Removal Of Anionic Pollutants Research Articles

Rapid mixing polymerization: A simple method for preparation of free standing polypyrrole film and powder for the removal of anionic pollutants

Polypyrrole has been synthesized by rapid mixing of the monomer and ferric chloride (FeCl3) solutions. By this method, free standing polypyrrole films at the air/water interface along with bulk polypyrrole powder (R-PPy) are formed as a result of a single step reaction. We have reported the characterization of R-PPy and its application for removal of anionic pollutants such as Eosin yellow, Eosin blue, Orange (II), Reactive orange, Orange G and Cr(VI) from aqueous medium. The materials synthesized were characterized by Scanning electron microscopy (SEM), Zeta potential measurement, Powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and Thermal gravimetric analysis (TGA). R-PPy shows an enhanced adsorption capacity compared to the polypyrrole (PPy) samples synthesized by conventional chemical polymerization method. The percentage removal of EY increases from 58.8 % for PPy to 95.3 % in R-PPy and for Cr (VI) removal, it is 40.2 % for PPy which increases up to 69.5 % on using R-PPy for a definite initial concentration of the pollutants. The reduced agglomeration due to the synthetic procedure and a more positive surface charge density on the R-PPy particles are the reason for improved adsorption capacity of R-PPy than that of conventionally synthesized PPy. We have studied the effect of initial concentration, adsorbent dose, solution pH and temperature on the adsorption capacity. The adsorption was found to follow pseudo second order kinetic model. The Langmuir adsorption capacity of R-PPy was found to be 273.2 and 103.6 mg/g for EY and Cr (VI), respectively at 303 K. The thermodynamic parameters revealed that the adsorption is endothermic and spontaneous.

Rosette-like Layered Double Hydroxides: Adsorbent Materials for the Removal of Anionic Pollutants from Water.

Rosette-like layered double hydroxide (roseLDH) crystals with interlayer CO32- anions were synthesized by the reaction of Mg(NO3)2, Al(NO3)3, and hexamethylenetetramine (HMT) at 140 °C over 4 days. Crystals as large as 20 μm were produced when using a specific range of HMT concentrations. The substitution of CO32- interlayer ions with ClO4- or Cl- anions was achieved by the addition of perchloric acid or hydrochloric acid, respectively, to dispersion of material in methanol. The products were denoted as CO32-roseLDH, ClO4-roseLDH, and Cl-roseLDH, respectively. These LDHs were characterized using X-ray diffraction under controlled relative humidity, as well as by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption experiment with anions such as phosphate (HPO42-) and nitrate (NO3-) was conducted by using ClO4-roseLDH and Cl-roseLDH. The results indicate that both anions were adsorbed through an ion-exchange mechanism. The maximum HPO42- adsorption capacity at equilibrium on ClO4-roseLDH was 1.6 mmol g-1 (49.6 mg P g-1), which corresponds to approximately 75% of the total positive layer charge. Cl-roseLDH showed a similar adsorption capability. Commercially available platelike LDH particles were essentially impermeable to water flow due to clogging, while the roseLDH crystals showed excellent permeability, an order of magnitude higher than that exhibited by the platelike LDH synthesized using a homogeneous precipitation method with different growth conditions. Anion adsorption during batch and flow-through test with the ClO4-roseLDH (mean particle diameter ∼ 38 μm) in a packed bed showed good uptake of HPO42- and NO3- from aqueous solutions. These results demonstrate the potential of roseLDH materials to serve as a column filler adsorbent of the hazardous anions.

Freely standing MgAl-layered double hydroxides nanosheets and their derived metal oxides on g-C3N4 thin-layer designed for obtaining synergic effect of adsorption and photocatalysis

Organic compound contamination in water is a serious threat to the public health and other organisms on earth. Here, we report a novel hierarchical architecture of freely standing MgAl-layered double hydroxides (LDH) nanosheets on g-C3N4 nanosheets for ultrafast dye removal from water. This open hierarchical structure consisted of interlaced g-C3N4 and MgAl-LDH nanosheets, and exhibited effective adsorption-photocatalysis synergic effect and high efficient removal of anionic pollutants from water under simulated sunlight irradiation. The rate constant of photocatalytic degradation toward congo red (CR) was high as 0.1011 min−1, which was 3.9 time than that of g-C3N4. It was demostrated that positively charged LDH layers were in favor of the enrichment of anionic pollutants around g-C3N4, which effectively shortened diffusion distance and thus accelerated the degradation of organic pollutant. Furthermore, it was found that –OH groups on surface of LDH suppressed the recombination of photo generated electron-hole pairs by capturing photo generated holes. Moreover, •O2– was demonstrated as the main reactive species in the photocatalytic degradation process. This adsorption-photocatalysis synergic system may be a promising candidate in adsorbing, removing and oxidizing organic contaminants from water body.

