Geopolymers Based on Fly Ash for Organic Dye Removal from Water

Removal of organic and synthetic dyes from water bodies is an environmental concern of highest priority as these are stable to biodegradation. A new mesoporous nanohybrid material was synthesized from titania and gelatin backbone in the presence of tetraethoxysilane and sodium dodecyl sulphate via sol–gel technique. These hybrid materials are better adsorbents for eliminating organic dyes such as congo red (CR), malachite green (MG), crystal violet (CV), methylene blue (MB) from their aqueous solutions. High surface area of inorganic material (titania) and the high density of ammonium groups, and carboxylate groups of the bio-polymeric backbone (gelatin) can serve as a selective adsorbent for the exclusion of anionic acid dye (CR) as well as cationic basic dyes (MG, CV, MB). All the four dyes have followed Langmuir isotherm for adsorption. The rate determining studies have followed pseudo-second-order kinetics for all dyes. Experimental studies and their results hold good and are in agreement with kinetic and isotherm modelling. Hybrid materials made are further used for the photocatalytic degradation of dyes by direct exposure to the sunlight to five repeated cycles. The biocompatible and biodegradable nature of the gelatin–titania-based nanohybrid material has a prospective for the various applications in the different fields like water treatment, pH-responsive drug delivery and controlled release, since it has elevated adsorption capacity (>70 mg/g), high pH sensitivity, easy renewal, and good reusability. Hence, an adsorbent that can remove dyes by adsorption and at the same time has the photocatalytic ability is being described in this work.

This study presents the results of synthesis and characterization of nanoparticles of cobalt ferrite (CoFe2O4) and nickel ferrite (NiFe2O4) using co-precipitation method followed by application for removal of hazardous organic textile dyes of thiazole yellow G (TYG) and alizarin yellow R (AYR). XRD analysis confirmed formation of cubic spinel structure with average crystallite sizes at 16.07nm and 13.84nm for CoFe2O4 and NiFe2O4, respectively. Field emission scanning electron microscopy (FESEM) analysis showed agglomeration of spherical shape morphology with uniformly distributed Co, Ni, Fe, and O elements. The surface area calculated from Brunauer-Emmett-Teller (BET) analysis was 64 m2/g and 62 m2/g for CoFe2O4 and NiFe2O4, respectively. Vibrating sample magnetometer (VSM) showed super-paramagnetic behavior for all samples with magnetic saturation (Ms) at 7.269 and 6.61emu/g for CoFe2O4 and NiFe2O4, respectively. The adsorption influencing parameters such as pH of solution, quantity of adsorbent, and contact time on dye removal efficiency were thoroughly investigated. Overall, acidic condition of samples with pH at 4 favored the maximum removal efficiency by CoFe2O4 as 98, 97, and 93%, and by NiFe2O4 as 96, 93, and 92%, respectively, for TYG, AYR, and mixture sample. The Langmuir adsorption isotherm model describes the equilibrium of all samples with the best fit of coefficient of determination (R2). The adsorption results fitted well with a pseudo-second-order kinetic model for all samples. The regeneration-reuse ability of adsorbents and cost estimation analysis of the dye removal process suggested that the economic suitability of nano-adsorbents for remediation of textile effluents was favored. The estimated thermodynamic parameters inferred that the removal of organic dyes onto the surface of CoFe2O4 and NiFe2O4 is a spontaneous, favorable, and exothermic physical adsorption process.

In the present study, we have synthesized magnesium oxide (MgO) nanoparticles by a facile and cost-effective chemical co-precipitation method with annealing at three different temperatures (350°C, 450°C, and 550°C) for the removal of various organic dyes. X-ray diffraction studies revealed that the prepared samples are having sizes below 20 nm and with pure phase. Phase transformation of hexagonal Mg(OH)2 nanoparticles to discretely cubical structured MgO nanoparticles has been observed with increasing the annealing temperatures which is also supported by the TGA/DSC analysis. Mg-O stretching vibration peaks in the range of 400-800 cm-1 obtained by FTIR spectroscopy support the formation of MgO nanoparticles. The observed Raman active bands for the annealed sample at 550°C confirm the formation of the nanocrystalline phase since these bands are typically absent in the bulk MgO as well as in Mg(OH)2. The surface morphology of the as-prepared Mg(OH)2 are aggregated nano-petals which changed into spherical shape for MgO annealed at 550°C as studied by field emission scanning electron microscopy (FESEM). The specific surface area of MgO nanoparticles annealed at 550°C using BET isotherms is found to be 37.487 m2g-1. The optical bandgaps of the prepared samples are found to be in the range of 4.4 to 5.1 eV using the Tauc plot. Adsorption studies with a variation of initial brilliant green dye concentration and contact time are carried out along with the studies of adsorption kinetic and isotherm models. Langmuir isotherm model is the most suitable model on the basis of correlation constant with maximum BG dye adsorption capacity onto MgO@550°C which is found to be 63.9 mg/g. The adsorption kinetics followed the pseudo-second-order model. Also prepared pristine MgO nanoparticles showed significant photocatalytic performance for the degradation of various dyes; brilliant green (BG: 88.91%), methylene blue (MB: 79.05%), crystal violet (CV: 76.49%), methyl orange (MO: 68.62%), and brilliant blue (BB: 40.44%) under visible irradiation. MgO nanoparticles could be a promising adsorbent and photocatalyst that may be employed in the treatment of effluents from industries.

