Synthesis of malachite@clay nanocomposite for rapid scavenging of cationic and anionic dyes from synthetic wastewater

Adsorption of As(III), Pb(II), and Zn(II) from Wastewater by Sodium Alginate Modified Materials

Sodium alginate (SA), polyvinyl oxide (PEO), and ceramic nanomaterials were used to prepare alginate composite gel. The present study examined the removal rate and adsorption capacity of alginate composite gel for removal of wastewater As(III), Pb(II), and Zn(II). Batch experiments were conducted to study the influence of experimental parameters such as pH and temperature, as well as the mechanism of As(III), Pb(II), and Zn(II) adsorption with the new adsorbent. The results showed the high efficiency of sodium alginate composite gel for removal of wastewater As(III), Pb(II), and Zn(II). Under the condition of the best liquid-solid ratio and the contact time, the removal rates of As(III), Pb(II), and Zn(II) were 67.42%, 95.31%, and 93.96%, respectively. The pseudo-second-order kinetic equation was superior to fit the adsorption kinetics process. The isothermal adsorption models of As(III) and Pb(II) fitted well with the Freundlich model, and Zn(II) fitted well with the Langmuir model. The results of SEM, EDS, XPS, and FTIR analyses revealed that the adsorption process occurred mainly via chemisorption. The results of the present study suggest that new adsorbents can be effectively utilized for As(III), Pb(II), and Zn(II) removal from water.

Adsorption of cationic dyes, drugs and metal from aqueous solutions using a polymer composite of magnetic/β-cyclodextrin/activated charcoal/Na alginate: Isotherm, kinetics and regeneration studies

In this work, we successfully synthesized novel polymer gel beads based on functionalized iron oxide (Fe3O4), activated charcoal (AC) particles with β-cyclodextrin (CD) and sodium alginate (SA) polymer (Fe3O4/CD/AC/SA), by a simple, reproducible and inexpensive method. These beads proved to be versatile and strong adsorbents with magnetic properties and high adsorption capacity. The composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometry, adsorption at -196 °C, high resolution transmission electron microscopy, thermogravimetric analysis and point of zero charge measurements. Two dyes, two drugs and one metal were used to test the adsorption capability of the prepared polymer nanocomposite. The adsorbent showed good removal efficiencies for the studied pollutants, especially the cationic dyes and the metal, when compared to other low-cost adsorbents. The saturated adsorption capacity of Fe3O4/CD/AC/SA reached 5.882 mg g-1 for methyl violet (MV), 2.283 mg g-1 for brilliant green (BG), 2.551 mg g-1 for norfloxacin (NOX), 3.125 mg g-1 for ciprofloxacin (CPX), 10.10 mg g-1 for copper metal ion (Cu(II)). The adsorption isotherm studies showed that data fitted well with Langmuir and Temkin isotherms models. The kinetic data showed good correlation coefficient with low error function for the pseudo-second order kinetic model. The data analysis was carried out using error and regression coefficient functions for the estimation of best-fitting isotherm and kinetic models, namely: chi-square test (χ2) and sum of the squares of errors (SSE). The activation energy was found to be 47.68 kJ mol-1 for BG, 29.09 kJ mol-1 for MV, 28.93 kJ mol-1 for NOX, 4.53 kJ mol-1 for CPX and 17.08 kJ mol-1 for Cu(II), which represent chemisorption and physisorption behavior of sorbent molecules. The polymer composites can be regenerated and easily separated from aqueous solution without any weight loss. After regeneration, the Fe3O4/CD/AC/SA beads still have good adsorption capacities up to four cycles of desorption and adsorption. The results indicate that the polymer gel beads are promising adsorbents for the removal of different categories of toxicants (like dyes, drugs and metal) in single adsorbate aqueous systems. Thus, the novel Fe3O4/CD/AC/SA beads can be effectively employed for a large-scale applications as environmentally compatible materials for the adsorption of different categories of pollutants.

Cationic Dye Removal Using Novel Magnetic/Activated Charcoal/β-Cyclodextrin/Alginate Polymer Nanocomposite

New magnetic iron oxide (Fe₃O₄)/activated charcoal (AC)/β-cyclodextrin (CD)/sodium alginate (Alg) polymer nanocomposite materials were prepared by direct mixing of the polymer matrix with the nanofillers. The obtained materials were utilized as nano-adsorbents for the elimination of methylene blue (MB), a hazardous water-soluble cationic dye, from aqueous solutions, and showed excellent regeneration capacity. The formation of the nanocomposites was followed by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDX), Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and adsorption of N₂ at −196 °C. The rate of adsorption was investigated varying several factors, namely contact time, pH, amount of adsorbent and MB concentration on the adsorption process. Studies dealing with equilibrium and kinetics were carried out in batch conditions. The obtained results indicated that the removal rate of MB was 99.53% in 90 min. Langmuir’s isotherm fitted better to the equilibrium data of MB. Fe₃O₄/AC/CD/Alg polymer beads shows amazing adsorption capacities in the elimination of cationic dyes (2.079 mg/g for polymer gel beads and 10.63 mg g⁻¹ for dry powder beads), in comparison to other adsorbent materials. The obtained adsorbent is spherical with hydrophobic cross-linked surface properties that enable an easy recovery without any significant weight loss of in the adsorbent used.

