Modeling of azo dyes adsorption on magnetic NiFe2O4/RGO nanocomposite using response surface methodology

Recent Progress and Prospects in Catalytic Water Treatment

Presently, conventional technologies in water treatment are not efficient enough to completely mineralize refractory water contaminants. In this context, the implementation of catalytic processes could be an alternative. Despite the advantages provided in terms of kinetics of transformation, selectivity, and energy saving, numerous attempts have not yet led to implementation at an industrial scale. This review examines investigations at different scales for which controversies and limitations must be solved to bridge the gap between fundamentals and practical developments. Particular attention has been paid to the development of solar-driven catalytic technologies and some other emerging processes, such as microwave assisted catalysis, plasma-catalytic processes, or biocatalytic remediation, taking into account their specific advantages and the drawbacks. Challenges for which a better understanding related to the complexity of the systems and the coexistence of various solid-liquid-gas interfaces have been identified.

Synthesis and characterizations of hybrid PEG-Fe3O4 nanoparticles for the efficient adsorptive removal of dye and antibacterial, and antibiofilm applications

PURPOSE

Dyes are highly toxic coloured compounds in nature that are largely applied in paper, food, textile and printing industries. Here, the adsorption technique was performed to remove methyl orange (MO) dye from water by polyethylene glycol (PEG) modified iron oxide nanoparticles (Fe₃O₄ NPs).

METHODS

The method used for Fe₃O₄ NPs synthesis was chemical precipitation. The particles were analyzed by transmission electron microscope, magnetometer, BET analyzer, fourier-transform infrared spectroscopy, X-ray powder diffraction, zetasizer and particle size analyzer. The influence of pH (4.0 to 10.0), NaCl concentration (0.01 mM to 2 M), adsorbent dosage (1 to 10 mg), and the role of surface charge on adsorptive removal were investigated.

RESULTS

The NPs size, zeta potential and surface area was found to be 26 ± 1.26 nm, 33.12 ± 1.01 mV and 119 m²/g respectively. The adsorption of MO on Fe₃O₄ NPs agreed best to Freundlich model (R² = 0.965) when compared with Langmuir model (R² = 0.249). By comparing pseudo-first-order kinetic model (R² = 0.937), kinetic adsorption study was better followed by pseudo-second-order kinetic model (R² = 1). The adsorption rate decreased with increasing NaCl concentration. At pH 4, maximum adsorption was noted. The particles were also exhibited excellent antibacterial and antibiofilm activities. The ROS formation, lipid peroxidation and oxidative stress were increased with increase in NPs concentration. The NPs precoated slides exhibited more than 50% growth inhibition.

CONCLUSION

The investigation denotes the versatile applications of the prepared particles for removing the dye stuffs from industrial effluents and as antibacterial and antibiofilm agent.

Linearized form effect on estimation adsorption parameters of three industrial dyes by lignocellulosic sorbent

CONTEXT

Textile industries discharge large amounts of untreated colored wastewater into ecosystems which have adverse effects on the human, living and aquatic environment. The aims of this study were: upgrading and testing the brewery waste adsorption affinity towards BEMACID red (B-R), BEMACID yellow (B-Y) and BEZAKTIV black (B-B), verified the effect of linear form modeling on adsorption parameters values and to find the limiting kinetic step in adsorption process.

METHODS

The adsorption efficiency of brewery waste towards three textile dyes: B-Y, B-R and B-B is tested. The evolution between the adsorption capacity and the operating conditions such as: pH solution, adsorbent mass, contact time and initial dye concentration is determined by kinetics measurements. Effect of a form of pseudo-first order, six forms of pseudo-second order, a form of intra-particle diffusion and a form of external mass transfer diffusion are tested to the prediction of kinetic parameters and to find the limiting kinetic step. In order to modeling the equilibrium data, a form of Freundlich and five forms of Langmuir isotherms are tested. The residual concentration of dye in solution was measured by spectrophotometer. Scanning Electron Microscope (SEM) was using to investigate the structure of raw adsorbent.

