A novel hydroxyl-riched covalent organic framework as an advanced adsorbent for the adsorption of anionic azo dyes

3D superhydrophilic polypyrrole nanofiber mat for highly efficient adsorption of anionic azo dyes

In the present work, adsorption of anionic azo dye, new coccine (NCC) on silica and silica-gel in an aquatic environment was discovered. Effective conditions such as adsorption time, pH, the influence of dosage on NCC adsorption using strong polycation, poly-diallyl-dimethylammonium chloride (PDADMAC) modified silica (PMS) and PDADMAC modified silica-gel (PMSG) were systematically studied. The removal of NCC using PMS and PMSG were much higher than that using raw silica and silica-gel without PDADMAC in all pH ranges from 3 to 10. The adsorption of NCC onto PMS and PMSG was achieved maxima at the same conditions of contact time 30 min, pH 6. The optimum adsorbent dosages of PMS and PMSG for NCC removal were 10 and 20 mg·mL−1, respectively. Experimental results of NCC adsorption isotherms onto PMS and PMSG at different ionic strength were fitted by Langmuir and Freundlich models. The NCC removal efficiencies using PMS and PMSG were higher than 87%, indicating that PMS and PMSG are novel and reusable adsorbents for removal of anionic dye. Based on adsorption isotherms, and surface group changes after PDADMAC modification and NCC adsorption examined by Fourier transform infrared spectroscopy (FTIR), we demonstrate that electrostatic interaction between positively charged adsorbents’ surfaces and negative sulfonic groups of NCC are the main driving force for anionic azo dye adsorption onto PMS and PMGS adsorbents.

Synthetic dyes used in the textile and paper industries pose a major threat to the environment. In the present research work, the adsorption efficiency of the natural adsorbent Strychnos potatorum Linn (Fam: Loganiaceae) seeds were examined against the reactive orange-M2R dye from aqueous solution by varying the process conditions such as contact time, pH, adsorbent dosage, and initial dye concentration on adsorption of anionic azo dye. This study compares different types of artificial neural networks which are feedforward artificial neural network (FANN) and nonlinear autoregressive exogenous (NARX) model to predict the efficiency of a cost-effective natural adsorbent Strychnos potatorum Linn seeds on removing reactive orange-M2R dye from aqueous solution. Twelve training algorithms of neural network were compared, and the prediction on the adsorption performance of anionic azo dye from aqueous solution using Strychnos potatonum Linn seeds was evaluated by using the root mean squared error (RMSE), mean absolute error (MAE), coefficient of determination (R2), and accuracy. For FANN model, Levenberg-Marquardt (LM) backpropagation with 19 hidden neurons was selected as the optimum FANN model, with R2 of 0.994 and accuracy of 87.20%, 98.21%, and 66.60% for training, testing, and validation datasets, respectively. For NARX model, LM with 8 hidden neurons was selected as the most suitable training algorithm, with R2 value of more than 0.99 and accuracy of 88.00%, 90.91%, and 75.00% for training, testing, and validation datasets, respectively. NARX model accurately predicted the adsorption of anionic azo dye from aqueous solution using Strychnos potatonum Linn seeds with better performance than FANN model.

Adsorption of anionic azo dyes from aqueous solution on cationic gemini surfactant-modified flax shives: Synchrotron infrared, optimization and modeling studies

Adsorption of anionic azo dyes using lignite coke by one-step short-time pyrolysis

Efficient adsorption of anionic azo dyes on porous heterostructured MXene/biomass activated carbon composites: Experiments, characterization, and theoretical analysis via advanced statistical physics models

Surface treated acid-activated carbon for adsorption of anionic azo dyes from single and binary adsorptive systems: A detail insight

Transport of anionic azo dyes from aqueous solution to gemini surfactant-modified wheat bran: Synchrotron infrared, molecular interaction and adsorption studies

Aiming to realize the wastewater treatment of various pollutants simultaneously, a dual-functional poly(ether amine)-polydopamine (PEA-PDA)-modified filter material was fabricated in this work for in situ separation of stable oil-in-water emulsion and adsorption of anionic azo dyes. PEA and PDA could be copolymerized via the Michael addition reaction on a polyurethane sponge substrate firmly. The as-prepared filter shows superhydrophilic and underwater superoleophobic wettability. After being squeezed in a glass tube, the material could separate different kinds of stabilized oil-in-water emulsions with high flux and efficiency. Besides, the PEA-PDA copolymer endows the material with the ability to adsorb large amounts of anionic azo dyes during the separation of emulsions with good adsorption capacity. Moreover, adsorbed dyes in the filter material could be easily desorbed in base aqueous solution and the whole process is conducted under gravity without external aid. This dual-functional material shows great potential for the application in industrial field because of its ability for the complex wastewater treatment.