Nano-engineered Adsorbent for the Removal of Dyes from Water: A Review

Background:

The huge quantity of wastewater, containing poisonous and hazardous dyes, is released by various industries which pollute water in direct and indirect ways. Most of the dyes are a dangerous class of water contaminants which have affected the environment drastically. Some dyes such as congo red, rhodamine B, methylene blue, methyl violet, and crystal violet are a serious threat to human beings.

Remediation Method:

Numerous methods are available for the removal of dyes from water. Adsorption, being a superior and eco-friendly technique, has advantage of eliminating organic dyes because of the availability of materials as adsorbents. The inexpensive nanomaterials are a more attractive choice for remediation of various dyes due to their unique properties and offer an adequate pathway to adsorb any organic dye from water to overcome its hazardous effects on human health.

Results:

In this review, we have discussed the latest literature related to various types of synthesis, characterization and uses as adsorbent for highly adsorptive removal capacity of nanoparticles for organic dyes.

Conclusion:

Adsorption technology provides an attractive pathway for further research and improvement in more efficient nanoparticles, with higher adsorption capacity, for numerous dyes to eliminate the dyes discharged from various industries and thus reduce the contamination of water. Therefore, nanocomposites may contribute to future prospective water treatment process.

Strong enhancement of methylene blue removal from binary wastewater by in-situ ferrite process

Dye wastewater containing heavy metal ions is a common industrial effluent with complex physicochemical properties. The treatment of metal-dye binary wastewater is difficult. In this work, a novel in-situ ferrite process (IFP) was applied to treat Methylene Blue (MB)-Cu(II) binary wastewater, and the operational parameters were optimized for MB removal. Results showed that the optimum operating conditions were OH/M of 1.72, Cu²⁺/Fe²⁺ ratio of 1/2.5, reaction time of 90min, aeration intensity of 320mL/min, and reaction temperature of 40°C. Moreover, the presence of Ca²⁺ and Mg²⁺ moderately influenced the MB removal. Physical characterization results indicated that the precipitates yielded in IFP presented high surface area (232.50m²/g) and a multi-porous structure. Based on the Langmuir model, the maximum adsorption capacity toward MB was 347.82mg/g for the precipitates produced in IFP, which outperformed most other adsorbents. Furthermore, IFP rapidly sequestered MB with removal efficiency 5 to 10 times greater than that by general ferrite adsorption, which suggested a strong enhancement of MB removal by IFP. The MB removal process by IFP showed two different high removal stages, each with a corresponding removal mechanism. In the first brief stage (<5min), the initial high MB removal (~95%) was achieved by predominantly electrostatic interactions. Then the sweep effect and encapsulation were dominant in the second longer stage.

Decolorization of reactive dye Remazol Brilliant Blue R by zirconium oxychloride as a novel coagulant: optimization through response surface methodology

The aim of the present study was to investigate the performance of a novel coagulant, i.e. ZrOCl₂, for the removal of anthraquinone-based reactive dye from aqueous solution. An ideal experimental setup was designed based on central composite design using response surface methodology to determine the individual and interactive effects of different operational variables (i.e. pH, coagulant dose and dye concentration) on treatment performance in terms of dye and chemical oxygen demand (COD) removal efficiencies. Total 92.58% dye and 85.33% COD removal were experimentally attained at optimized conditions at low coagulant dose, i.e. 156.67 mg/L for the dye concentration of 105.67 mg/L at pH 2. To validate the working pH of the metal coagulant, the static charge of ZrOCl₂ was measured using Eh value. The performance of the coagulant was validated with experimental and predicted values in the selected data set, and R² values for both responses were found to be 0.99 and 0.95 respectively, which shows the reliability of the experimental design. Further, the toxicity of the coagulant was assessed and no such toxicity was found even up to the concentration of 500 mg/L, proclaiming the disposal of sludge may not exhibit any threat to humans. Experimental results suggested that the ZrOCl₂ could be used as an eco-friendly coagulant for dye wastewater treatment.

Fabrication of novel metal ion imprinted xanthan gum-layered double hydroxide nanocomposite for adsorption of rare earth elements

The work focus to enhance the properties of xanthan gum (XG) by anchoring metal ions (Fe, Zr) and encapsulating inorganic matrix (M@XG-ZA). The fabricated nanocomposite was characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), surface area (BET) and zeta potential analysis. The adsorption of Sc, Nd, Tm and Yb was investigated after screening of synthesized materials in detail to understand the influence of pH, contact time, temperature and initial REE (rare earth element) concentration both in single and multicomponent system via batch adsorption. The adsorption mechanism was verified by FTIR, SEM and elemental mapping. The SEM images of Zr@XG-ZA demonstrate scutes structure, which disappeared after adsorption of REEs. The maximum adsorption capacities were 132.30, 14.01, 18.15 and 25.73 mg/g for Sc, Nd, Tm and Yb, respectively. The adsorption efficiency over Zr@XG-ZA in multicomponent system was higher than single system and the REEs followed the order: Sc > Yb > Tm > Nd. The Zr@XG-ZA demonstrate good adsorption behavior for REEs up to five cycles and then it can be used as photocatalyst for the degradation of tetracycline. Thus, the work adds a new insight to design and preparation of efficient bifunctional adsorbents from sustainable materials for water purification.