Copper(II) adsorption on Ca-rectorite, and effect of static magnetic field on the adsorption

Electro/magnetic superposition effects on diclofenac degradation: Removal performance, kinetics, community structure and synergistic mechanism

Electric and magnetic fields characterized by high efficiency, low consumption and environment-friendly performance have recently generated interest as a possible measure to enhance the performance of the biological treatment process used to remove refractory organics. Few studies have been carried out to-date regarding the simultaneous application of electric and magnetic fields on biofilm process to degrade diclofenac. In this study, 3DEM-BAF was designed to evaluate the electrio-magnetic superposition effect on diclofenac removal performance, kinetics, community structure and synergistic mechanism. The results show that 3DEM-BAF could significantly increase the average removal rate of diclofenac by 65.30 %, 57.46 %, 9.48 % as compared with that of BAF, 3DM-BAF, 3DE-BAF, respectively. The diclofenac degradation kinetic constants and dehydrogenase activity of 3DEM-BAF were almost 6.72 and 2.53 times higher than those of BAF. Microorganisms of 3DEM-BAF in the Methylophilus and Methyloversatilis genera were distinctively enriched, which was attributed to the screening function of electric field and propagation effect of magnetic field. Moreover, three processes were found to contribute to diclofenac degradation, namely electro-magnetic-adsorption, electro-chemical oxidation and electro-magnetic-biodegradation. Thus, the simultaneous application of electric and magnetic fields on biofilm process was demonstrated to be a promising technique as well as a viable alternative in diclofenac degradation enhancement.

Application of magnetic fields to wastewater treatment and its mechanisms: A review

Magnetic field (MF) has been applied widely and successfully as an efficient, low-cost and easy-to-use technique to enhance wastewater treatment (WWT) performance. Although the effects of MF on WWT were revealed and summarized by some works, they are still mysterious and complex. This review summarizes the application of MF in magnetic adsorption-separation of heavy metals and dyes, treatment of domestic wastewater and photo-magnetic coupling technology. Furthermore, the mechanisms of MF-enhanced WWT are critically elaborated from the perspective of magnetic physicochemical and biological effects, such as magnetoresistance, Lorentz force, and intracellular radical pair mechanism. At last, the challenges and opportunities for MF application in WWT are discussed. For overcoming the limitations and taking advantages of MFs in WWT, fundamental research of the mechanisms of the application of MFs should be carried out in the future.

Magnetic field assisted adsorption of pollutants from an aqueous solution: A review

The magnetic field is a special substance that exists objectively and transmits the magnetic force between objects. Magnetic fields (MFs) are gradually attracting attention as a facile, universal adsorption enhancement method, especially under the condition of low concentration of pollutants. By adjusting the type and parameters of the magnetic field, enhancement of adsorption capacity, rate and selectivity can be targeted. Many studies have focused on the adsorbent separation based on magnetic properties under MF assistant, and no review have come up in recent years on the pollution enhanced-adsorption technique using MFs. The present review brings out a series of magnetic field and summarizes adsorption-assisted enhancement mechanism of MFs in different situations. This review article aimed at helping researchers obtain quick ideas of MFs and application for pollutant adsorption.

Removal of fluoride ions using a polypyrrole magnetic nanocomposite influenced by a rotating magnetic field

The impact of a varying rotating magnetic field in stimulating adsorption of fluoride ions onto a polypyrrole magnetic nanocomposite synthesized via in situ a polymerization process was evaluated. Under the effect of a rotating magnetic field, improved removal of adsorbate (10 mg L⁻¹) from aqueous solution using the polypyrrole magnetic nanocomposite was observed, with a maximum removal of 78.2% observed at a magnetic field intensity of 0.019 T. Particle aggregation resulting from the force owing to the gradient on the particles as the magnetic field was increased resulted in improved fluoride removal. This aggregation of particles leads to an improved chain collision and expanse of particle interaction with the fluoride solution. The process of adsorption of fluoride by the PPy/Fe₃O₄ nanocomposite followed both the Freudlich isotherm and the Temkin isotherm. Interestingly, under the effect of the rotating magnetic field, the adsorption process was best described by the Freundlich isotherm.

The impact of a varying rotating magnetic field in stimulating adsorption of fluoride ions onto a polypyrrole magnetic nanocomposite synthesized via in situ a polymerization process was evaluated.