Lipophilicity in dye-cellulose fibre binding

Adsorption of anionic azo dye, new coccine (NC), onto large α-alumina beads in aqueous media was systematically investigated as functions of pH and NaCl concentration. Adsorption amounts of NC decrease with increasing pH of solutions due to less positive charges of α-Al2O3 surface at high pH. At a fixed pH, the NC adsorption increases with decreasing NaCl concentration, indicating that NC molecules mainly adsorb onto α-Al2O3 by electrostatic attraction. Experimental results of NC adsorption isotherms onto α-Al2O3 at different pH, and ionic strength can be represented well by two-step adsorption model. The effects of NC on surface charge and surface modification of α-Al2O3 at the plateau adsorption are evaluated by streaming potential and Fourier transform infrared spectroscopy with attenuated total reflection technique (FTIR-ATR), respectively. On the basis of adsorption isotherms, surface charge effect, and surface modification, we suggested that the formation of a bridged bidentate complex between aluminum ions of α-Al2O3 and two oxygen atoms of a sulfonic group induced the adsorption of NC onto α-Al2O3.

In this work, chitosan/magnetite nanoparticles (ChM) were quickly synthesized according to our previous report based on co-precipitation reaction under ultrasound (US) irradiation. Besides ChM was in-depth structurally characterized, showing a crystalline phase corresponding to magnetite and presenting a spheric morphology, a “nanorod”-type morphology was also obtained after increasing reaction time for eight minutes. Successfully, both morphologies presented a nanoscale range with an average particle size of approximately 5–30 nm, providing a superparamagnetic behavior with saturation magnetization ranging from 44 to 57 emu·g−1. As ChM nanocomposites have shown great versatility considering their properties, we proposed a comparative study using three different amine-based nanoparticles, non-surface-modified and surface-modified, for removal of azo dyes from aqueous solutions. From nitrogen adsorption–desorption isotherm results, the surface-modified ChMs increased the specific surface area and pore size. Additionally, the adsorption of anionic azo dyes (reactive black 5 (RB5) and methyl orange (MO)) on nanocomposites surface was pH-dependent, where surface-modified samples presented a better response under pH 4 and non-modified one under pH 8. Indeed, adsorption capacity results also showed different adsorption mechanisms, molecular size effect and electrostatic attraction, for unmodified and modified ChMs, respectively. Herein, considering all results and nanocomposite-type structure, ChM nanoparticles seem to be a suitable potential alternative for conventional anionic dyes adsorbents, as well as both primary materials source, chitosan and magnetite, are costless and easily supplied.

Removal of cationic and anionic azo dyes from aqueous solutions by adsorption on maize stem tissue

Dyes from several industry effluents are major concern of environmental pollution. In this study, the efficiency of a cost-effective natural adsorbent Strychnos potatorum Linn (Fam: Loganiaceae) seeds on removing reactive orange-M2R dye from aqueous solution was investigated using batch adsorption isotherms at 30 ± 1 °C and 120 rpm. The efficacy of the adsorbent system was also studied at various parameters viz. contact time, pH, adsorbent dosage and initial dye concentration. Maximum adsorption (q e = 9 mg/g) was observed at pH 2.0, equilibrium time 6 h, initial dye concentration of 100 mg/L and adsorbent dosage of 0.2 g/100 mL. The unit adsorption of dye, q e (mg/g) increased with increase in contact time and initial dye concentration, while it decreased with increase in adsorbent dosage. The adsorption kinetic studies revealed that it follows pseudo-second-order reaction model. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms with good agreement. These investigations suggest that Strychnos potatorum Linn seeds (SPS) could be used as a low-cost adsorbent in treating textile effluents for dye removal applications. The adsorbent (SPS) was also characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopic technique.

Highly Efficient Adsorption of Anionic Azo Dyes by Porous Heterostructured Mxene / Biomass Activated Carbon Composites from Wastewater: Experimental, Characterization, and Theoretical Analysis