Razvoj i karakterizacija raznih katjonskih sorbenata na bazi lignocelulozne kore tikvice

The aim of this study is to develop miscellaneous cationic sorbents based on the lignocellulosic biomass of Lagenaria vulgaris fruit, with the property of efficient sorption of anionic pollutants from aqueous solutions. The lignocellulosic gourd shell (LGS biomass), as a potentially valuable agro-waste, was examined and used for the synthesis of sorbents. The preparation of synthesis precursor (LVAT) was performed by alkaline pretreatment of LGS biomass. Pretreatment under weak alkaline conditions with green carbonate solution was carried out for partial delignification and extraction of depolymerized hemicellulose, thereby achieving higher material porosity and activation of cellulose microfibrils. This activation involves the translation of available -OH functional groups into -ONa form (alkali-cellulose), while maintaining the initial biomass composition. Synthesis of the cationic sorbents was performed in three ways. Different N-reagents, such as tertiary amino and quaternary ammonium compounds, were used in the cation modification of LGS biomass and LVAT precursor, to determine the effects of reagent structure and hydrophobicity on the synthesis outcome, and primarily on the sorption properties of the resulting sorbents. The synthesized cationic sorbents were characterized by physico-chemical methods and tested for the removal of anionic pollutants from water, especially phosphates and nitrates. The various chemical modifications of lignocellulosic biomass provide a scientific contribution to a better understanding of the mechanism of anions sorption on the sorbent surface.

Recyclable polyvinyl alcohol sponge containing flower-like layered double hydroxide microspheres for efficient removal of As(V) anions and anionic dyes from water.

Layered double hydroxides (LDHs) are very promising adsorbents for the removal of anionic pollutants from water. However, the low adsorption efficiency and recycling difficulty of conventional LDH powders are obstacles to practical applications. Herein, a novel Zn/Fe-LDH composite sponge was successfully fabricated using a simple in-situ hydrothermal method. Characterization studies revealed that the composite sponge contained flower-like Zn/Fe LDH microspheres uniformly dispersed throughout a poly vinyl alcohol (PVA) sponge matrix. The specific surface area of the Zn/Fe-LDH composite sponge was 42.5 m2 g-1, approximately 5 times higher than the pristine PVA sponge (8.9 m2 g-1). Adsorption experiments revealed that Zn/Fe-LDH composite sponge exhibited a much higher adsorption ability for As(V) anions and methyl orange (MO) compared with a Zn/Fe-LDH powder or the pristine PVA sponge. The maximum adsorption capacity for As(V) was found to be 85.7 mg g-1. Furthermore, the Zn/Fe-LDH composite sponge showed high thermal stability, good mechanical stability and easy recoverability, thereby allowing reuse. Results guide the development of improved, low cost water treatment materials.

A novel alginate-based composite adsorbent for the removal of anionic pollutants

A novel alginate-based composite adsorbent for the removal of anionic pollutants

Treatment of heavy metal ions in wastewater using layered double hydroxides: A review

ABSTRACTHeavy metal ions are toxic, and their toxicities change with different valence states, charges, and radii. Among the methods used for heavy metal ion removal, adsorption is widely employed due to its low cost and simple operation. As natural anionic clays, layered double hydroxides (LDHs) have drawn considerable attention for their use in the removal of anionic pollutants (such as heavy metal anions) due to their high removal efficiency and environmental friendliness. This article reviews the effects of the charge, type, and radius of the cations in the laminates of LDHs and the anions in the LDH interlayers, as well as the charge and radius of the heavy metals and the conditions (such as pH, coexisting ions, and temperature) on removing heavy metal ions with LDHs. The removal mechanisms have also been discussed. LDHs are hugely promising as an application for removing heavy metal ions that exist in different ionic forms by controlling the type and condition of LDHs.