Rotating Magnetic Field-Assisted Adsorption Mechanism of Pollutants on Mechanically Strong Sodium Alginate/Graphene/l-Cysteine Beads in Batch and Fixed-Bed Column Systems

Novel, efficient bioadsorbent sodium alginate/graphene/l-cysteine (SA/GR/l-Cys) beads were prepared and used for magnetic field (MF)-assisted adsorption of pollutants. SA/GR/l-Cys has excellent mechanical properties, with a breaking stress of 3.5 MPa at 79.8%, an elastic modulus of 5.0 MPa, low swelling properties (average swelling ratio <300%), and good adsorption properties toward organic pollutants and heavy metal ions. A rotating magnetic field (RMF) was shown to have a better influence than a static magnetic field (SMF) on adsorption, with enhanced adsorption capacities 5-fold greater than those of the SMF. We investigated the different adsorption mechanisms of model contaminants through Fourier transform infrared spectroscopy, ζ potential, and X-ray photoelectrons spectroscopy. Formation of new hydrogen bonds, change in ζ potential, and acceleration in chemical reactions strongly influenced the adsorption process under the RMF. In fixed-bed column adsorption, the breakthrough time for column adsorption increased, and the adsorption capacity improved by 30.66%. The costs and practical applications of SA/GR/l-Cys under RMF were also analyzed. This work demonstrated that SA/GR/l-Cys could serve as a promising adsorbent for water pollutants under RMF exposure and could be used in practical applications.

Effect of a magnetic field on the adsorptive removal of methylene blue onto wheat straw biochar

Biochar pyrolyzed from wheat straw was innovatively used for the adsorptive removal of cationic dye methylene blue through exposure to a magnetic field. The adsorption capability of the biochar pyrolyzed at 200 °C exceeded that of samples pyrolyzed at higher temperatures. The surface acidic functional groups of wheat straw biochar were deduced to be more sensitive to the effects of the external magnetic field. The enhancement of the magnetic field achieved by increases in the initial dye concentration, and a decrease in the biochar dosage and solution pH, were more significant compared with those caused by other conditions. Kinetic experiments indicated that chemisorption occurred during adsorption. The qmax values for dye adsorption without, and with, an external magnetic field were found to be 46.6 and 62.5mg/g, respectively. These demonstrated that wheat straw biochar could be used for the efficient adsorption of pollutants when assisted by an external magnetic field.

Fe3O4/ Rectorite Composite: Preparation, Characterization and Absorption Properties from Contaminant Contained in Aqueous Solution

A series of Fe3O4/rectorite composite were prepared with chemical coprecipitation method by adding magnetic Fe3O4 particles into rectorite as different weight ratios. The samples were tested and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively; and the adsorption property of heavy metal ions and organic dye contained in aqueous solution on the samples and magnetic recovery rate of the composite were studied. The results show that the main magnetic phase of Fe3O4 presents spinel structure, the Fe3O4/rectorite composite has well superparamagnetic, magnetism increases with the weight of Fe3O4 particles increasing, the composite has high magnetic recovery rate, and the adsorption isotherms of metal ions Cu2+, Zn2+, Cd2+, methyl orange and methylene blue from aqueous solution on the samples indicate the absorption capacity of the Fe3O4/rectorite composite is lower slightly than nature rectorite, but it is still very high.

Measurement of Cu and Zn adsorption onto surficial sediment components: new evidence for less importance of clay minerals

Clay minerals in surficial sediment samples, collected from the Songhua River in China, were separated via sedimentation after removal of Fe/Mn oxides and organic materials; Cu and Zn adsorption onto the sediment components was then evaluated. Clay minerals were examined via X-ray diffraction and scanning electron microscopy. Clay minerals were found to consist mainly of illite, kaolinite, chlorite and an illite/smectite mixed layer. Non-clay minerals were dominated by quartz and orthoclase. The retention of Cu and Zn by clay minerals was 1.6 and 2.5 times, respectively, greater than that of the whole, untreated surficial sediment. Compared to the other critical components in sediments related to metal sorption (Mn oxides, Fe oxides and organic materials), the adsorption capacity of clay minerals was found to be relatively lower on a unit mass basis. These data suggest that, although clay minerals may be important in the adsorption of heavy metals to aquatic sediments, their role is less significant than Fe/Mn oxides and organic materials.

