Removal of basic dye by modified Unye bentonite, Turkey

Facile fabrication of amino-functionalized MIL-68(Al) metal-organic framework for effective adsorption of arsenate (As(V))

An amino-functionalized MIL-68(Al) metal–organic framework (amino-MIL-68(Al) MOF) was synthesized by solvothermal method and then characterized by FESEM, XRD, FTIR, EDX-mapping, and BET-BJH techniques. In order to predict arsenate (As(V)) removal, a robust quadratic model (R² > 0.99, F-value = 2389.17 and p value < 0.0001) was developed by the central composite design (CCD) method and then the genetic algorithm (GA) was utilized to optimize the system response and four independent variables. The results showed that As(V) adsorption on MOF was affected by solution pH, adsorbent dose, As(V) concentration and reaction time, respectively. Predicted and experimental As(V) removal efficiencies under optimal conditions were 99.45 and 99.87%, respectively. The fitting of experimental data showed that As(V) adsorption on MOF is well described by the nonlinear form of the Langmuir isotherm and pseudo-second-order kinetic. At optimum pH 3, the maximum As(V) adsorption capacity was 74.29 mg/g. Thermodynamic studies in the temperature range of 25 to 50 °C showed that As(V) adsorption is a spontaneous endothermic process. The reusability of MOF in ten adsorption/regeneration cycles was studied and the results showed high reusability of this adsorbent. The highest interventional effect in inhibiting As(V) adsorption was related to phosphate anion. The results of this study showed that amino-MIL-68(Al) can be used as an effective MOF with a high surface area (> 1000 m²/g) and high reusability for As(V)-contaminated water.

Sodium Docusate Surface-Modified Dispersible and Powder Zinc Peroxide Formulation: An Adsorbent for the Effective and Fast Removal of Crystal Violet Dye, an Emerging Wastewater Contaminant

Crystal violet (CV) dye is one of the most toxic dyes majorly generated by textile industries. It may cause health issues if enters human beings. A lot of research has been reported for the removal of CV dye from wastewater; however, most of them are time-consuming and hardly remove more than 95% of the CV dye. In the last few years, we have tested several materials, and most of them have exhibited very low efficacy toward adsorption of CV including zinc peroxide (ZnO2). To enhance adsorption efficacy, dispersibility, and stability, the surfaces of several reported materials were modified using different wetting agents and nonionic surfactants. Interestingly, ZnO2, which was earlier very less effective after surface modification by sodium salt of dioctyl sulfosuccinate, efficiently adsorbed >99.5% of CV from contaminated water within 5 min of contact time at pH ∼10. The adsorption capacity obtained for the sodium docusate surface-modified zinc peroxide (ZnSD) adsorbent was found to be 123 mg/g, which is much better than the other reported for CV removal. Different physiochemical experiment parameters like pH, contact time, initial dye concentration, adsorbent dosages, and temperature were optimum to achieve maximum adsorption of the CV dye. The adsorption rate and adsorption mechanism studies show that the adsorption of CV follows pseudo-second-order kinematics and the Freundlich isotherm model. The adsorption results are consistent, and even treated water can be reutilized for various applications.

Biocomposite of sodium-alginate with acidified clay for wastewater treatment: Kinetic, equilibrium and thermodynamic studies

Clay-based composites were prepared, characterized, and applied for the elimination of Blue FBN (BFBN) and Rose FRN (RFRN) dyes. The Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Thermogravimetric (TGA) and X-ray diffraction analyses were performed to check the interaction of dye molecule with adsorbents. The analysis showed a successful interaction between adsorbent and dyes ions. The experimental data was best fitted with Freundlich isotherm for both dyes (BFBN and RFRN). The findings revealed that at 80 min the adsorption grasped equilibrium in the case of both dyes and succeeded the pseudo-second-order kinetics model. Furthermore, the enthalpy (ΔH°), Gibbs free energy (ΔG°) and entropy (ΔS°) changes suggested that adsorption was exothermic, physical and spontaneous in nature. The maximum adsorption capacities were determined as 76.39% for BFBN and 59.85% for RFRN dye at pH 2.0 and 30 °C. Composites found to be stable at higher temperature and regenerated using MgSO₄ eluting agent. The textile effluent colour was removed up to 50.35 and 54.95% using raw and modified clay, respectively. The modified clay showed promising efficiency for adsorption of synthetic BFBN and RFRN dyes from aqueous solution, which could be a viable option for the treatment of industrial wastewater and textile effluents.

A manganese-oxidizing bacterial consortium and its biogenic Mn oxides for dye decolorization and heavy metal adsorption

Manganese (Mn) contamination is a common environmental problem in the world and manganese oxidizing bacteria (MOB) play important roles in bioremediation of heavy metal and organic pollution. In this study, a novel MOB consortium AS containing core microbes of Sphingobacterium and Bacillus was acclimated from Mn-contaminated rivulet sediments. The MOB consortium AS presented good Mn(II) removal performance under 500-10,000 mg/L Mn(II), with Mn(II) removal capacities ranging from 481 to 3478 mg/L. In coexistence systems of Mn(II) and Fe(II), Ni(II), Cu(II), and Zn(II), the MOB consortium AS removed 98%, 91%, 99%, and 76% of Mn(II), respectively. Additionally, the MOB consortium AS could utilize multiple carbon sources (e.g., Chitosan, β-Cyclodextrin, and Phenanthrene) to remove Mn(II), with Mn(II) removal efficiencies ranging from 11% to 97%. Meanwhile, XRD, XPS, FTIR, SEM, and EDS analyses reflected that biogenic Mn oxides (bio-MnOx-C) contained C, O, Mn (Mn(II) and Mn(IV)) and embodied in rhodochrosite and birnessite. The bio-MnOx-C exhibited second-order kinetic reaction for removal of dye, with corresponding decolorization capacities of 22.0 mg/g for methylene blue and 23.8 mg/g for crystal violet. In addition, bio-MnOx-C showed adsorption capacities of 159.0 mg/g for Cu(II), 130.7 mg/g for Zn(II), and 123.3 mg/g for Pb(II). Overall, this study illustrates consortium AS and bio-MnOx-C have great potentials in remediation of pollution caused by heavy metals and organic pollutants.