Highly efficient organic dye removal from waters by magnetically recoverable La2O2CO3/ZnFe2O4-reduced graphene oxide nanohybrid

Synthetic organic dyes, which are resistant to biodegradation, pose a notable health risk, potentially leading to cancer and respiratory infections. Researchers have addressed this concern by exploring physicochemical methods to remove organic dyes from wastewater. A particularly promising solution involves modified biochar adsorbents, which demonstrate high efficiency in organic dye removal. Biochar, a charcoal-like material derived from biomass pyrolysis, offers advantages such as low cost, eco-friendliness, high efficiency and reusability. Beyond its role in sustainable soil remediation, biochar proves effective in removing organic dyes from wastewater after undergoing physical or chemical modification. Acid-base activation or metal-heteroatom impregnation enhances biochar's adsorption capacity. This comprehensive review examines the attributes of biochar, common methods for production and modification, and the impacts of raw materials, pyrolysis temperature, heating rate and residence time. It further elucidates the biochar adsorption mechanism in the removal of organic dyes, assessing factors influencing efficiency, including biochar feedstock, solution pH, adsorption temperature, particle size, initial dye concentration, biochar dosage and reaction time. It explores challenges, opportunities, reusability and regeneration methods of biochar in treating organic dye wastewater. It also discusses recent advances in organic dye removal using adsorption-based biochar. The review ultimately advocates for enhancing biochar's adsorption performance through post-modification.

Treatment of colored wastewater is one of the important challenges of environmental engineers. Adsorption is one of the most efficient methods in dye removal. The aim of this study was to prepare a magnetic adsorbent with Fe3O4 nanoparticles as an inexpensive adsorbent to remove basic violet 16 (BV16) dye from aqueous media. In this experimental study, the effect of parameters such as initial solution pH, adsorbent dose, initial dye concentration, and contact time on the adsorption rate was investigated. The residual dye concentration was read at 545 nm by using a spectrophotometer. Physical, surface, and magnetic properties of the adsorbent were analyzed using Brunauer–Emmett–Teller (BET), Vibrating-Sample Magnetometer (VSM), X-ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning electron microscope (SEM) techniques. Adsorption data were described by Langmuir and Freundlich isotherms and reaction kinetics. The results showed that with increasing the contact time and increasing the adsorbent dose, the amount of dye removal by the adsorbent increased and with decreasing the initial concentration of dye, the amount of removal increased. The results also showed that with increasing pH, the removal efficiency of the process increased linearly. According to resuls, the highest BV16 dye adsorption efficiency was 99%, which was obtained at determined values of studied parameters including pH of 7, adsorbent dose: of 0.5 g/L, initial BV16 dye concentration of 25 mg/l, mixing speed of 250 rpm, and contact time of 45 min. Moreover, according to results, removal of BV16 dye using adsorption onto clinoptilolite zeolite magnetized with Fe3O4 nanoparticles obey a second-order kinetic model and Freundlich model (R2>0.99). According to SEM images, the adsorbent surface used is non-uniform and has many pores and also the morphology of the adsorbent surface is preserved after loading of Fe3O4 nanoparticles. According to VSM images, the magnetic saturation in composite is 18.11 emu/g. Results hihlighted the adsorption of BV16 dye onto clinoptilolite zeolite magnetized with Fe3O4 nanoparticles was a useful technique and could provide high efficiency in removal of studied dye from aqueous solutionsl; thus, it mabe be effective and useful in removal other similar pollutants.