Adsorption of Sr(II) and Eu(III) on Na-rectorite: Effect of pH, ionic strength, concentration and modelling

The surface charge characteristics of Na-rectorite (NaAl4[Si,Al]8O20(OH)4·n H2O) were studied by potentiometric acid-base titrations. Sr(II) and Eu(III) adsorptions on Na-rectorite as a function of pH, ionic strength, and Sr(II)/Eu(III) concentrations were carried out to investigate the surface interactions between Sr(II)/Eu(III) with Na-rectorite. The results indicated that the adsorptions of Sr(II) and Eu(III) on Na-rectorite increased with increasing pH and decreased with increasing ionic strength and initial Sr(II)/Eu(III) concentrations, and that the affinity of Na-rectorite for Eu(III) was much higher than for Sr(II). The experimental data of Sr(II)/Eu(III) adsorption were simulated by the diffuse-layer model (DLM) well with the aid of FITEQL 3.2. Simultaneous adsorptions of Sr(II) and Eu(III) on Na-rectorite were also modeled using the DLM. The adsorption mechanisms of Sr(II) and Eu(III) on Na-rectorite may be dominated by ion exchange interaction at low pH or moderate pH, and by surface complexation interaction at high pH.

An FTIR investigation of hexadecyltrimethylammonium intercalation into rectorite

Rectorite is an interstratified clay mineral made at 1:1 ratio of an orderly arrangement of a nonswelling component illite and a swelling component smectite. Due to the presence of two distinct types of components, it is of great interest to study the adsorption of long chain alkylammonium in rectorite. In this study, we conducted batch experiments and used X-ray diffraction (XRD) and Fourier Transform infrared (FTIR) spectroscopy to characterize the interlayer configuration of intercalated long chain hexadecyltrimethylammonium (HDTMA) in rectorite. The FTIR results showed that a monomer-like intercalation with extensive gauche conformers was formed at surfactant loading less than the cation exchange capacity (CEC) of the mineral. At a higher surfactant loading the CH2--symmetric and anti-symmetric vibrations shifted to lower frequencies, suggesting a more ordered all-trans surfactant interlayer configuration. The thermogravimetric and derivative of thermogravimetric analayses showed a high pyrolysis temperature for the monomer-like gauche conformers and lower pyrolysis temperature for the all-trans configuration of the intercalated HDTMA. The XRD analysis confirmed the monomer-like conformation with a d-spacing of 25.2 angstroms at the low surfactant intercalation and a vertical all-trans configuration with a d-spacing of 49.5 angstroms at an HDTMA intercalation of 3.20 CEC. In addition to conformation analyses of intercalated surfactant in the interlayer using FTIR, the absorbance measured by peak height at 1470, 2850, and 2917 cm(-1) increased linearly with surfactant loading, providing a faster, yet efficient method to quantify the amount of surfactant adsorbed.

Removal of Cu(II) from aqueous solution by adsorption onto acid-activated palygorskite

A series of activated palygorskite clay by HCl with different concentrations was prepared and applied as adsorbents for removal of Cu(II) from aqueous solutions. The effects of contact time, adsorbent dosages and pHs of suspension on the adsorption capacities for Cu(II) were investigated. The results showed that adsorption capacity of activated palygorskites increased with increasing the HCl concentration and the maximum adsorption capacity with 32.24 mg/g for Cu(II) is obtained at 12 mol/L of HCl concentration. The variations in IR spectra and pH of solution after adsorption Cu(II) confirmed that the numerous amount of silanol groups (Si-OH) originated by acid treatment were mainly responsible for Cu(II) adsorption onto acid-activated palygorskite. Kinetic studies indicated that the adsorption mechanisms in the Cu(II)/acid-activated palygorskite system followed the pseudo-second-order kinetic model with a relatively small contribution of film diffusion. Equilibrium data fitted well with Freundlich isotherm model compared to Langmuir isotherm model, indicating that adsorption takes place on heterogeneous surfaces of the acid-activated palygorskite. Adsorption-desorption studies presented that activated palygorskite has lower adsorption and desorption efficiencies using Cu(CH3COO)2 than that of other inorganic copper salts, such as CuSO4, Cu(NO3)2, and CuCl2.

Sorption of Radiocaesium onto Powdered and Compacted Rectorite Studied by Batch and Capillary Methods

The sorption of radiocaesium onto Na-rectorite as a function of pH value under ambient conditions was studied by batch and capillary methods. The results indicated that the sorption of Cs+ions was dependent on the ionic strength and, to a lesser extent, on the pH value. The distribution coefficients for Cs+ion sorption onto powdered rectorite (as determined via the batch technique) were much higher than those of Cs+ions onto compacted rectorite (as determined by capillary test), thereby suggesting that the sorption of Cs+ions onto rectorite was strongly dependent on the density of rectorite, i.e. the interlaminary space of the compacted rectorite contributes significantly on Cs+ion sorption. The distribution coefficients calculated from theoretical calculations, experimental measurements and the diffusion coefficients of Cs+ions were compared and discussed in detail. The sorption and diffusion mechanisms in compacted rectorite were also discussed.