A novel-green adsorbent based on betaine-modified magnetic nanoparticles for removal of methyl blue

A potential adsorbent based on betaine-modified magnetic iron oxide nanoparticles (BMNPs) was successfully synthesized by facile method, characterized and applied for methyl blue (MB) removal from aqueous solution. The characterization results of FTIR, transmission electron microscopy (TEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) showed that the prepared nanoparticles could be well dispersed in water and exhibited excellent superparamagnetism. These properties imply the potential to recycle BMNPs from wastewater through magnetic field. In the adsorption process, the effects of main experimental parameters such as pH of MB solution, initial concentration of MB, contact time, and adsorption capacity for MB were studied and optimized. These results demonstrated that large amounts of quaternary ammonium groups existing on the surface of BMNPs could promote absorption of MB via electrostatic forces. Additionally, the adsorption kinetics of MB was found to follow a pseudo-second-order kinetic model and the adsorption equilibrium data fitted very closely to the Langmuir adsorption isotherm model. The maximum adsorption capacity for MB was calculated to be 136mgg^-1 at room temperature. Moreover, the BMNPs showed good reusability with 73.33% MB adsorption in the 5th cycle.

Heterocoagulated clay-derived adsorbents for phosphate decontamination from aqueous solution

A series of nanocomposite adsorbents were prepared by heterocoagulation of negatively charged delaminated montmorillonite (Mt) and positively charged synthetic layered double hydroxide (LDH) colloids with different LDH loading amounts. The mineralogy and physicochemical properties of the resulting nanocomposites were characterized. Their potential applications for phosphate (P) removal from aqueous solution, as a function of P concentration (2.5-200 mg/L), contact time (1 min-48 h) and pH (3-10), were evaluated by using batch adsorption modes. It was found that the adsorption data could be well described by both Freundlich and Langmuir isotherm models. The maximum adsorption capacity of three different LDH heterocoagulated montmorillonites (LDH-Mts) for P removal was found to increase with LDH loadings, reaching 12.6, 16.2 and 23.3 mg/g respectively; Adsorption kinetic data revealed that 90% of adsorption onto LDH-Mts was completed within 1 h (h) and the adsorption process could be well described by the pseudo-second-order model. These results demonstrated that heterocoagulation of Mt and LDH could preserve the adsorption capacity of LDH for P and enhance the stability of both clay minerals, and LDH-Mts could be effectively used as a potential promising filtration medium for P removal.

Adsorption characteristics and mechanism of sewage sludge-derived adsorbent for removing sulfonated methyl phenol resin in wastewater

Sulfonated methyl phenol resin (SMP) is one of the most popular organic additives in drilling fluid.

Ultra-high uptake and selective adsorption of organic dyes with a novel polyoxomolybdate-based organic–inorganic hybrid compound

[(4-Hap)₄(Mo₈O₂₆)] was used to conduct rapid and efficient selective uptake of organic dyes.

A review on applicability of naturally available adsorbents for the removal of hazardous dyes from aqueous waste

The effluent water of many industries, such as textiles, leather, paper, printing, cosmetics, etc., contains large amount of hazardous dyes. There is huge number of treatment processes as well as adsorbent which are available for the processing of this effluent water-containing dye content. The applicability of naturally available low cast and eco-friendly adsorbents, for the removal of hazardous dyes from aqueous waste by adsorption treatment, has been reviewed. In this review paper, we have provided a compiled list of low-cost, easily available, safe to handle, and easy-to-dispose-off adsorbents. These adsorbents have been classified into five different categories on the basis of their state of availability: (1) waste materials from agriculture and industry, (2) fruit waste, (3) plant waste, (4) natural inorganic materials, and (5) bioadsorbents. Some of the treated adsorbents have shown good adsorption capacities for methylene blue, congo red, crystal violet, rhodamine B, basic red, etc., but this adsorption process is highly pH dependent, and the pH of the medium plays an important role in the treatment process. Thus, in this review paper, we have made some efforts to discuss the role of pH in the treatment of wastewater.

Equilibrium and kinetic studies on free cyanide adsorption from aqueous solution by activated carbon

Adsorption equilibrium and kinetics of free cyanide onto activated carbon were investigated in the batch tests, and the effects of contact time (1-72 h) and initial cyanide concentrations in the range of 102-532 mg/L were studied. Linear regression was used to determine the best fit of equilibrium and kinetics expressions. The two-parameter models including Freundlich, Dubinin-Radushkevich, Temkin and four different linearized forms of Langmuir and three-parameter models including Redlich-Peterson and Koble-Corrigan were employed for fitting the equilibrium data and it was found that, three-parameter models fitted the data better than the two-parameter models and among the three-parameter models the equilibrium data are best represented by Koble-Corrigan model. A number of kinetic models including fractional power, zero order, first order, pseudo-first order, Elovich, second order, intraparticle diffusion and four different linearized forms of pseudo-second order models were tested to fit the kinetic data. The latter was found to be consistent with the data. Intraparticle diffusion plots show that the adsorption process of free cyanide is a two steps process. In the first step, the adsorption of cyanide is fast while in the second step, cyanide adsorption slows down.