Magnetic SiO2@CoFe2O4 nanoparticles decorated on graphene oxide as efficient adsorbents for the removal of anionic pollutants from water

In this study, magnetic nanocomposites viz. SiO2@CoFe2O4 nanoparticles decorated on graphene oxide were synthesized using solvothermal and sol-gel processes. The prepared nanocomposite materials were used as magnetic adsorbents for the removal of organic and inorganic pollutants (acid black 1 dye and Cr(VI) ions as model pollutants) from aqueous solution. The structure, morphology and other physico-chemical properties of nanocomposites were characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), vibrating sample magnetometer (VSM), X-ray photo spectroscopy (XPS), zeta potential and Fourier transform infrared (FT-IR) spectroscopy. Batch mode adsorption studies were conducted with the prepared nanocomposites to determine the maximum adsorption capacity of acid black 1 dye and Cr(VI) ions as a function of contact time, pH, adsorbent dosage and initial adsorbate concentrations. Different kinetic and isotherm models were tested to describe and elucidate the adsorption mechanisms. Based on the experimental results obtained, the synthesized materials proved to exhibit considerable potential for the removal of acid black 1 and Cr(VI) ions from aqueous solution.

Priprema i korišćenje katjonskog sorbenta na bazi tenzidom modifikovane kore tikve sudovnjače

The surface of the bottle gourd shell (BGS), a solid agricultural residue of Lagenaria vulgaris Ser. was chemically modified using a cationic surfactant, hexadecyltrime-thylammonium chloride (HTAC). The success of the modification was confirmed by FTIR spectroscopy. Chemical characterization of the lignocellulosic BGS biomass and the surfactant modified bottle gourd shell (MBGS) was carried out using the compositional and elemental analysis. The amount of surfactant sorbed on the BGS surface was measured as a function of the surfactant bulk concentration. Sorption isotherms were used to verify self-assembly models of cationic surfactant sorption onto oppositely charged MBGS substrates. The shape of sorption isotherms was applied to describe the behavior of the surfactant/BGS system. The surfactant modified shell was tested as a sorbent for the removal of phosphate and nitrate from contaminated aqueous solutions. The sorption of anionic pollutants on MBGS was performed in a series of batch sorption experiments at 20ºC. It was found that the MBGS yielded sorption efficiency was 40% for phosphate and 22% for nitrate. The sorption mechanism involving the ion exchange might be responsible for the uptake of anions. The morphology and surface properties of the MBGS sorbent before and after sorption of anionic pollutants were analyzed by SEM methods. Compared to other non-surfactant sorbents, the advantage of MBGS as a sorbent is that it can be used for the removal of anionic pollutants not only from aqueous solutions but also from the emulsified oil wastewater or nonpolar effluents.

Preparation of a new modified clay with amino acid for anionic pollutant removal from water

Modified montmorilonite (Mt) as clay mineral with amino acid (M-AA) was synthesized by cation exchange method and used to remove anionic pollutants from water. The modified clay was characterized by X-ray diffraction (XRD) and zeta potential. XRD results showed that aminoacid can be intercalated into the Mt and increase the interlayer space of Mt. Positive zeta potential of modified Mt confirmed the modification of Mt with amino acid. The adsorption of pollutants onto modified Mt as a function of their initial concentration and solution pH was investigated. The removal efficiency was increased with increasing the pollutant initial concentration, however it decreased with increasing pH of solution. The maximum adsorption capacities of modified Mt with amino acid was 5 times larger than unmodified Mt. The regeneration studies were carried out up to 10 cycles for modified Mt and obtained results showed that modified adsorbent could also be effectively used for anionic pollutant removal from surface water for multiple adsorption-desorption cycles. adsorption, Montmorillonite, amino acid, anionic pollutant, water

Diethylenetriamine-assisted synthesis of amino-rich hydrothermal carbon-coated electrospun polyacrylonitrile fiber adsorbents for the removal of Cr(VI) and 2,4-dichlorophenoxyacetic acid

