Sorption of basic and acid dyes from aqueous solutions onto oxihumolite

Microporous Activated Carbon from Pisum sativum Pods Using Various Activation Methods and Tested for Adsorption of Acid Orange 7 Dye from Water

This work demonstrates the preparation of high-surface-area activated carbon (AC) from Pisum sativum pods using ZnCl2 and KOH as activating agents. The influence of CO2 and N2 gases during the carbonization process on the porosity of AC were studied. The highest specific surface area of AC was estimated at 1300 to 1500 m2/g, which presented characteristics of microporous materials. SEM micrographs revealed that chemical activation using an impregnation reagent ZnCl2 increases the porosity of the AC, which in turn leads to an increase in the surface area, and the SEM image showed that particle size diameter ranged between 48.88 and 69.95 nm. The performance of prepared AC for adsorption of Acid Orange 7 (AO7) dye was tested. The results showed that the adsorption percentage by AC (2.5 g/L) was equal to 94.76% after just 15 min, and the percentage of removal increased to be ~100% after 60 min. The maximum adsorption capacity was 473.93 mg g-1. A Langmuir model (LM) shows the best-fitted equilibrium isotherm, and the kinetic data fitted better to the pseudo-second-order and Film diffusion models. The removal of AO7 dye using AC from Pisum sativum pods was optimized using a response factor model (RSM), and the results were reported.

A Review of the Removal of Dyestuffs from Effluents onto Biochar

The study provides a review of various applications of biomass-derived biochars, waste-derived biochars, and modified biochars as adsorbent materials for removing dyestuff from process effluents. Processing significant amounts of dye effluent discharges into receiving waters can supply major benefits to countries which are affected by the water crisis and anticipated future stress in many areas in the world. When compared to most conventional adsorbents, biochars can provide an economically attractive solution. In comparison to many other textile effluent treatment processes, adsorption technology provides an economic, easily managed, and highly effective treatment option. Several tabulated data values are provided that summarize the main characteristics of various biochar adsorbents according to their ability to remove dyestuffs from wastewaters.

Cladium mariscus Saw-Sedge versus Sawdust—Efficient Biosorbents for Removal of Hazardous Textile Dye C.I. Basic Blue 3 from Aqueous Solutions

Bio-based waste materials are more often used as effective and cheap adsorbents to remove toxic organic compounds such dyes. Batch adsorption of C.I. Basic Blue 3 (BB3) onto Cladium mariscus saw-sedge was studied in comparison with sawdust obtained from various species of wood in order to explore their potential application as low-cost sorbents for basic dye removal from wastewaters. The effect of phase contact time (1–240 min), initial dye concentration (50–200 mg/L), and the auxiliaries presence (10–60 g/L NaCl and 0.1–0.75 g/L anionic surfactant) on BB3 uptake was investigated. The adsorption kinetic data followed the pseudo-second order equation rather than pseudo-first order one. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The monolayer sorption capacities decreased from 44.29 to 42.07 mg/g for Cladium mariscus saw-sedge and from 28.69 to 27.5 mg/g for sawdust with temperature increasing from 20 to 50 °C. The thermodynamic parameters such as the change in free energy (∆G°), enthalpy (∆H°), and entropy (∆S°) were calculated, too.

Mitigation of Fe(0) nanoparticles toxicity to Trichosporon cutaneum by humic substances

Zero-valent iron nanoparticles (nZVI) are a relatively new option for the treatment of contaminated soil and groundwater. However, because of their apparent toxicity, nZVI in high concentrations are known to interfere with many autochthonous microorganisms and, thus, impact their participation in the remediation process. The effect of two commercially available nZVI products, Nanofer 25 (non-stabilized) and Nanofer 25S (stabilized), was examined. Considerable toxicity to the soil yeast Trichosporon cutaneum was observed. Two chemically different humic substances (HSs) were studied as a possible protection agent that mitigates nZVI toxicity: oxidized oxyhumolite X6 and humic acid X3A. The effect of addition of HSs was studied in different phases of the experiment to establish the effect on cells and nZVI. SEM and TEM images revealed an ability of both types of nZVI and HSs to adsorb on surface of the cells. Changes in cell surface properties were also observed by zeta potential measurements. Our results indicate that HSs can act as an electrosteric barrier, which hinders mutual interaction between nZVI and treated cell. Thus, the application of HS seems to be a promising solution to mitigating the toxic action of nZVI.

Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies

Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r²>0.99) and Langmuir (r²>0.99) isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r²>0.99) and intra-particle diffusion (r²>0.98) models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively.

Remazol Black B removal from aqueous solutions and wastewater using weakly basic anion exchange resins

In this study, the use of the weakly basic anion exchange resins of phenol-formaldehyde (Amberlyst A 23), polyacrylate (Amberlite IRA 67) and polystyrene (Lewatit MonoPlus MP 62) matrices for removal of the reactive dye Remazol Black B (RBB) from aqueous solution and wastewater were investigated. RBB sorption on the anion exchangers was a time dependent process. Color reduction percentiles of 75.2, 33.9 and 25.1% in wastewater treatment were found after 216 h of phase contact time with Lewatit MonoPlus MP 62, Amberlyst A 23 and Amberlite IRA 67, respectively. Inorganic salts and anionic surfactant action influenced RBB uptake by the anion exchangers. The amounts of dye retained by the anion exchangers increased with a rise in temperature. The maximum sorption capacities calculated from the Langmuir model were 66.4, 282.1 and 796.1 mg g−1 for Amberlite IRA 67, Amberlyst A 23 and Lewatit MonoPlus MP 62, respectively. Regeneration of phenol-formaldehyde and polystyrene resins were possible using 1 M NaOH, 2 M KSCN, 1M KSCN in 40–60% methanol as well as 1 M NaOH in 60% methanol.

Complexation-flocculation of organic contaminants by the application of oxyhumolite-based humic organic matter

Control of hazardous organic micropollutants is a challenging water quality issue. Dissolved humic organic matter (DOM) isolated from oxyhumolite coal mined in Bohemia was investigated as a complexation agent to remove polycyclic aromatic hydrocarbons (PAHs) and functionalized phenols from water by a two-stage process involving complexation and flocculation. After the formation of humic-contaminant complexes, ferric salts were added resulting in the precipitation and flocculation of the DOM and the associated pollutants. Flocculation experiments with ferric ion coagulants indicated that precipitation of oxyhumolite DOM together with the complexed contaminants occurred at lower ferric ion concentrations than with the reference DOM in acidic environments (pH approximately 3.5). The complexation-flocculation removal rates for non-reactive PAHs characterized by small localization energies of pi-electrons correlated well with the complexation constants. On the other hand, the combined complexation-flocculation removal rates for activated PAHs including trans-stilbene, anthracene and 9-methyl anthracene, as well as functionalized polar phenols, were higher than predicted from the complexation coefficients. Methodological studies revealed for the first time that the ferric ion coagulant contributed to enhanced removal rates, most probably due to ferric ion-catalyzed pollutant degradation resulting in oxidized products.