Removal of Methylene Blue from Aqueous Solution by Mixture of Reused Silica Gel Desiccant and Natural Sand or Eggshell Waste

A greener one-pot synthesis of nanostructured SiO2 for the efficient emerging contaminant removal from simulated textile wastewater

Emerging contaminants are a group of chemicals that have the potential to enter the environment and cause potentially adverse effects on the ecosystems and their components. Currently, the interest in achieving the removal of emerging contaminants from water bodies and wastewater has grown considerably, which is reflected in several publications on the synthesis of nanomaterials capable of adsorbing them. Among emerging pollutants, methylene blue (MB) is a widely used model dye for the study of adsorption processes on nanomaterials. In this work, we report a facile and greener one-pot synthesis of SiO2 nanoparticles (SiO2NPs) than the classical Stöber method, involving a cheaper Si source than TEOS, only water as solvent, and shorter reaction times under neutral conditions at room temperature, i.e. a new sol-gel strategy with favorable greenness attributes. A multi-technical characterization of SiO2NPs (XRD, FTIR, UV-vis DR, TEM, SEM, EDX, Z-potential, and N2 adsorption-desorption isotherms at 77 K) confirmed the formation of spherical NPs, with amorphous and polydisperse nature, negatively charged surface, and mesoporous structure. Several batch adsorption experiments of MB were performed by varying pH, contact time, model dye concentration, and SiO2NPs dosage, and the kinetic and thermodynamic behavior of the removal reaction was elucidated. It was determined that the adsorption process followed a pseudo-second-order kinetic model and a Langmuir isotherm model. SiO2NPs showed high efficiency towards MB removal after 30 min of contact time (maximum adsorption capacity = 165.6 mg g-1) and high reusability for up to seven cycles without appreciable loss of adsorption efficiency. In addition, this work reports the first successful application of SiO2NPs as a cationic dye nanoadsorbent under simulated conditions of real textile wastewater (high pH, very high concentration of MB and dissolved salts, and high COD), proving that NPs are suitable for conditioning water resources contaminated with industrial dyes.

Utilizing Chamaerops humilis in removing methylene blue dye from water: an effective approach

Removing dyes, particularly methylene blue, from wastewater is crucial due to their detrimental effects on environmental and human health. Adsorption, recognized as a simple and efficient technique, is frequently employed to eliminate various dyes from water. Although activated carbon is a favored adsorbent for wastewater treatment, its high cost often restricts its use. As a result, there is increasing interest in utilizing inexpensive, natural materials, and waste products as alternative adsorbents. Sawdust from the European fan palm tree, specifically Chamaerops humilis, a widely available and cost-effective by-product, has demonstrated effective dye removal from wastewater. This study explored the impact of various factors such as time, agitation, adsorbent quantity, dye concentration, pH, and temperature on the adsorption of methylene blue using Chamaerops humilis sawdust. Optimal dye adsorption conditions were identified at a temperature of 25 °C, a pH of 8, an adsorbent dosage of 100 mg, a contact time of 120 min, and a dye concentration of 20 mg L-1, achieving a removal efficiency of 93.5%. Moreover, the Langmuir isotherm model described the adsorption dynamics more accurately, suggesting a maximum sorption capacity of 22.7 mg g-1 for the sawdust. Additionally, adsorption kinetics aligned better with the pseudo-second-order model than the pseudo-first-order model, underscoring the efficacy of this method in treating dye-polluted water.

Photodecoration of tungsten oxide nanoparticles onto eggshell as an ultra-fast adsorbent for removal of MB dye pollutant

Nowadays, the use of natural wastes and adsorbents along with their modification by simple and new methods based on metal oxides to remove dye pollutants has been the focus of many researchers. In this study, for the first time, simple and low-cost modification of eggshell (EGS) with tungsten oxide (WO3) based on the photochemical modification method as a green, ultra-fast, cost-effective, and biodegradable adsorbent is reported to remove of methylene blue (MB) dye pollutant. The EGS modified by WO3 was investigated by EDX, EDX mapping, XRD, FE-SEM, and UV-Vis Diffuse Reflectance (DRS) analyses. The obtained results show that the modified EGS by WO3 has more than ten times (78.5%) the ability to remove MB dye pollutant within 3 min compared to bare EGS (11%). Various parameters including dye pollutant pH, dye concentration, adsorbent dosage, and reusability of the WO3/EGS adsorbent for removal of MB dye pollutant were investigated and the result show that the adsorbent capacity of WO3/EGS is 1.64 mg g-1. EGS adsorbent The synthesis of WO3/EGS adsorbent with a novel photochemical method as a fast and very cheap adsorbent with excellent efficiency can be a promising alternative adsorbent for various purposes in removing dye pollutants from water environments.