An environmentally benign and efficient hydrothermal carbonization method is widely applied for the preparation of carbon-based adsorbents. However, the adsorption capacity toward anionic species would be influenced due to the negatively charged surface of the traditional hydrothermal carbonaceous materials; moreover most of the carbonaceous materials were in the form of powder which restricted the practical applications. Herein, amino-rich hydrothermal carbon-coated electrospun polyacrylonitrile fiber (PAN@NC) adsorbents were obtained through one-step hydrothermal carbonization approach assisted by diethylenetriamine using polyacrylonitrile (PAN) fibers as the templates, which showed highly efficient adsorption for anionic pollutants. The PAN@NC fibers were characterized in detail to confirm their structures and composition. The flexible and robust PAN@NC fiber membrane exhibited high adsorption capacity and good regeneration and recycling ability toward the anionic metal ion Cr(VI) and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). According to the Langmuir model, the adsorption behaviors showed monolayer adsorption capacities of 290.70mg/g and 164.47mg/g for Cr(VI) and 2,4-D, respectively, which were higher than that of many other adsorbents. Recycling study indicated that the removal efficiencies for both pollutants retained above 90% after five cycles. These findings demonstrate that PAN@NC fibers are promising adsorbents for the removal of anionic pollutants from wastewater solutions.

Removal of anionic pollutants by pine bark is influenced by the mechanism of retention

The use of organic biosorbents for anion removal from water has been less studied than for cationic compounds. In this work, the removal capacity of pine bark for potential anionic pollutants (fluoride, phosphate, arsenate and dichromate) was assessed in column experiments, designed to study the process of transport. The results showed that pine bark has a very low retention capacity for phosphate, arsenate or fluoride, and in turn, very high for dichromate, with retention values close to 100% and less than 2% desorption of the adsorbed dichromate. The large differences observed between anions suggest that differences in the retention mechanism of each anion exist. In the case of phosphate and arsenate, electrostatic interactions with the mostly negatively charged functional groups of the pine bark determine the low retention capacity. Dichromate retention might proceed through reduction of chromium (VI) to chromium (III), what improves the efficiency of the removal.

Alkylguanidinium based ionic liquids in a screening study for the removal of anionic pollutants from aqueous solution

Monoalkylguanidinium bis-trifluoromethane sulfonimides are highly efficient adsorbents for the sequestration of organic anions from aqueous solutions and display strongly enhanced adsorption properties compared to conventional imidazolium ILs.

Enhanced Electrokinetic Transport of Sulfate in Saline Soil

The electrokinetic transport of sulfate was investigated as a means of treating and restoring a sulfate-accumulating saline soil. The electrokinetic treatment decreased the electrical conductivity of the soil, an indicator of soil salinity, to 58.6, 73.1, and 83.5 % for 7, 14, and 21 days, respectively. More than 96 % of the chloride and nitrate were removed within 7 days. However, the removal of sulfate was highly influenced by the anode material. An iron anode removed sulfate effectively, whereas sulfate was hyper-accumulated in the anodic region when an inert anode was used. The iron anode was oxidized in a sacrificial anodic reaction, which competed with the electrolysis reaction of water at the anode, and finally, the reaction prevented the severe acidification of the soil in the anodic region. However, the competing reactions produced hydrogen ions at the anode and the ions were transported toward the cathode, which, in turn, acidified the soil, especially in the anodic region. The acidification switched the surface charge of the soil from negative to positive, increasing the interaction between the soil surface and sulfate and thus inhibiting the transport of sulfate under the electric field. The zeta potential analysis of the soil provided an explanation. The results indicate that preventing severe acidification is an important factor which influences the transport of anions and iron anode for the enhanced removal of anionic pollutants by electrokinetic remediation.

Preparation of cross-linked magnetic chitosan with quaternary ammonium and its application for Cr(VI) and P(V) removal

Pollutants that exist in anionic species are issues of concern in water treatment. Compared to cationic pollutants, the removal of anionic pollutants by adsorption is more difficult because most adsorbents carry predominantly negative charges in neutral and alkaline environments. In this study, a cross-linked chitosan derivative with quaternary ammonium and magnetic properties (QM-chitosan) was prepared and employed to remove chromium(VI) and phosphorus(V) (Cr(VI) and P(V)) from aqueous environments. The QM-chitosan was characterized by Fourier transform infrared spectrometry (FT-IR), thermogravimetric analysis (TGA), energy dispersive X-ray (SEM-EDX) and zeta potential. Batch experiments show that QM-chitosan can effectively remove Cr(VI) and P(V), and the main mechanism was believed to be electrostatic interaction. A pseudosecond-order model was fitted to describe the kinetic processes of Cr(VI) and P(V) removal. The adsorption isotherms of both Cr(VI) and P(V) on the QM-chitosan were well fitted by the Langmuir isotherm equation. The saturated adsorption capacity of P(V) (2.783mmol/g) was found to be higher than that of Cr(VI) (2.323mmol/g), resulting from the size of the H2PO4− ions being smaller than that of the HCrO4− ions. However, the theoretical calculation and experimental results showed that QM-chitosan had a stronger affinity for Cr(VI) than P(V). The adsorption–desorption of the QM-chitosan was evaluated, and high regeneration rates were demonstrated.