RESULTS

The results of kinetics measurements show that the perfect adsorption operating conditions are: acidic medium for all dyes (pH = 2 and pH = 3), low mass adsorbent (m = 40 mg), equilibrium time t = 40 min and for initial concentration of 250 mg/L. Also the results prove that the adsorption mechanism is controlled by both steps of diffusions (interne and extern diffusion) and fitted well by the first and the second linearized form of pseudo-second order model with correlation coefficient R² = 0.99. The results of isotherms modeling show that the second and the third linearized forms of Langmuir giving the best removed amount for B-Y equal 200 and 219.4 mg/g respectively compared to others linearized forms.

CONCLUSION

In summary, the effect of linear forms used either in the medellization of isotherms or kinetic data is significant in the prediction of adsorption parameters, also brewery waste has a significant B-Y dye adsorption affinity compared to others dyes, the descending order of maximum adsorption capacity finding is: qe = 209 mg/g for B-Y, qe = 152 mg/g for B-R and finally qe = 108 mg/g for B-B.

Effects of catalyst preparation method and reaction parameters on the ultrasound assisted Photocatalytic oxidation of reactive yellow 84 dye

In this study, the Heterogeneous Sono-photocatalytic Process was used to degrade Reactive Yellow 84 (RY 84) dye dissolved in water over iron containing TiO₂ and TiO₂-Ce catalysts. The catalysts were prepared by sol-gel and incipient wetness impregnation methods and characterized using XRD, SEM, Nitrogen adsorption, UV-Vis DRS and ICP-AES measurements. The TiO₂ catalyst containing 1% (in weight) iron, prepared by incipient wetness impregnation technique and calcined at 300 °C (1%Fe/TiO₂-300 °C (IW)) was found to be the most effective catalyst. Parametric study was carried out over this catalyst and COD removal of 55% and TOC removal of 38% were achieved while the decolorization efficiency reached 100% after 45 min of reaction at the optimum conditions of, (25 mg/L of RY 84 solution, 0.5 g/L of catalyst, 5 mM of H₂O₂, a temperature of 25 °C, pH = 6 and US at a power of 40 W). Decolorization of RY 84 obeyed the first order kinetics with an activation energy of 20.7 kJ/mol. Sonication increased the decolorization efficiency of the heterogeneous Fenton process (UV + Catalyst+H₂O₂) from 92.7% to 97.5% after 30 min of reaction, with the COD and TOC reductions increasing from 87% to 90% and 48% to 57% after 120 min of reaction, respectively. US also decreased the toxicity of the RY 84 dye. The results obtained from this study show that, iron containing TiO₂ and TiO₂-Ce catalysts could be efficiently used in the hybrid process of ultrasound assisted heterogeneous photocatalytic oxidation in a wide range of experimental conditions.

Phosphoric Acid Activated Carbon from Melia azedarach Waste Sawdust for Adsorptive Removal of Reactive Orange 16: Equilibrium Modelling and Thermodynamic Analysis

Waste wood biomass as precursor for manufacturing activated carbon (AC) can provide a solution to ever increasing global water quality concerns. In our current work, Melia azedarach derived phosphoric acid-treated AC (MA-AC400) was manufactured at a laboratory scale. This novel MA-AC400 was tested for RO16 dye removal performance as a function of contact time, adsorbent dosage, pH, temperature and initial dye concentration in a batch scale arrangement. MA-AC400 was characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering (DLS) and fluorescence spectroscopy. MA-AC400 is characterized as mesoporous with BET surface area of 293.13 m² g^-1 and average pore width of 20.33 Å. pH_PZC and Boehm titration confirm the acidic surface charges with dominance of phenolic functional groups. The average DLS particle size of MA-AC400 was found in the narrow range of 0.12 to 0.30 µm and this polydispersity was confirmed with multiple excitation fluorescence wavelengths. MA-AC400 showed equilibrium adsorption efficiency of 97.8% for RO16 dye at its initial concentration of 30 mg L^-1 and adsorbent dose of 1 g L^-1. Thermodynamic study endorsed the spontaneous, favorable, irreversible and exothermic process for RO16 adsorption onto MA-AC400. Equilibrium adsorption data was better explained by Langmuir with high goodness of fit (R², 0.9964) and this fitness was endorsed with lower error functions. The kinetics data was found well fitted to pseudo-second order (PSO), and intra-particle diffusion kinetic models. Increasing diffusion constant values confirm the intraparticle diffusion at higher RO16 initial concentration and reverse was true for PSO chemisorption kinetics. MA-AC400 exhibited low desorption with studied eluents and its cost was calculated to be $8.36/kg.