Design of Nickel-Containing Nanocomposites Based on Ordered Mesoporous Silica: Synthesis, Structure, and Methylene Blue Adsorption

Mesoporous materials containing heteroelements have a huge potential for use as catalysts, exchangers, and adsorbents due to their tunable nanometer-sized pores and exceptionally large internal surfaces accessible to bulky organic molecules. In the present work, ordered mesoporous silica containing Ni atoms as active sites was synthesized by a new low-temperature method of condensation of silica precursors on a micellar template from aqueous solutions in the presence of nickel salt. The homogeneity of the resulting product was achieved by introducing ammonia and ammonium salt as a buffer to maintain a constant pH value. The obtained materials were characterized by nitrogen sorption, X-ray and neutron diffraction, scanning electron microscopy, infrared spectroscopy, and thermal analysis. Their morphology consists of polydisperse spherical particles 50-300 nm in size, with a hexagonally ordered channel structure, high specific surface area (ABET = 900-1200 m2/g), large pore volume (Vp = 0.70-0.90 cm3/g), average mesopore diameter of about 3 nm, and narrow pore size distribution. Adsorption tests for methylene blue show sorption capacities reaching 39-42 mg/g at alkaline pH. The advantages of producing nickel silicates by this method, in contrast to precipitation from silicon alkoxides, are the low cost of reagents, fire safety, room-temperature processing, and the absence of specific problems associated with the use of ethanol as a solvent, as well as the absence of the inevitable capture of organic matter in the precipitation process.

Enhanced Sorption Performance of Natural Zeolites Modified with pH-Fractionated Humic Acids for the Removal of Methylene Blue from Water

This work explores the effect of humic acids (HA) fractionation on the sorption ability of a natural zeolite (NYT)-HA adduct. HA were extracted from compost, fractionated via the pH fractionation method, and characterized via UV-Vis spectroscopy and gel permeation chromatography. The HA samples were immobilized onto NYT via thermal treatment. The resulting adducts (NYT-HA) were tested for their ability to remove methylene blue (MB) from an aqueous solution. It was found that the sorption performance of NYT-HA strongly depends on the chemical characteristics of humic acids. Sorption capacity increased with the molecular weight and hydrophobicity degree of the HA fractions. Hydrophobic and π-π interactions are likely the primary mechanisms by which MB interacts with HA. The sorption kinetic data conform to the pseudo-second-order model. The Freundlich isotherm model adequately described the sorption equilibrium and revealed that the uptake of MB onto NYT-HA is endothermic in nature.

Surface activity, kinetics, thermodynamics and comparative study of adsorption of selected cationic and anionic dyes onto H3PO4-functionalized bagasse from aqueous stream

The discharge of dyes into the water body creates toxicity to aquatic organisms because of their aromatic structure and difficult degradation. So, the treatment of dye-contaminated wastewater is required before releasing it. In the present study, thermally treated (600 °C) and H3PO4 (55%)-functionalized bagasse, henceforth called thermochemically activated bagasse (TCAB), was synthesized as potential adsorbent for the effective removal of selected cationic and anionic dyes from their aqueous stream. TCAB characterization was done employing FT-IR, SEM, XRD, zeta potential, BET, and PZC techniques. The comparative study shows that the relative adsorption on TCAB followed the sequence, methyl red (185 mg/g) > safranin (178 mg/g) > congo red (146 mg/g) > brilliant green (139 mg/g) > malachite green (130 mg/g) > bromocresol green (94 mg/g). The adsorption efficiency was investigated concerning the effect of change in TCAB dose (0.05-0.3 g/100 mL), initial dye concentration (20-200 mg/L), pH (4.0-10.0), ionic strength (0.1-0.5 M KCl), urea concentration (0.1-0.5 M) and temperature (25-45 °C). The representative adsorption isotherms belong to typical L-type. The time-dependent dye removal was best explained by the pseudo-second-order (PSO) kinetic model (R2 = 0.9859-0.9991), while equilibrium data were best explained by the Freundlich model (R2 = 0.9881-0.9961). Thermodynamic study showed the spontaneous (ΔG0 <0) and exothermic nature (ΔH0 <0) of the adsorption of different cationic and anionic dyes. The cyclic adsorption ability of TCAB for different dyes was checked up to three cycles (185 to 168 mg/L for MR, 178 to 165 mg/L for SF, 146 to 130 mg/L for CR, 139 to 127 mg/L for BG, 130 to 114 mg/L for MG and 94 to 80 mg/L for BCG), and no significant decrease in the adsorption capacity was noticed. So, the present study provides valuable insights into the adsorption of cationic and anionic dyes onto H3PO4-functionalized bagasse. Addressing the adsorptive aspects enhances the clarity, reliability and applicability of the study's findings and contributes to its overall scientific impact.