Removal of nitrates from spiked clay soils by coupling electrokinetic and permeable reactive barrier technologies

BACKGROUND This work aims to describe the removal of a model anion (nitrate) from clay soils using electrokinetically assisted soil flushing coupled with permeable reactive barriers consisting of beds of anion exchange resin and to assess the influence of the electric field on the efficiency of this technology. RESULTS Experiments have been carried out at bench scale with spiked soil using electric fields ranging from 1.0 to 2.0 V cm−1. Results show that removal of nitrates with this remediation technology is very efficient. About 90% of the nitrates contained in the soil can be removed in less than 1 week of operation with energy consumptions below 75 kWh m−3. An electric field of 1.2 V cm−1 was used because no improvements were found operating at higher voltages. CONCLUSIONS The proposed technology for the removal of nitrates is very effective, making it very promising for the removal of anionic pollutants from soils. The main path of change observed is the direction from anode to cathode. Dispersion in the axial direction is very small. © 2014 Society of Chemical Industry

Efficient and Ecological Removal of Anionic Pollutants by Cationic Starch-Clay Bionanocomposites

Efficient and Ecological Removal of Anionic Pollutants by Cationic Starch-Clay Bionanocomposites

Removal of Anionic Pollutants from Waters and Wastewaters and Materials Perspective for Their Selective Sorption

The presence of some anionic species, such as nitrate, nitrite, chloride, sulfide, fluoride, and cyanide, in water supplies may represent a serious environmental problem. In this work, the main sources and harmful effects of their bioaccumulation on living organisms are reviewed, as well as the most adopted technologies for their uptake. The major advantages and disadvantages of each methodology are also listed. In general, ion-exchange has been elucidated as the most suitable removal process. In view of that the most promising materials used to remove anionic pollutants from aqueous solutions are highlighted in this review. In particular, the major efforts towards the development of low-cost and easily available effective sorbents for water decontamination are covered. For instance, natural waste solid materials and derivatives have emerged as promising low-cost exchangers for selective anions uptake. Besides, a number of structural modifications including the introduction of more suitable surface functional groups or compensation species into the sorbent matrix have been investigated in order to enhance sorbents selectivity and capacity for anionic pollutants. The influence of speciation and removal conditions is also focused.

A novel bentonite-based adsorbent for anionic pollutant removal from water

A novel adsorbent, HO-CaBen, was prepared by the modification of bentonite, which shows good potential as a cheap and effective adsorbent for anionic contaminants removal from aqueous solutions. The adsorbent HO-CaBen was characterized by XRD and FTIR. The effects of equilibrium time, pH and temperature on adsorption some typical anionic contaminants were studied by the batch adsorption process. The adsorption capacities for fluoride, phosphate, Orange II, and SDBS are 50.07, 29.1, 239.5, and 298.5mgg−1, respectively. These values are higher than those reported for low-cost adsorbents. The adsorption mechanism of the anion on HO-CaBen is anion/OH− exchange reaction and is verified by theoretical calculation results. These results indicated that HO-CaBen was a promising adsorbent for anion removal from wastewater treatment by bentonite.

Multivariate statistical modelling of mass transfer in a membrane-supported biofilm reactor

The main objective of this work is to develop an overall mass transfer model applicable to a particular case of membrane supported biofilm, the ion-exchange membrane bioreactor (IEMB). A multivariate projection to latent structures (PLS) model of the anionic membrane transport in an IEMB was developed and analyzed to establish the mass transfer limiting variables for the removal of anionic pollutants (nitrate and perchlorate) from drinking water. The proposed PLS model accounts for the biological contribution to the mass transfer and predicts the anionic fluxes across the ion-exchange membrane with a prediction improvement of at least 50% when compared with a simplified mechanistic Donnan dialysis-based transport model. The PLS model allowed for predicting the transport of target anions using only operational physicochemical data, therefore, the use of several assumptions as in mechanistic model building was avoided as well as the need for biofilm characterization. To decrease the model complexity, several techniques which select the most informative predictors were also successfully used. The analyses of important predictors to each anionic transport model show that transport driving force related variables were the most important. Moreover, at least 30% of the model information is related with biocompartment bulk variables.