Preparation of sodium alginate/polyvinyl alcohol composite nanofiber membranes for adsorption of dyes

In this research, electrospinning was used to prepare sodium alginate (SA)/polyvinyl alcohol (PVA) composite nanofiber membranes. Effects of electrospinning parameters on the morphology and fiber diameter were investigated, and an orthogonal design was chosen to optimize the parameters. The optimized nanofiber membranes were applied as an adsorbent for the removal of methylene blue (MB), basic fuchsin (BF), and methyl orange (MO). Kinetic and isotherm of adsorption and effects of different experimental conditions such as pH, contact time, and initial dye concentration on adsorption capacity were investigated. It was found that the optimum parameters for the nanofiber membranes were SA/PVA blend ratios (3:7), electric field strength (20 kV), flow rate (0.05 mL/h), and distance (12.5 cm) between the syringe needle and collector, and the mean fiber diameter of the optimized membranes was 99.58 nm. The adsorption of nanofiber membranes was well described by the pseudo-second-order adsorption kinetic model and the Langmuir model, indicating that the adsorption mechanism was chemisorption by a monolayer. Based on the Langmuir model, the adsorption capacities for MB, BF, and MO were 9.25 mg/g, 9.02 mg/g, and 7.35 mg/g, respectively.

A comparative study of the kinetics and isotherm of adsorption of a cationic dye by different natural wastes

In many countries, water pollution from industrial wastewater is a serious problem. This type of pollution can have a harmful impact on the environment, to reduce the effects of these pollutants, several physico-chemical methods are implemented, in particular adsorption on bioadsorbents, it is a common process to remove traces of pollutants from water, the aim of our work is to realize a comparative experimental study of isotherms and adsorption kinetics of methylene blue (MB) on three substrates: sugar cane bagasse (SCB), almond shell (AS) and walnut shell (WS). The results of equilibrium kinetics show that walnut shell (WS) binds better to methylene blue than other substrates. The results also show that the adsorption kinetics are described by the expression of the pseudo-second order model. The isotherms of adsorption of methylene blue (MB) by sugarcane bagasse (SCB), walnut shell (WS) and almond shell are perfectly described by Langmuir's model and that walnut shell adsorbs methylene blue better than other substrates.

Magnetic core-modified silver nanoparticles for ibuprofen removal: an emerging pollutant in waters

In this work we present a novel procedure for ibuprofen adsorption from waters employing magnetic core-modified silver nanoparticles. We demonstrate that 93% adsorption of ibuprofen is achieved in 45 min by means of a simple method, for neutral pH and room temperature, also using a low dose of adsorbent, equal to 7 mg in 500 µL of suspension. The characterization of the adsorbent, before and after adsorption, was carried out by means of field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, BET analysis, Fourier-transform infrared spectroscopy and differential scanning calorimetry. It is worth pointing out that ibuprofen can be desorbed and the adsorbent can be reused, remaining unaltered for the first three cycles, and showing 89.3% adsorption efficiency after the third regeneration. A three-parameter model and the Langmuir isotherm characterize the kinetics and isotherm of adsorption.

Removal of Agrochemicals from Waters by Adsorption: A Critical Comparison among Humic-Like Substances, Zeolites, Porous Oxides, and Magnetic Nanocomposites

The use of humic-like substances, zeolites, various porous oxides (i.e., Al, Fe, or Si oxides), and magnetic nanocomposites in the adsorption of agrochemicals from water was critically reviewed. Firstly, the adsorbents were characterized from the structural, textural, and physico-chemical points of view. Secondly, the fundamental aspects of the adsorption of various agrochemicals on the solids (dependence on pH, kinetics, and isotherm of adsorption) were studied and interpreted on the basis of the adsorbent features. Thirdly, iterative processes of agrochemical removal from water by adsorption on the reported solids were described. In particular, in some cases the residual concentration of agrochemicals in water was lower than the maximum concentration of agrochemicals that the Italian regulations allow to be released in wastewater, surface waters, or sink water.

Structural and adsorptive properties of silica-alumina and clay materials of mineral and synthetic origin

Location on territory of Ukraine of great deposits of aluminosilicates together with good facilities for their processing and standardization promotes the study of this raw material, results of which could be useful for the developers of enterosorbents. For search the specific sorptive activity a comparative examination of several materials of silica-alumina and clay nature has been carried out in this work. The X-ray phase analysis, a measuring of specific surface area by the low temperature adsorption–desorption of nitrogen and the method of isotherm of adsorption have been used. It is shown that silica-alumina and clay materials have much less specific surface as compared to silica gel Syloid® 244 FP and carbon sorbent SCN. The sorbents of montmorillonite type (smectite, saponite) are characterized by the highest adsorptive capacity in relation to methylene blue and congo red dyes. Synthetic zeolites NaA and NaX effectively absorb the ions of zinc from solution, significantly overcoming Syloid® 244 FP and SCN which were taken as preparations of comparison. Therefore, on the basis of NaA and NaX the selective enterosorbents for elimination from the organism of toxic metals could be created.

Electoplating plants’ wastewater treatment from copper ions with a modified carbonaceous slurry

The article presents a technique of the granulated sorption material production based on the chemical water treatment slurry. The sorption has been studied in statical and dynamic conditions. The sorption effectiveness by copper ions was 90.5 %. The isotherm of adsorption and a curve of adsorption in dynamic conditions of cations of copper has been plotted by the granulated material. During the experiment the dynamic exchange capacity, full exchange capacity of the granulated material has been determined. The filtrate quality indicators in water passage through sorption material loads in accordance with MPC of domestic drinking and recreational purposes water bodies. The granulated sorption material extract was tested for acute lethal toxicity for Poecilia Reticulate Peters fish and Daphnia Magna Crustacea. The obtained results affirmed that the granulated sorption material was not practically hazardous and did not bring secondary pollution to wastewaters. The authors have presented a technological scheme of electroplating wastewaters ion-exchange treatment.

Purification of Gas Emissions of Chemical Industry Enterprises by Carbonaceous Cutting

It is proposed to purify gas emissions of industrial enterprises by the adsorption method. As a sorption material, power industry waste is used — the cuttings for chemical treatment of water of water reclamation at Kazan CHPP-1, which is formed during coagulation and liming of natural water. The chemical composition of the cuttings, its technological characteristics, the isotherm of adsorption of hydrogen sulphide cuttings, its sorption capacity and water absorption are determined. The optimum characteristics of a batch adsorber with a fixed cuttings layer are calculated. The calculation of the economic and ecological effect of the modernization of the technological scheme for cleaning gas emissions from the hydrogen sulphide line produced by the thiocol OJSC "Kazan Plant of Synthetic Rubber" is given.

On the fractality of the Freundlich adsorption isotherm in equilibrium and non-equilibrium cases

This work relates the fractal properties of the adsorbent to the exponent of the Freundlich Isotherm of adsorption.