiO₂ xerogel displays an adsorption capacity of 169.23 mg·g^-1 for RhB dye at 25 °C and pH = 3. The adsorption process of hydrophobic ZrO₂-SiO₂ xerogel to RhB followed a pseudo-second-order kinetic model. Fitting results from the D-R model of adsorption indicate that the adsorption of RhB onto the hydrophobic ZrO₂-SiO₂ xerogels is mainly physical, accompanied by a spontaneous heat absorption process. The regeneration and recycling properties of hydrophobic xerogels were investigated, and their recoverability and reusability were demonstrated.

Zirconia-Doped Methylated Silica Membranes via Sol-Gel Process: Microstructure and Hydrogen Permselectivity

In order to obtain a steam-stable hydrogen permselectivity membrane, with tetraethylorthosilicate (TEOS) as the silicon source, zirconium nitrate pentahydrate (Zr(NO₃)₄·5H₂O) as the zirconium source, and methyltriethoxysilane (MTES) as the hydrophobic modifier, the methyl-modified ZrO₂-SiO₂ (ZrO₂-MSiO₂) membranes were prepared via the sol-gel method. The microstructure and gas permeance of the ZrO₂-MSiO₂ membranes were studied. The physical-chemical properties of the membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), and N₂ adsorption–desorption analysis. The hydrogen permselectivity of ZrO₂-MSiO₂ membranes was evaluated with Zr content, temperature, pressure difference, drying control chemical additive (glycerol) content, and hydrothermal stability as the inferred factors. XRD and pore structure analysis revealed that, as n_Zr increased, the MSiO₂ peak gradually shifted to a higher 2θ value, and the intensity gradually decreased. The study found that the permeation mechanism of H₂ and other gases is mainly based on the activation–diffusion mechanism. The separation of H₂ is facilitated by an increase in temperature. The ZrO₂-MSiO₂ membrane with n_Zr = 0.15 has a better pore structure and a suitable ratio of micropores to mesopores, which improved the gas permselectivities. At 200 °C, the H₂ permeance of MSiO₂ and ZrO₂-MSiO₂ membranes was 3.66 × 10⁻⁶ and 6.46 × 10⁻⁶ mol·m⁻²·s⁻¹·Pa⁻¹, respectively. Compared with the MSiO₂ membrane, the H₂/CO₂ and H₂/N₂ permselectivities of the ZrO₂-MSiO₂ membrane were improved by 79.18% and 26.75%, respectively. The added amount of glycerol as the drying control chemical additive increased from 20% to 30%, the permeance of H₂ decreased by 11.55%, and the permselectivities of H₂/CO₂ and H₂/N₂ rose by 2.14% and 0.28%, respectively. The final results demonstrate that the ZrO₂-MSiO₂ membrane possesses excellent hydrothermal stability and regeneration capability.

Active MgO-SiO2 hybrid material for organic dye removal: A mechanism and interaction study of the adsorption of C.I. Acid Blue 29 and C.I. Basic Blue 9

A comparative analysis was performed concerning the removal of two different organic dyes from model aqueous solution using an inorganic oxide adsorbent. The key element of the study concerns evaluation of the influence of the dyes' structure and their acid-base character on the efficiency of the adsorption process. The selection of sorbent material for this research - an MgO-SiO₂ oxide system synthesized via a modified sol-gel route - is also not without significance. The relatively high porous structure parameters of this material (A_BET = 642 m²/g, V_p = 1.11 mL and S_p = 9.8 nm) are a result of the proposed methodology for its synthesis. Both organic dyes (C.I. Acid Blue 29 and C.I. Basic Blue 9) were subjected to typical batch adsorption tests, including investigation of such process parameters as time, initial adsorbate concentration, adsorbent dose, pH and temperature. An attempt was also made to estimate the sorption capacity of the oxide material with respect to the analyzed organic dyes. To achieve the objectives of the research - determine the efficiency of adsorption - it was important to perform a thorough physicochemical analysis of the adsorbents (e.g. FTIR, elemental analysis and porous structure parameters). The results confirmed the significantly higher affinity of the basic dye to the oxide adsorbents compared with the acidic dye. The regeneration tests, which indirectly determine the nature of the adsorbent/adsorbate interactions, provide further evidence for this finding. On this basis, a probable mechanism of dyes adsorption on the MgO-SiO₂ oxide adsorbent was proposed.