The adsorption of crystal violet (CV) and malachite green (MG) dyes using carbon-coated Zn-Al-layered double hydroxide (C-Zn-Al LDH) was investigated in this work. The characterisation of both Zn-Al LDH and C-Zn-Al LDH was performed using XRD, SEM, TEM, EDX, XPS, FTIR, BET and TGA. The results indicated that carbon particles were effectively coated on Zn-Al LDH surface. The average total pore volume and pore diameter of C-Zn-Al LDH were observed as 0.007cc/g and 3.115nm. The impact of parameters like initial dye concentration, pH and adsorbent dosage on the dye removal efficiency was confirmed by carrying out Box-Behnken design experiments. Langmuir isotherm was well suited for both CV and MG adsorption among other isotherm models. The adsorption capacity was maximally obtained as 129.87 and 126.58mg/g for CV and MG respectively. Pseudo-second order fits the adsorption kinetics than any other kinetic models for both the dyes. The thermodynamic study indicates that the adsorption process of CV was exothermic, whereas for MG was endothermic. Electrostatic attraction, H-bonding, n-π and π- π interactions were mainly influenced in the adsorption process. This study concludes that C-Zn-Al LDH is an efficient adsorbent for the CV and MG dye removal from aqueous solutions. Graphical abstract ᅟ Graphical abstract contains text below the minimum required font size of 6pts inside the artwork, and there is no sufficient space available for the text to be enlarged. Please provide replacement figure file.Graphical abstract contains text is rewritten with the maximum required font size inside the artwork and provided sufficient space between the text which is enlarged.The new Graphical abstract is attached as an image in the attachment file for your further usage.

ZIF-8 metal-organic network/poly(vinyl alcohol) composite for adsorptive removal of various organic dyes

β-Cyclodextrin network crosslinked by novel phosphonium-based tetrakiscarboxylic acid derived from PH3 tail gas: Synthesis and application for rapid removal of organic dyes from wastewater

Rapid industrialization has led to significant environmental challenges, particularly in wastewater treatment, where the removal of heavy metal ions and organic dyes is critical. This study presents the synthesis and characterization of a high-performance hydrogel adsorbent, (nanoclay)x@poly-γ-glutamic acid (γ-PGA)/polyethyleneimine (PEI) hydrogel adsorbent (denoted as NxPP, x = 0, 20, 40, 60, and 80), for the efficient removal of heavy metal ions (Cu2+, Fe3+, and Zn2+) and organic dyes (Methylene blue, as a typical example) from wastewater. The hydrogel was prepared using a one-pot method, combining γ-PGA and PEI with varying amounts of nanoclay. The N80PP hydrogel demonstrated exceptional adsorption capacities, achieving 224.37 mg/g for Cu2+, 236.60 mg/g for Fe3+, and 151.95 mg/g for Zn2+ within 30 min, along with 88.18 mg/g for Methylene blue within 5 h. The incorporation of nanoclay significantly enhanced the mechanical properties, with compressive strength reaching 560.49 kPa. The hydrogel exhibited excellent reusability, maintaining high adsorption capacity after five cycles. The adsorption kinetics followed a pseudo-second-order model, and the isotherms fit the Freundlich model, indicating a multilayer adsorption mechanism. This study highlights the potential of NxPP hydrogels as a versatile and sustainable solution for wastewater treatment.

Removal of basic dyes from aqueous solution by adsorption onto binary iron-manganese oxide coated kaolinite: Non-linear isotherm and kinetics modeling

Central composite design for optimizing the organic dyes remediation utilizing novel graphene oxide@CoFe2O4 nanocomposite

Preparation of amino/hydroxy dual-functionalized hypercrosslinked polymers for effective removal of organic dyes from water.

This work aimed to use effective, low-cost, available, and natural adsorbents like eggshells for removal of hazardous organic dye result from widely number of industries and study the influence of different eggshell particle size (75, 150) Mm. The adsorbent was characterized by SEM, EDX, BET and FTIR . The initial pH of dye solutions varying from 4 to 10 , the initial concentrations of methyl violet (MV) 2B range (20-80) mg/L, dosage range (0.5-10) g, contact time (30-180) min, and particles size of the adsorbent (75, 150) Mm were selected to be studied. Two adsorption isotherms models have been used to fit the experimental data. Langmuir and Freunlich models were found to more represent the experiments with high correlation coefficient. The results showed that the variation in particle size of eggshells powder statistically has slight effect on the removal of (MV). The highly percentage of dye removal (97.27%) by using eggshells was observed with particle size of 75Mm, pH 4, at room temperatures for 30 min, 10 g adsorbent dose and 20 mg/L initial dye concentration.

Heterogeneous sono-Fenton-like process using magnetic cobalt ferrite-reduced graphene oxide (CoFe2O4-rGO) nanocomposite for the removal of organic dyes from aqueous solution